## Contributions:
_Mini-courses (each lecture will last 50 minutes + 10 minutes for questions and discussions)Mini-course I: Horizons for surface waves in fluids. (The speaker could not come to the Workshop) Alberto Saa (UNICAMP, Brazil) Abstract: Surface waves on stationary flows will be revisited. We will focus on the linear regime for the waves, where an effective geometrical formulation is available and the notion of horizon for surface waves makes sense. We will show also that such fluid configurations can be studied experimentally in rather simple hydrodynamics setups which could be considered as simplified analogs of real spacetime phenomena. Mini-course II: Black Holes: classical and quantum aspects. (PDF File)Alessandro Fabbri (Università di Bologna, Italy) Abstract: Lecture 1: Black holes in General RelativityAbstract: We review the classical properties and the causal structure of various black hole solutions in General Relativity and discuss the stability issue (in GR and beyond). Lecture 2: The Hawking effect and physical implicationsAbstract: After reviewing the analogy between the laws of black hole mechanics and the laws of thermodynamics, we discuss in some detail the Hawking effect (quantum particle creation by black holes) and how the quantum effects modify the background geometry (backreaction problem). Lecture 3: Analog gravity and analog Hawking radiation: the experimental searchAbstract: The Hawking effect is not specific to gravity. An analog of it can be found in fluids undergoing supersonic flow (called acoustic black holes). We discuss ongoing attempts to observe it in condensed matter systems, and focus on a proposal to detect it through correlation measurements in Bose-Einstein condensates. Mini-course III: Quantum field theory in curved space-time (PDF File)Marc Casals (CBPF, Brazil)Abstract: In this mini-course we will study the quantization of matter fields in a classical curved background space-time. We will start by presenting the formalism for the canonical quantization of the scalar field in a general curved space-time. We will then look at some flat space-time examples: the Casimir effect and Rindler (accelerated) observers. In curved space-time, we will first look at cosmological particle production. The last part of the course will be dedicated to quantum black holes; in particular, Hawking radiation, quantum states and the laws of black hole mechanics. Special session in honor of Prof. Kirill Bronnikov (each talk will last 50 minutes + 10 minutes for questions and discussions)Talk I: Black hole, a difficult birth. ach seminar will last 50 minutes (PDF File)Jean Eisenstaedt (OPM, France)Abstract: Why did black holes have been invented so lately? more than fifty years after the birth of GR! For sure, as far as the Schwarzschild horizon was seen to be singular, it was not possible to think about black holes. At the time general relativity was not well understood; a neo-Newtonian interpretation dominated. The invention of black holes was intimately linked to cosmology, particularly to Lemaître's and Robertson's views. Talk II: Black hole entropy from matter shells: non-extremal and extremal black holes and a solution to the debate. (PDF File)José P. Lemos (IST, Portugal)Abstract: Black hole entropy, S, is one of the most fascinating issues in contemporary physics, as one does not yet strictly know what are the degrees of freedom at the fundamental microlevel, nor where are they located precisely. In addition, extremal black holes, in contrast to non-extremal ones, present a conundrum, as there are two mutually inconsistent results for the entropy of extremal black holes. There is the usual Bekenstein-Hawking S = A/4 value, where A is the horizon area, obtained from string theory and other methods, and there is the prescription S = 0 obtained from the fact that for extremal black holes the period of the Euclidean time is not fixed in a classical calculation of the action. In order to better understand black hole entropy in its generality, and in particular in the extremal limit, we exploit a matter based framework and use a thermodynamic approach for an electrically charged thin shell. We find the entropy function for such a system. We then take the shell radius into its gravitational radius (or horizon) limit. This limit is the quasiblack hole limit. We show that (i) for a non-extremal shell the gravitational radius limit yields S=A/4, and (ii) for an extremal shell the calculations are very subtle and interesting. The horizon limit gives an entropy which is a function of the horizon radius alone, but the precise functional form depends on how we set the initial shell. The values 0 and A/4 are certainly possible values for the extremal black hole entropy. This formalism clearly shows that non-extremal and extremal black holes are different objects. The formalism suggests that for non-extremal black holes all possible degrees of freedom are excited, whereas in extremal black holes, in general, only a fraction of those degrees of freedom manifest themselves. We conjecture that for extremal black holes the entropy S is restricted to the interval between 0 and A/4. Talk III: Quasi-black holes: general conception and physical applications. (PDF File)Abstract: Objects that are on the verge of being extremal black holes but actually are distinct in many ways are called quasi-black holes (QBH). General properties of their space-time geometry are reviewed. The main ones are (i) their geometry remains perfectly regular everywhere, in spite of the existence of infinite redshifts, (ii) in the limit, outer and inner regions become mutually impenetrable and disjoint, although, in contrast to the usual black BHs, this separation is of a dynamic nature, rather than purelyOleg Zaslavskii (University of Kharkov, Ukraine) causal. This general conception of QBH allows us to derive Smarr mass-formula for black holes and black hole entropy without a black hole. Also, we discuss self-consistent definition of the entropy in the extremal case. Physical recitation of QBHs including Majumdar-Papapetrou systems and their generalization to the scalar field are discussed. Talk IV: Wormholes and black universes: phantoms and stability. (PDF File)Kirill Bronnikov (VNIIMS, Russia)Abstract: We construct explicit examples of globally regular static, spherically symmetric solutions in general relativity with scalar and electromagnetic fields, describing traversable wormholes with flat and AdS asymptotics and regular black holes, in particular, black universes. (A black universeis a regular black hole with an expanding, asymptotically isotropic space-time beyond the horizon.component) The existence of such objects requires invoking scalars with negative kinetic energy (``phantoms'', or ``ghosts''), which are not observed under usual physical conditions. To account for that, the so-called ``trapped ghosts'' have been introduced, i.e., scalars whose kinetic energy is only negative in a restricted strong-field region of space-time and positive outside it. An alternative source is represented by ``invisible ghosts'', i.e., phantom scalar fields sufficiently rapidly decaying in the weak-field region. The resulting configurations contain different numbers of Killing horizons, from zero to four. An important problem is the stability of all such configurations under small perturbations. The existing results of stability studies will be briefly reported. Advanced seminars (each seminar will last 45 minutes + 5 minutes for questions)Seminar I: The horizon and infinity for spin-3 3D black holes. A no go theorem.Abstract: In three dimensions, fields carrying spin-3 charge can be built using the Chern-Simons formulation. However, making compatible the regularity of the horizon with the expected asymptotics is a notably difficult problem.Max Bañados (PUC, Chile) Here we show that, working at level of spacetime connections, it may actually be impossible to build a static and circularity symmetric black hole carrying spin-3 charge and at the same time a regular horizon. Seminar II: A topological gravity model in 4D. (PDF File) Olivier Piguet (UFV, Brazil)Abstract: General Relativity (RG) in 3 dimensions space-time with a cosmological constant and in the absence of matter may be described as a topological Chern-Simons theory for the (A)dS gauge group SO(n,4-n). It has no local degrees of freedom. We present here a model, inicially due to Chamseddine, of gravity in 4 dimensions which may be obtained from a 5-dimensional Chern-Simons theory with de Sitter SO(1,5) as a gauge group. It does have local degrees of freedom even in the absence of matter, and we show cosmological solutions which can be compared with the solutions of standard RG. Seminar III: Waves propagating in black holes and acoustic analogues spacetimes: scattering and absorption properties. Luís Carlos B. Crispino (UFPA, Brazil) Abstract: We review recent investigations on scattering and absorption by black holes and acoustic analogues. After introducing some basic concepts, we start discussing the propagation of the massless uncharged scalar field in the Schwarzschild black hole spacetime, and then explore some scattering and absorption properties of bosonic fields in Reissner-Nordström, Kerr, Schwarzschild-de Sitter, and Bardeen black hole geometries. We also present some results for the scattering and absorption of waves by acoustic analogues of black holes, namely, the canonical acoustic black hole and the draining bathtub.Seminar IV: Squeeze and decoherence of vacuum fluctuations in relativistic stars. (PDF File)Daniel Vanzella (IFSC-USP, Brazil)Abstract: Some compact-object configurations can trigger an exponential growth of vacuum fluctuations of fields properly coupled to the spacetime geometry. This effect can be seen as a squeezing process for the unstable modes. In addition, along with the squeezing, decoherence takes place due to interaction of the unstable modes with metric fluctuations and, indirectly, with the stable modes of the same field, which act as an environment. As a result, in a characteristic time scale, the exponentially enhanced vacuum fluctuations seed classical perturbations whose backreaction on the background geometry can be treated classically. Seminar V: Testing interacting dark energy.Elcio Abdalla (USP, Brazil)To be added Seminar VI: (Super) Graphity. (PDF File)Jorge Zanelli (CECS, Chile) Abstract: Graphene is a remarkable material of enormous technological appeal, but it provides also an interesting mathematical laboratory to test some of the features of gravity in 2+1 dimensions. Here I will explore the potentiality of a supersymmetic system describing graphene when the spin degree of freedom and the corresponding local SU(2) gauge invariance are included. A black hole with hair in 2+1 dimensions is shown to exist in this theory. Seminar VII: Quantum black holes and their lepton signatures at the LHC. (PDF File)Abstract: We discuss a field theoretical framework to describe the interactions of non-thermal quantum black holes (QBHs) with particles of the Standard Model. We propose a non-local Lagrangian to describe the production of these QBHs which is designed to reproduce the geometrical cross section for black hole production. This model is implemented into CalcHEP package and is publicly available at the High Energy Model Database (HEPMDB) for simulation of QBH events at the LHC and future colliders. We present the first phenomenological application of the $QBH@HEPMDB$ model with spin-0 neutral QBH giving rise the e+e− and eμ signatures at the LHC@8TeV and $LHC@13TeV$ and produce the respective projections for the LHC in terms of limits on the reduced Planck mass and the number of the extra-dimensions. (arXiv:1412.2661)Alexander Belyaev (University of Southampton, UK)Seminar VIII: Charged fluid in General Relativity: from compact stars to quasi-black holes and regular black holes. Vilson Zanchin (UFABC, Brazil)Abstract: We study the physical and geometrical properties of charged fluids aiming models for compact objects. The start motivation are Bonnor stars, i.e., regular static compact configurations in equilibrium composed of an extremal dust fluid, a charged dust fluid where the mass density is equal to the charge density in appropriate units and up to a sign, joined to a suitable exterior vacuum solution. These configurations obey the Majumdar-Papapetrou system of equations, in one case, the system is a particular setup of Newtonian gravity coupled to Coulomb electricity and electrically charged matter or fluid, in the other case, the system is a particular setup of general relativity coupled to Maxwell electromagnetism and electrically charged matter or fluid. The corresponding gravitational potential is a specially simple function of the electric potential field and the fluid, when there is one, is made of extremal dust. As a preparation, we analyze the Newton-Coulomb theory with an electrically charged fluid} in a Majumdar-Papapetrou context. We show that within the Newtonian theory, in vacuum, the Majumdar-Papapetrou relation for the gravitational potential in terms of the electric potential, and its related Weyl relation, are equivalent, in contrast with general relativity where they are distinct. We then study the analogue type systems in the Einstein-Maxwell theory with an electrically charged fluid, i.e., we analyze general systems, Weyl type systems, including Majumdar-Papapetrou systems, and also the very interesting Weyl-Guilfoyle systems, i.e., general relativistic charged fluids with nonzero pressure. Several special properties of such systems are reviewed. We then study the exact solutions given by Guilfoyle (GRG {\bf 31}, 1645 (1999)). These are solutions representing spherically symmetric charged perfect fluid distributions whose metric potentials and electromagnetic fields are related in some particularly simple form. We show that, for certain range of the parameters of the model, there are objects which correspond to charged stars satisfying the Buchdahl-Andr\'easson bound, quasiblack holes and regular charged black holes. The regular black holes interior region is filled by a charged phantom-like fluid, or, in the limiting case, de Sitter, and whose exterior region is Reissner-Nordstr\"om. The boundary between both regions is a smooth boundary surface, except in the limiting case where the boundary is made of a massless electrically charged spherically symmetric coat. There are several type of solutions: regular non-extremal black holes with a timelike smooth boundary, regular extremal black holes with a timelike smooth boundary, and regular black holes with a null matter boundary. The main physical and geometrical properties of such charged regular solutions are analyzed. Seminar IX: Massive ghosts and stability in higher derivative quantum gravity. (PDF File)Ilya Shapiro (UFJF, Brazil)Abstract: We discuss the problem of stability of classical solutions in higher derivative quantum gravity, especially for the cosmological and black hole backgrounds. Seminar X: Scalar hair: from the BBMB solution to Kerr black holes with scalar hair.Carlos Herdeiro (University of Aveiro, Portugal)Abstract: Black holes are one of the most fascinating predictions of the General Theory of Relativity. According to the conventional picture that emerged in the 1970s as a corollary of the uniqueness theorems, black holes are extremely constrained objects, determined by only a few global charges. For instance, two black holes with the same total mass and angular momentum must be precisely equal, in sharp contrast with stars. Such simplicity of black holes became immortalized in John Wheeler's mantra "Black holes have no hair". In this talk, I will start by reviewing the history and some key physical/mathematical properties of black holes in General Relativity. I will then discuss a novel mechanism that allows black holes to have 'hair' and challenges the standard paradigm. Some possible astrophysical consequences will be addressed. Seminar XI: Activity at the center of galaxies: the case of Hydra-Centaurus group of galaxies. (PDF File)Horacio Dottori (UFRGS, Brazil) Abstract: Three main ideas underly presently the paradigm of nuclear activity in the center of galaxies: 1- The various types of activity that we see presently in the local Universe are diverse spatial projections of the same phenomenon having cylindrical symmetry; 2- The activity in QSOs and Seyfert galaxies are the same phenomenon, however with different intensity and 3- At the center of every galaxy there is an active or dormant Black Hole, resized along the time by the fusion of smaller Black Holes that goes along with the merge of the host galaxies, as suggested by ΛCDM models. We will discuss in this talk the case of the Hydra-Centaurus group, a nearby cluster of galaxies which host the active radio-galaxy Centaurus A (NGC 5128), which is undergoing a merge of and elliptical galaxy with an spiral galaxy and the interesting M83 (NGC 5236), whose central pseudo-bulge is suffering a intense transformation due to a process of fusion of smaller galaxies and star formation. Hydra-Centaurus is paradigmatic in the sense that being at a distance of a few megaparsecs present an intensity of merging similar to cluster of galaxies at distances z=1 or 2. We will discuss in more detail the 3-D spectroscopy of the central region of M83, obtained with GMOS instaled at the 8 m GEMINI-S telescope. Oral communications (each communication will last 25 minutes + 5 minutes for questions)Communication I: Black hole formation in Planck era. (PDF File)Yaser Tavakoli (UFES, Brazil) Abstract: For a spherically symmetric distribution of (homogeneous) matter, loop quantum gravity leads to a modification of evolution equation of the gravitational collapse. This gives rise to resolution of the classical singularity that form at collapse end-state. In this talk, we review recent developments in investigation of quantum gravity effects on late time stages of gravitational collapse and the formation of the possible non-singular black hole exterior. In particular, we consider a spherically symmetric model for gravitational collapse whose classical final state is a Schwarzschild black hole. In this framework, we investigate how quantum gravity modifies the exterior Schwarzschild geometry in Planck era. We further obtain a threshold mass, which is comparable with the Planck mass, for the formation of a very small non-evaporating (quantum) black hole. Communication II: Greybody factors for higher dimensional rotating black holes. (PDF File)Ednilton S. de Oliveira (UFPA, Brazil)Abstract: The study of the massless scalar field propagating around rotating black holes in spacetimes with cosmological constant is presented. The solution to the Klein-Gordon equation in rotating spacetimes cannot, in general, be expanded in terms of the spherical harmonics. When all black-hole angular momenta are set equal and the number of spacetime dimensions is odd, the solution enjoys an enhanced symmetry, and, therefore, it is cohomogeneity-1, so that its angular part is analytically known. Results to the greybody factors are found analytically and numerically. The matched asymptotic expansion method is used to compute low-frequency greybody factors for the s-wave. These results are consistent with the ones previously obtained for non-rotating black holes. Numerical greybody factor results can be obtained for any values of the wave and spacetime parameters – as wave angular momentum and frequency, black hole spin, cosmological constant value, etc. Numerical and analytical results are shown to be in excellent agreement. Numerically, it is possible to probe superradiant scattering. Superradiance is shown to occur for a certain range of parameters and to be more efficient as higher is the cosmological constant absolute value. The behavior of the greybody factors at high frequencies is drastically different when asymptotically flat, dS or AdS cases are considered; while greybody factors tend asymptotically to the unity in the former cases, in the latter they tend to zero in the same limit. Communication III: Hawking radiation for non-asymptotically and dilatonic black holes using gravitational anomaly. (PDF File)Glauber Tadaiesky Marques (UFRA, Brazil)Abstract: The d-dimensional scalar eld action may be reduced, in the background geometry of a black hole, to a twodimensional e ective action. In the near-horizon region, it appears a gravitational anomaly: the energy-momentum tensor of the scalar eld is notconserved anymore. This anomaly is removed by introducing a term related to the Hawking temperature of the black hole. Even if the temperature term introduced is not covariant, a gauge transformation may restore the covariance.We apply this method to compute the temperature of the dilatonic non-asymptotically at black holes. We compare the results with those obtained through other methods .Communication IV: Test particle motion in boson star space-times. (PDF File)Betti Hartmann (IFSC-USP, Brazil). Abstract: Boson stars are globally regular objects that are made of self-interacting scalar fields. Depending on the mass of the scalar field these can be as dense as neutron star or even black holes. In this talk I will discuss the test particle motion of uncharged as well as charged test particles in boson star space-times. The obtained results can be used to understand extreme-mass-ratio inspirals (EMRIs) as well as astrophysical plasmas. Communication V: Gravitational Waves and the post-Newtonian Theory. (PDF File)Riccardo Sturani (IFT - UNESP, Brazil)Abstract: In a few weeks the gravitational wave large interferometric detectors will resume data taking, with coalescing compact binaries being the best candidate sources for a first direct detection.In this talk we give an overview of the importance of fundamental gravity computations within the post-Newtonian approximation to General Relativity for the predictions of the expected gravitational waveforms. Communication VI: Physical properties of perturbed Kerr black holes Initial data. (PDF File)Rodrigo Panosso Macedo (Friedrich-Schiller-Universität Jena, Germany)Abstract: We construct initial data corresponding to a single perturbed Kerr black hole in vacuum. These data are defined on specific hyperboloidal slices, which means that future null infinity is included in our domain. We excise the singular interior of the black hole and assume a marginally outer trapped surface as inner boundary of the computational grid. Some physical properties of the initial data are studied with the calculation of the Bondi Mass, together with a multipole decomposition of the horizon. We probe the standard picture of gravitational collapse by assessing a family of Penrose-like inequalities.Communication VII: Superradiance in Analogue Models of Gravity. (PDF File) Abstract: Experimental research on analogue systems started only very recently. The first analogues of an event horizon were constructed in the laboratory using gravity waves on water and ultrashort pulses in optical fibers. In 2010, the classical analogue of the stimulated emission by a white hole was detected for the first time. Since a white hole is the time reversal of a black hole, this result attests to the generality of the Hawking radiation process. At the same time, some first hints of Hawking radiation in optical systems were reported. Last year, claims to link an instability arising in critical flows and Hawking radiation appeared in the literature. Another potential target for analogue gravity is the experimental observation of superradiance, a phenomenon in which incident waves are amplified after being reflected by a special kind of scattering potential. Superradiance was first studied by Zel’Dovich for electromagnetic waves incident on a conductive rotating cylinder, but also pertains to black holes and analogue black holes. In this seminar, I will discuss some of the experimental realizations of analogue models of gravity. The main focus will be shallow water wave systems and, in particular, I will analyse the possibility of observing superradiance in the laboratory.Maurício Richartz (UFABC, Brazil)Posters 1. Adriano Oliveira (IFES, Brazil): Estrelas de nêutrons para modelos de gravidade modificada.2. Álefe Freire (UFES, Brazil): Non linear effects on general relativity and dark matter in galaxies.3. Aline Vale (UFSJR, Brazil): Limits on Torsion Parameters from tt production at the LHC.4. André Kuerten (UFABC, Brazil): Black strings generated by a LTB collapse metric in the brane.5. Elena Konstantinova (IFET-MG, Brazil): Geometric defects in graphene and Kekule method.6. Eddy Giusepe Chirinos Isidro (UFES, Brazil): Modelos simples de Lemaître-Tolman-Bondi (LTB).7. Fabrício Matos Ferreira (UFJF, Brasil): Topological gravity and conformal operators in d = 4 and in higher dimensions.8. Felipe de Melo Santos (UFES, Brazil): Dynamical system analysis of a cosmological model based on a Scalar Field.9. Fernando Marroquim (UFSJR, Brazil): Heavy Majorana Neutrino Production at Sqrts=13TeV in Proton-Proton Colisions(LHC).10. Filipe de Oliveira Salles (UFJF, Brazil): Gravitational waves and perspectives for quantum gravity.11. Guilherme Peixoto (UFJF, Brazil): Form factors and non-local multiplicative anomaly for fermions with background torsion.12. Júnior Toniato (CBPF, Brazil): Black holes in geometric scalar gravity.13. Marina Machado Cunha e Mello (UFABC, Brazil): Electrically charged compact objects in a dynamical spacetime.14. Poliane Teixeira (UFJF, Brasil): Functional renormalisation group for scalar field in curved space-time.15. Rogério Cavalcanti (UFABC, Brazil): Extended Gregory-Laflamme method and realistic black strings.16. Sebastião Mauro Filho (UFJF, Brazil): Equations for metric perturbations in the theory of fourth order gravity.17. Tays Andrade (UFES, Brazil): Dynamical system analysis of a cosmological model based on a perfect fluid.18. Tibério de Paula Netto (UFJF, Brazil): On newtonian analysis in higher derivative gravity models.19. Zui Oporto (UFV, Brazil): Loop Quantization of a Model for D=1+2 (Anti)de Sitter Gravity Coupled to Topological Matter. |