ABSTRACT: The analysis of the Planck 2015 CMB data has set the stringest constraints on primordial non-Gaussianity from inflation. The latter is nowadays a high precision test of the inflationary model. What are the prospects for the future? Are there interesting new signatures not tested yet which could reveal new physics? After a very short summary of (some) of the 2015 Planck results on primordial non-Gaussianity, I will focus on two points. First, I will discuss a possible new window on the physics of inflation and primordial non-Gaussianity which has been proposed recently, based on the analysis of tiny deviations from the black-body spectrum of the Cosmic Microwave Background. Then I will focus on some new non-Gaussian signatures, in particular specific features arising in the context of modified gravity during inflation.
ABSTRACT: In this talk I describe recent progress in Effective Quantum Gravity and focus in particular on the recently discovered non-local effects. I discuss how this non-locality might show up in cosmology and astrophysics. I then describe a new connection between Higgs inflation and Starobinsky inflation models using this effective field theory.
TITLE: Constraining models of extended gravity using Gravity Probe B and LARES experiments
ABSTRACT: We consider models of extended gravity and in particular, generic models containing scalar-tensor and higher-order curvature terms, as well as a model derived from noncommutative spectral geometry. Studying, in the weak-field approximation (the Newtonian and post-Newtonian limit of the theory), the geodesic and Lense-Thirring processions, we impose constraints on the free parameters of such models by using the recent experimental results of the Gravity Probe B (GPB) and Laser Relativity Satellite (LARES) satellites. The imposed constraint by GPB and LARES is independent of the torsion-balance experiment, though it is much weaker.
TITLE: Covariant Effective Field Theory of Gravity
ABSTRACT: After reviewing the EFT approach to low energy quantum gravity and its covariant generalization I discuss possible applications to cosmology and black holes physics. To conclude I analyze the limitations of the approach and future perspective.
G. Dvali TITLE: TBA
TITLE: Relativistic effects in the galaxy number counts bispectrum as a new tool in cosmology.
ABSTRACT: In the near future cosmology will enter a new era in which the use of Newtonian gravity will no longer be sufficient in studying large scale structure (LSS). The next generation of LSS survey will probe the Universe with high precision and at very different scales, where non-linear and relativistic effects can play a key role. In this talk, I will present a new coordinate system, called geodesic light-cone (GLC) coordinates, useful to take in account such non-linear effects. In particular, I will show how, using the GLC gauge, one can determine the galaxy number counts in a purely geometric way, and up to second order in cosmological perturbation theory in the Poisson gauge. To conclude, I will present the numerical results for the leading non-linear and relativistic contributions to the number counts bispectrum, comparing them with the usual term from weakly non-linear Newtonian gravitational clustering and showing when the lensing-like contributions can become non negligible or even dominate the signal.
TITLE: Manifestly diffeomorphism invariant classical Exact Renormalisation Group
ABSTRACT: We construct a manifestly diffeomorphism invariant Wilsonian (Exact) Renormalization Group for classical gravity, and begin the construction for quantum gravity. We demonstrate that the effective action can be computed without gauge fixing the diffeomorphism invariance, and also without introducing a background space-time. We suggest how this programme may completed to a fully quantum construction.
TITLE: Black hole engineering in short scale modified gravity.
TITLE: Analogous Hawking radiation in Bose-Einstein condensates
ABSTRACT: I shall discuss realistic realisations of a sonic event horizon in a 1D Bose-Einstein condensate, and present possible experimental (quantum and classical) signatures of analogous Hawking radiation in these systems.
TITLE: Overview of gravitational waves observations by LIGO/VIRGO collaborations
TITLE: Reconstruction of inflationary models from observational data
ABSTRACT: Quantitative information about details of inflation obtained from recent CMB observational data on the primordial spectrum of scalar (density) perturbations suggests going further and reconstructing infla- tionary models phenomenologically using some additional assumptions, mainly aesthetic ones, about the form of the spectrum in the region of smaller scales and smooth behaviour at low space-time curvature. I remind an old result on the reconstruction of the inflaton potential in General Relativity, obtained without expanding the power spectrum in a power series at some scale, and generalize it to the case of f(R) gravity. Predictions for the tensor-to-ratio following from the simplest and most elegant assumptions are summarized.
TITLE: Quantum Black Holes: theory and phenomenology
ABSTRACT: Quantum gravity may allow black holes to decay into white holes. If so, the lifetime of a black hole would be shorter than the one given by Hawking evaporation, solving the information paradox. A concrete calculation can be performed using loop quantum gravity technics, supporting this picture. Interestingly, this could open to a new window for quantum-gravity phenomenology, in connection with the existence of primordial black holes. I discuss in particular the possibility to observe an astrophysical emission in the radio and in the gamma wavelengths, and I will briefly overview the ongoing research to understand the possible consequences of the model for cosmology.
TITLE: How classical spacetimes could emerge from quantum gravity
ABSTRACT: One of the central questions of Quantum Gravity is: how to recover classical spacetime from a fundamentally quantum description of geometry? Pragmatically speaking, the experimentalist does not measure geometry directly, but rather infers it by studying the propagation of matter. Thus, given a certain dynamics for the matter content of the system, every geometry which is consistent with such dynamics is equally good. Taking this point of view, we will show that QFT on a fundamental quantum geometry (of the FLRW type) is equivalent to QFT on an effective classical geometry (of the same type). However there is a surprise: this emergent classical geometry depends on the wavenumber of the scalar mode under consideration! The situation is thus similar to condensed matter physics, where photons propagating through a medium behave as massive particles following different paths depending on their energy. We will take this result seriously, and investigate measurable effects, focusing in particular on deformation of Lorentz-invariant dispersion relation.
TITLE: Particles with non-Abelian charges
ABSTRACT: The first-quantized (worldline) approach to quantum field theory coupled to a non-Abelian gauge field can be obtained by studying the propagation of ”colored” particles, i.e. particles with non-Abelian charges. We employ auxiliary worldline fields to generate the ”color” degrees of freedom of the particle and show how to use such models to compute QCD amplitudes.
TITLE: Anisotropic Power Spectrum from Rotational Symmetry Breaking Excited Initial States
ABSTRACT: An anisotropic power spectrum could result from an isotropic inflationary phase if initial states that break rotational invariance had been excited by new physics, active at energies higher than the scale of inflation, that picked up a preferred direction. Requiring that the coefficient of the dipole and other odd higher multipole terms in the primordial power spectrum to be imaginary, or zero, we constrain the form of these excited initial states. In a high scale model of inflation and for large occupation numbers, only the quadrupole term is shown to survive, and we analytically constrain its coefficient to be —B— 0.06. We also investigate the effect of these excited initial states on the bispectrum. As for any excited state, the amplitude of the non-gaussianity for the local configurations is enhanced. However, due to the special form of these anisotropic excited states, one finds a modulation of the non-gaussianity around a mean value depending on the angle that short and long wavelength modes make with the preferred direction. The maximal variations with respect to the mean value occur for the configurations which are coplanar with the preferred direction and the amplitude of the non-gaussianity increases (decreases) for the short wavelength modes aligned with (perpendicular to) the preferred direction. For a high scale model of inflation, with ε ≃ 0.01, the difference between these two configurations is about 0.27, which could be used to identify this particular mechanism of rotational symmetry breaking.
D.V. Gal’tsov, E.A. Davydov
TITLE: HYM-ation: Yang-Mills cosmology with Horndeski coupling
ABSTRACT: We propose new mechanism for ination using classical SU(2) Yang-Mills (YM) homogeneous and isotropic eld non-minimally coupled to gravity via Horndeski prescription. This is the unique generally and gauge covariant ghost-free YM theory with the curvature-dependent action leading to second-order gravity and Yang-Mills eld equations. We show that its solution space contains de Sitter boundary to which the trajectories are attracted for some nite time, ensuring the robust ination with a graceful exit. The theory can be generalized to include the Higgs eld leading to two-steps inationary scenario, in which the Planck-scale YM-generated ination naturally prepares the desired initial conditions for the GUT-scale Higgs ination.
TITLE: Bianchi type-III Power law model in f(R,T) gravity
ABSTRACT: An anisotropic Bianchi type-III universe is investigated in presence of perfect fluid within the framework of f(R,T) gravity where R is the Ricci scalar and T is the trace of the source of matter, for the choice of functional f(R,T) = R+2f(T) and f(R,T) = f1(R)+f2(T). We have shown that the field equations of f(R,T) gravity are solvable for any arbitrary function of a scale factor. To get a physically realistic model of the universe, we have assumed a simple power-law form of a scale factor. The exact solutions of the field equations are obtained which represent an expanding model of the universe starts expanding with a big bang at t = 0. The physical behaviours of the model are discussed.
TITLE: Lovelock Black Hole Thermodynamics
ABSTRACT: I will talk about the effects of higher curvature corrections from Lovelock gravity on the phase structure of asymptotically AdS black holes, treating the cosmological constant as a thermodynamic pressure.
TITLE: Electromagnetic fields with vanishing scalar invariants
ABSTRACT: We determine the class of p-forms which possess vanishing scalar invariants (VSI) at arbitrary order in a n-dimensional spacetime. In particular, we prove that the corresponding spacetime must belong to the ”degenerate” Kundt family. Although the result is theory-independent, we discuss, in particular, the special case of Maxwell fields, both at the level of test fields and of the full Einstein-Maxwell equations. These describe various classes of non-expanding electromagnetic waves. We further point out that a subset of these solutions possesses a ”universal” property, i.e., they also solve any generalized (non-linear and with higher derivatives) electrodynamics, possibly also coupled to Einstein’s gravity
TITLE: Spacetime-noncommutativity regime of Loop Quantum Gravity
ABSTRACT: A recent study by Bojowald and Paily provided a path toward the identification 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 modifications 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, which has been already studied extensively for other reasons.
F. del Monte
TITLE: Multimetric supergravities
ABSTRACT: In the last few years a new class of theories has been discovered consistently describing massive spin-2 fields nonlinearly interacting with a single massless one. These multimetric gravities provide a solution to the problem of the so-called Boulware-Deser ghost, previously thought to unavoidably plague any interacting theory of massive spin-2 particles. We note that their action in the vielbein formulation admits a natural extension in terms of integral forms on a supermanifold, which will be locally supersymmetric by construction, and thus will describe a new class of couplings between supergravity and massive spin-2 multiplets. We propose superfield actions for N=1 multimetric supergravities in spacetime dimensions up to four, and discuss the problems related to their component expansion, comparing them with the simpler case of multi-gauge fields.
TITLE: Gravitational collapse in the AS scenario: a Kuroda-Papapetrou RG-improved model
ABSTRACT: According to Wheeler, the gravitational collapse is the ”greatest crisis in Physics of all time”. In this work the structure of the singularity produced by a collapse of a null-fluid will be discussed in the framework of AS scenario. Under the assumption of spherical symmetry, it will be shown that the generic singularity arising in the collapse of a null-dust is spacelike and ”whimper”, according to the Tipler classification. The spacetime is therefore extendible but the Cosmic Censorship Conjecture is violated in its weak formulation.
TITLE: The many saddle points configuration of a quantum black hole
ABSTRACT: The Hawking paradox cannot be solved by considering the classical back-reaction of the Hawking evaporation to the geometry. Thus, the resolution must be that quantum gravity effects are already visible at IR. By considering the path integral approach to quantum gravity, I will show that, in 2 dimensions, the ”Black Hole state is described by a sum over complex saddle points. In higher dimensions, I will argue that the Hawking paradox is rooted to the probably un-correct assumption that, after a large time, the classical saddle point (the Schwarzschild black hole) dominates the Black Hole evolution. Finally, I will argue that the resolution of the paradox may be found by looking at the next to leading order saddle point approximation.
TITLE: Horizon quantum mechanics and corpuscular black holes
ABSTRACT: Quantum physics lends a view of space-time as an emergent structure that shows classical features only at some observational level. The space-time manifold can be viewed as a purely theoretical arena, where quantum states and observables are defined with the additional freedom of changing coordinates. We focus on spherically symmetric quantum sources, and we compute the probability they are black holes. The gravitational radius is promoted to quantum mechanical operator acting on the horizon wave-function. This horizon quantum mechanics supports some features of BEC models of black holes. When N bosons are self-confined in a volume of the size of the Schwarzschild radius, horizon quantum mechanics shows that its related uncertainty is connected to the typical energy of Hawking modes: it is suppressed as N increases, contrarily to a simple very massive particle. The spectrum of these systems is formed by a discrete ground state and a continuous Planckian distribution at the Hawking temperature representing the radiation. Assuming the internal scatterings give rise to the Hawking radiation, the N-particle state can be collectively described by a single-particle wave-function. The partition function follows together with the usual entropy area law, with a logarithmic correction related to the Hawking component. The back-reaction of radiating modes is also shown to reduce the Hawking flux, eventually stopping it.
TITLE: Particlelike solutions in modified gravity: the Higgs monopoles
ABSTRACT: In this talk we will discuss the possible relation between the Higgs field and gravity. We will focus on the Higgs inflation model which is favored by the Planck observations. However such a model requires combined constraints at cosmological and gravitational scales, i.e. for compact objects. In particular we will show that Higgs inflation gives rise to particlelike solutions around compact objects, dubbed Higgs monopoles, characterized by the nonminimal coupling parameter, the mass and the compactness of the object. For large values of the nonminimal coupling, forbidden compactnesses appear.
TITLE: The Wheeler-DeWitt Equation in Distorted Gravity
ABSTRACT: Even if a full and complete theory of Quantum Gravity and Quantum Cosmology is absent, the Wheeler-DeWitt equation appears as a natural instrument for the quantization of the gravitational field. In this context we setup a Sturm-Liouville problem with the cosmological constant considered as the associated eigenvalue. We will discuss the effects of some modifications of General Relativity, like Gravity’s Rainbow, GUP and Horava-Lifshitz theory on the Wheeler-DeWitt Equation. An application to inflation will be discussed.
M. De Laurentis
TITLE: Cosmological inflation in F (R, G) gravity
ABSTRACT: Cosmological inflation is discussed in the framework of F(R,G), gravity where F is a generic function of the curvature scalar R and the Gauss-Bonnet topological invariant G. The main feature that emerges in this analysis is the fact that this kind of theory can exhaust all the curvature budget related to curvature invariants without considering derivatives of R, Rμν, Rλσμν etc., in the action. Cosmological dynamics results driven by two effective masses (lengths) are related to the R scalaron and the G scalaron working respectively at early and very early epochs of cosmic evolution. In this sense, a double inflationary scenario naturally emerges.
TITLE: Kerr-Schild Way to Quantum Gravity
ABSTRACT: Contrary to known opinion that role of gravity in particle physics is negligible, we show that the exclusively high spin/mass ratio of the spinning particles creates the Kerr gravity with a strong topological defect of the space-time. Using for regularization a supersymmetric scheme of phase transition, we show that the consistent with gravity spinning particles get the features of the famous MIT and SLAC bag models.
TITLE: Thermodynamics of Local causal horizon for higher derivative gravity.
ABSTRACT: By imposing the Clausius equation on a small patch of a local causal horizon(LCH) one can obtain the Einstein equation and interpret it as an equation of state. In the past decades the equation of state derivation has been extended to theories beyond general relativity(for theories of gravity without derivatives of curvature in the action) assuming the entropy that one associates with the LCH to have a Noethersque form. In this talk I will discuss about a modification to the Noethersque entropy so that one can further extend the derivation to higher derivative theories. Also a method will be discussed such that the derivation is further extended to non minimally coupled theories. Finally some remarks and comment about current status of the equation of state approach will be made.
TITLE: Unparticle parameters in the light of the hydrogen ground state
ABSTRACT: In 2007 a seminal paper by Georgi proposed an extension of the Standard Model of particle physics by including scale invariant fields called unparticle stuff. It stands for a low-energy effective description of a so-called Banks-Zaks sector which exhibits scale invariance below anenergy scale ΛU. One key feature of unparticle fields is an apparentfractional number of (un)particles determined by the non-integer canonical scaling dimension dU. The inherent interactions with conventional matter can be used to prove the existence of unparticle stuff experimentally. In this talk, a review on the unparticle theory and its static potential will be given. We consider the unparticle impact on the hydrogen atom energy levels and derive corrections to the ground state by using Rayleigh-Schrödinger perturbation theory. Through comparison with experimental data, we find constraints on the energy scale ΛU as a function of the scaling dimension dU.