FR4: Italian and Other Speakers Print E-mail

Speaker: Alexei Aksenov

Title: Kinetics of GRB plasma

Authors: A.G. Aksenov, R. Ruffini, G.V. Vereshchagin

Abstract: Starting from a nonequilibrium configuration we analyse the essential role of the direct and the inverse binary and triple interactions in reaching an asymptotic thermal equilibrium in homogeneous isotropic electron-positron-photon plasma. We focus on the energies in the range 0.1-10 MeV. We integrate numerically integro-partial differential relativistic Boltzmanns equation with the exact QED collisional integrals taking into account all binary and triple interactions in the plasma. We show that first, when detailed balance is reached for all binary interactions on a timescale t_{k}≲10⁻¹⁴sec, photons and electron-positron pairs establish kinetic equilibrium. Successively, when triple interactions fulfill the detailed balance on a timescale t_{eq}≲10⁻¹²sec, the plasma reaches thermal equilibrium. It is shown that neglecting the inverse triple interactions prevents reaching thermal equilibrium. Our results obtained in the theoretical physics domain find also applications in astrophysics and cosmology.

Speaker: Lorenzo Amati

Title: Spectral-energy correlations in GRB: recent updates and implications

Author: L. Amati

Abstract: The correlation between the photon energy at which the redshift corrected nuFnu spectrum peaks (hence called "peak energy", Ep,i) and the isotropic equivalent radiated energy (Eiso), is one of the most intriguing and debated observational evidences in Gamma- Ray Bursts (GRB) astrophysics. I present the updated Ep,i - Eiso correlation and discuss its main implications for the physics and geometry of the GRB emission, with particular emphasis on the properties of Swift GRBs and the location in the Ep,i-Eiso plane of sub-energetic long GRBs, GRB/SN events, short GRBs and the recently discovered sub-class of long GRBs without association with a hypernova.

Speakers: Marco Valerio Battisti

Title: Quantum features of the FRW singularity from a generalized uncertainty principle point of view

Authors: M.V.Battisti and G.Montani

Abstract: The quantum dynamics of the Friedmann-Robertson-Walker Universe with a massless scalar field is analyzed in the Generalized Uncertainty Principle framework. The system is quantized using an extended formulation of the Heisenberg algebra and the scalar field is regarded as a relational clock for the dynamics. The behavior of the Universe near the classical singularity is analyzed via the motion of suitable wave packets. Such a dynamics appears to be non-singular, but no evidence for a quantum bounce arises.

Speakers: Volodia Belinski and Marco Pizzi

Title: The fields of a naked singularity and black hole in mutual equilibrium

Authors: G. Alekseev, V. Belinski, A. Paolino, M. Pizzi

Abstract: An asymptotically flat static solution of Einstein-Maxwell equations which describes the field of two Reissner - Nordstrom sources in equilibrium is presented. It was shown that the equilibrium is possible only when one of the sources is a black hole and another one is a naked singularity. The diagrams of the force lines of electrical field is constructed.

Speaker: Riccardo Benini

Title: Quasi-classical and Quantum properties of the Mixmaster model

Authors: R. Benini, G. Montani

Abstract: In this talk we discuss several properties of the Mixmaster model. The ADM Hamiltonian framework is here adopted, and the dynamics reduced to the physical degrees of freedom. On the quasi-classical level, the Hamilton-Jacobi equation and the mechanical-statistical point of view are discussed in some detail; the operator-ordering to be used on the quantum level is also fixed. A full description of the Schroedinger dynamics is then provided, and the eigenfunctions, the energy levels and the properties of the spectrum are analized both analytically and numerically.

Speaker: Maria Grazia Bernardini

Title: GRB970228 and a class of GRBs with an initial spikelike emission.

Authors: M. G. Bernardini, C. L. Bianco, L. Caito, M. G. Dainotti, R. Guida, R. Ruffini

Abstract: On the basis of the recent understanding of the Swift sources GRB050315 and GRB060218, we return to GRB970228, the first Gamma-Ray Burst (GRB) with detected afterglow. It appears to be the prototype for a recently proposed new class of GRBs with "an occasional softer extended emission lasting tenths of seconds after an initial spikelike emission''. Detailed theoretical computation of the GRB970228 light curves in selected energy bands both for the prompt and the late afterglow emission are presented and compared with observational BeppoSAX data. From our analysis we conclude that, far from forming a new class of sources straddling both short and long bursts, GRB970228 and likely the ones of the above mentioned new class of GRBs are "canonical" GRBs have only one peculiarity: they exploded in a galactic environment, possibly the halo, with a very low value of ISM density.

Speaker: Carlo Luciano Bianco

Title: The "canonical GRB" scenario

Authors: C.L. Bianco, M.G. Bernardini, L. Caito, P. Chardonnet, M.G. Dainotti, R. Guida, R. Ruffini, S.-S. Xue.

Abstract: In our model we define a "canonical GRB" light curve with two sharply different components: the Proper-GRB (P-GRB), emitted when the optically thick fireshell of electron-positron plasma originating the phenomenon reaches transparency, and the afterglow, emitted due to the collision between the remaining optically thin fireshell and the CircumBurst Medium (CBM). Our "canonical GRB" scenario, originating from the gravitational collapse to a black hole, will be presented and discussed.

Speaker: Donato Bini

Title: Strains and axial outflows in the field of a rotating black hole

Author: D. Bini

Abstract: We study the behaviour of an initially spherical bunch of accelerated particles emitted along trajectories parallel to the symmetry axis of a rotating black hole. We find that, under suitable conditions, curvature and inertial strains compete to model the shape of axial outflows of matter contributing to generate jet-like structures. This is a purely kinematical effect which does not account by itself for physical processes underlying the formation of jets.

Speaker: Letizia Caito

Title: GRB060614: a progress report

Authors: L. Caito, M.G. Bernardini, C.L. Bianco, M.G. Dainotti, R. Guida, R. Ruffini

Abstract: GRB 060614 is examined within our theoretical framework. This burst displays unusually an hard-multipeaked emission followed by an extended soft one. The most interesting peculiarity of this source is that, although it lasts about one hundred seconds and its redshift is very low (0.125), there is no evidence of an associated supernova explosion. This source belongs to a distinct alternative GRB class, which has its prototype in GRB 970228.

Speaker: Salvatore Capozziello

Title: Dark Energy and Dark Matter or Extended Gravity?

Author: S. Capozziello

Abstract: Higher order theories of gravity have recently attracted a lot of interest as alternative candidates to explain the observed cosmic acceleration, the flatness of the rotation curves of spiral galaxies and other relevant astrophysical phenomena. Very likely, what we call “dark matter” and “dark energy” are nothing else but signals of the breakdown of General Relativity at large scales. Furthermore, PPN-parameters deduced from Solar System experiments do not exclude, a priori, the possibility that such theories could give small observable effects also at these scales. We review these results giving the basic ingredients of such an approach.

Speaker: Nakia Carlevaro

Title: Study of the Quasi-isotropic Solution near the Cosmological Singularity in Presence of Bulk-Viscosity

Authors: N. Carlevaro, G. Montani

Abstract: This talk is fucused on the analysis of the dynamical behavior of a quasi-isotropic Universe in the presence of a cosmological fluid endowed with bulk viscosity. The viscosity coefficient is expressed as a power-law of the fluid energy density: $\zeta=\zeta_0 \epsilon^{s}$. Then the exponent s is fixed equal to 1/2 as the only case in which viscosity plays a significant role in the singularity physics but it does not dominate the Universe dynamics. Following the line of the work by E.M. Lifshitz and I.M. Khalatnikov, the Einstein and hydrodynamic equations are analyzed up to first and second order in time. As main result is shown that the quasi-isotropic solution exists only for particular values of the bulk viscosity coefficient $\zeta_0$. When the dissipative effects become too relevant, the solution of the LK model can not be addressed. In fact, when $\zeta_0$ approaches a threshold value, the approximation scheme fails and the model becomes non self-consistent. By requiring that the viscosity parameter be under its critical value the behavior of the density contrast is analyzed in presence of bulk viscosity: the evolution, toward the singularity, is damped until remaining constant if $\zeta_0$ assumes its critical value.

Speaker: Sabrina Casanova

Title: The galactic plane survey performed by the Milagro detector

Authors: S. Casanova

Abstract: TBA

Speaker: Valery Chechetkin

Title: Mechanism of explosion of supernovae

Author: V. Chechetkin

Abstract: TBA

Speaker: Christian Cherubini

Title: On the Energetics of the Dyadotorus

Authors: Christian Cherubini, Simonetta Filippi

Abstract: A quasilocal mechanical energy is defined and discussed in the case of a Kerr-Newman black hole. Possible astrophysical implications for QED effects around charged and rotating black holes are discussed.

Speaker: Francesco Cianfrani

Title: Boost symmetry in the Quantum Gravity sector

Author: F. Cianfrani

Abstract: We perform a canonical quantization of gravity in a second-order formulation, taking as configuration variables those describing a 4-bein, not adapted to the space-time splitting. We outline how, neither if we fix the Lorentz frame before quantizing, nor if we perform no gauge fixing at all, is invariance under boost transformations affected by the quantization.

Speaker: Christian Corda

Title: Tuning the stochastic background of gravitational waves with theory and observations

Authors: C. Corda, S. Capozziello and M. F. De Laurentis

Abstract: The stochastic background of gravitational waves (SBGWs) is analyzed wih the auxilium of the WMAP data. We emphasize that, in general, in the literature about the SBGWs, old COBE data are used. After this, we face the problem of how the SBGWs and f(R) gravity theories can be related, showing, vice versa, that a revealed SBGWs could be a powerly probe for a given theory of gravity. In this way, it will also be shown that the conformal treatment of SBGWs can be used to parametrize in a natural way f(R) theories. Because F(R) theories admit, in general, a third scalar polarization of GWs, at the end of the talk the cross-correlation between the Virgo interferometer and the Minigrail resonant sphere for the potential detection of a scalar SBGWs in the massless case is shown.

Speaker: Stefano Covino

Title: Direct Measurement of the Initial Lorentz Gamma Factor for Gamma-Ray Burst Afterglows

Author: S. Covino

Abstract: Gamma-ray burst are thought to be produced by highly relativistic outflows. Although upper and lower limits for the outflow initial Lorentz factor are available, observational efforts to derive a direct determination of this fundamental parameter have so far failed or provided ambiguous results. As a matter of fact, the shape of the early-time afterglow light curve is strongly sensitive on the Gamma Lorentz Factor which determines the time of the afterglow peak, i.e. when the outflow and the shocked circumburst material share a comparable amount of energy. We now comment early-time observations of the near-infrared afterglows of GRB 060418 and GRB 060607A performed by the REM robotic telescope. For both events, the afterglow peak was singled out and allowed us to determine the initial fireball Lorentz, Γ ∼ 400.

Speaker: Maria Giovanna Dainotti

Title: GRB060218 and GRBs associated with Supernovae Ib/c

Authors: M.G. Dainotti, M.G. Bernardini, C.L. Bianco, L. Caito, R. Guida, R. Ruffini

Abstract: The Swift satellite has given continuous data in the range 0.3-150 keV from 0 s to 106 s for GRB060218 associated with SN 2006aj. These data offer the unprecedented opportunity to probe theoretical models for Gamma-Ray Bursts (GRBs) connected with Supernovae (SNe). We fit the entire set of data of this extremely long duration GRB (T_{90} ~ 2100 s), including the prompt emission. The baryon loading B = 10^{-2} coincides with the upper limit for the dynamical stability of the electron-positron-baryon plasma generating the GRB. Such an extreme value is here encountered for the first time. The effective CircumBurst Medium (CBM) density shows a radial dependence n_{cbm} \propto r^{-\alpha}, with \alpha \simeq 1, and ranges between 10^{-6} < n_{cbm} < 1 particle/cm3. Such a low effective CBM density, essential to explain the high T_{90} value, is interpreted as due to a fragmentation in the accelerated baryonic shell. This fragmentation, consistent with the instabilities implied by a baryon loading B = 10^{-2}, leads to an actual CBM density n_{cbm}^{act} \simeq 1.0 particle/cm3. Analogies with the fragmented density of the Novae are outlined. The smallest possible black hole, formed by the gravitational collapse of a neutron star in a binary system, appears to explain the especially low energetics of these GRBs associated with SNe.

Speaker: Massimo Della Valle

Title: Supernovae and GRBs: when stars fade in the shade

Author: M. Della Valle

Abstract: In this talk I'll shortly review (with an observational perspective) the "status" of the Supernova-GRB connection.

Speaker: Ruben Farinelli

Title: Transition layers around compact objects (black holes and neutron stars): Evolution of their hydrodynamical structure and size as a function of the mass accretion rate

Author: Ruben Farinelli

Abstract: Accretion from a Keplerian disk into a sub-Keplerian rotating central object, which can be either a black hole (BH) or a neutron star (NS), should produce a transition layer (TL) region, whose radial extension strongly anti-correlates with an effective Reynolds (Re) number of the flow, related to the mass accretion rate. The TL main characteristics are determined by a set of physical quantities, such as Re-number, the mass accretion rate, the electron temperature of the infalling flow, the strength of the magnetic field and the viscosity. We present numerical results on the structure of the TL obtained from a full magneto-hydrodinamical treatment of the problem. We show that at low mass accretion rates (dm/dt << 1) the TL radial profile of the velocity field is characterized by a freefall-like behaviour in the innermost part of the region. On the other hand, as dm/dt increases, the qualitative behaviour of the radial velocity field is completely different for the NS and BH cases. The main reason for this difference is not, as it was previously expected, due to the direct radiation pressure coming from the NS (which is absent in BH) but it is due to the fact that the firm surface of the NS acts as a mirror, reflecting the radiation produced by release of gravito-kinetic energy in the TL. As a consequence of this fundamental difference, in systems hosting a NS the TL layer height-scale must increase as dm/dt increases, to allow matter to reach the NS firm surface. On the contrary, the radiation pressure gradient finally stops the infalling material. This effect is not present in the case of BH, where matter flows within the event horizon.

Speaker: Filippo Frontera

Title: The Cosmic X-ray background at the peak of its emission: new results and implications

Author: F. Frontera

Abstract: I will report on an accurate measurement of the CXB in the 15--50 keV range performed with the PDS instrument aboard the BeppoSAX satellite. Our measurement is the best available after that obtained over 25 years ago with the first High Energy Astronomical Observatory satellite mission (HEAO--1), that provided a CXB intensity well below the extrapolation of several lower energy measurements recently performed with focusing telescopes. For this reason it is questioned. I will discuss our results and its astrophysical implications.

Speaker: Walter Greiner

Title: Supercritical fields and short living giant atoms

Author: W. Greiner

Abstract: I outline the basics and also discuss the recent ideas of testing supercriticality in collisions of the type U+Cm where we expect large sticking times of the giant atoms.

Speaker: Dafne Guetta

Title: Selection effects in GRB redshift determination

Author: D. Guetta

Abstract: TBA

Speaker: Roberto Guida

Title: GRB050315 and the Amati relation

Authors: R. Guida, M.G. Bernardini, C.L. Bianco, L. Caito, M.G. Dainotti, R. Ruffini

Abstract: The existence of the phenomenological Amati relation is discussed within our theoretical GRB model. In this framework we perform a reanalysis of GRB050315, a canonical GRB which follow this relation. Possible reasons for some of the outliers of this relation are given.

Speaker: Vahe Gurzadyan

Title: Dark energy, vacuum fluctuations vs observational data

Author: Vahe Gurzadyan

Abstract: The correlations in the cosmic microwave background radiation pixelized temeperature maps will be discussed with the determination of the excursion sets and their properties.

Speaker: Hagen Kleinert

Title: The Many Uses of Mutivalued Fields in Theoretical Physics

Author: H. Kleinert

Abstract: I show that multivalued fields, i.e., which do not possess commuting derivatives, play an essential role in understanding gauge theories of many physical systems such as superfluids, superconductivity, quark confinement. They also provide us with a method to predict the physical laws in curved space from those in flat space.

Speaker: Orchidea Maria Lecian

Title: Scalar-tensor analysis of an exponential Lagrangian for the Gravitational Field

Authors: Orchidea Maria Lecian, Giovanni Montani

Abstract: Within the scheme of modified gravity, an exponential Lagrangian density will be considered, and the corresponding scalar-tensor description will be addressed for both positive and negative values of the cosmological constant. For negative values of the cosmological term, the potential of the scalar field exhibits a minimum, around which scalar-field equations can be linearized. The study of the deSitter regime shows that a comparison with the modified-gravity description is possible in an off-shell region, i.e., in a region where the classical equivalence between the two formulations is not fulfilled. Furthermore, despite the negative cosmological constant, an accelerating deSitter phase is predicted in the region where the series expansion of the exponential term does not hold. For positive values of the cosmological constant, the quantum regime is analyzed within the framework of Loop Quantum Cosmology.

Speaker: Luca Lusanna

Title: The York Map and the Role of Non-Inertial Frames in the Geometrical View of the Gravitational Field

Author: L. Lusanna

Abstract: The role of non-inertial frames in a class of models of general relativity is clarified by means of Dirac's theory of constraints. The identification of a York canonical basis allows to give the interpretation of the gauge variables as generalized inertial effects and to identify the Dirac observables of the gravitational field with generalized tidal effects. York time is the gauge variable controlling the clock synchronization convention. Differently from special relativity, the instantaneous 3-spaces are dynamically determined and at least part of dark matter could have inertial origin.

Speaker: Luis Juracy Rangel Lemos

Title: TBA

Authors: Luis Juracy Rangel Lemos, Sabrina Casanova

Abstract: High energy protons predicted in the fireshell scenario for Gamma Ray Bursts (GRBs) scatter off the interstellar medium close to the GRBs. The pions produced in the inelastic pp collision will further decay in two high energy gamma rays. A distribution for the resulting pions and gamma rays are given. The pion distribution predicted by the Fermi model is here compared with the experimental measurements and with recent models for the inelastic pp interactions.

Speaker: Costantino Sigismondi

Title: Solar radius in 2006

Author: C. Sigismondi

Abstract: A program of recovering solar diameter from eclipse is tested with 2006 data (Egypt-total eclipse and French Guyana-annular eclipse). Errors in UTC timing and lunar and solar ephemerides are discussed in order to detect diameter's fluctuations and oblateness parameter.

Title: Perturbations to Astronomical Tides in Pescara Seaport

Author: C. Sigismondi, G. Bernardini

Abstract: Fast Fourier Transform of sea levels measured each second with an ultrasonic distance sensor in Pescara Seaport show high frequency (less than 1 hour) long waves. A comparison with nearby seaports is made. Those seiches, which are the fastest gravity waves, with amplitudes occasionally up to 40 cm, appear to be typical signatures for central Adriatic sea level.

Speaker: Lev Titarchuk

Title: On the Nature of X-ray Power and Energy Spectra from Black Holes and Neutron Stars. A New Method of Black Hole Mass Determination

Author: Lev Titarchuk

Abstract: We present a new paradigm to interpret the observed X-ray spectral/temporal characteristics of accreting galactic black hole (BH) and neutron star (NS)systems. This paradigm is based on a generic models of spectral and power spectra formations which we have developed over the last decade. The paradigm provides a physical picture for the primary region of Comptonization close to the central object. It relates the dynamical evolution of this region to the spectral state of the source and identifies the mechanisms responsible for many of the temporal and spectra features observed. This model has successfully explained the observed correlations between low QPO frequency and photon index reported in a number of Galactic BH sources. Furthermore, the model shows how the mass of the central object can be obtained from these correlations and provides a new way to use their high frequency properties to distinguish between NSs and BHs. To date the development of the paradigm and its application to the study of BHs and NSs is documented in more than 60 papers published in leading refereed journals. The overall aim of this study is to arrive at a synthesis of the information contained in timing and spectral data that explains and forms a comprehensive understanding of compact accreting objects and helps to guide the planning of future observations and missions.

Speaker: Gregory Vereshchagin

Title: Pair creation and plasma oscillations

Authors: R. Ruffini, G.V. Vereshchagin, S.-S. Xue

Abstract: We evidence the existence of plasma oscillations of electrons-positron pairs created by the vacuum polarization in an uniform electric field with E < Ec. Our general treatment, encompassing also the traditional, well studied case of E > Ec , shows the existence in both cases of a maximum Lorentz factor acquired by electrons and positrons and allows determination of the a maximal length of oscillation. We quantitatively estimate how plasma oscillations reduce the rate of pair creation and increase the time scale of the pair production. These results are particularly relevant in view of the experimental progress in approaching the field strengths E < Ec.

Speaker: She-Sheng Xue

Title: Photoproduction in degenerate electron systems by Onset of Magnetic Field

Authors: Hagen Kleinert and She-Sheng Xue

Abstract: The energy bands of a semiconductor are lowered by an external magnetic field. When a field is switched on, the straight-line trajectories near the top of the occupied valence band are curved into Landau orbits and Bremsstrahlung is emitted until the electrons have settled in their final Fermi distribution. We calculate the radiated energy, which should be experimentally detectable, and suggest that a semiconductor can be cooled by an oscillating magnetic field.

Speaker: Alexandar F. Zakharov

Title: Dark matter and dark energy of alternative theories of gravity and cosmology

Authors: Alexandar F. Zakharov, F. De Paolis, A. A. Nucita, G. Ingrosso

Abstract: In the last years generalizations of the classical Einstein-Hilbert Lagrangian were introduced to explain observational phenomena such as the accelerating Universe, large-scale structure, rotation curves etc. Usually, these approaches were successful like the standard general relativity (with dark matter and dark energy). Recently, gravitational microlensing has been investigated in the framework of the weak field limit of fourth order gravity theory. However, solar system data (i.e. planetary periods and light bending) can be used to put strong constraints on the parameters of this class of gravity theories. We find that these parameters must be very close to those corresponding to the Newtonian limit of the theory. We also discuss constraints on conformal cosmological models from from cosmological SNe Ia data.

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