XXI Conferenza SIGRAV Relatività Generale e Fisica della Gravitazione

Program

 Monday Tuesday Wednesday Thursday Friday 9:00 9:40 Mario Lattanzi Marco Genovese Francesco Vissani Gabriele Veneziano 9:45 10:25 Monica Colpi Alessandra Silvestri Nicola Pinamonti Nicolao Fornengo Leonardo Gualtieri 10:30 11:10 Andrea Possenti Bruno Giacomazzo Maria Alessandra Papa Giovanni Losurdo Giulia Ricciardi 11:10 11:35 coffee break coffee break coffee break coffee break coffee break 11:35 12:15 Fedele Lizzi Claudia Maraston Sergio Ferrara Marica Branchesi Paolo Salucci 12:20 13:00 Giulio Magli Barbara Lanzoni Pietro Frè Alessandro Nagar Final Discussion and Conclusions 13:00 13:40 lunch break lunch break lunch break lunch break lunch break 13:40 14:30 lunch break 14:30 18:35 14:30-15:00 Award Ceremony 15:00-15:40 Nazzareno Mandolesi 15:45-16:25 Sergei Odintsov 16:30-17:00 Coffee break 17:00-17:30 Simone Giombi 17:35-18:05 Michele Liguori 18:10-18:40 Giovanni Marozzi 18:45-19:15 Giulia Pagliaroli parallel sessions: A and B Excursion to the country side parallel sessions: A and C parallel sessions: B and C Refreshment and buffet dinner 18:30-20:00 Assemblea dei soci SIGRA social dinner Science popularization lecture by Gabriele Veneziano, at ACSAL 18:30-20:00 Consiglio direttivo SIGRAV

The schedule of parallel sessions will be the following:

 14:30-15 Invited seminar 15:05-15:25 presentation 15:30-15:50 presentation 15:55-16:15 presentation 16:20-16:50 coffee Break 16:50-17:20 Invited seminar 17:25-17:45 presentation 17:50-18:10 presentation 18:15-18:35 presentation

A  Classical and Quantum Theoretical Gravity. Chairmen:  Roberto Casadio, Lorenzo Fatibene

 Parallel Session A: Classical and Quantum Theoretical Gravity Tuesday, September  16, 2014 14:30 15:00 Alfio Bonanno (Invited) Compatibility of Planck and BICEP2 in asymptotically safe inflation 15:05 15:25 Emanuele Battista Restricted and full 3-body problem in effective field theories of gravity 15:30 15:50 Gabriele Gionti Comparing two double string theory actions 15:55 16:15 Alessio Orlandi Black holes as self-sustained quantum states, and Hawking radiation Coffee break 16:50 17:20 Alessandro  Spallicci  (Invited) Self-force driven motion in curved spacetime and orbital evolution 17:25 17:45 Francesco Becattini Local thermodynamical equilibrium and the β frame for a quantum relativistic fluid 17:50 18:10 Bianca Letizia Cerchiai The geometry of exceptional Lie groups, supergravity and integrable models 18:15 18:35 Francesco Vietri f(R) gravity in the Kaluza-Klein framework: general theory and cosmological models
 Parallel Session A: Classical and Quantum Theoretical Gravity Thursday, September  18, 2014 14:30 15:00 Alessandro Tronconi (Invited) Signatures of quantum gravity in a Born-Oppenheimer context 15:05 15:25 Luca Lusanna Einstein’s gravity: Hamiltonian version of curvature tensors and Dirac observables 15:30 15:50 Simon Garruto Extended Gravity 15:55 16:15 Andronikos  Paliathanasis Invariant solutions of the Wheeler-DeWitt equation Coffee break 16:50 17:20 Giampiero Esposito (Invited) Self-dual road to non-commutative gravity with twist: a new perspective 17:25 17:45 Aneta Wojnar Invariant solutions and Noether symmetries in Hybrid Gravity 17:50 18:10 Sergio Benenti Cosmologia Analitica 18:15 18:35 Maria Cristina Paolella Hojman symmetries in cosmology

B  Astrophysics and Cosmology. Chairmen:  Antonaldo Diaferio, Alberto Vecchiato

 Parallel Session B: Astrophysics and Cosmology Tuesday, September  16, 2014 14:30 15:00 Luigi Piro  (Invited) The Hot and Energetic Universe: from present to future with the ATHENA mission 15:00 15:30 Lorenzo Iorio (Invited) New clock effects in general relativity for counter-revolving test particles 15:30 15:50 Eloisa Bentivegna Quanti buchi neri può contenere l’universo? Cosmologie analitiche e numeriche per un reticolo di singolarità di Schwarzschild 15:50 16:10 Ruben Farinelli Numerical solutions of the modified Lane-Emden equation in f(R)-gravity Coffee break 16:50 17:20 Enzo Branchini (Invited) Cosmic structure evolution as a test to Einstein’s gravity theory: an observational perspective 17:20 17:40 Cristiano De Boni Galaxy cluster mass accretion rate 17:40 18:00 Luca Valenziano Investigating the dark Universe with the Euclid satellite 18:00 18:20 Carlo Burigana Towards a next CMB space mission: scientific goals and feasibility
 Parallel Session B: Astrophysics and Cosmology Friday, September  19, 2014 14:30 15:00 Dragan Hajdukovich (Invited) The basis for a new model of the Universe 15:00 15:20 Riccardo Moriconi Chaos Removal in the f(R)-gravity: the Mixmaster model 15:20 15:40 Roberto De Pietri The dependence on the stiffness of the Equation of State of the threshold for the onset of the bar-mode instability of Neutron Stars in full General Relativity 15:40 16:00 Massimiliano Rinaldi Inflation from scale-invariant gravity Coffee break 16:50 17:20 Stefano Camera (Invited) Gravity on the Largest Cosmic Scales with Forthcoming Experiments 17:20 17:50 Marco Bruni Structure formation from small scales to the horizon: a  nonlinear post-Friedmann framework. 17:50 18:20 Francesca Vidotto Planck stars 18:20 18:40 Cosimo  Stornaiolo A phenomenological approach to Quantum Cosmology

C  Experimental Gravity. Chairmen: Enrico Calloni, Giancarlo Cella

 Parallel Session C: Experimental Gravity Thursday, September  18, 2014 14:30 15:05 Luciano Di Fiore (Invited) The space antennas for the detection and study of gravitational waves 15:05 15:40 Ettore Majorana Archimedes: an experiment for the verification of the Archimedes force on vacuum 15:40 16:15 Zappia/Galano Towards a learning progression of the cause of seasons Coffee break 16:50 17:25 Martina Delaurentis (Invited) The generation and application of squeezed light for high sensitivity optical experiments 17:25 18:00 Benjamin Canuel MIGA: an hybrid atom-optical interferometer for gravitational waves physics and geosciences
 Parallel Session C: Experimental Gravity Friday, September  19, 2014 14:30 15:05 Franco Frasconi (Invited) Status of Gravitational Waves search with long ground based interferometric detectors 15:05 15:40 Nicola Poli (Invited) Precision tests of gravity with atom interferometers 15:40 16:15 Matteo Luca Ruggiero (Invited) GINGER and tests of fundamental gravity Coffee break 16:50 17:25 Alberto Vecchiato Astrometric tests of gravitational theories 17:25 18:00

AMALDI MEDALS

N. Mandolesi: Cosmology from Planck

Abstract: After a short introduction of the experiment that kept me busy for 20+ years, I will review the main cosmological results obtained by Planck in 2013. Then I will provide some forecast about the next cosmological Planck release which is expected to happen within this year and is awaited with even more interest after the BICEP2 claim.

S. Odintsov: The universe evolution history from modified gravity: the unification of inflation with dark energy.

Abstract: The introduction to the description of the universe evolution history within modified gravity is given. Basic/pioneer works on gravitational alternative for inflation and dark energy are briefly reviewed. Special attention is paid to the unification of the inflation with late-time cosmic acceleration within F(R) gravity.

The corresponding possibility in string-inspired gravity, modified Gauss-Bonnet gravity and non-local gravity is also mentioned. The account of quantum effects (conformal anomaly) with viable exponential F(R) gravity leads to unification of realistic inflation with dark era indistinguishable from LCDM.

It is indicated that neutron stars maybe good laboratory for the search of modified gravity manifestations via the occurrence of compact supermassive objects. Some perspectives are briefly mentioned.

SIGRAV PRIZES

Simone Giombi:  Higher spin gravity and holography
Abstract: Higher spin gravity theories are generalizations of Einstein gravity that involve towers of interacting massless fields of all spins (including, in particular, the graviton) and can be consistently constructed in the presence of a non-zero cosmological constant.

In recent years, these theories have received particular attention in the context of the so called AdS/CFT correspondence, a remarkable “holographic” duality between a quantum theory of gravity in anti-de Sitter space and a quantum field theory in one lower dimension.

This correspondence suggests that, despite appearing highly non-trivial,  higher spin gravity theories in AdS may in fact be equivalent to rather simple quantum field  theories, as simple as a free field theory. In this talk,  I will give an overview of higher spin theories with a focus on their role in the AdS/CFT correspondence.

In particular, I will review some recent calculations of one-loop quantum effects in higher spin gravity. These  calculations suggest that these models have better ultraviolet properties than pure Einstein gravity, and may be interesting  theories of quantum gravity in their own right.

Michele Liguori:  CMB constraints on Modified Gravity
Abstract. Temperature anisotropies of the Cosmic Microwave Background (CMB)  are  sensitive to low-redshift Physics via the Integrated Sachs-Wolfe (ISW)  and lensing effects. In light of this, I will show  how we can be able to use CMB data in order to set constraints on  different models of cosmological Modified Gravity. I will then discuss  actual CMB experimental constraints on f(R) and Chameleon-type models,  recently obtained from Planck data, and argue that, even though Large Scale  Structure observations remain our main tool to study dark energy and modified  gravity, high precision CMB datasets can provide interesting complementary  measurements.

Giovanni Marozzi:  Non-linear effects in cosmology
Absract: 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. I will show how, using the GLC gauge, one can solve non-perturbative the geodesic deviation equation, obtain an exact solution of the Jacobi Map and, through a coordinate transformation, obtain perturbative expression for cosmological observables in the Poisson gauge. Second order perturbative expressions can be used in the analysis of the weakly non-linear regime. In particular, I will show the second order result for the galaxy number counts and I will use it to evaluate the probably most important new terms in the relative bispectrum, comparing the outcome with the usual term from weakly non-linear Newtonian gravitational clustering.

Giulia Pagliaroli:  Neutrinos as a probe of Supernova physics and as a trigger for GW search

Abstract: Next galactic Core-Collapse Supernova should occur within a 50 year scale. Neutrinos and Gravitational Waves arrive simultaneously at the observer frame and in pristine conditions, bringing with them unique information about the astrophysical event. Thanks to the theoretical results and to the test bench of SN1987A it is possible to refine our ability to properly extract maximum information from the future observations. In order to  investigate the astrophysics of the source, we construct   a parameterized model describing the emission of electron antineutrinos. Moreover this model allows us to improve strategies for GW search with a resulting increase in sensitivity, live-time coverage and confidence of detection. An overview of the power of a joint search of neutrinos and GWs will also be presented.

PLENARY SIGRAV

LUNEDI’ 15 mattina

Monica Colpi (UNIMIB) The Gravitational Universe

Abstract: The last century has seen enormous progress in our understanding of the Universe. We know the life cycles of stars, the structure of galaxies, the remnants of the big bang, and have a general understanding of how the Universe evolved. We have come remarkably far using electromagnetic radiation as our tool for observing the Universe. However, gravity is the engine behind many of the processes in the Universe, and much of its action is dark. Opening a gravitational window on the Universe will let us go further than any alternative. Gravity has its own messenger: Gravitational waves, ripples in the fabric of spacetime. They travel essentially undisturbed and let us peer deep into the formation of the first seed black holes, exploring redshifts as large as twenty, prior to the epoch of cosmic re-ionisation. eLISA will be the first ever mission to study the entire Universe with gravitational waves. eLISA is an all-sky monitor and will offer a wide view of a dynamic cosmos using gravitational waves as new and unique messengers to unveil The Gravitational Universe. I will describe how exquisite and unprecedented measurements of black hole masses and spins will make it possible to trace the history of black holes across all stages of galaxy evolution, and at the same time constrain any deviation from the Kerr metric of General Relativity. eLISA has guaranteed sources in the form of verification binaries in the Milky Way, and can probe the entire Universe, from its smallest scales around singularities and black holes, all the way to cosmological dimensions.

Andrea Possenti (OAC-INAF) Searching Gravitational Waves in the nanoHz band: the role of SRT in the Pulsar Timing Array(s)

Abstract: Due to evolutionary reasons and intrinsic properties, some radio pulsars behave as highly stable clocks and their regular observation can provide quantitative measurements of the properties of the space-time in their environment as well as along the line-of-sight from the source to the observer. The talk will introduce the concepts behind the so-called Pulsar Timing Array(s), which are the most promising instruments for obtaining a direct detection of the gravitational waves in the nanoHz frequency range, likely produced by (an ensemble or single) supermassive black-hole binaries. The involvement of the Sardinia Radio Telescope (SRT) in this intriguing experiment(s) will be also discussed.

Fedele Lizzi (UNINA) Quantum spacetime and noncomutative geometry

Abstract: Starting from physical motivation I will argue that there are indications that at high energy scales the structure of spacetime has to be that of  a quantum geometry. Such a geometry must to be described by operators (possibly noncommuting) which replace the usual geometrical concepts. I will then review physical aspects of some of these quantum geometries based on the spectral properties of observables.

Giulio Magli (POLIMI) The final state of spherically symmetric perfect fluids’ collapse: new insights

Abstract: Spherical symmetry is a useful test-bed for open problems of astrophysical interest in General Relativity. Among them, a very relevant open one is that of the final state of gravitational collapse and, therefore, of the validity of a ”Cosmic Censorship” hypothesis. In particular, the final state of the gravitational collapse of spherically symmetric isotropic fluids is still a matter of debate. What makes isotropic fluids’ collapse one of the most intriguing problem in gravitational collapse theory is that, on one hand, these fluids are useful to model stars in astrophysics and, on the other, that they are a obvious, physically natural generalization of the so-called Lemaitre–Tolman–Bondi dust solutions, which play a distinct role both in cosmology and gravitational collapse. The main difficulty in approaching the formation of blackholes or naked singularities in perfect fluids is, of course, that few exact solutions are known. So motivated, we present here a conditioned approach, which allows the analisys of perfect fluid spacetimes for general equations of state provided that certain regularity assumptions – which do hold for many known solutions – are satisfied. In this way we get  a quite general picture of barotropic perfect fluids as well as for some other cases of interest. The qualitative picture emerging from these results shows that a crucial role is played by the behaviour of the pressure in the neighborhood of the singular boundary.

MARTEDI’ 16 mattina

Enrico Barausse  (Institut d’Astrophysique de Paris) Compact objects as probes of astrophysics, gravity and fundamental physics

Abstract: Observations of compact objects such as neutron stars and black holes, in isolation or in binary systems, are not only interesting in themselves, but also constitute an ideal testing ground for galaxy formation models, cosmology, as well as gravitation and fundamental physics. I will discuss examples of these tests that can be performed with existing electromagnetic observations of these objects, as well as with future gravitational-wave detections.

Mario Lattanzi (OATO) Astrometric Cosmology in the Era of Gaia

Abstract: The accurate measurement of the motions of stars in our Galaxy can provide access to cosmological signatures in its disk and halo, while astrometric experiments from within our Solar System can uniquely probe possible deviations from General Relativity. This talk will introduce to the fact that astrometry has reached such levels, thanks also to impressive technological advancements, to become a key player in the field of local cosmology and experimental gravitation.

It will be shown how accurate absolute kinematics at the scale of the Milky Way can, for the first time in situ, account for the predictions the CDM model has made for the Galactic halo, and eventually map out the distribution of dark matter, or other formation mechanisms, required to explain the signatures recently identified in the old component of the thick disk.

Finally, special notes will dwell on to what extent the ESA satellite Gaia, operating in space since January of this year, can fulfill the expectations of astrometric cosmology and on what must instead be left to future, specifically designed, experiments.

Alessandra Silvestri (SISSA) Testing general relativity on cosmological scales

Abstract: More than a decade after its discovery, cosmic acceleration still poses a puzzle for modern cosmology and a plethora of models of dark energy or modified gravity, able to reproduce the observed expansion history, have been proposed as alternatives to the cosmological standard model. In recent years it has become increasingly evident that probes of the expansion history are not sufficient to distinguish among the candidate models, and that it is necessary to combine those with observations that probe the dynamics of inhomogeneities. Future cosmological surveys will map the evolution of inhomogeneities to high accuracy, allowing us to test the relationships between matter overdensities, local curvature, and the Newtonian potential on cosmological scales. I will discuss theoretical issues involved in finding an optimal framework to study deviations from General Relativity on cosmological scales, giving an overview of recent progress, with a focus on model-independent approaches. In particular I will discuss the phenomenology driven parametrization in terms of two functions of time and space, as well as the theory driven effective field theory formalism for dark energy and its implementation in CAMB.

Claudia Maraston (ICG-Portsmouth, UK) The effect of modified gravity on galaxy models

Abstract: The physical properties of galaxies are predicted, or derived from data, via so-called stellar population models. These models provide the integrated properties, such as the spectral energy distribution and mass-to-light ratio, of complex stellar systems, as a function of physical parameters, formation timescale, chemical composition and dark to luminous matter, which are key to studying galaxy formation. Up to the now, stellar population models were calculated using models for individual stars which assume ordinary gravity in the hydrostatic equilibrium equation and in the stellar atmospheres for line formation. In this work we make the first attempt to evaluate the impact of modified gravity on stellar population models, using modified gravity parameters which obey constraints from cosmology. I shall introduce the topic and present early results.

Barbara Lanzoni (UNIBO) Searching for intermediate-mass black holes in globular clusters

Abstract: Black holes with masses between a few 100 and 100,000 solar masses (commonly named “intermediate-mass black-holes”, IMBHs) are expected to exist in nature, but no convincing evidence has been collected so far in support of such a prediction.

The empirical proof of their existence is crucial for understanding many “hot topics” of the modern Astrophysics and Physics research. IMBHs would naturally explain the formation of super-massive BHs, which are observed in the centre of all massive galaxies at any redshift, with a major impact on the comprehension of the formation and evolution of cosmic structures. Moreover, IMBHs would highly boost the chance of revealing gravitational waves with the current and next generation of gravitational wave detectors (e.g., VIRGO, LIGO, LISA).

Globular clusters are thought to be the ideal habitat for IMBHs and their presence is predicted to produce a number of observable fingerprints: a power-law central cusp in the stellar density and velocity dispersion profiles, X-ray and radio emission due to the matter accreting onto the BH, a quenching of the central mass segregation. In this talk I summarize the main techniques used to unveil the presence of IMBHs in the core of globular clusters and the main results obtained to date in this field of the research.

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MERCOLEDI’ 17 mattina (6 interventi)

Sergio Ferrara (CERN) The simplest supergravity embedding of Starobinsky and Chaotic Inflation

Abstract: Motivated by the fourth order supergravity realization of the(Planck favored) Starobinsky model we depart from this theory but keeping the same supermultiplet structure.In this way the single field inflaton potential which describes chaotic inflation(BICEP favored)is also obtained

Pietro Frè (UNITO) Inflaton potentials in supergravity: n=1 and n=2 a General overview.

Abstract: a general overview is presented of the possible inclusion of inflaton potentials in supergravity. The case of F term and D term mechanisms is discussed. Special attention is given to scalar manifolds that are symmetric spaces both in the n=1 and n=2 case. The role of c-map between special Kahler geometry and quaternionic geometry in understanding the generation of Starobinsky like potentials is emphasized.

Marco Genovese (INRIM) Testing quantum gravity on an Optical bench

Abstract: The aim of building a theory unifying general relativity and quantum mechanics, the so called quantum gravity, has been a key element in theoretical physics research for the last 60 years.  Several attempts in this sense have been considered, some of them with huge efforts in term of work of hundreds of scientists. However, for many years no testable prediction emerged from these studies. In the last few years this common wisdom was challenged. A first series of testable proposals concerned photons propagating on cosmological distances, with the problem of extracting QG effects from a limited (uncontrollable) observational sample affected by various propagation effects. More recently, effects in interferometers  connected to non-commutativity of position variables in different directions were considered both for cavities with microresonators and two coupled interferometers, the so called “holometer”. In particular this last idea led to the planning of a double 40 m interferometer at Fermilab.

Here, in a first part of the talk, we present a work demonstrating how the use of quantum correlated light beams in coupled interferometers could lead to significant improvements allowing an actual simplification of the experimental apparatuses to probe the non-commutativity of position variables,  prompting the possibility of testing QG in experimental configurations affordable in a traditional quantum optics laboratory with current technology.

In a second part of the talk we present an experiment, base on entangled photons, addressed to visualise Page – Wootters  mechanics aimed to solve the problem of time in canonical quantization of gravity when applied to cosmology.

Nicola Pinamonti (UNIGE) Quantum field theory on curved spacetime and semiclassical Einstein equations

Abstract: After reviewing the theory of quantum fields propagating on curved backgrounds, we shall consider their backreaction on gravity.

This will be done in the case of a free massive quantum scalar fields and using the Einstein equations in a semiclassical fashion. The analysis we would like to present requires a careful study of the ultraviolet divergences and their renormalization, which is required in order to obtain meaningful expressions for the expectation values of the stress energy tensor in quantum theories. The resulting stress tensor will have a nontrivial effect on the curvature on cosmological spacetimes too. In the latter case, the semiclassical Einstein equations become a well posed dynamical system provided the quantum state for matter is chosen in an appropriate way.

The question of existence of exact solutions of such system will be discussed and some implication for cosmology will be presented.

Maria Alessandra Papa (MPI Golm,DE) Searching for continuous gravitational waves

Abstract: Compact object like neutron stars are likely to be emitting continuous gravitational waves which may be detectable by ground-based gravitational wave detectors. In this talk I will review recent developments connected to searches for this type of signals.

Bruno Giacomazzo (UNITN) General Relativistic Simulations of Binary Neutron Stars: Gravitational Waves and Gamma-Ray Bursts

Abstract: I will present results of fully general relativistic simulations of binary neutron star (BNS) mergers and I will discuss in particular their gravitational wave (GW) and electromagnetic (EM) signals. BNSs are among the most powerful sources of GWs that will be detected in the next few years by advanced Virgo and LIGO. GWs emitted from BNSs will contain important information about the NS structure, such as the NS equation of state. Moreover BNS can also emit strong EM counterparts and in particular they are thought to be behind the central engine of short gamma-ray bursts (SGRBs). I will therefore discuss what we can learn from a detection of GWs from BNS mergers and the connection between BNS mergers and SGRB engines.

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GIOVEDI’ 18 mattina

Francesco Vissani (GSSI) Neutrino Astronomy

Abstract: The peculiar presence of neutrinos in weak interaction processes has drawn a wide interest since the beginning and has led scientists to discuss the various cases when they are detectable. The theoretical modeling of various objects the sun regarded as a nuclear reactor, of the cosmic ray collisions  with the terrestrial atmosphere, of the gravitational collapse of a core of a star, of the neutrino radiation emanating from the Earth crust,  etc, have all succesfully found their observational counterpart, leading to the birth of neutrino astronomy. New astrophysical sources of neutrinos have been envisaged; further surprising observations have been are still being made in these years, witnessing a very lively moment of this scientific discipline.

In this talk, we offer an overview of neutrino astronomy, recalling the specific features of this radiation and the characteristic of the the neutrino telescopes devoted to the observation of neutrinos of various energies. We discuss various neutrinos sources that have been observed and emphasize interesting goals, concerning low and high energy neutrino astronomy, that are still to be reached. The close connection between theory and experiment in neutrino astronomy is emphasized.

Nicolao Fornengo (UNITO) Shedding light to the darkness: status of particle dark matter signals

Abstract: About a quarter of the matter/energy content of the Universe is ascribed to the presence of dark matter, for which one of the most plausible solutions is that it is composed by a new, yet undiscovered, fundamental particle-physics state (the other possible solution being a modification of the fundamental theory of gravity). After reviewing the current results on astrophysical particle dark matter searches, through a full multi-wavelength and multi-messenger approach, I will introduce recent ideas which potentially have the power to more deeply investigate the hypothesis that dark matter is indeed an elementary particle, most notably the study of cross-correlations of electromagnetic signals (from radio to gamma-rays) with gravitational probes (weak lensing observables, like the cosmic shear, or the large scale structure matter distribution).

Giovanni Losurdo  (INFN-FI) Advanced Virgo and the worldwide search for gravitational waves

Abstract: Advanced Virgo is the project to upgrade the Virgo interferometric detector of gravitational waves, with the aim of increasing the number of observable galaxies (and thus the detection rate) by three orders of magnitude. The construction will be completed by the end of 2015. Advanced Virgo will be part of a network with the two Advanced LIGO detectors in the US and GEO HF in Germany. In this talk we discuss the status and plans of the Advanced Virgo project in the framework of the world-wide effort for the direct detection of gravitational waves and the opening of a new observation window on the universe.

Marica Branchesi (UNIURB) Multi-messenger Astronomy with Gravitational Waves and Electromagnetic Radiation

Abstract: The observation of the sky at different wavelengths has revolutionized our view of the Universe. From radio waves to gamma rays, the multi-wavelength astronomy has unveiled new classes of astrophysical sources and contributed to probe their nature and fundamental laws of physics. In the coming years, the upgrading of ground-based gravitational wave detectors, LIGO and Virgo will reach sensitivities that should make possible to detect gravitational wave signals and open a new window to the Universe. The simultaneous availability of space and ground-based electromagnetic telescopes will offer a great opportunity to extend the study of the Universe into a new unexplored multi-messenger context. In this perspective, the value, the challenges and the strategies of joining gravitational waves and electromagnetic observations will be outlined.

Alessandro Nagar (IHES) The effective-one-body (EOB) modelling of coalescing compact binaries

Abstract: I will review the state-of-the-art analytic effective one body (EOB) approach to the general-relativistic two-body dynamics and its completion using numerical relativity (NR) simulations. I will discuss in detail three cases: i) coalescence of (spinning) black hole binaries (BBHs); ii) tidal effects in coalescing neutron star binaries and the EOS-universality at merger; iii) the BBH scattering problem and the determination of the scattering angle in EOB

and NR. I will present several examples about how NR simulations can inform the EOB model so to build a comprehensive EOBNR model of the two-body dynamics and waveforms in general relativity. Implications for gravitational wave data analysis are discussed.

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VENERDI 19 mattina

Gabriele Veneziano (Collège de France, Paris) Aspects of high-energy gravitational scattering

Abstract: I will summarize recent -and not so recent- work dealing with various aspects of high-energy gravitational scattering both at the classical and at the quantum level.

Leonardo Gualtieri (UNIROMA1) Oscillations of stars and black holes in the eve of the advanced gravitational wave detectors.

Abstract: Neutron stars and black holes are characterized by their quasi-normal modes of oscillations, which can be an unique probe to still unexplored regimes of the fundamental interactions. The oscillation modes of a black hole depend on the properties of the black hole spacetime, and thus carry information on the gravitational interaction in its strong-field regime. The oscillation modes of a neutron star depend on the equation of state of the matter at supra-nuclear density composing its core, and thus carry information on the hadronic interaction at extremedensities. Hopefully, in few years gravitational wave detectors will be able to observe oscillations of neutron stars and black holes, testing gravity in the strong-field regime, and shedding light on the behaviour of matter at supra-nuclear densities.

Giulia Ricciardi (UNINA) Reviews on semileptonic B decays

Abstract: A precise knowledge of semi-leptonic decays of B mesons brings several advantages to flavour physics and in particular contribute considerably to the analysis of the unitarity triangle.

They can be studied in the context of the heavy flavour effective theory:

leptonic and hadronic contributions factorize, and we have a better control of the effects of strong interactions. On the experimental side, they are not helicity suppressed as leptonic decays, and the large amount of data due to the Beauty factories, before, and LHCb, now, favour their use as precision tests of the Standard Model. We will review latest

developments.

Paolo Salucci (SISSA) Dark matter without matter.

Abstract: After 30 years from the discovery of an elusive invisible component, diffuse in the whole Universe, our understanding of this phenomenon is still scarce. The well-known idea that a massive particle, namely a colliosion-less non-baryonic one, is the maker of the impressive “dark phenomenology”,  is immediate but in severe difficulty in explaining the latter in its many subtle details. There is a mounting evidence that the dark phenomenon is too complex and too well self-organized to be  just the outcome of the cosmological evolution of the luminous/dark structures of the Universe. While a dark sector in the worldmassive particles  seems to be unsupported by observations and experiments, the possibility of a dark sector in the “world of  forces”,  opens up. To follow this new paradigm is far from simple, in fact, its crucial aspect is that the entire dark phenomenology must be naturally and automatically accounted in that it is exactly the imprint of its existence.

Eugenio Coccia (UNIROMA2) Only a few years before the detection of gravitational waves.

Abstract: Gravitational waves were predicted 99 years ago by Einstein and their detection motivates today about one thousand scientists, analyzing data from existing detectors, constructing new apparatuses and developing advanced technologies and data analysis algorithms. The goal is to confirm the Einstein prediction and to get unique information on gravitational physics at extreme conditions, on compact cosmic objects (black holes and neutron stars)  and on processes in the very early universe.

The status of this field of research will be reviewed, and the global strategy for the gravitational waves detection and the experimental efforts in the next decades will be reported.

Abstracts Session A

Alfio Bonanno

Compatibility of Planck and BICEP2 in asymptotically safe inflation

Abstract:  TBA

Alessandro Tronconi

Signatures of quantum gravity in a Born-Oppenheimer context

Abstract: In the context of canonical quantum gravity (Wheeler-DeWitt equation) we obtain a general equation describing the lowest order corrections coming from the quantum gravitational effects to the spectrum of cosmological perturbations. The scalar and tensor spectra are explicitly estimated for the de Sitter and the slow-roll cases. We find a departure from standard inflationary predictions at large scales and a possible loss of power in the scalar sector at low multipoles.

Giampiero Esposito

Self-dual road to non-commutative gravity with twist: a new perspective

Abstract: The field equations of non-commutative gravity can be obtained by replacing all exterior products by twist-deformed exterior products in the action functional of general relativity and are here studied by requiring that the torsion 2-form should vanish and that the Lorentz-Lie-algebra-valued part of the full connection 1-form should be self-dual. Two other conditions, expressing self-duality of a pair 2-forms occurring in the full curvature 2-form, are also imposed. This leads to a systematic solution strategy, here displayed for the first time, where all parts of the connection 1-form are first evaluated, and hence the full curvature 2-form, and eventually all parts of the tetrad 1-form, when expanded on the basis of γ matrices. By assuming asymptotic expansions which hold up to first order in the non-commutativity matrix in the neighbourhood of the vanishing value for non-commutativity, we find a family of self-dual solutions of the field equations. This is generated by solving first an inhomogeneous wave equation on 1-forms in a classical curved spacetime (which is itself self-dual and solves the vacuum Einstein equations), subject to the Lorenz gauge condition. In particular, when the classical undeformed geometry is Kasner spacetime, the above scheme is fully computable out of solutions of the scalar wave equation in such a Kasner model.

Alessandro  Spallicci

Self-force driven motion in curved spacetime and orbital evolution

Abstract: We adopt the Dirac-Detweiler-Whiting radiative and regular effective field in curved spacetime. Thereby, we derive straightforwardly the first order perturbative correction to the geodesic of the background in a covariant form, for the extreme mass ratio two-body problem. The correction contains the self-force contribution and a background metric dependent term. We then examine radial fall that has historically played a momentous role. It is one of the most classical problems, the solutions of which represent the level of understanding of gravitation in a given epoch. A gedankenexperiment in a modern frame is given by a small body, like a compact star or a solar mass black hole, captured by a supermassive black hole. The mass of the small body itself and the emission of gravitational radiation cause the departure from the geodesic path due to the back-action, that is the self-force. For radial fall, as any other non-adiabatic motion, the instantaneous identity of the radiated energy and the loss of orbital energy cannot be imposed and provide the perturbed trajectory. First, we present the effects due to the self-force computed on the geodesic trajectory in the background field. Compared to the latter trajectory, in the Regge-Wheeler, de Donder (harmonic) and all others smoothly related gauges, a far observer concludes that the self-force pushes inward (not outward) the falling body, with a strength proportional to the mass of the small body for a given large mass; further, the same observer notes an higher value of the maximal coordinate velocity, this value being reached earlier on during infall. Later, we implement a self-consistent approach for which the trajectory is iteratively corrected by the self-force, this time computed on osculating geodesics. Finally, we compare the motion driven by the self-force without and with self-consistent orbital evolution. Subtle differences are noticeable, even if self-force effects have hardly the time to accumulate in such a short orbit.

Emmanuele Battista

Restricted and full 3-body problem in effective field theories of gravity

Abstract:  The quantum corrections to the Newtonian potential obtained in effective field theories of gravity are shown to produce tiny but non-negligible effects. For example, in the restricted problem of 3 bodies, the coordinates of Lagrangian points are slightly modified, and the planetoid is no longer at equal distance from the two bodies of large mass in the configuration of stable equilibrium. For example, in the Sun-Earth-Moon and in the Jupiter-Ganimede-Adrastea systems the difference in the coordinates of Lagrangian points occur at the fifth decimal digit. Furthermore, the gradient of the effective potential obtained by virtue of rotation effects and of the choice of quantum corrections to the Newtonian potential displays departures from the case of Newtonian theory, no matter which signs are chosen in the evaluation of quantum corrections. The equations of the full 3-body problem are also under investigation in the presence of such quantum corrections, and we have developed detailed formulae for the integration of variational equations for given initial conditions.”

Luca Lusanna

Einstein’s gravity: Hamiltonian version of curvature tensors and Dirac observables

Abstract: The Hamiltonian version of the Riemann and Weyl curvature tensors and of the Ricci and Weyl scalars of the Newman-Penrose approach are given in the framework of ADM tetrad gravity. Then the status of the search of the Dirac observables of GR is reviewed with some comments on its canonical quantization.

[1] L. Lusanna and M.Villani, Hamiltonian Expression of Curvature Tensors in the York Canonical Basis: I) The Riemann Tensor and Ricci Scalars, (e-Print: arXiv:1401.1370)

[2] L. Lusanna and M.Villani,  Hamiltonian Expression of Curvature Tensors in the York Canonical Basis: II) The Weyl Tensor, Weyl Scalars, the Weyl Eigenvalues and the Problem of the Observables of the Gravitational Field, (e-Print: arXiv:1401.1375) to appear in Int.J.Geom.Met.Mod.Phys.

Simon Garruto

Extended Gravity

Abstract: We shall show equivalence between Palatini-$f(\calR)$ theories and Brans-Dicke (BD) theories at the level of action principles in generic dimension with generic matter coupling. We do that by introducing the Helmholtz Lagrangian associated to Palatini-$f(\calR)$ theory and then performing frame transformations in order to recover Einstein frame and Brans-Dicke frame. This clarifies the relation among different formulations and the transformations among different frames. Additionally, it defines a formulation {\it a l\’a Palatini} for the Brans-Dicke theory which is dynamically equivalent to metric BD (unlike the standard Palatini-formulation of metric BD theory which are {\it not} dynamically equivalent). In conclusion we discuss interpretation of extended theories of gravitation and perspectives.

Francesco Becattini

Local thermodynamical equilibrium and the β frame for a quantum relativistic fluid

Abstract: We discuss the concept of local thermodynamical equilibrium in relativistic hydrodynamics in a quantum statistical framework without an underlying kinetic description suitable for strongly interacting fluids. We show that the appropriate definition of local equilibrium naturally leads to the introduction of a relativistic hydrodynamical frame in which the four-velocity vector is the one of a relativistic thermometer at equilibrium with the fluid, parallel to the inverse temperature four- vector β, which then becomes a primary quantity. We show that this frame is the most appropriate for the expansion of stress-energy tensor from local thermodynamical equilibrium and that therein the local laws of thermodynamics take on their simplest form. We discuss the difference between the β frame and Landau frame and present an instance where they differ.

Gabriele Gionti

Comparing two double string theory actions

Abstract: It is fairly well known that for bosonic string theory coupled with B field, in which the background metric G and B are constant, a dual Lagrangian can be defined. Therefore, in principle, it seems possible to introduce a doubled string theory action in which each string coordinate and its dual are introduced as independent variables in the same Lagrangian, which exhibits an O(D,D) invariance. This procedure was suggested by the observation that, once compactified on Tori, there exists the T(oroidal)-Duality symmetry of the mass spectrum, at the level of the solution of the equations of motion, by virtue of the fact that momentum modes and winding modes are interchangeable as well as their compactification Radii (R to 1/R). This and others observations seems to suggest that, for the compact dimensions, String Theory degrees of freedom need to be doubled since the right phase space is made out of each string coordinates and its corresponding dual.

I confront and contrast two doubled string theory actions: the Tseytlin and the Hull actions which are, respectively, non-Lorentz and Lorentz invariant. The Tseytlin action has second class constraints, while the Hull action do not have Dirac’s constraints but a self-duality condition is imposed to reduce the degree of freedom of the theory to the physical one. Treating this as gauge fixing condition, it generates second class constraints. In each case, a Dirac constraint analysis and quantization is done. It is shown that the two actions can be derived one from the other by using the Pasti-Tonin-Sorokin method. Quantizing the free theory, via the Dirac’s brackets, shows that the theory is non-commutative at Quantum Level. Since closed strings carry the gravitational mode (gravitons), it is believed that the effective gravitational action derived from this quantum theory in interaction (via n-point string amplitudes in which T-Dualilty invariant graviton vertex operators are used) should be an extended theory of gravity different from the known effective theory of gravity coming from ordinary string theory.

Bianca Letizia Cerchiai

The geometry of exceptional Lie groups, supergravity and integrable models

Abstract: For the last several years I have been pursuing a project of mapping the geometry of the exceptional Lie groups G2, F4, E6, E7, E8 and how they act as symmetries of different physical models. The method used to construct the corresponding Lie algebras utilizes the Tits’ formula, which exploits the Jordan algebraic structure, arranging the groups into magic squares and highlighting the role of the octonions. I have written a Mathematica program to generate the fundamental smallest-dimensional irreducible representations and the adjoint of each of the exceptional Lie algebras. In order to compute the corresponding group representations at the global level, I have developed a method based solely on the roots, which for the compact form is a generalization of the Euler angles for SU(2), while for the non compact forms it is based on the Iwasawa decomposition.

Then I have applied this knowledge of the geometric structure of the exceptional Lie groups to the investigation of their action on various physical models, such as supergravity, where they describe the electric magnetic duality of the theory as well as the stabilizer of the scalar manifolds and of certain black hole orbits under the attractor mechanism, and integrable systems. Further applications include the study of the structure of amplitudes in supergravity theories, integrable Toda systems, and confinement in gauge field theories with an exceptional Lie group as symmetry.

Alessio Orlandi

Black holes as self-sustained quantum states, and Hawking radiation

Abstract: We investigate the proposal that black holes are Bose-Einstein condensates of gravitons starting form the Klein-Gordon equation for a massless scalar (graviton) field coupled to a static matter current. The (spherically symmetric) classical field reproduces the Newtonian potential generated by the matter source, and the corresponding quantum state is given by a coherent superposition of scalar modes with continuous occupation number. However, if the source is given by the scalar field itself, one finds that (approximately) only one mode is allowed, and the system approaches a Bose-Einstein condensate confined in a region of the size of the Schwarzschild radius. This radius is then shown to correspond to a proper horizon, by means of the horizon wave-function of the quantum system, with an uncertainty in size naturally related to the expected typical energy of Hawking modes. We finally speculate that a phase transition should occur during the gravitational collapse of a star, ideally represented by a static matter current and Newtonian potential, that leads to a black hole, again ideally represented by the Bose-Einstein condensate of gravitons, and suggest an effective order parameter that could be used to investigate this transition.

Andronikos  Paliathanasis

Invariant solutions of the Wheeler-DeWitt equation

Abstract:  We determine the Lie point symmetries of the Wheeler DeWitt (WDW) equation in a general minisuperspace. It is shown that these symmetries are related the conformal algebra of the minisuperspace. We consider the consider the Lagrangian of the field equations and show how the Lie point symmetries of the WDW equation are related with the Noether point symmetries of this Lagrangian. Furthermore we show how the Lie point symmetries can be used in order to determine invariant solutions of the WDW equation.

Cosimo  Stornaiolo

A phenomenological approach to Quantum Cosmology

Abstract:  In this talk I review the formulation of a phenomenological approach to quantum cosmology in terms of tomograms and present the most recent achievements obtained.

Sergio Benenti

Cosmologia Analitica

Abstract:   Una  sistemazione assiomatica dei modelli cosmologici isotropi.

Maria Cristina Paolella

Hojman symmetries in cosmology

Abstract: We present a new approach to find exact solutions for cosmological models. By requiring the existence of a symmetry transformation vector for the equations of motion of the given cosmological model (without using either Lagrangian or Hamiltonian), one can find corresponding Hojman conserved quantities. With the help of these conserved quantities, the analysis of the cosmological model can be simplified. We show that the Hojman conserved quantities exist in the case of minimal and non minimal scalar-tensor models and allow to find exact solutions for the cosmic scale factor and the scalar field.

Francesco Vietri

f(R) gravity in the Kaluza Klein framework : general theory and cosmological models.

Abstract:  The aim of this paper is to study f (R) theories in a multidimensional space-time, focusing  our attention on the Kaluza-Klein’s geometry in five dimensions.  In particular we want to apply our considerations to cosmological scenarios, searching for solutions of  Bianchi’s type in which the four-dimensional manifold evolves in isotropic way while the extra-dimension  has its own dynamic. Under these statements we will investigate the link that an f (R) theory can establish  between the observable universe and the fifth dimension that is not observable.