Home
 IK10: Italian and Other Speakers
 Speaker: George Alekseev Title: Interaction of black holes with external gravitational and electromagnetic fields Author: George Alekseev Abstract: The so called "monodromy transform" approach, developed by the author, provides a unified general base for construction of solutions with commuting space-time symmetries for Einstein, Einstein - Maxwell and some other field equations in General Relativity as well as for the effective actions of some string gravity models. In all cases, this approach gave rise to a reformulation of the symmetry reduced nonlinear field equations in terms of a system of linear singular integral equations on the spectral plane which admit, in particular, formulation of principal algorithms for solution of initial and characteristic initial value problems and an explicit construction of infinite hierarchies of exact solutions with (finitely) arbitrary number of free parameters. In this communication, some general features of this approach will be outlined. Among different possible applications of this approach (stationary axisymmetric fields, nonlinear interaction of various types of gravitational and electromagnetic waves, dynamics of inhomogeneous cosmological models), we concentrate now on the constructing of solutions for black holes interacting with external gravitational and electromagnetic fields. We present in a simple explicit form the solutions for a Schwarzshild and Kerr black holes immersed in the external asymptotically homogeneous magnetic fields and the solution for a Reissner - Nordstr\"om black hole accelerated by asymptotically homogeneous electric field and describe some related features of the black hole dynamics. Speaker: Lorenzo Amati Title: The correlation between peak photon energy and radiated energy in GRB Author: Lorenzo 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. Speaker: Volodia Belinski Title: On the equilibrium between charged masses in General Relativity Authors: G. Alekseev, V. Belinski Abstract: An asymptotically flat static solution of Einstein-Maxwell equations which describes the field of two Reissner - Nordstrom sources in equilibrium is presented. Very simple analytical forms were found for the solution as well as for the equilibrium condition which guarantees the absence of any struts on the symmetry axis. This condition shows that the equilibrium is not possible for two black holes or for two naked singularities. However, in the case when one of the sources is a black hole and another one is a naked singularity, the equilibrium is possible at some distance separating the sources. It is interesting that for appropriately chosen parameters even a neutral Schwarzschild black hole can be "suspended" freely in the field of a naked singularity, which phenomenon is due to the repulsive forces produced by a naked singularity.  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 CircumBurst Medium (CBM) 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: Connecting vectors and relativistic strains Authors: Donato Bini, Andrea Geralico Abstract: The definition of relative accelerations and strains among a set of comoving particles is studied in connection with the geometric properties of the frame adapted to a "fiducial observer". A relativistically complete and correct definition of strains is given taking into account the transport law of the chosen spatial triad along the observer's congruence. The celebrated idea of Szekeres' compass of inertia is then generalized, contributing also to the theory of relativistic gravity gradiometer. The observer-dependent form of our analysis might be very useful when thinking about general relativistic tests on space stations orbiting compact objects like black holes and also in other interesting gravitational situations. 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: Pascal Chardonnet Title: TBA Authors: TBA Abstract: TBA Speaker: Christian Cherubini Title: Extracting energy from acoustic black holes Authors: Christian Cherubini, Simonetta Filippi Abstract: Analog curved spacetimes emerging from non relativistic consensed matter systems can be very useful to understand General Relativistic effects. Scattering problems on rotating acoustic black holes in particular can be studied in the time domain by using numerical methods only. In order to obtain high quality results in simulations, tools developed by numerical relativists in the case of rotating Kerr black holes must be adopted, i.e. constrained evolution schemes for strongly symmetric and non symmetric hyperbolic systems of PDEs and excision techniques in horizon penetrating coordinates. In this talk such a program is presented and analogies between astrophysical and acoustic black holes are discussed in relation with Press and Teukolsky's relativistic black hole bomb". More in detail we develop an unstability which allows to extract energy from the central engine of the system by imposing a mirror at some distance from the central object. Speaker: Alessandro Chieffi Title: The massive stars evolution: the H and He burning phases Authors: Alessandro Chieffi Abstract: I will review the properties of massive stars in the H and He burning phases together to the influence of mass loss on the properties of these stars Speaker: Francesco Cianfrani Title: Particles and fields within a unification scheme Authors: Francesco Cianfrani, Giovanni Montani Abstract: we discuss properties of particles and fields in a multi-dimensional space-time, where the geometrization of gauge interactions can be performed. For instance, in a 5-dimensional Kaluza-Klein manifold we argue that the motion of charged spinning bodies is obtain in a Papapetrou-like formulation. For what concern spinors, we outline how the gauge coupling can be recognized by a proper dependence on extra-coordinates and by the dimensional reduction procedure. Finally applications to the Electro-Weak model are presented. 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: Roberto De Pietri Title: Numerical 3D simulation of dynamical instabilities of rotating relativistic self gravitating polytropic mater Author: R. De Pietri. Abstract: We present results on dynamical instabilities in rapidly rotating polytropic self-gravitating matter. Using 3D numerical simulations in full General Relativity, we analyse the effect of over-criticality on the development of the bar-mode instability, the effects of compactness on the position of the threshold for the onset of the dynamical bar-mode instability and the appearance of other dynamical non-axisymmetric instabilities beside the bar-mode one. By using an extrapolation technique we accurately determine the threshold for a wide range of compactnesses. Our calculations of the threshold are in good agreement with the Newtonian prediction and improve the previous post-Newtonian estimates. In addition, we find that for stars with sufficiently large mass and compactness, the m=3 deformation is the fastest growing one. For all of the models considered, the non-axisymmetric instability is suppressed on a dynamical timescale with an m=1 deformation dominating the final stages of the instability. The presented results suggest that an odd-mode deformation represents a general and late-time feature of non-axisymmetric dynamical instabilities both in full General Relativity and in Newtonian gravity. Speaker: Simonetta Filippi Title: Generalized axisymmetric models of self-gravitating systems Authors: Simonetta Filippi, Christian Cherubini, Remo Ruffini, Alonso Sepulveda Abstract: Non-homogeneous axisymmetric models of self-gravitating systems are discussed by using functional methods and integrability conditions are established in the case of barotropic and baroclinic configurations. For various velocity profiles, in the case of polytropic index n=1, analytic approaches are tempted by using the matching techinque developed by Williams in 1987 in order to find the density profile and in particular the configuration's surface. Speaker: Federico Fraschetti Title: TBA Authors: TBA Abstract: TBA Speaker: Andrea Geralico Title: Perturbations of a Reissner-Nordstrom black hole by a charged massive particle at rest Authors: Andrea Geralico, Donato Bini, Remo Ruffini Abstract: A new perturbative solution describing a two-body system consisting of a Reissner-Nordstrom black hole and a charged massive particle at rest is presented. The general properties of the perturbed metric, completely reconstructed analytically, are discussed. The perturbed electromagnetic field is also analyzed by plotting the associated lines of force. 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: Cristiano Guidorzi Title: A direct link between the prompt and the late multi-band afterglow of a=20 gamma-ray burst: the case of GRB 070311 Author: Cristiano Guidorzi Abstract: I present prompt gamma-ray, early IR/optical, late optical and X-ray observations of the peculiar FRED GRB 070311 discovered by INTEGRAL. In particular the H-band light curve taken by REM covers the tail of the gamma-ray prompt emission and shows two peaks, the second of which coincides with an enhancement in the gamma-ray flux. Remarkably the late optical and X-ray afterglow underwent a major rebrightening between 3x10^4 s and 2x10^5 s after the burst with an X-ray fluence comparable with that of the prompt emission. Its time profile can be described as the combination of a time-rescaled version of the prompt gamma-ray pulse and an underlying power law. This supports a common origin for both prompt and late X-ray/optical afterglow rebrightening of GRB 070311 within the external shock scenario. In particular, the late rebrightening would be the result of a refreshed shock due to a second slower shell emitted after the first: the former may have generated the GRB itself, while the latter caught up with the fireball blastwave at late times and produced the rebrightening. Speaker: Vahe Gurzadyan Author: Vahe Gurzadyan Title: On the dark energy and vacuum fluctuations Abstract: The value of the dark energy due to relevant vacuum fluctuations will be discussed along with its redshift dependence in comparison with available observational data.  Speaker: Roy Kerr Author: Roy Kerr Title: The interior of black holes Abstract: TBA Speaker: Massimiliano Lattanzi Author: Massimiliano Lattanzi Title: Decaying majoron dark matter and neutrino masses Abstract: Neutrino masses may arise from spontaneous breaking of ungauged lepton number. Due to quantum gravity effects the associated Goldstone boson - the majoron - will pick up a mass. We determine the lifetime and mass required by cosmic microwave background observations so that the massive majoron provides the observed dark matter of the Universe. The majoron decaying dark matter scenario fits nicely in models where neutrino masses arise a la seesaw, and may lead to other possible cosmological implications. Speaker: Orchidea Maria Lecian Title: The role of torsion in fermion interactions Authors: Orchidea Maria Lecian, Giovanni Montani Abstract: The different behaviors of vectors and spinors under local space-time transformations allow one to formulate a gauge theory of the Lorentz group, where suitable bein projections of the contortion field are identified with Lorentz connections. As a result, a propagating torsion field with the spin-current density as a source is predicted from Yang-Mills equations. Both first and second order approaches are developed, and a comparison with PGT is established. Speaker: Vanessa Mangano Title: Swift observations of GRB 060614 Author: Vanessa Mangano Abstract: GRB 060614 is a remarkable nearby GRB (z=0.125) observed by Swift with puzzling properties, which challenge current progenitor models: the lack of any bright supernova down to very strict limits and the vanishing spectral lags are typical of short GRBs, strikingly at odds with the long (102 s) duration of this event. However, the burst presents optical, UV and X-ray afterglows in remarkable agreement with standard jetted fireball models. In particular, spectral analysis of BAT and XRT data in the overlap time interval and after, show that the peak energy of the burst decays and crosses the XRT energy band within 500 s from the trigger. The afterglow shows the first jet break simultaneously detected in optical, UV and X-rays. Moreover, the UVOT light curves possibly show evidence of the passage of the injection frequency across the optical band between 10 and 30 ks from the trigger. Speaker: Michael Rotondo Title: Electrodynamics for neutron stars: generalized analytical solutions Authors: Michael Rotondo, Vladimir Popov, Remo Ruffini, She-Sheng Xue Abstract: The relativistic Thomas-Fermi equation and energetic equation of beta equilibrium are used to describe degenerate neutrons, protons and electrons in neutron stars. The analytical approach is adopted to found equilibrium configurations which obey the global neutrality. Several generalized exact solutions are presented and discussed. Speaker: Kjell Rosquist Title: Gravitationally induced electromagnetic effects Author: Kjell Rosquist Abstract: We discuss the relation between the gravitational and electromagnetic fields as governed by the Einstein-Maxwell field equations. It is emphasized that the tendency of the gravitational field to induce electromagnetic effects increases as the size of the system goes down. This is because the charge-to-mass ratio Q/M is typically larger in smaller systems. For most astrophysical systems, Q/M is << 1 while for a Millikan oil drop, Q/M ~ 10^6. Going all the way down to elementary particles, the value for the electron is Q/M ~ 10^21. For subatomic systems there is an additional phenomenon which comes into play. This is the fact that the gravitational field, according to general relativity, tends to become dominated by the spin at distances of the order of the Compton wavelength. The relevant quantity which governs this behavior is the ratio S/M^2 where S is the (spin) angular momentum. For an electron S/M^2 ~ 10^44. Therefore, the gravitational field becomes dominated by gravitomagnetic effects in the subatomic domain. To analyze this situation we use the asymptotic structure in the form of the multipole fields. Some important consequences for the electromagnetic fields of charged particles with spin are pointed out. In particular, the gravitational field may induce corrections to the Coulomb field which can be tested experimentally. Speaker: Remo Ruffini Title: The physics of GRBs Authors: Remo Ruffini, Maria Grazia Bernardini, Carlo Luciano Bianco, Donato Bini, Letizia Caito, Pascal Chardonnet, Maria Giovanna Dainotti, Federico Fraschetti, Andrea Geralico, Roberto Guida, Michael Rotondo, Gregory V. Vereshchagin, She-Sheng Xue. Abstract: The fundamental role of recent astrophysical observations pertaining to GRBs are shown to promote a revival of fundamental issues in GRBs, in black hole physics and in relativistic quantum field theory. The possibility to observe for the first time the process of vacuum polarization at the energy scale of 10^54 ergs is presented. The profound consequences of the results on the physics of neutron stars and on black hole electrodynamics are presented and discussed. Some new perspectives in relativistic quantum field theory are as well outlined. Speaker: Costantino Sigismondi Title: Relativistic Corrections to Lunar Occultations Author: Costantino Sigismondi Abstract: Relativistic light bending by solar gravitational field affects timings of lunar occultations. The example of Venus occultation of June 18, 2007 is discussed and preliminary observational results are compared with JPL and IMCCE ephemerides. Speaker: Leonardo Testi Title: Science with ALMA: the cool side of the Universe Author: Leonardo Testi Abstract: ALMA is going to be the world leading observatory at millimeter wavelengths in the coming decades, the project is now in its main construction phase with early science activities e3nvisaged for 2010 and full science operations for 2012. In this talk I will review the concept, science goals and construction status of ALMA. Speaker: Gregory V. Vereshchagin Title: On vacuum polarization and plasma oscillations Authors: Gregory V. Vereshchagin, Remo Ruffini, She-Sheng Xue Abstract: Vacuum polarization in a strong electric field results in electron-positron pair creation. We study collective effects in the pair plasma emerged in this way, including vacuum polarization itself, back-reaction of the plasma on initial electric field and plasma oscillations. With this goal we consider energy conservation and electromagnetic field equations, comparing these to the traditional Vlasov-Boltzmann treatment. We conclude that under certain conditions plasma oscillations may occur in a weak electric field. We present single equation describing these oscillations in the weak field limit. Time and length scales of oscillations are discussed. Speaker: She-Sheng Xue Title: Energetically favorable electrodynamical configuration for neutron stars Author: She-Sheng Xue, Vladimir Popov, Michael Rotondo, Remo Ruffini Abstract: We use the relativistic Thomas Fermi equation and energetic equation of beta equilibrium to describe degenerate neutrons, protons and electrons in neutron stars. An analytical approach are adopted to analyze these equations, implemented with the global neutrality: total proton and electron numbers are the same. We find a unique configuration of protons and electrons distributions which has an critical electric field at the surface of neutron stars. It is shown that such an electrodynamic configuration is (i) energetically stable against the Coulomb repulsion; and (ii) energetically favorable, against the configuration which obeys the local neutrality: proton and electron number-densities are the same in neutron stars.

 Visitors: 137056244
 We have 1 guest online