### Enlaces

 Aquí podrá encontrar la lista de los anuncios de los seminarios impartidos en nuestro grupo durante los últimos años.

Seminarios año 2017 | Subir

#### Lugar: Dpto. de Física Teórica I (Facultad de Ciencias Físicas, UCM)

Título/Title: Properties of Rotating Black Holes in Odd Dimensions

Abstract: On this talk, we will discuss about the properties of rotating Abelian black holes in odd-dimensional spacetimes, and show how the case when all angular momenta are equal becomes much simpler. This simplification also applies to theories with Chern-Simons terms, a cosmological constant, or scalar fields.

We will concentrate on the effects that do not appear in 4 dimensions and address subjects such as non-uniqueness, near-horizon geometry, radially excited solutions, etc.

#### Lugar: Dpto. de Física Teórica I (Facultad de Ciencias Físicas, UCM)

Título/Title: The smooth and clumpy universe: present and asymptotic behaviour(s)

Abstract: On this talk, we will present a review on dark energy singularities and abrupt events. We will start with a classical description of several models, including their behaviour at the perturbative level. Then, we will contrast our results with observational data. On the second part of the talk, we will focus on the quantum analysis of these singularities/abrupt events. The analysis will encompass also modified theories of gravity. Finally, if time allows, we will as well show how phantom dark energy models might not at all imply dark energy singularities in Einstein-Cartan theory.​

#### Lugar: Sala de Juntas CFMAC, CSIC (Serrano, 113 bis)

Título/Title: Deformed relativistic symmetries: decoherence and dimensional reduction at the Planck scale

Ponente/Speaker: Michele Arzano (Universidad de Roma - La Sapienza, Italy)

Abstract: I will start with a brief introduction to the framework of deformed relativistic symmetries based on Lie-group momentum spaces whose curvature sets a fundamental (Planckian) UV scale at the kinematical level. I will then show how these models can be related to a fundamental decoherence at the Planck scale and how they are relevant for the phenomenon of “dimensional reduction”, ubiquitous in a variety of approaches to quantum gravity.

#### Lugar: Sala de Juntas CFMAC, CSIC (Serrano, 113 bis)

Título/Title: Tension and constraints on modified gravity parametrizations of Geff(z) from growth rate and Planck data

Ponente/Speaker: Savvas Nesseris (Instituto de Física Teórica, Spain)

Abstract: Some of the current cosmological data, i.e. weak lensing (WL), growth rate, seem to be in tension with Planck15/LCDM and indicate consistently that there is a lack of gravitational power in structures on intermediate-small cosmological scales. This lack of power may be expressed through different cosmological parameters in a degenerate manner. In this talk, after a brief overview of WL and Redshift Space Distortion (RSD), I will present an updated and extended compilation of growth rate data based on recent RSD measurements and use it to test its consistency with the best fit Planck15/LCDM.

#### Lugar: Dpto. de Física Teórica I, (Facultad de Ciencias Físicas, UCM)

Título/Title: Mapas de Galaxias Modernos, Espectros de Potencias de Galaxias y Forecast

Abstract: La cosmología, entendida como rama de la física moderna, cuenta con tan solo cien años de historia desde su fundación en el contexto de la Teoría General de la Relatividad. Desde entonces las observaciones han ido aumentando a un ritmo vertiginoso, convirtiendo a la cosmología en una ciencia de precisión. Los últimos satélites encargados de medir el fondo cósmico de microondas, WMAP y Planck, así como el análisis de Supernovas Ia, nos han permitido conocer con precisión la composición del universo. Dicha composición requiere del enigmático fluido conocido como energía oscura, cuya dinámica es desconocida. Sin embargo, en los próximos años, las nuevas generaciones de mapas de galaxias (EUCLID, DESI, J-PAS…) nos permitirán conocer mucho más acerca de la energía oscura. En esta charla se presentarán distintos mapas de galaxias. Se expondrán varios efectos observables en los mapas de galaxias que dependen del modelo cosmológico. Y finalmente, concluiremos con las técnicas para estimar errores en los parámetros cosmológicos.

#### Lugar: Sala de Conferencias CFMAC, CSIC (Serrano, 121)

Título/Title: Gravity at the horizon: new probes of gravity and cosmic acceleration

Ponente/Speaker: Miguel Zumalacárregui (Nordita, Sweden/UC Berkeley, USA)

Abstract: Gravity is core to many unsolved problems in physics, including the properties of black holes, the nature of space-time and the origin of the universe. The desire to better comprehend gravity and the mounting evidence for cosmic acceleration have led to the proliferation of both alternatives to Einstein's theory and efforts to test them. I will present recent progress to understand these theories and determine the properties of gravity using gravitational waves and the large scale structure of the universe: The speed of gravitational waves will provide the most stringent test for a large class of theories, while a new generation of galaxy surveys will be sensitive to new relativistic effects on the largest cosmological scales. I will also introduce /hi_class/ (href="www.hiclass-code.net"), an accurate, fast and flexible code to compute cosmological predictions in a very large class of gravitational theories.

#### Lugar: Dpto. de Física Teórica I, (Facultad de Ciencias Físicas, UCM)

Título/Title: Relaciones universales I-LOVE-QNM para modos cuasi-normales de estrellas de neutrones que contienen materia exótica

Abstract: Se analizará el espectro de modos cuasi-normales de modelos realistas de estrellas de neutrones estudiando los modos axiales y polares. Consideraremos diferentes ecuaciones de estado que satisfacen la ligadura de 2 masas solares, la mayor parte de ellas conteniendo materia exótica. Se presentarán relaciones fenomenológicas nuevas entre la frecuencia y el tiempo de amortiguamiento de los modos. Estas nuevas relaciones son independientes de la ecuación de estado y relacionan el espectro de modos cuasi-normales con propiedades globales de la estrella. También, se presentarán relaciones universales entre las propiedades de los modos cuasi-normales y los parámetros I-LOVE-Q de estos modelos de estrellas de neutrones.

#### Lugar: Sala de Conferencias CFMAC, CSIC (Serrano, 121)

Título/Title: Gran explosión, constante cosmológica y gravedad cuántica: maravillas del siglo

Ponente/Speaker: Gianluca Calcagni (Instituto de Estructura de la Materia, CSIC, Spain)

Abstract: Tres cuestiones han caracterizado la física moderna de las últimas décadas. La primera es si singularidades tales como las de dentro de los agujeros negros o la Gran Explosión inicial que dio origen al cosmos se pueden resolver. La segunda es sobre la determinación de la verdadera naturaleza de la componente principal y más misteriosa del Universo, la llamada energía oscura o constante cosmológica. Ni el problema de la Gran Explosión ni el de la constante cosmológica se pueden acomodar en la relatividad general de Einstein o en modelos ordinarios de interacciones de partículas. Una posibilidad es que dichos problemas se puedan resolver unificando física cuántica y gravitación, pero es muy difícil formular una teoría y verificarla experimentalmente. Así, la tercera cuestión es cómo cuantizar la gravedad y extraer predicciones observables. En esta charla introduciremos estos temas de forma accesible a un público general.

#### Lugar: Dpto. de Física Teórica I, (Facultad de Ciencias Físicas, UCM)

Título/Title: Primordial perturbations in Hybrid (Loop) Quantum Cosmology

Ponente/Speaker: Laura Castelló Gomar (Instituto de Estructura de la Materia, CSIC, Spain)

Abstract: A lot of attention has been devoted recently to the consideration of quantum corrections to the power spectrum of primordial fluctuations, as a possible fundamental window on the Early Universe to explore quantum geometry phenomena. We present a framework for the quantum description of the evolution of cosmological scalar perturbations, starting from a formalism designed to preserve covariance, which allows us to extract physical predictions for those quantum modifications. We show how a Born-Oppenheimer ansatz leads to the recovery of a Mukhanov-Sasaki equation in which the coefficients are provided by expectation values on the background geometry. We also discuss technical tools and develop a procedure to deal with these quantum corrections beyond the most direct approximations. The case of hybrid Loop Quantum Cosmology is commented here. However, the presented scheme is general and aims at increasing the ability to discriminate between the predictions of different quantization proposals for cosmological perturbations.

#### Lugar: Sala de Juntas CFMAC, CSIC (Serrano, 113 bis)

Título/Title: Unruh-deWitt detectors: The Unruh effect and beyond

Abstract: The Unruh deWitt model describes particle detectors. These are two-level quantum systems in motion along certain space-time trajectories and coupled to quantum fields. This model is able to describe the so called Unruh effect: accelerated observers interact with the vacuum of a quantum field as if they were immersed in a thermal bath with a temperature proportional to its acceleration. We will discuss some aspects of this effect, unraveling the notion of thermal equilibrium for quantum fields and making use of the so called KMS (Kubo-Martin-Schwinger) condition.Moreover, we will see that the Unruh effect is not the end of the story, because in many scenarios some peculiarities of particle detectors are decisive, for instance the switching process, or the introduction of more than one detector. We will discuss some recent discoveries as well. We will study how thermalization takes place, looking for a thermalization time scale. Finally we will discuss when the monotonic behavior with “temperature” can be lost, inquiring into the counterintuitive, not well-understood yet Anti-Unruh effect.

#### Lugar: Dpto. de Física Teórica I, (Facultad de Ciencias Físicas, UCM)

Título/Title: Low-energy effects in super-renormalizable gravity models

Ponente/Speaker: Breno Loureiro Giacchini (Centro Brasileiro de Pesquisas Físicas, Brasil)

Abstract: Local gravitational theories with more than four derivatives have remarkable quantum properties. Namely, they are super-renormalizable and may be unitary in the Lee-Wick sense, if the massive poles of the propagator are complex. It is important, therefore, to explore also the IR limit of these theories and identify observable signatures of the higher derivatives. In this talk we present recent results in this direction. Specifically, we discuss the viability of a gravitational seesaw-like mechanism, which could be a mean of avoiding the Planck suppression of the higher derivatives' effects. Also, we show that the modified Newtonian potential in these theories is always a real quantity, besides being regular at the origin, even if complex poles are allowed in the propagator. Finally, we consider the bending of light within the general six-derivative model and discuss the possibility of the experimental detection of higher derivatives through a frequency-dependent gravitational scattering.

Seminarios año 2016 | Subir

#### Lugar: Sala de Conferencias CFMAC, CSIC (Serrano, 121)

Título/Title: Loops for dummies

Ponente/Speaker: Guillermo A. Mena Marugán (Instituto de Estructura de la Materia, CSIC, Spain)

Abstract: La Gravedad Cuántica de Lazos ("Loop Quantum Gravity" en inglés) es uno de los formalismos más sólidos como candidato para proporcionar una cuantización consistente de la Relativad General. Su aplicación a modelos que describen el origen y evolución del Universo ha dado lugar a una nueva disciplina física conocida como Cosmología Cuántica de Lazos. Su desarrollo está cambiando de raíz la visión que teníamos del Cosmos. En este coloquio comentaremos las ideas fundamentales en las que se basan la Gravedad y la Cosmología Cuántica de Lazos, y presentaremos en un tono informal (acorde a la filosofía de los "talks for dummies") algunos de sus avances más importantes.

#### Lugar: Sala de Conferencias CFMAC, CSIC (Serrano, 121)

Título/Title: Playing with the Misner space and the topology

Ponente/Speaker: Juan Margalef Bentabol (Instituto de Estructura de la Materia, CSIC, Spain/ Universidad Carlos III de Madrid, Spain)

Abstract: Topology is essential in many branches of mathematics, however, in physics, it is often taken for granted as it usually plays no crucial role. I will try to show that on some cases topology turns out to be essential in order to understand some pathological behaviors that arise in general relativity. Namely I will talk about the so-called Misner space, which shows extremely pathological behaviors that can be neatly understood through topology. Besides I will introduce the g-boundary, a topological construction introduced by Hawking and Geroch in an attempt to define properly what a singularity is, and I will prove that in the case of the Misner space, one obtains the expected g-boundary.

#### Lugar: Dpto. de Física Teórica I, (Facultad de Ciencias Físicas, UCM)

Título/Title: Spontaneous symmetry breaking and the Unruh effect

Abstract: In this work we consider the ontological status of the Unruh effect. Is it just a formal mathematical result? Or the temperature detected by an accelerating observer can lead to real physical effects such as phase transitions? In order to clarify this issue we use the Thermalization Theorem to explore the possibility of having a restoration of the symmetry in a system with spontaneous symmetry breaking of an internal continuous symmetry as seen by an accelerating observer. We conclude that the Unruh effect is an ontic effect rather than an epistemic one, giving rise, in the particular example considered here, to a phase transition (symmetry restoration) both for global and gauge symmetries (inverse Higgs mechanism) in the region close to the accelerating observer horizon.

#### Lugar: Sala de Juntas CFMAC, CSIC (Serrano, 113 bis)

Título/Title: What model-independent reconstruction techniques really say about extended theories of gravity

Ponente/Speaker: Álvaro de la Cruz Dombriz (University of Cape Town and National Institute for Theoretical Physics, Republic of South Africa)

Abstract: Model independent techniques are crucial to test both the present ΛCDM cosmological paradigm and alternative theories making the least possible number of assumptions about the Universe. Whether cosmography is able to distinguish between different gravitational theories or not has remained so far an open question. I will present the bounds on model parameters for three different extensions of General Relativity, namely quintessence, F(Torsion) and f(R) theories. Using extensive data from the Union2.1 SN catalogue, BAO data and H(z) differential age compilations, and through a Monte Carlo analysis using a Metropolis-Hastings algorithm with a Gelman-Rubin convergence criterion this technique is shown to be capable of providing 1-σ and 2-σ constraints. I shall compare these results to the truncated ΛCDM paradigm, showing that the permitted regions of coefficients are significantly modified and in general widened compared to values reported in the existing literature. Finally Bayesian selection criteria AIC and BIC will provide further insight on the limitations of the method.

#### Lugar: Aula 5A (Facultad de Ciencias Físicas, UCM)

Título/Title: Didáctica de Materia Oscura

Abstract: De acuerdo con las observaciones actuales, la componente más abundante de la materia en el universo no se encuentra entre las partículas que conocemos dentro del modelo estándar de partículas e interacciones fundamentales. Este nuevo tipo de materia se conoce como materia oscura. Existen numerosas evidencias de su existencia, sin embargo, no se ha detectado a través de ningún proceso más allá de sus efectos gravitacionales. Por ello, la naturaleza de la materia oscura y sus características fundamentales continúan siendo un misterio, una de las cuestiones abiertas más importantes dentro de la física actual.

#### Lugar: Sala de Conferencias CFMAC, CSIC (Serrano, 121)

Título/Title: Indirect searches of TeV Dark Matter at the Galactic Center

Ponente/Speaker: Viviana Gammaldi (SISSA, Italy)

Abstract: I will discuss several aspects of the indirect search of Dark Matter (DM) at the Galactic Center (GC). I will show that the gamma-ray flux observed by HESS from the J1745-290 GC source is well fitted as the secondary gamma-rays photons generated from DM annihilating into Standard Model particles in combination with a simple power-law background. The model independent fits are performed for all the possible channels of annihilation. The best fits are obtained for WIMP masses above ∼ 10 TeV. They require an enhancement factor of ∼ 10^3 and a background spectral index compatible with the Fermi-LAT data. I will investigate the possibility that the expected enhancement may be related with hydrodynamics in N-body simulation or a possible DM spike induced by the Super Massive Black Hole. I will also discuss the possibility that the latter could be related with the spatial tail detected in the gamma-ray signal by HESS II in 2015. These TeV DM masses are practically unconstrained by direct detection searches or colliders experiments, but they can be tested with the observations of other cosmic-rays.

#### Lugar: Sala de Conferencias CFMAC, CSIC (Serrano, 121)

Título/Title: Learning to live with space-time singularities with the help of non-Riemannian geometry

Ponente/Speaker: Diego Rubiera (Universidad de Lisboa, Portugal)

Abstract: Space-time singularities are a conceptually disturbing aspect of Einstein's General Theory or Relativity (GR), in that they represent a breakdown on the fabric of space-time that severely compromises predictability of our physical theories. Their existence are endemic in GR, as they unavoidably arise under quite generic conditions. Seeking inspiration from the macroscopic description of crystalline structures with defects on their microstructure in solid state physics, we consider classical effective geometries going beyond the Riemannian geometry of GR. In such geometries, metric and affine connection are regarded as independent degrees of freedom, which avoids any troubles with higher-order derivative field equations and ghost-like instabilities. Using electrovacuum fields, we show that spherically symmetric black hole solutions avoid the presence of geodesically incomplete curves via wormholes, thus allowing for information and time-like observers to be well defined at all times. From the propagation of scalar waves in these geometries we show that the potential presence of curvature divergences entails no danger for the transit of physical observers.

#### Lugar: Dpto. de Física Teórica I, (Facultad de Ciencias Físicas, UCM)

Título/Title: Observational imprints of the interacting multiverse

Ponente/Speaker: Salvador Robles Pérez (Estación Ecológica de Biocosmología)

Abstract: The most controversial feature of the multiverse may be its testability. We present a novel paradigm of the multiverse where non-local interactions and other quantum correlations may exist among the universes of the multiverse. The interactions among universes may: i) determine some global properties of a single universe without violating its notion of causal closure; ii) produce a landscape structure of vacuum states that might lead to different process of vacuum decay; and iii) induce a pre-inflationary stage in the evolution of the universe that cannot be reproduced by any known matter content. All these effects would leave distinctive and distinguishable imprints in the properties of the CMB, making the whole proposal (and the underlying theories) testable.

#### Lugar: Sala de Conferencias CFMAC, CSIC (Serrano, 121)

Título/Title: Unitary dynamics selecting a quantization of the Dirac field in cosmology

Ponente/Speaker: Beatriz Elizaga de Navascués (Instituto de Estructura de la Materia, CSIC, Spain)

Abstract: It is well known that linear canonical transformations are not generally implemented as unitary operators in QFT. Such transformations include the dynamics that arises from linear field equations on the background spacetime. This evolution is specially relevant in nonstationary backgrounds, where there is no time-translational symmetry that can be exploited to select a quantum theory. We investigate whether it is possible to find a Fock representation for the canonical anticommutation relations of a Dirac field, propagating on a homogeneous and isotropic cosmological background, such that the field evolution is unitarily implementable. First, we restrict our attention to Fock representations that are invariant under the group of spatial isometries of the background. Then, we prove that there indeed exist Fock representations such that the dynamics is implementable as a unitary operator. Finally, once a convention for the notion of particles and antiparticles is set, we show that these representations are all unitarily equivalent.

#### Lugar: Sala de seminarios FT-I, Facultad de CC. Físicas, UCM

Título/Title: Late-time cosmology in f(R) gravity

Ponente/Speaker: João Morais (UPV)

Abstract: Since the discovery of the current acceleration of the Universe by the Supernova Cosmology Project and the High-Z Supernova Search Team in 1998, several proposals have been put forward to explain the nature of the dark energy fluid that governs such late-time behaviour. Among these different proposals, the modified theories of gravity, which have since then been the focus of a renewed interest, try to obtain the late-time acceleration through modifications of the Einstein-Hilbert action. In this talk, we will focus on metric f(R) theories of gravity, a particular class of modified theories of gravity, which replace the Ricci scalar R in the action by a general function f(R). In a first step we review the "designer" or "reconstruction" approach, which tries to derive viable f(R) actions from cosmological models. We apply this methodology to the modified Generalized Chaplygin Gas and obtain the compatible f(R). This model is constrained, using the latest Planck 2015 data, within the cosmographic approach and through the computation of the effects on the matter power spectrum as observed today. The matter power spectrum is computed using the full theory of linear perturbations for metric f(R) theories without any approximation in the perturbed equations.

#### Lugar: Sala de seminarios FT-I, Facultad de CC. Físicas, UCM

Título/Title: Spacetime-noncommutativity regime of Loop Quantum Gravity

Ponente/Speaker: Michele Ronco (Universidad de Roma - La Sapienza, Roma, Italia)

Abstract: A recent study by Bojowald and Paily provided a path toward the identication of an effective quantum-spacetime picture of Loop Quantum Gravity, applicable in the "Minkowski regime", the regime where the large-scale (coarse-grained) spacetime metric is flat.

A pivotal role in the analysis is played by Loop-Quantum-Gravity-based modications to the hypersurface deformation algebra, which leave a trace in the Minkowski regime. We here show that the symmetry-algebra results reported by Bojowald and Paily are consistent with a description of spacetime in the Minkowski regime given in terms of the kappa-Minkowski noncommutative spacetime, whose relevance for the study of the quantum-gravity problem had already been proposed for independent reasons.

#### Lugar: Sala de Conferencias CFMAC, CSIC (Serrano, 121)

Título/Title: Hamiltonian formulation of parametrized field theories: incorporating boundaries and gauge symmetries

Ponente/Speaker: Fernando Barbero (Instituto de Estructura de la Materia, CSIC, Spain)

Abstract: Parametrized field theories have been used as a test bed for polymer quantization techniques in Loop Quantum Gravity. In this talk I will review the Hamiltonian formulation for singular (constrained) systems and discuss several issues that play a relevant role in the Hamiltonian description of parametrized models when boundaries and internal gauge symmetries are present. For concreteness I will concentrate on the discussion of the scalar field subject to several types of boundary conditions and electromagnetism.

#### Lugar: Sala de seminarios FT-I, Facultad de CC. Físicas, UCM

Título/Title: Quantum corrections to the Higgs potential on a curved background

Abstract: I will present recent results on finite gravitational corrections to the Higgs effective potential. In particular, 1-loop corrections due to the Higgs self-interactions are computed in a perturbed FRW background by mode summation. For this aim, the Klein-Gordon equation is solved to first order in perturbations and to zero order in the adiabatic approximation.

Dimensional regularization techniques are used to compute not only the divergent parts of the effective potential but also the finite ones. The obtained results amount to the presence of inhomogeneities in the Higgs vacuum expectation value which translate into variations on the masses of elementary particles. Possible observable signatures within the Solar System and on cosmological scales will be discussed.

#### Lugar: Sala de Juntas CFMAC, CSIC (Serrano, 113-bis)

Título/Title: Einstein-Yang-Mills-Lorentz Black Holes

Abstract: Since the discovery of the first non-abelian solution to the Einstein-Yang-Mills (EYM) theory done by Bartnik and McKinnon, a large number of properties and different solutions have been obtained. As they manifestly violate the non-hair conjecture, they have attracted much attention and encouraged a deep search for other black hole geometries.

In this talk, first we will review the most relevant particle-like and black hole solutions for such a theory. In addition, we will focus on the EYM-SO(N) model and establish a particular equivalence between this case and a certain class of theories with torsion within Riemann-Cartan space-times, in order to simplify the problem of finding exact solutions to the EYM equations. Finally, solutions for the torsion-free and the non-vanishing torsion with rotation and reflection symmetries will be presented by the explicit use of this method.

#### Lugar: Sala de Conferencias CFMAC, CSIC (Serrano, 121)

Comentarios: QUINFOG seminars

Título/Title: Uniqueness of the Fock quantization of Dirac fields with unitary dynamics

Ponente/Speaker: Beatriz Elizaga Navascués (Instituto de Estructura de la Materia, CSIC, Madrid, Spain)

Abstract: It is well known that linear canonical transformations are not generally implemented as unitary operators in QFT. Such transformations include the dynamics that arises from the field equations on the background spacetime. This evolution is specially relevant in nonstationary backgrounds, where there is no time-translational symmetry that can be exploited to select a quantum theory. We investigate whether it is possible to find a Fock representation for the canonical anticommutation relations of a Dirac field, propagating on a homogeneous and isotropic cosmological background, such that the field evolution is unitarily implementable. First, we restrict our attention to Fock representations that are invariant under the group of spatial isometries of the background. Then, we prove that there indeed exist Fock representations such that the dynamics is implementable as a unitary operator. Finally, once a convention for the notion of particles and antiparticles is set, we show that these representations are all unitarily equivalent.

#### Lugar: Sala de seminarios FT-I, Facultad de CC. Físicas, UCM

Título/Title: Clasificación completa de singularidades cosmológicas

Abstract: El descubrimiento de la expansión acelerada del universo ha motivado la consideración de singularidades cosmológicas más allá de los clásicos Big Bang y Big Crunch. La primera de ellas fue el Big Rip, pero, a medida que se han ido proponiendo nuevos modelos, han ido apareciendo muchas más posibilidades. Incluso se están proponiendo nuevos escenarios no singulares como estado final posible para el Universo, tales como el Little Big Rip o el Pseudorip.

En esta charla se propondrá un intento sistemático de derivar todas estas familias de singularidades y escenarios, y algunas nuevas más, a partir de desarrollos en serie generalizados del parámetro de deceleración del universo o del índice barotrópico y se relacionará con resultados anteriores para determinar la fuerza de estas singularidades, ya que en muchos caso son débiles y no podrían considerarse un final para el universo.

#### Lugar: Sala de Conferencias CFMAC, CSIC (Serrano, 121)

Título/Title: Fast oscillating fields cosmology

Abstract: The ubiquity of scalar fields in cosmology is not only owed to its simplicity, but mainly because it intrinsically respects the large degree of isotropy observed in the universe. On the contrary, the evolution of a coherent vector field is clearly anisotropic. However, we will show that the energy-momentum tensor of homogeneous fields of arbitrary spin in an expanding universe is always isotropic in average provided the fields remain bounded and evolve rapidly compared to the rate of expansion. This property enlarge the plausible candidates to solve cosmological problems to higher spin theories.

In the second part of the talk, we will discuss the perturbations of a fast oscillating scalar field under a power law potential, following an effective approach as well as the exact system solution in the sub/super-Hubble limits.

#### Lugar: Sala de seminarios FT-I, Facultad de CC. Físicas, UCM

Título/Title: Colapso de materia cuántica autogravitante sobre una geometría cuántica

Ponente/Speaker: Javier Olmedo (Universidad Estatal de Lousiana, Baton Rouge, EEUU)

Abstract: En esta charla voy a resumir los últimos avances en relación a la cuantización de espacio-tiempos esféricamente simétricos en gravedad cúantica de lazos. Resumiré brevemente el escenario en ausencia de materia. Después, consideraré el acoplo con una cáscara autogravitante, fina, esférica y sin masa. Introduciré una redefinición del álgebra de ligaduras de tal modo que la ligadura escalar conmute consigo misma. Mostraré que esto se puede llevar a cabo también en el nivel cuántico. Además proporcionaré los observables cuánticos del modelo y definiré las componentes de la métrica a partir de ellos como observables parametrizados. Finalmente discutiré las consecuencias físicas.

#### Lugar: Sala de Conferencias CFMAC, CSIC (Serrano, 121)

Título/Title: Is Cosmography a useful tool to target extended theories of gravity?

Abstract: Model-independent methods in cosmology have become an essential tool in order to deal with an increasing number of theoretical alternatives for explaining the late-time acceleration of the Universe. In principle, this provides a way of testing the Cosmological Concordance model under different assumptions and to rule out whole classes of competing theories. One such model-independent method is the so-called cosmographic approach, which relies only in the homogeneity and isotropy of the Universe on large scales. We show that this method suffers from many shortcomings, providing biased results depending on the auxiliary variable used in the series expansion and is unable to rule out models or adequately reconstruct theories with higher-order derivatives in either the gravitational or matter sector. Consequently, in its present form, this method seems unable to provide reliable or useful results for cosmological applications.

#### Lugar: Sala de seminarios FT-I, Facultad de CC. Físicas, UCM

Título/Title: Higher derivative actions and inflation in string theory

Ponente/Speaker: Francisco Pedro (Instituto de Física Teórica, CSIC, Madrid, España)

Abstract: In this talk I will explore some aspects of higher derivative (>2) supergravity actions. I will review how the vacua and scalar potential of the bosonic sector of type IIB string compactifications can get modified in the presence of such corrections and will use them to build a viable inflationary model, where the inflaton is a geometric modulus, parametrising the size of the compactification space.

Seminarios año 2015 | Subir

#### Lugar: Sala de Conferencias 121

Título/Title: Phase Space Noncommutativity: From Gravity to Quantum Mechanics

Ponente/Speaker: Catarina Bastos (Instituto Superior Técnico (IST), Lisboa, Portugal)

Abstract: A phase-space noncommutativity (NC) is considered in the context of a Kantowski-Sachs cosmological model. Then, the interior of a Schwarzschild black hole is analyzed. One deduces the thermodynamics and show that the Hawking temperature and entropy exhibit an explicit dependence on the momentum noncommutativity parameter, η. Furthermore, the t=r=0 singularity is analysed in the noncommutative regime and it is shown that the wave function vanishes in this limit.

Quantumness and separability criteria for continuous variable systems are discussed for the case of a NC phase-space quantum mechanics. In particular, the quantum nature and the entanglement configuration of NC two-mode Gaussian states are examined. Finally, a more general measurement disturbance uncertainty principle is presented in a Robertson-Schrödinger formulation. It is shown that it is stronger and having nicer properties than Ozawa’s uncertainty relations. In particular is invariant under symplectic transformations. One shows also that there are states of the probe (measuring device) that saturate the matrix formulation of measurement disturbance uncertainty principle.

#### Lugar: Sala de sem. FT-I, Fac. de Física UCM

Título/Title: Aplicaciones del grafeno en física fundamental. Renormalización, campos gauge y curvatura con fermiones de Dirac sin masa en dos dimensiones

Ponente/Speaker: José González Carmona (IEM, CSIC, Madrid, Spain)

Abstract: El descubrimiento del grafeno ha supuesto toda una revolución, no solo por el considerable potencial de este material para aplicaciones tecnológicas, sino también por ofrecer un banco de pruebas donde experimentar con una gran variedad de fenómenos de física fundamental.

En esta charla repasaremos algunos de los efectos que derivan del comportamiento de las excitaciones electrónicas del grafeno como fermiones de Dirac sin masa, haciendo énfasis en cómo el grado de libertad adicional (pseudoespín) de las excitaciones conduce a signaturas no convencionales que se pueden medir en el sistema electrónico.

#### Lugar: Sala de Juntas 121

Comentarios: ILQGS

Título/Title: Intrinsic time in quantum geometrodynamics

Ponente/Speaker: Eyo E. Ita (US Naval Academy)

#### Lugar: Sala de Conferencias 121

Título/Title: Sistema de dos niveles en las cercanías de un agujero negro de Schwarzschild

Ponente/Speaker: Jose Sánchez (IEM, CSIC, Madrid, Spain)

Abstract: La búsqueda de agujeros negros no es tarea fácil. Mediante el estudio del espectro de emisión espontánea de un sistema de dos niveles, se propone una posibilidad para la misma. Se discuten aspectos básicos de la cuantización de campos cuando consideramos espacio tiempos no planos y se discuten algunos de los efectos derivados. Igualmente se discuten los aspecto básicos de la óptica cuántica para sistemas de dos niveles, llegando a la llamada ecuación maestra.

#### Lugar: Sala de Juntas 121

Comentarios: ILQGS

Título/Title: Loop Quantum Cosmology, Non-Gaussianity, and CMB anomalies

Ponente/Speaker: Ivan Agulló (LSU, USA)

#### Lugar: Sala de Juntas 121

Comentarios: ILQGS

Título/Title: Squeezed spin-networks and entanglement

Ponente/Speaker: Eugenio Bianchi (Penn State University, USA)

#### Lugar: Sala de sem. FT-I, Fac. de Física UCM

Título/Title: Effective field theory approach to modified gravity with applications to inflation and dark energy

Ponente/Speaker: Shinji Tsujikawa (Tokyo University of Science, Japan)

#### Lugar: Sala de Juntas 121

Comentarios: ILQGS

Título/Title: 3D Holography

Ponente/Speaker: Bianca Dittrich (Perimeter Institute, Canada)

#### Lugar: Sala de Juntas 121

Comentarios: ILQGS

Título/Title: Numerical investigations of the EPRL model

Ponente/Speaker: Benjamin Bahr (DESY, Germany)

#### Lugar: Sala de Conferencias 121

Título/Title: Sparsity of the Hawking flux

Ponente/Speaker: Matt Visser (Victoria University of Wellington, New Zealand)

Abstract: The Hawking flux that reaches spatial infinity is extremely sparse and thin, with the Hawking quanta dribbling out of the black hole one-by-one. The typical time between quanta reaching infinity is larger than the timescale set by the energy of the quanta by factors of many hundreds. Among other things, this means that the Hawking evaporation of a black hole should be viewed as a sequential cascade of 3-body decays.

#### Lugar: Sala de Conferencias 121

Título/Title: Constraining the early universe with primordial black holes

Ponente/Speaker: Sam Young (Dept. of Physics and Astronomy, University of Sussex, United Kingdom)

Abstract: Primordial black holes (PBHs) could have formed very early in the history of the universe after inflation ended. They are a viable dark matter candidate and represent a unique probe to study the small scales of the early universe, not visible by other means. I will discuss how PBHs have been used to constrain the small scales, and how this depends strongly on the non-Gaussianity parameters, as well as how PBHs can be used to constrain the large scales in the early universe.

#### Lugar: Sala de sem. FT-I, Fac. de Física UCM

Título/Title: “The magnificent seven and friends”: Horndeski theories self-tuning to de Sitter

Abstract: The cosmological constant problem is not alleviated in the context of alternative theories of gravity generically. Focusing attention on theories with equations containing non-higher than second order derivatives, Horndeski theories, there is a dynamical adjustment mechanism able to screen any value of the cosmological constant. Under the assumption that the gravity's vacuum is described by a de Sitter geometry, the late time accelerated expansion of the universe can be understood as the result of that adjustment mechanism. I will present the Horndeski models able to carry out that kind of screening, which, therefore, have a de Sitter critical point for any type of material content. I will summarize the cosmological consequences of the resulting models, emphasizing the case with symmetry under shift redefinitions of the field.

#### Lugar: Sala de sem. FT-I, Fac. de Física UCM

Título/Title: Non-linear evolution of the BAO scale in alternative theories of gravity

Ponente/Speaker: Miguel Zumalacárregui (ITP Heidelberg, Germany / Nordita, Sweden)

Abstract: The scale of Baryon Acoustic Oscillations (BAO) imprinted in the matter distribution is known to suffer sub-percent deviations from being a perfect standard ruler due to non-linear corrections. However, such corrections have never been computed in alternative theories of gravity. I will give an overview of historical and recent developments in alternative theories of gravity and present the first computation of the BAO shift based on perturbation theory (à la Bellini-Sawicki) and a peak-background split (à la Sherwin-Zaldarriaga), valid for any Horndeski theory. The BAO shift is modified by the enhanced growth of linear perturbations, as well as by novel, non-linear gravitational effects. The modified gravity result can range from a negligible to order-unity correction at z=0 depending on the model, and in some cases presents a characteristic time evolution. Although small, this effect might be within the reach of future galaxy surveys, and might have implications for BAO reconstruction in theories other than Einstein's.

#### Lugar: Sala de sem. FT-I, Fac. de Física UCM

Título/Title: Quantum cosmology: Games without frontiers

Ponente/Speaker: Ana Alonso Serrano (IFF, CSIC, Madrid, Spain)

Abstract: In classical General Relativity, the presence of horizons excises parts of the spacetime making inaccessible physical observations beyond them. But, is it so quantum mechanically? We develop a canonical quantization of a minisuperspace model whose classical solutions possess horizons, in order to check that this is not the case: Quantum gravitational states with support in spacetime configurations that exclusively describe either each region of the whole spacetime are not consistent, due to quantum correlations that appear across the horizon, making the physical states of the different regions not separable but entangle.

#### Lugar: Sala de Juntas 121

Comentarios: ILQGS

Título/Title: Generalized GFT condensates and Cosmology

Ponente/Speaker: Lorenzo Sindoni (Albert Einstein Institute, Germany)

#### Lugar: Sala de Conferencias 121

Título/Title: Modifying General Relativity: is it worth?

Ponente/Speaker: Diego Sáez-Gómez (U. of Lisbon and ACGC, Portugal - U. of Cape Town, South Africa)

Abstract: In this talk I will review some models of modified gravities and their features from a classical point of view. Over the last years, modified gravities have drawn much attention within the cosmological context since they can reproduce with great accuracy the late-time acceleration and even the inflationary epoch. I will show the pros and cons of some of the main proposals.

#### Lugar: Sala de Juntas 121

Comentarios: ILQGS

Título/Title: Separability and quantum mechanics

Ponente/Speaker: Fernando Barbero (CSIC, Madrid, Spain)

#### Lugar: Sala de Juntas 121

Comentarios: ILQGS

Título/Title: An explicit computation of the evaporation of a quantum black hole

Ponente/Speaker: Jorge Pullin (Louisiana State University, Baton Rouge, EE.UU.)

#### Lugar: Sala de Conferencias 121

Título/Title: Graphene: Dirac fermions in curved spaces

Ponente/Speaker: Alberto Cortijo (Instituto de Ciencia de Materiales de Madrid, CSIC)

Abstract: It is well known that the low energy electronic excitations in graphene are described by the massless Dirac equation. It might seem natural in terms of effective field theories that when a graphene sheet is corrugated the description in terms of Dirac fermions can still be valid, but in a curved background. In this seminar we review the consequences of assuming such viewpoint and we compare it with the usual approach adopted in solid state physics.

#### Lugar: Sala de Juntas 121

Comentarios: ILQGS

Título/Title: Quantum curves

Ponente/Speaker: Muxin Han (Florida Atlantic University, Boca Raton, EE.UU.)

#### Lugar: Sala de Juntas 121

Comentarios: ILQGS

Título/Title: Cosmology with group field theory condensates

Ponente/Speaker: Steffen Gielen (Imperial College, Londres, Reino Unido)

#### Lugar: Sala de sem. FT-I, Fac. de Física UCM

Título/Title: Anomaly-induced effective action and Starobinsky model of inflation

Ponente/Speaker: Ilya L. Shapiro (Universidade Federal de Juiz de Fora, Brasil)

Abstract: The effective action of gravity contains the main information about quantum effects, but in most cases it can not be calculated exactly. An important exception is the one-loop effective action for massless conformal invariant matter fields, which can be obtained by integrating trace anomaly. The integration constant is an arbitrary conformal functional of the background metric, but for the zero-order cosmology this functional is irrelevant and the solution becomes exact. The most important applications include systematic classification of vacuum states in the vicinity of the black hole and the Starobinsky model of inflation. The last is based on the non-local anomaly-induced metric, however the most relevant part is a local term which is just a square of the scalar curvature. The modified version of the model does not require special choice of initial conditions and is based on the interpolation between stable and unstable inflationary solutions.

#### Lugar: Sala de Juntas 121

Comentarios: ILQGS

Título/Title: No firewalls in quantum gravity

Ponente/Speaker: Alejandro Pérez (Centre de Physique Théorique, Marsella, Francia)

#### Lugar: Sala de sem. FT-I, Fac. de Física UCM

Título/Title: A bridge between the microscopic structure of space-time and effective geometries: the crystal lessons

Ponente/Speaker: Diego Rubiera-García (Universidad de Fudan, Shanghái, China)

Abstract: A striking mathematical and physical resemblance exists between quantum gravity effective geometries arising from a hypothetical microstructure of space-time pervaded by creation and annihilation of wormholes (space-time foam), and the continuized version of crystalline structures. If the latter contains defects on its microstructure, the macroscopic effective description must be done in terms of a metric-affine geometry with nonmetricity and torsion. Using a crystal-motivated action in a simplified scenario, we find the presence of Wheeler's geons: self-consistent topologically non-trivial gravito-electromagnetic entities, representing the gravitional analog of point defects.

What lessons can we extract from this analogy?

#### Lugar: Sala de Juntas 121

Comentarios: ILQGS

Título/Title: Rainbows from quantum gravity

Ponente/Speaker: Andrea Dapor (Universidad de Varsovia, Polonia)

#### Lugar: Sala de Conferencias 121

Título/Title: CMB: beyond the standard statistical scenario

Abstract: In this talk I will review the basic hypotheses which motivate the statistical framework used to analyze the cosmic microwave background radiation (CMB), and discuss how that framework can be enlarged as we relax those hypotheses. In particular, I will try to separate as much as possible the questions of gaussianity, homogeneity and isotropy from each other, while giving particular emphasis to their signatures and the enhanced "cosmic variances" that become increasingly important as our putative Universe becomes less symmetric. After reviewing the basic formalism I will present a few model-independent statistical tests, including some new results, which can be applied to CMB data when searching for large scale “anomalies”.

Seminarios año 2014 | Subir

#### Lugar: Sala de Conferencias 121

Título/Title: Topological Quantum Computation - From Concepts To Experiment

Abstract: Quantum computers hold the promise to allow one to solve problems that cannot be efficiently treated on classical computers. To date, the construction of a quantum computer remains a fundamental scientific and technological challenge, due the influence of unavoidable noise which affects the fragile quantum states. In our talk, we begin with a general introduction to quantum computation and then introduce the basic idea of quantum error correction based on topological quantum codes, which allow one to protect quantum information during storage and processing. We then discuss a recent experimental realization of a quantum error correcting code in which a logical qubit was distributed over seven trapped-ion qubits. This encoding not only allowed us to detect arbitrary single-qubit errors, but also to realize for the first time quantum computations on an encoded qubit. This quantum error correcting code represents a fully functional instance of a topologically encoded qubit, or color code, and opens a route toward fault-tolerant quantum computing.

#### Lugar: Sala de Juntas 121

Comentarios: ILQGS

Título/Title: Invariance of Connections and Measures in Loop Quantum Cosmology

#### Lugar: Sala de Juntas 121

Comentarios: ILQGS

Título/Title: SL(2,C) Chern-Simons Theory and Spinfoam Gravity with a Cosmological Constant

Ponente/Speaker: Hal Haggard (Bard College, Nueva York, EEUU) & Aldo Riello (Perimeter Institute for Theoretical Physics, Waterloo, Canadá)

#### Lugar: Sala de sem. FT-I, Fac. de Física UCM

Título/Title: Sala de sem. FT-I, Fac. de Física UCM

Ponente/Speaker: Franco D. Albareti (Instituto de Física Teórica, IFT-CSIC/UAM, Madrid)

Abstract: A comoving cutoff is used to renormalize the vacuum stress-energy tensor of a scalar field in RW geometries in a covariant way. At the IR regime (late times) a matter-like contribution dominates. A phenomenological bound to the comoving cutoff is obtained from the current abundance of dark matter. It is also shown that this "dark matter" could support perturbations with a negligible speed of sound, thus it could seed the formation of structures. Besides, I will present the latest results on the possible variation of the fine structure constant using SDSS-III/BOSS QSO spectra with [OIII] emission lines.

#### Lugar: Sala de Juntas 121

Comentarios: ILQGS

Título/Title: Lorentz transformations from abstract quantum theory: a thought experiment

Ponente/Speaker: Philipp Hoehn (Perimeter Institute for Theoretical Physics, Waterloo, Canadá)

#### Lugar: Sala de Juntas 121

Comentarios: ILQGS

Título/Title: New applications for LQG

Ponente/Speaker: Jerzy Lewandowski (Universidad de Varsovia, Polonia)

#### Lugar: Sala de Juntas 121

Comentarios: ILQGS

Título/Title: White holes

Ponente/Speaker: Carlo Rovelli (Centre de Physique Théorique, Centre National de la Recherche Scientifique, Marsella, Francia)

#### Lugar: Sala de Juntas 121

Comentarios: ILQGS

Título/Title: Phenomenological consequences of quantum geometries in LQC

Ponente/Speaker: Brajesh Gupt (Penn State University, State College, EE.UU.)

#### Lugar: Sala de Juntas 121

Comentarios: ILQGS

Título/Title: Casimir effect on a quantum geometry

Ponente/Speaker: Javier Olmedo (Louisiana State University, Baton Rouge, EE.UU.)

#### Lugar: Sala de Conferencias 121

Comentarios: Seminario de Gravitación y Cosmología

Título/Title: Statistical and entanglement entropy for black holes in quantum geometry

Ponentes/Speakers: Alejandro Pérez (Centre de Physique Théorique, Centre National de la Recherche Scientifique, Marsella, Francia)

Abstract: I will discuss the relationship between entanglement (or geometric) entropy with statistical mechanical entropy of horizon degrees of freedom when described in the framework of isolated horizons in loop quantum gravity. We show that, once the relevant degrees of freedom are identified, the two notions coincide. The key ingredient linking the two notions is the structure of quantum geometry at Planck scale implied by loop quantum gravity, where correlations between the inside and outside of the black hole are mediated by eigenstates of the horizon area operator.

#### Lugar: Sala de Conferencias 121

Título/Title: Supernovae as probes of cosmic parameters: estimating the bias from under-dense lines of sight

Ponente/Speaker: Vinicius Busti (Astrophysics, Cosmology and Gravity Center, University of Cape Town, Ciudad del Cabo, Sudáfrica)

Abstract: Correctly interpreting observations of sources such as type Ia supernovae (SNe Ia) require knowledge of the power spectrum of matter on AU scales—which is very hard to model accurately. Because under-dense regions account for much of the volume of the universe, light from a typical source probes a mean density significantly below the cosmic mean. The relative sparsity of sources implies that there could be a significant bias when inferring distances of SNe Ia, and consequently a bias in cosmological parameter estimation. While the weak lensing approximation should in principle give the correct prediction for this, linear perturbation theory predicts an effectively infinite variance in the convergence for ultra-narrow beams. In this talk, I will adopt an observational viewpoint and discuss some approximations to see the effects of under-dense lines of sight might have in parameter estimation. Also, I will address tests to decide what is the best way to describe light propagation in the real Universe.

#### Lugar: Sala de sem. FT-I, Fac. de Física UCM

Título/Title: The cosmological constant problem: a lesson from Helium-3

Abstract: The effective gravity emerging for relativistic quasiparticles in superfluid 3He-A provides a direct connection between the properly determined vacuum energy and the cosmological constant lambda. This connection is non-trivial, and requires a detour via the masses of the "gravitons" in the associated bi-metric gravity. Although the cosmological constant lambda turns out to be huge—it is determined by the effective Planck scale—, the cosmological term (the stress-energy tensor associated to lambda) is in fact naturally non-constant and vanishes in the equilibrium vacuum, as dictated by thermodynamics. This suggests that the equilibrium state of any condensed-matter system, and perhaps also the final state of the Universe, is not gravitating.

#### Lugar: Sala de Conferencias 121

Título/Title: Junction conditions in gravity theories

Ponente/Speaker: José M. M. Senovilla (Universidad del País Vasco, Bilbao, España)

Abstract: I will present the method to obtain the proper junction conditions in general theories of gravity, highlighting the differences specific to General Relativity (GR) and its peculiarities. As an illustrative example I will consider F(R) Lagrangian theories explicitly.
The discussion will analyze two different junction levels: allowing for branes/thin shells or not. In the former case I will argue that the generic brane/shell construction is crucially different to that in GR. In the latter case I will show that properly matched solutions in GR are no longer solutions of F(R)—and other—theories.
(An exceptional case arises in theories with a Lagrangian quadratic in the curvature: gravitational double layers are feasible, and this leads to new Physics—but I will probably have no time to describe this)

#### Lugar: Sala de Juntas 121

Comentarios: ILQGS

Ponente/Speaker: Jorge Pullin (Louisiana State University, Baton Rouge, EE.UU.)

#### Lugar: Sala de sem. FT-I, Fac. de Física UCM

Ponente/Speaker: Gianluca Calcagni (Instituto de Estructura de la Materia, IEM-CSIC, Madrid, España)

Abstract: Se revisan los problemas cosmológicos de la Gran Explosión (¿El universo nació de una singularidad inicial como predice la relatividad clásica?) y de la energía oscura (¿Por qué el universo reciente está acelerando?) en algunos enfoques de gravedad cuántica y teorías que van más allá del Modelo Estándar. Aunque no haya todavía ninguna solución consolidada y satisfactoria de ambos problemas, las observaciones cosmológicas modernas pueden proporcionar una valiosa información sobre diversos modelos exóticos de física de partículas y de gravedad.

#### Lugar: Sala de Juntas 121

Comentarios: ILQGS

Título/Title: LQC and the very early universe

Ponente/Speaker: Ivan Agullo (Louisiana State University, Baton Rouge, EE.UU.), Aurélien Barrau (Laboratoire de Physique Subatomique et de Cosmologie, Grenoble, Francia) y Guillermo A. Mena Marugán (Instituto de Estructura de la Materia, IEM-CSIC, Madrid, España)

#### Lugar: Sala de Juntas 121

Comentarios: ILQGS

Título/Title: Linking canonical and covariant LQG

Ponente/Speaker: Antonia Zipfel (Universidad de Varsovia, Polonia)

#### Lugar: Sala de Juntas 121

Comentarios: ILQGS

Título/Title: Continuum limit and renormalization

Ponente/Speaker: Laurent Freidel (Perimeter Institute for Theoretical Physics, Waterloo, Canadá)

#### Lugar: Sala de Conferencias 121

Título/Title: Averaging and modified gravity theories: An overview of tools able to explain the cosmological late-time acceleration

Abstract: One possible explanation for the present observed acceleration of the Universe is the breakdown of homogeneity and isotropy due to the formation of non-linear structures. How the formation of non-linear structures and subsequent inhomogeneities affect the averaged cosmological expansion rate and may eventually lead to late-time acceleration is usually referred to asbackreaction mechanism. General Relativity together with dust matter scenarios have until recently been considered as the sole ingredients for averaged calculations. We shall present the backreaction formalism in more general scenarios, including imperfect fluids as well as extended theories of gravity, and apply an averaging procedure to them in order to determine possible backreaction effects.

#### Lugar: Sala de sem. FT-I, Fac. de Física UCM

Título/Title: Cosmological solutions in bigravity

Ponente/Speaker: Prado Martín-Moruno, (Instituto Superior Técnico, Lisboa, Portugal)

Abstract: Bigravity theories, which are formulated using two mutually interacting dynamical metrics, were initially introduced by Isham, Salam, and Strathdee in the seventies. These theories have recently attracted considerable attention since Hassan and Rosen found a bigravity theory which is potentially stable, that is, free of the Boulware–Deser ghost which otherwise affects these theories. As bigravity can be interpreted to describe two different universes, I will present a simple way to study the cosmology of such a classical bi-universe in general situations. I will pay particular attention to the interplay of both gravitational sectors and how one can extract conclusions about the dynamics of one universe from the knowledge about the occurrence of violent events in the other universe.

#### Lugar: Sala de Conferencias 121

Comentarios: Seminario IEM

Ponente/Speaker: Gianluca Calcagni (Instituto de Estructura de la Materia, IEM-CSIC, Madrid, España)

Abstract: Se revisan los problemas cosmológicos de la Gran Explosión (¿El universo nació de una singularidad inicial como predice la relatividad clásica?) y de la energía oscura (¿Por qué el universo reciente está acelerando?) en algunos enfoques de gravedad cuántica y teorías que van más allá del Modelo Estándar. Aunque no haya todavía ninguna solución consolidada y satisfactoria de ambos problemas, las observaciones cosmológicas modernas pueden proporcionar una valiosa información sobre diversos modelos exóticos de física de partículas y de gravedad.

#### Lugar: Sala de Juntas 121

Comentarios: ILQGS

Título/Title: S-matrices for General Boundary QFT on Anti de Sitter spacetime

Ponente/Speaker: Max Dohse (Universidad Nacional Autónoma de México, Morelia, México)

#### Lugar: Sala de sem. FT-I, Fac. de Física UCM

Título/Title: Emergent electromagnetism: some training towards a theory of emergent gravity

Ponente/Speaker: Carlos Barceló (Instituto de Astrofísica de Andalucía (IAA-CSIC), Granada, España

Abstract: TBA

#### Lugar: Sala de Conferencias 121

Comentarios: ILQGS

Título/Title: Discussion on simplicity constraints in spin foam models

Ponentes/Speakers: Marc Geiller (PennState University, State College, PA, EE.UU.) y Simone Speziale (Centre de Physique Théorique de Marseille, Marsella, Francia)

#### Lugar: Sala de Conferencias 121

Comentarios: ILQGS

Título/Title: Quantum group spin nets: refinement limit and relation to spin foams

Ponentes/Speakers: Sebastian Steinhaus (Perimeter Institute for Theoretical Physics, Waterloo, Canadá)

#### Lugar: Sala de Conferencias 121

Comentarios: ILQGS

Título/Title: A new vacuum for loop quantum gravity

Ponentes/Speakers: Bianca Dittrich (Perimeter Institute for Theoretical Physics, Waterloo, Canadá)

#### Lugar: Sala de Juntas 121

Comentarios: Seminario de Gravitación y Cosmología

Título/Title: Loop quantization of spherically symmetric vacuum spacetimes

Ponentes/Speakers: Javier Olmedo (Instituto de Física, Universidad de la República, Montevideo, Uruguay)

Abstract: We provide a quantization of spherically symmetric vacuum spacetimes within loop quantum gravity. Concretely, a modification of the classical constraints that preserves the classical constraint surface leaves us with a constraint algebra free of structure functions. We then adopt the Dirac quantization scheme together with a representation mimicking the one of loop quantum gravity. We find the solutions to the constraints and a suitable inner product. Eventually, we provide the physical Hilbert space out of them together with the quantum observables of the model, some of them without classical counterpart.

#### Lugar: Sala de Conferencias 121

Comentarios: Seminario de Gravitación y Cosmología en colaboración con la Embajada de Francia

Título/Title: The Shape of Space, from Black Holes to the Universe

Ponentes/Speakers: Jean-Pierre Luminet (Centre National de la Recherche Scientifique, Observatoire de Paris, Francia)

Abstract: The description of the shape of our physical space at various scales (length scales or energy scales) involves a rich variety of geometrical models, each depending on the underlying physical theory. Imaging distorted space and time by gravitational and quantum fields is a big challenge of modern fundamental physics. I shall discuss such space representations for describing the shape of space around black holes, next the global shape of our universe in the framework of cosmic topology, and eventually give hints on the shape of spacetime at the quantum scale. Striking movies and color visualizations will be displayed.

#### Lugar: Sala de Juntas 121

Comentarios: Seminario de Gravitación y Cosmología

Título/Title: Semiclassical limit of Loop Quantum Gravity: from graphs to manifolds

Ponentes/Speakers: Iñaki Garay (Universidade Federal do Pará, Belém, Brasil)

Abstract: The building blocks of a quantum theory of General Relativity are expected to be discrete structures. Loop Quantum Gravity is formulated using a basis of spin networks (wave functions over oriented graphs with colored edges), thus realizing the aforementioned expectation. Semiclassical states should, however, reproduce the classical smooth geometry in the appropriate limits. The question of how to recover a continuous geometry from these discrete structures is, therefore, relevant in this context. Here we explore this problem using properties of Voronoi graphs.

#### Lugar: Sala de Juntas 121

Comentarios: ILQGS

Título/Title: Matter matters in asymptotically safe quantum gravity

Ponentes/Speakers: Pietro Donà (International School for Advanced Studies, Trieste, Italia)

Seminarios año 2013 | Subir

#### Lugar: Sala de Juntas 121

Comentarios: ILQGS

Título/Title: Towards the resolution of the CGHS singularity in LQG

Autor/Author: Saeed Rastgoo (Universidad Nacional Autónoma de México, Morelia, México)

Abstract: TBA

#### Lugar: Sala de Juntas 121

Comentarios: ILQGS

Título/Title: Bianchi IX LQC: What can we learn from shape dynamics?

Autor/Author: Tim Koslowski (University of New Brunswick, Fredericton, Canadá)

Abstract: TBA

#### Lugar: Sala de Juntas 121

Comentarios: ILQGS

Título/Title: Bianchi IX LQC: Quantization ambiguity and effective description

Autor/Author: Asieh Karami (Universidad Nacional Autónoma de México, Morelia, México)

Abstract: TBA

#### Lugar: Sala de Juntas 121

Comentarios: ILQGS

Título/Title: Holographic special relativity: observer space from conformal geometry

Autor/Author: Derek Wise (Friedrich-Alexander-Universität, Erlangen, Alemania)

Abstract: TBA

#### Lugar: Sala de Juntas 121

Comentarios: ILQGS

Título/Title: Black hole entropy from LQG: higher dimensions and generalized theories

Autor/Author: Norbert Bodendorfer (PennState University, State College, PA, EE.UU.)

Abstract: TBA

#### Lugar: Despacho 417.

Comentarios: Asymptotic Safety Seminar

Título/Title: Probing the quantum nature of spacetime by diffusion

Autor/Author: Gianluca Calcagni (Instituto de Estructura de la Materia, IEM-CSIC, Madrid, España)

Abstract: TBA

#### Lugar: Sala de Juntas 121.

Comentarios: ILQGS

Título/Title: The imaginary part of the GR action and the large-spin 4-simplex amplitude

Autor/Author: Yasha Neiman (PennState University, State College, PA, EE.UU.)

Abstract: TBA

#### Lugar: Sala de Juntas 121.

Comentarios: ILQGS

Título/Title: A loop quantum multiverse?

Autor/Author: Martin Bojowald (PennState University, State College, PA, EE.UU.)

Abstract: TBA

#### Lugar: Sala de Juntas 121.

Comentarios: ILQGS

Título/Title: Hamiltonian spinfoam gravity.

Autor/Author: Wolfgang Wieland (Centre de Physique Théorique, Centre National de la Recherche Scientifique, Marsella, Francia)

Abstract: TBA

#### Lugar: Sala de Juntas 121.

Comentarios: ILQGS

Título/Title: Bianchi I Loop Quantum Cosmology.

Autor/Author: Brajesh Gupt (Louisiana State University, Baton Rouge, LA, EE.UU.)

Abstract: TBA

#### Lugar: Sala de Juntas 121.

Comentarios: ILQGS

Título/Title: Quantum reduced loop gravity.

Autor/Author: Emanuele Alesci y Francesco Cianfrani (Universidades de Varsovia y Breslavia, Polonia)

Abstract: TBA

#### Lugar: Sala de Juntas 121.

Comentarios: ILQGS

Título/Title: Gravity electroweak unification.

Autor/Author: Stephon Alexander (Dartmouth College, Hanover, New Hampshire, EE.UU.)

Abstract: TBA

#### Lugar: Sala de Juntas 113 Bis.

Comentarios: Seminario Física Gravitacional

Título/Title: Cosmic singularities and varying constants cosmologies.

Autor/Author: Mariusz P. Dabrowski (Instituto de Física, Universidad de Szczecin, Szczecin, Polonia)

Abstract: I will review standard and exotic cosmological singularities paying special attention to those which are of a weak type and do not necessarily exhibit geodesic incompletness. Then, I will discuss whether some of these singularities can be weakened, strengthened, or avoided due to the time-variation of the physical constants such as the speed of light $c$ and the gravitational constant $G$.

#### Lugar: Sala de Juntas 113 Bis.

Comentarios: ILQGS

Título/Title: Dinamical Chaos and the volume gap.

Autor/Author: Hal Haggard (Centre de Physique Théorique, Centre National de la Recherche Scientifique, Marsella, Francia)

Abstract: TBA

#### Lugar: Sala de Juntas 121.

Comentarios: ILQGS

Título/Title: Entanglement in loop quantum gravity.

Autor/Author: Eugenio Bianchi (Perimeter Institute for Theoretical Physics, Waterloo, Canadá.)

Abstract: TBA

#### Lugar: Sala Junt. 121

Comentarios: Seminario Física Gravitacional

Título/Title: Finite Quantum Gravity and M-Theory

Autor/Author: Leonardo Modesto (Universidad de Fudan, Shanghai, China)

Abstract: We hereby present a class of higher derivative theories that realizes an ultraviolet completion of Einstein gravity. This class is marked by a non­polynomal entire function (form factor), which averts extra degrees of freedom (including ghosts) and improves the high energy behaviour of the loop amplitudes. By power counting arguments, it is proved that the theory is (super-­)renormalizable in any dimension, i.e. only one-­loop divergences survive. Furthermore, in odd dimensions there are no counter terms for pure gravity and the theory turns out to be "finite". Consequently, by introducing an infinite tower of massive states coming from dimensional reduction, quantum gravity is finite in even dimension, as well. Comparing these theories with superstring and string field theories, a unique form factor is singled out. In view of this, we can modify the 10-­dimensional supergravity and finally get a ultraviolet completion of 11-­dimensional supergravity by an "oxidation process". The result is a finite "Quantum M-­theory".

Seminarios año 2012 | Subir

#### Lugar: Sala de Juntas 121.

Comentarios: ILQGS

Título/Title: Coarse graining: toward a cylindrically consistent dynamics.

Autor/Author: Bianca Dittrich (Perimeter Institute for Theoretical Physics, Waterloo, Ontario, Canadá.)

Abstract: TBA

#### Lugar: Sala de Juntas 121.

Comentarios: ILQGS

Título/Title: Twistorial structure of loop quantum gravity transition amplitudes.

Autor/Author: Simone Speciale (Centre de Physique Théorique, Centre National de la Recherche Scientifique, Marsella, Francia.)

Abstract: TBA

#### Lugar: Sala de Juntas 121.

Comentarios: ILQGS

Título/Title: Renormalization of Tensorial Group Field Theories.

Autor/Author: Sylvain Carrozza (Albert Einstein Institut, Potsdam, Alemania.)

Abstract: TBA

#### Lugar: Sala de Juntas 121.

Comentarios: ILQGS

Título/Title: Horizon entropy from loop gravity.

Autor/Author: Eugenio Bianchi (Perimeter Institute for Theoretical Physics, Waterloo, Ontario, Canada.)

Abstract: TBA

#### Lugar: Sala de Juntas 121.

Comentarios: ILQGS

Título/Title: Lifting General Relativity to Observer Space.

Autor/Author: Derek Wise (Friedrich-Alexander University, Erlangen-Nürnberg, Alemania.)

Abstract: TBA

#### Lugar: Sala de Juntas 121.

Comentarios: Seminario Física Gravitacional

Título/Title: Lattice Loop Quantum Cosmology.

Autor/Author: Edward Wilson-Ewing, (Centre de Physique Théorique, Centre National de la Recherche Scientifique, Marsella, Francia.)

Abstract: TBA.

#### Lugar: Sala Conf. 121.

Comentarios: Seminario Física Gravitacional

Título/Title: Representación Hamiltoniana Alternativa para la Relatividad General.

Autor/Author: Ricardo Rosas, (CINVESTAV, México)

Abstract: TBA.

#### Lugar: Sala Junt. 113B.

Comentarios: Seminario Física Gravitacional

Título/Title: Introduction to multifractional spacetimes

Autor/Author: Gianluca Calcagni (Instituto de Estructura de la Materia, IEM-CSIC, Madrid, España)

Abstract: We review the recent construction of a multi-scale fractal spacetime where power-counting renormalizable field theories can be defined. Applications to quantum gravity are discussed.

#### Lugar: Sala Junt. 113 B.

Comentarios: Seminario Física Gravitacional

Título/Title: Computable framework of loop quantum gravity.

Autor/Author: Tomasz Pawloswki (Warsaw University, Varsovia, Polonia)

Abstract: TBA

#### Lugar: Despacho 411.

Comentarios: ILQGS

Título/Title: Flux coherent states.

Autor/Author: Lorenzo Sindoni (MPG - Albert Einstein Institute, Golm, Alemania.)

Abstract: TBA

#### Lugar: Sala Conf. 121.

Comentarios: Seminario Física Gravitacional

Título/Title: Can effects to quantum gravity be observed in the cosmic microwave background?

Autor/Author: Manuel Krämer (Universidad de Colonia, Colonia, Alemania)

Abstract: We investigate the question whether small quantum-gravitational effects can be observed in the anisotropy spectrum of the cosmic microwave background radiation. An observation of such an effect is needed in order to discriminate between different approaches to quantum gravity. Using canonical quantum gravity with the Wheeler-DeWitt equation, we find a suppression of power at large scales. Current observations only lead to an upper bound on the energy scale of inflation, but the framework is general enough to study other situations in which such effects might indeed be seen.

#### Lugar: Sala Conf. 121.

Comentarios: Seminario Física Gravitacional

Título/Title: Nonsingular Charged Black Holes in Extensions of General Relativity à la Palatini.

Autor/Author: Gonzalo Olmo (Departamento de Física Teórica, Universidad de Valencia)

Abstract: I present the field equations of a quadratic extension of general relativity (GR) formulated in the Palatini approach (assuming that metric and connection are independent fields). Then I discuss static, spherically symmetric solutions with an electric field (Reissner-Nordstrom black holes). Unlike in GR, all the solutions of this theory present a central core whose area is proportional to the Planck area times the number of charges. Some of these solutions are nonsingular. In this case, the mass-to-charge ratio implies that the core matter density is independent of the specific amounts of charge and mass and of order the Planck density.

#### Lugar: Sala Juntas, 121.

Comentarios: ILQGS. Seminario telefónico

Título/Title: Graviton Corrections to Maxwell's Equations.

Autor/Author: Richard Woodard (Institute of Fundamental Theory, University of Florida, Gainesville, FL - EE.UU.)

Abstract: TBA

#### Lugar: Sala Juntas, 121.

Comentarios: ILQGS. Seminario telefónico

Título/Title: Path integral measure and triangulation independence in discrete gravity.

Autor/Author: Sebastian Steinhaus (MPG - Albert Einstein Institut, Potsdam, Alemania.)

Abstract: TBA

#### Lugar: Sala Juntas, 121.

Comentarios: ILQGS. Seminario telefónico

Título/Title: Effective Field Theories for Quamtum Gravity form Shape Dynamics.

Autor/Author: Tim Koslowski (Perimeter Institute for Theoretical Physics, Waterloo, Canada.)

Abstract: TBA

#### Lugar: Sala Juntas, 121.

Comentarios: ILQGS. Seminario telefónico

Título/Title: Black hole evaporation in LQG.

Autor/Author: Jacobo Díaz-Polo (Louisiana State University, Baton Rouge, EE.UU.)

Abstract: TBA

#### Lugar: Sala Juntas, 121.

Comentarios: ILQGS. Seminario telefónico

Título/Title: Continuous formulation of the LQG phase space.

Autor/Author: Marc Geiller (Université Paris Diderot, Paris, Francia)

Abstract: TBA

#### Lugar: Sala Juntas, 121.

Comentarios: ILQGS. Seminario telefónico

Título/Title: Classical limit of SF on arbitrary triangulation.

Autor/Author: Claudio Perini (Penn State University, State College, EE.UU.)

Abstract: TBA

#### Lugar: Sala Juntas, 121.

Comentarios: ILQGS. Seminario telefónico

Título/Title: Physics of Bianchi models in LQC.

Autor/Author: Parampreet Singh (Louisiana State University, Baton Rouge, EE.UU.)

Abstract: TBA

#### Lugar: Sala Conf. 121.

Comentarios: Seminario Física Gravitacional

Título/Title: Spin networks and classical dynamics for loop quantum gravity.

Autor/Author: Etera Livine (Laboratoire de Physique, ENS Lyon, Lyon, Francia)

Abstract: TBA.

Seminarios año 2011 | Subir

#### Lugar: Sala Conf. 415, 121.

Comentarios: Seminario Física Gravitacional

Título/Title: Statistical concordance model of CMB.

Abstract: Careful scrutiny of CMB maps have motivated several works in which anisotropic inflation could explain known large-angle CMB anomalies. After summarizing general aspects of some of these models, I intend to make a critical review of this approach. In particular, I will argue that: 1) some anomalies are not a signature of statistical anisotropy; 2) non-gaussianity, though barely explored in this context, is equally likely to produce large-angle anomalies; 3) it's hard to assess the real statistical significance of known anomalies; and 4) in the context of Lambda-CDM model, only one of the known anomalies corresponds to a physical observable.

#### Lugar: Sala Juntas, 121.

Comentarios: ILQGS. Seminario telefónico

Título/Title: A canonical formalism for simplicial gravity.

Autor/Author: Philipp Hoehn (University of Utrecht, Utrecht, Holanda)

Abstract: TBA

#### Lugar: Despacho 415, 121.

Comentarios: ILQGS. Seminario telefónico

Título/Title: Plebanski sectors of the new spin foam models.

Autor/Author: Jonathan Engle (Florida Atlantic University, Boca Ratón, EE.UU.)

Abstract: TBA

#### Lugar: Sala Conf., 121.

Comentarios: ILQGS. Seminario telefónico

Título/Title: Inhomogeneous loop quantum cosmology.

Autor/Author: William Nelson (Penn State University, State College, EE.UU.).

Abstract: TBA

#### Lugar: Sala Juntas, 121.

Comentarios: ILQGS. Seminario telefónico

Título/Title: New variables in arbitrary dimensions.

Autor/Author: Norbert Bodendorfer y Andreas Thurn (Universidad de Erlangen, Erlangen, Alemania)

Abstract: TBA

#### Lugar: Sala Juntas, 121.

Comentarios: ILQGS. Seminario telefónico

Título/Title: The Feynman diagramatics for the spin foam models.

Autor/Author: Jacek Puchta (University of Warswaw, Varsovia, Polonia).

Abstract: TBA

#### Lugar: Campus Central CSIC.

Organizadores/Local Organizing Committee: J. Fernando Barbero González, Guillermo A. Mena Marugán, Luis J. Garay Elizondo, Eduardo J. Sánchez Villaseñor, Iñaki Garay Elizondo, Mercedes Martín-Benito, Gonzalo Olmo Alba, Tomasz Pawlowski, Mikel Fernández Méndez, Daniel Martín de Blas, Javier Olmedo Nieto.

#### Lugar: Sala Juntas, 121.

Comentarios: ILQGS. Seminario telefónico

Título/Title: Quantum geometry: its dynamics, symmetries and statistics in the group field theory formalism.

Autor/Author: Daniele Oriti (Albert Einstein Institute, Potsdam, Alemania).

Abstract: TBA

#### Lugar: Sala Juntas, 121.

Comentarios: ILQGS. Seminario telefónico

Título/Title: The 1/N expansion in colored tensor models.

Autor/Author: Razvan Gurau (Perimeter Institute for Theoretical Physics, Waterloo, Canadá).

Abstract: TBA

#### Lugar: Sala Juntas, 121.

Comentarios: ILQGS. Seminario telefónico

Título/Title: Simplicity constraints and the role of the Immirzi parameter in quantum gravity.

Autor/Author: James Ryan (Albert Einstein Institute, Potsdam, Alemania).

Abstract: TBA

#### Lugar: Sala Juntas, 121.

Comentarios: ILQGS. Seminario telefónico

Título/Title: Observational signatures in LQC.

Autor/Author: Ivan Agulló (PennState University, State College, EE.UU.).

Abstract: TBA

#### Lugar: Sala Juntas, 121.

Comentarios: ILQGS. Seminario telefónico

Título/Title: Quantum deformation of 4d spin foam models.

Autor/Author: Winston Fairbairn (Hamburg University, Hamburgo, Alemania).

Abstract: TBA

#### Lugar: Sala Juntas, 121.

Comentarios: ILQGS. Seminario telefónico

Título/Title: The principle of relative locality.

Autor/Author: Laurent Freidel (Perimeter Institute for Theoretical Physics, Waterloo, Canadá).

Abstract: TBA

#### Lugar: Sala Conf., 121.

Comentarios: Seminario Física Gravitacional

Autor/Author: Fernando Barbero (Instituto de Estructura de la Materia, Universidad CSIC).

Abstract: TBA.

#### Lugar: Sala Juntas, 121.

Comentarios: ILQGS. Seminario telefónico

Título/Title: Semiclassicality of the Loop Quantum Universe.

Autor/Author: Tomasz Pawlowski (University of New Brunswick, Fredericton, Canadá).

Abstract: TBA

#### Lugar: Sala Conf., 121.

Comentarios: Seminario Física Gravitacional

Título/Title: On the Electromagnetic Nature of Dark Energy and the Origin of Cosmic Magnetic Fields.

Abstract: Out of the four components of the electromagnetic field, Maxwell's theory only contains two physical degrees of freedom. However, in an expanding universe, consistently eliminating one of the "unphysical" states in the covariant (Gupta-Bleuler) formalism turns out to be difficult to realize. In this talk we explore the cosmological consequences of the presence of this third electromagnetic polarization. Although the new state cannot be produced from charged matter, it can be excited gravitationally. In fact, primordial quantum fluctuations produced during inflation can give rise to super-horizon temporal electromagnetic modes whose energy density behaves as a cosmological constant. The value of the effective cosmological constant is shown to agree with observations provided inflation took place at the electroweak scale. On the other hand, on sub-horizon scales, because of the high electric conductivity of the cosmic plasma, the new state gives rise to both vorticity and magnetic fields. Present upper limits on vorticity coming from CMB anisotropies are translated into lower limits on the present value of cosmic magnetic fields. We find that fields $B_{\lambda} > 10^{-12}$ G can be typically generated with coherence lengths ranging from sub-galactic scales up to the present Hubble radius.

#### Lugar: Sala Juntas, 121.

Comentarios: ILQGS. Seminario telefónico

Título/Title: Spinfoam Cosmology.

Autor/Author: Francesca Vidotto (Centre de Physique Théorique de Luminy, Marsella, Francia).

Abstract: TBA

#### Lugar: Sala Juntas, 121.

Comentarios: ILQGS. Seminario telefónico

Título/Title: Inflationary observables and observational constraints in LQC.

Autor/Author: Gianluca Calgani (Albert Einstein Institute, Potsdam, Alemania).

Abstract: TBA

#### Lugar: Sala Conf., 121.

Comentarios: Seminario Física Gravitacional

Título/Title: Colliding black holes in 3+1 and higher dimensions.

Autor/Author: Ulrich Sperhake (Departamento de Física y Astonomía, CSIC-IEEC).

Abstract: TBA

Seminarios año 2010 | Subir

#### Lugar: Sala Conf., 121.

Comentarios: Seminario Física Gravitacional

Título/Title: Diffeomorphism Symmetry in Group Field Theories.

Autor/Author: Florian Girelli (School of Physics, University of Sydney, Sydney, Australia).

Abstract: TBA

#### Lugar: Sala Juntas, 121.

Comentarios: ILQGS. Seminario telefónico

Título/Title: Bubble divergences in state-sum models.

Autor/Author: Matteo Smerlak (ENS, Lyon).

Abstract: TBA

#### Lugar: Sala Juntas, 121.

Comentarios: Seminario Física Gravitacional

Título/Title: Conserved structures in states of Loop Quantum Gravity.

Autor/Author: Jonathan Hackett (Perimeter Institute of Theoretical Physics, Ontario, Canadá).

Abstract: TBA

#### Lugar: Sala Conf., 121.

Comentarios: Seminario Física Gravitacional

Título/Title: A classical setting for Loop Quantum Gravity.

Autor/Author: Iñaki Garay (University of Erlangen-Nürnberg).

Abstract: We will review the U(N) framework for Loop Quantum Gravity and describe the corresponding phase space of the SU(2) intertwiners in terms of spinors (imposing appropriate constraints). We will show how its quantization leads back to the standard Hilbert space of intertwiner states. Then, we will take care of the gluing of these intertwiner states in order to construct spin network states. In particular, we will translate the usual loop gravity holonomy observables to our classical framework. Finally, we will propose a way to derive our phase space structure from an actionprinciple which induces non-trivial dynamics for the spin network states. As an specific example, we will discuss the application of our framework to states living on the simple 2-vertex graph and discuss the properties of the resulting Hamiltonian.

#### Lugar: Sala Juntas, 121.

Comentarios: ILQGS. Seminario telefónico

Título/Title: LQG dynamics:insights from parameterized field theory.

Abstract: TBA.

#### Lugar: Sala Conf., 121.

Comentarios: ILQGS. Seminario telefónico

Título/Title: New results: operator spin foams, SL(2,C).

Autor/Author: Jerzy Lewandowski (Universidad de Varsovia).

Abstract: TBA.

#### Lugar: Sala Conf., 121.

Comentarios: Seminario Física Gravitacional

Título/Title: Horizon effects for surface waves: wave channels and circular jumps.

Autor/Author: Gil Jannes (Université de Nice Sophia Antipolis).

Abstract: Surface waves in classical fluids experience a rich array of black/white hole horizon effects. The dispersion relation depends on the characteristics of the fluid (in our case, water and silicon oil) as well as on the fluid depth and the wavelength regime. In some cases, it can be tuned to obtain a relativistic regime plus high-frequency dispersive effects. I discuss two types of ongoing analogue white-hole experiments: deep water waves propagating against a counter-current in a wave channel and shallow waves on a circular hydraulic jump.

#### Lugar: Sala Conf., 121.

Comentarios: Seminario Física Gravitacional.

Título/Title: Introducción a cosmología cuántica de lazos vista desde mis vivencias.

Autor/Author: Mercedes Martín Benito (Departamento de Química y Física Teóricas, IEM - CSIC).

Abstract: TBA

#### Lugar: Sala Juntas, 121.

Comentarios: ILQGS. Seminario telefónico

Título/Title: LQG with all the degrees of freedom

Autor/Author: Jerzy Lewandowski (Universidad de Varsovia).

Abstract: TBA.

#### Lugar: Sala Conf., 121.

Comentarios: Seminario Física Gravitacional

Título/Title: Sobre la ambigüedad en la cuantización de teorías de campo

Autor/Author: Jerónimo A. Cortez, UNAM (Méjico).

Abstract: TBA.

#### Lugar: Sala Juntas, 121.

Comentarios: ILQGS. Seminario telefónico

Título/Title: The cosmological constant (non)-problem

Autor/Author: Eugenio Bianchi (Marsella).

Abstract: TBA.

#### Lugar: Sala Conferencias, 121.

Comentarios: Seminario Física Gravitacional.

Título/Title: Evolution Picture in Loop Quantum Cosmology.

Autor/Author: Mercedes Martín Benito (Departamento de Química y Física Teóricas, IEM - CSIC).

Abstract: In general relativity there is not a fixed time that leads to a fixed concept of physical evolution. As a consequence, in the particular case of quantum cosmology, in order to interpret the physical observables as evolving in time, the construction of a well-defined picture of unitary evolution is needed. Usually it is provided by a massless scalar field playing the role of the internal time. Rather than using that suitable clock, here we develop the concept of physical evolution in quantum cosmology when the internal time is one of the geometry degrees of freedom, both in the Wheeler-DeWitt quantization and in Loop Quantum Cosmology. For concreteness, we apply our analysis to the vacuum Bianchi I cosmologies.

#### Lugar: Sala Conferencias, 121.

Comentarios: Seminario Física Gravitacional.

Título/Title: The Skeleton of Chaotic Eigenstates.

Autor/Author: Fabio Revuelta Peña (Grupo de Sistemas Complejos, Universidad Politécnica de Madrid ).

Abstract: The correspondence between Classical and Quantum Mechanics is well understood in integrable systems but it still an open problem when the system is no longer integrable and chaos takes place. The field that studies the quantum manifestations of classically chaotic systems is usually known as "Quantum Chaos". Periodic Orbits (OPs) have a dramatic influence on the classical dynamics of a chaotic system, when the motion is no longer confined to invariant tori due to their breakdown according to KAM Theorem. The influence of the periodic orbits (POs) on the density of states of a chaotic system has been known for a very long time since Gutwiller's celebrated Trace Formula . Unfortunatelly, this expression is not usefull for practical reasons, as the number of POs that must be considered increases exponentially. One of the most surprising phenomena in Quantum Chaos is scarring. Scar functions were originally defined as eigenstates that had an enhanced probability density concentrated over unstable POs. This definition was later generalized to groups of eigenstates . More recently, it has been demonstrated that scarring does not only take place over the unstable POs but also over their invariant manifolds. Scarring allows one to identify classical structures that create the eigenstates of a system, thus identifying the classical skeleton of purely quantum objects. In this talk, we will briefly summarize the history of scar functions and discuss some of their most important properties.

#### Lugar: Sala Juntas, 121.

Comentarios: Seminario Física Gravitacional.

Título/Title: Dynamics for a 2-vertex Quantum Gravity Model.

Autor/Author: Iñaki Garay (Institute for Theoretical Physics III, University of Erlangen-Nürnberg).

Abstract: In spite of the several approaches to implement the dynamics within the loop quantum gravity theory, it is still an open problem. In this talk we will discuss a tentative dynamics for the simplest class of graphs in loop quantum gravity: Two vertices linked with an arbitrary number of edges. This model represents two regions, in and out, separated by a boundary surface. We will use the U(N) framework recently introduced by E. Livine and collaborators in order to identify area creation and annihilation operators. Finally, we will propose a Hamiltonian operator invariant under area-preserving deformations of the boundary surface and we will explore physical applications and possible generalizations.

#### Lugar: Sala Conf., 121.

Comentarios: Seminario Física Gravitacional.

Título/Title: Non-singular cosmologies à la Palatini.

Autor/Author: Gonzalo J. Olmo (IEM - CSIC).

Abstract: I will discuss how modifications of Einstein's theory using the Palatini formalism can lead to the resolution of the big bang singularity in several cases of interest.

#### Lugar: Sala Conf., 121.

Comentarios: Seminario Física Gravitacional.

Título/Title: The two faces of quantum sound.

Abstract: TBA

#### Lugar: Sala Juntas, 121.

Comentarios: Seminario Física Gravitacional.

Título/Title: Conformal geometry in GR: Dealing with initial singularities and stability questions.

Autor/Author: Christian Luebbe (Queen Mary University, London).

Abstract: TBA

#### Lugar: Sala Conf., 121.

Comentarios: Seminario Física Gravitacional.

Título/Title: How sharp is the Universe's memory?

Autor/Author: Tomasz Pawlowski (IEM).

Abstract: TBA

#### Lugar: Sala Juntas, 121.

Comentarios: Seminario Física Gravitacional.

Autor/Author: Fernando Barbero (IEM, CSIC).

Abstract: TBA

Seminarios año 2007 | Subir

Nombre: Dr. Andrés Cano.

Afiliación: Instituto de Astrofísica de Andalucía (CSIC), Granada.

Título: Defect-Induced Damping of the Lattice Vibrations: a Key Factor at Low Temperatures.

Fecha: 25 de abril de 2007.

 Nombre: Dr. Tomasz H. Pawlowski. Afiliación: Penn State University, E.E.U.U. Título: Dynamics of an Isotropic Universe from Loop Quantum Cosmology. Fecha: 19 de marzo de 2007.
 Nombre: Dr. Hanno Sahlmann. Afiliación: Utrecht University, Holanda. Título: Toy Black Holes, and Entropy Quantization: Aspects of Black Holes in Loop Quantum Gravity. Fecha: 12 de diciembre de 2007.
 Nombre: Jacobo Díaz-Polo. Afiliación: Universidad de Valencia, Valencia. Título: Entropía de Agujeros Negros en Loop Quantum Gravity. Fecha: 30 de mayo de 2007.
 Nombre: Gil Jannes. Afiliación: Instituto de Astrofísica de Andalucía (CSIC), Granada. Título: El Mecanismo de Higgs. Fecha: 19 de febrero de 2007.
 Nombre: Gil Jannes. Afiliación: Instituto de Astrofísica de Andalucía (CSIC), Granada. Título: Agujeros Negros en Condensados de Bose-Einstein: Estabilidad y Modos Cuasinormales. Fecha: 26 de abril de 2007.
 Nombre: Prof. Abhay Ashtekar. Afiliación: Penn State University, University Park, PA, E.E.U.U. Título: Diffeomorphism Invariance in Loop Quantum Gravity (ILQC seminar). Fecha: 27 de febrero de 2007.
 Nombre: Prof. Martin Bojowald. Afiliación: Penn State University, University Park, PA, E.E.U.U. Título: KITP Program on Singularities Summary (ILQG seminar). Fecha: 24 de abril de 2007.
 Nombre: Prof. Alejandro Corichi. Afiliación: Universidad Nacional Autónoma de México, Morelia, México. Título: Relation between Schroedinger and Polymer Quantum Mechanics (ILQG seminar). Fecha: 6 de marzo de 2007.
 Nombre: Prof. Laurent Freidel. Afiliación: Perimeter Institute, Waterloo, Canadá. Título: Matter Coupling to 3d Quantum Gravity and EFT (I y II) (ILQG seminar). Fecha: 15 y 22 de mayo de 2007.
 Nombre: Prof. Kirill Krasnov. Afiliación: Perimeter Institute, Waterloo, Canadá. Título: Non Metric Gravity (ILQG seminar). Fecha: 20 de marzo de 2007.
 Nombre: Prof. Jorge Pullin. Afiliación: Louisiana State University, Baton Rouge, E.E.U.U. Título: Loop Quantization of Spherically Symmetric Spacetimes (ILQG seminar). Fecha: 27 de marzo de 2007
 Nombre: Prof. Lee Smolin. Afiliación: Perimeter Institute, Waterloo, Canadá. Título: Emergent Chiral Excitations of Quantum Geometries: Progress Report (ILQG seminar). Fecha: 3 de abril de 2007.
 Nombre: Prof. José Antonio Zapata. Afiliación: Universidad Nacional Autónoma de México, Morelia, México. Título: Effective Theories, Continuum Limit and Background Independence in LQG (ILQG seminar). Fecha: 10 de abril de 2007.
 Nombre: Dr. Michele Arzano. Afiliación: Perimeter Institute, Waterloo, Canadá. Título: Kapppa Poincaré Space-Time Symmetries (ILQG seminar). Fecha: 13 de marzo de 2007.
 Nombre: Dr. Dan Christensen. Afiliación: Univesity of Western Ontario, London, Canadá. Título: Computations Involving SN, SF, QG and LGT (ILQG seminar). Fecha: 30 de octubre de 2007.
 Nombre: Dr. Jonathan Engle. Afiliación: Centre de Physique Théorique de Marseille, Marsella, Francia. Título: The LQG Vertex: A Proposal (ILQG seminar). Fecha: 18 de septiembre de 2007.
 Nombre: Dr. Garrett Lisi. Afiliación: Fundación Foundational Questions in Physics and Cosmology, E.E.U.U. Título: A Connection with Everything (ILQG seminar). Fecha: 13 de noviembre de 2007.
 Nombre: Dr. Radu Roiban. Afiliación: Penn State University, University Park, PA, E.E.U.U. Título: UV Properties of N=8 Supergravity: Is It Finite? (ILQG seminar) Fecha: 13 de febrero de 2007.
 Nombre: Dr. David Sloan. Afiliación: Penn State University, University Park, PA, E.E.U.U. Título: Strong Gravity and the BKL Conjecture (ILQG seminar). Fecha: 16 de octubre de 2007.
 Nombre: Dr. Johannes Tambornino. Afiliación: Perimeter Institute, Waterloo, Canadá. Título: Relational Observables and Cosmological Perturbation Theory (ILQG seminar). Fecha: 4 de septiembre de 2007.
 Nombre: Dr. Kevin Vandersloot. Afiliación: University of Portsmouth, Portsmouth, Reino Unido. Título: Schwarzschild Interior with Loop Quantum Effects (ILQG seminar). Fecha: 27 de noviembre de 2007.

Seminarios año 2006| Subir

Nombre: Prof. Abhay Ashtekar.

Afiliación: Penn State University, University Park, PA, E.E.U.U.

Título: Quantum Nature of the Big Bang.

Fechas: 17 de octubre de 2006.

 Nombre: Prof. Carsten Gundlach. Afiliación: University of Southampton, Reino Unido. Título: Formulations of the Einstein Equations for Binary Black Hole Evolutions. Fecha: 18 de abril de 2006.
 Nombre: Dr. José M. Pé-Curto Velhinho. Afiliación: Universidade da Beira Interior, Covilha, Portugal. Título: Formal Aspects of Semi-Classical Analysis in Loop Quantum Gravity. Fecha: 1 de febrero de 2006.
 Nombre: Dr. Ulrich Sperhake. Afiliación: University of Jena, Alemania. Título: A Review of Black-Hole Binary Simulations in Numerical Relativity. Fecha: 15 de marzo de 2006.
 Nombre: Dr. Madhavan Varadarajan. Afiliación: Raman Research Institute, Bangalore, India. Título: Quantum Fields at Any Time. Fecha: 20 de octubre de 2006.
 Nombre: Javier Molina Sánchez. Afiliación: Universidad de Guelph, Canadá. Título: Cálculo de la autofuerza electromagnética en espaciotiempo curvo. Fecha: 27 de marzo de 2006.
 Nombre: Prof. Abhay Ashtekar. Afiliación: Penn State University, University Park, PA, E.E.U.U. Título: Loop Quantum Gravity: Frequently Asked Questions (ILQG seminar). Fecha: 19 de septiembre de 2006.
 Nombre: Prof. Alejandro Corichi. Afiliación: Universidad Autónoma de México, Morelia, México. Título: Quantum Isolated Horizons: The Planck Scale Regime (ILQG seminar). Fecha: 14 de noviembre de 2006.
 Nombre: Prof. Carlo Rovelli. Afiliación: Centre de Physique Théorique de Marseille, Francia. Título: Spinfoam Graviton Propagator: Introduction (ILQG seminar). Fecha: 26 de septiembre de 2006.
 Nombre: Dr. Bianca Dittrich. Afiliación: Perimeter Institute, Waterloo, Canadá. Título: Approximate Observables (ILQG seminar). Fecha: 28 de noviembre de 2006.
 Nombre: Dr. Robert Oeckl. Afiliación: Universidad Autónoma de México, Morelia, México. Título: Quantum Gravity, Probabilities and General Boundaries (ILQG seminar). Fecha: 17 de octubre de 2006.
 Nombre: Dr. Simone Speziale. Afiliación: Perimeter Institute, Waterloo, Canadá. Título: Spinfoam Graviton Propagator (ILQG seminar). Fecha: 3 de octubre de 2006.
 Nombre: Winston Fairbairn. Afiliación: Ecole Normale, Lyon, Francia. Título: Fermions in 3d Spinfoam Quantum Gravity (ILQG seminar). Fecha: 7 de noviembre de 2006.

Seminarios año 2005 | Subir

 Nombre: Aleksandar Mikovic. Afiliación: Universidade Lusofona, Lisboa, Portugal. Título:Spin foam models of quantum gravity Fechas: 24 de febrero 2005
 Nombre: Sergio Dain. Afiliación: Max-Planck-Institut für Gravitationsphysik, Albert-Einstein-Institut, Golm, Alemania. Título: On the existence of initial data containing black holes. Fecha: 16 de junio 2005.
 Nombre: Sascha Husa Afiliación: Max-Planck-Institut für Gravitationsphysik, Albert-Einstein-Institut, Golm, Alemania. Título: Light and shadow in Numerical Relativity. Fecha: 22 de junio 2005.
 Nombre: Olivier Sarbach. Afiliación: Theoretical Astrophysics and Relativity Group, California Institute of Technology, Estados Unidos. Título: The initial-boundary value problem in General Relativity and numerical applications. Fecha: 26 de julio 2005.
 Nombre: Jesús Salas. Afiliación: Grupo de modelización, simulación y matemática industrial, Escuela Politécnica Superior, Universidad Carlos III, Madrid, España. Título: ¿Qué podemos aprender del límite q->0 del modelo de Potts? Fecha: 15 de noviembre de 2005.

Seminarios año 2004 | Subir

 Nombre: Alejandro Corichi. Afiliación: Instituto de Ciencias Nucleares, UNAM, México. Título: Agujeros Negros en Gravedad Cuántica de Lazos. Fecha: 29 de abril de 2004
 Nombre: Jorge Pullin Afiliación: Louisiana State University, Estados Unidos Título: Gravedad Cuántica Discreta Consistente Fecha: 5 de julio de 2004
 Nombre: Francisco Guinea. Afiliación: Instituto de Ciencia de Materiales de Madrid, CSIC. Título: Supresión de efectos cuánticos y decoherencia inducida por contactos metálicos. Fecha: 22 de abril de 2004.