Amati Lorenzo

Institute: INAF IASF Bologna

Title: Gamma-ray Bursts: open issues and recent highlights

Belinski Vladimir

Institute: ICRANet 

Bernardini Maria Grazia

Institute: University of Rome “Sapienza”

Title: A complete analysis of GRB060607A within the fireshell model: prompt emission, X-ray flares and late afterglow phase

Abstract: GRB060607A is a very distant ($z=3.082$) and energetic event ($E_{iso}\sim 10^{53}$ erg). Its main peculiarity is that the peak of the near-infrared (NIR) afterglow has been observed with the REM robotic telescope and, interpreting it as the afterglow onset as predicted by the fireball forward shock model, it is possible to infer the initial Lorentz gamma factor of the emitting system. We analyze GRB060607A within the fireshell model. We deal only with the Swift BAT and XRT observations, that are the basic contribution to the GRB emission and that are neglected in the current literature. The numerical modelling of the fireshell dynamics allows to calculate all its characteristic quantities, in particular the exact value of the Lorentz gamma factor at the tranparency. We show that the observed temporal variability of the prompt emission can be produced by the interaction of the fireshell with overdense CircumBurst Medium (CBM) clumps. The light curves obtained are well in agreement with the observations in all the \emph{Swift} BAT energy bands as well as the time-integrated spectrum in different time intervals. The flares observed in the decaying phase of the X-ray afterglow are also produced by the interaction of the fireshell with CBM clumps, but in a region in which the typical dimensions of the clumps are smaller than the visible area of the fireshell and the peak energy lies in the X-ray band due to the hard-to-soft evolution. We show that it is possible to obtain flares with $\delta t/t_{tot}$ compatible with the observations accounting for the three-dimensional structure of the CBM clumps. As pointed out by the observations, the remaining part of the X-ray light curve and the NIR emission probably have a different origin than the prompt emission. We sketch a possible scenario in which this second component arises from the injection of slower material into the fireshell: this produces also a modification in the comoving thermal spectrum which explains both the observed X-ray and NIR emission.

Bianco Carlo

Institute: University of Rome “Sapienza”

Title: The fireshell equations of motion

Abstract: The Fireshell originating a Gamma-Ray Burst (GRB) encompasses an optically thick regime followed by an optically thin one. In the first one the fireshell self-accelerates from a Lorentz gamma factor equal to 1 all the way to 200-300. The physics of this system is based on the continuous annihilation of electron-positron pairs in an optically thick e+e- plasma with a small baryon loading. In the following regime, the optically thin fireshell, composed by the baryons left over after the transparency point, ballistically expands into the CircumBurst Medium (CBM). The kinematics and dynamics of the fireshell during both regimes will be analyzed, and a comparison with corresponding treatments in the current literature will be presented. Particular attention will be devoted to the analysis of the transparency point, since it represents both the final outcome of the optically thick regime and the initial condition of the optically thin one. Some consequences on the interpretation of the observed GRBs' light curves and spectra will be presented. In particular, it will be presented the possible identification of the proper GRB (P-GRB), the flash emitted when the fireshell becomes transparent, in the case of GRB 080916C, whose full details will be presented in a next talk by L. Izzo et al. In the present talk, in the optically thick regime the fireshell will be approximated, for simplicity, as an expanding shell with constant width in the laboratory frame, following Ruffini et al., A&A, 350, 334 (1999). Possible deviations from such an approximation will be discussed in a next talk by G. De Barros et al.

Title: The extended afterglow luminosity evolution over the equitemporal surfaces

Abstract: Due to the ultrarelativistic velocity of the fireshell (Lorentz gamma factor 10^2 - 10^3), photons emitted at the same time in the laboratory frame (i.e. the one in which the center of the fireshell is at rest) from the fireshell surface but at different angles from the line of sight do not reach the observer at the same arrival time. Then, the signal we detect at a given value of the arrival time is a superposition of signals coming from different times in the laboratory frame. Therefore, they correspond to different values of the fireshell radius. Within the fireshell model, we trace back the beginning of the "plateau" phase in the GRB afterglow X-ray light curves to a collision between the decelerating front layer of the fireshell and a slower inner shell. It occurs at the end of the prompt emission phase. To determine the radius at which this collision occurs, and therefore the dynamics of the slower inner shell, it is fundamental to analyze the distribution of the extended afterglow bolometric luminosity over single EQTSs, in order to determine the radius from which it comes the most of the observed emission at any value of the arrival time. The computation will be separately performed over different selected EQTSs encompassing all the extended afterglow regimes, from the prompt emission all the way to the latest phases. The temporal evolution of the luminosity distribution over the EQTSs will be then presented, together with the corresponding temporal evolution of the EQTS apparent size in the sky.

Caito Letizia 

Institution: University of Rome “Sapienza”

Title: The classification of gamma-ray bursts: the typical cases of GRB 060614 and GRB 071227

Abstract: The traditional separation between Short Hard Bursts and Long Soft Bursts, yet enabled by many observations of the recent years, has been finally infringed by the explosion of GRB 060614.

GRB 060614 is the first clear example of a nearby long duration burst without a bright SN Ib/c emission observed, crucial issue that undermines the fundamental assumption of the standard scenario according to which all long GRBs originate from Supernovae explosions. Although its duration makes it hardly classifiable as a short GRB, it is not either a typical long GRB since it occurs in a low star forming region.

This "anomalous" situation finds a natural interpretation within the fireshell scenario: GRB 060614 belongs to the class of "fake" short bursts or, better, of canonical GRBs "disguised" as short ones. Similarly to the prototypical GRB 970228, the morphology, made of an initial spikelike emission followed, in the 15-150 KeV energy band, by a deflated but mostly energetic tail, is due to the particularly low density of the environment. The first, hard spikelike emission is identified with the Proper Gamma-Ray Burst (P-GRB), while the softer tail is the peak of the afterglow. This interpretation is compatible with the merging of a neutron-star/white dwarf binary system as progenitor of the burst.

We have considered the possibility that the source GRB 071227, classified in literature as a short GRB and presenting some similar characteristics of GRB 060614, could be another example of disguised short burst. Similarly to GRB 060614 this GRB shows, in addition to its spiky structure followed by a strongly deflated tail, an energetic compatible with that of underluminous and in fact it is very close to us. Though the explosion of this source is in a high-density region, the hipothesys of another disguised burst has been soon ruled out. We have instead checked if it could be an example of "genuine" short burst. The results of our analysis shows that this burst is a typical long GRB within the fireshell scenario. As for GRB 060614, this is not in contradiction with the lack of any SN associated. On the contrary, this is a further confirmation of the same nature and origin of both long and short bursts, that implies the necessity of a new classification scheme based on different criteria and characteristic parameters.

Chechetkin Valery

Institution: M I PH U , Moscow, Russia

Cianfrani Francesco

Institution: University of Rome “Sapienza”

Title: Higgs Field from a Scalar-Tensor Theory with Barbero-Immirzi Variables

Abstract: The Hamiltonian formulation of a scalar field non-minimally coupled to gravity is performed in a first-order approach. It is shown how the scalar field itself enters into the definition of the discrete spatial structure proper of Loop Quantum Gravity. This result suggests to work in the Einstein frame, where the scalar field is minimally-coupled to a fictitious metric. Within this scheme the Higgs potential naturally arises and a non-vanishing vacuum expectation value is predicted for the scalar field.

Costa Enrico

Institution:

Title: The future of X-ray Polarimetry: a new window in the sky

Abstract: Notwithstanding the very attractive predictions of theoretical analysis the polarimetry is a relatively undigged field. The recently developed Gas Pixel Detector can image the tracks of photoelectrons in a gas and combines imaging and polarimetric capabilities. In the focus of an X-ray telescope it can perform polaimetry of X-ray sources with a dramatic improvement of sensitivity with respect to conventional instrumentation. We show, in particular, the potentialities of a pathfinder achieved by the addition of two polarimeters to the HXMT satellite.

De Barros Gustavo

Institute: University of Rome “Sapienza”

Frontera Filippo

Institute: Physics Department - University of Ferrara

Title: Laue lenses for soft gamma-ray observations: status and scientific prospects

Abstract: I will report on the status of focusing telescopes for hard X/soft gamma-rays (>70/100 keV), now under development at the Physics Department of the Ferrara University. They are based on the use of mosaic crystals in trnsmission configuration (Laue lenses). I will show the first results of a lens prototype and discuss the astrophysical open issues that can be settled by means of deep gamma-ray observations, that can be made possible with these new generation instruments.

Han Wenbiao

Institute: University of Rome “Sapienza”

Title: Plasma oscillation in spatially inhomogeneous electric fields

Abstract: We study the back-reaction of electron-positron pairs created in spatially inhomogeneous electric fields, based on pair-production rate, Maxwell equations, conservations of particle-number and energy-momentum. Numerically integrating a set of partial differential equations. we find that electric field and charged current are oscillating in space and time, leading to a wave propagating in the direction of electric field gradient. In the Sauter field case, we present a detailed analysis describing properties of such wave.

Izzo Luca 

Institute: University of Rome “Sapienza”

Title: GRB 090423 : a canonical GRB at redshift z = 8.1

Abstract: GRB090423 is the most distant GRB ever observed, with redshift z of about 8.1, a T90 duration is of 10.2 +- 1.1 s and an estimated Peak Energy of 48.6 +- 6.2 keV. We analyze Swift-BAT data in the band 15-150 keV and XRT data in the band 0.2-10 keV within the "fireshell" model. We can fit the source, for a total energy of the dyadosphere of 4.80 x 1053 ergs, with a gravitational collapse to a ˜ 20 solar mass black hole. Possible solutions for such an e+e- black holes ranges from Mu = 1-50 solar masses for values of xi ranging from 0.15 to 0.88. Among these different Mu and xi we select one with Mu = 20 solar masses, and the corresponding xi = 0.233. We obtain an initial Lorentz gamma factor of 960 and a CBM average density in the range n = 10-1 - 10-2 particles/cm3 up to size of 1018 cm, that corresponds to 1 light year. The conclusions are that this collapse occurred from a star by an almost complete gravitational collapse without any remnant up to a size of 1 light year. This is very different from all the other GRBs observed at smaller z factor, where an agreement with binary neutron stars or neutron stars / white dwarfs is possible..

Kerr Roy 

Institute: ICRANet

Lacquaniti Valentino

Institute: University of Rome “Sapienza”

Title: Cosmological Implementation of a Reduced 5-D Dynamics with Matter

Abstract: In this work we deal with a revised formulation of the 5D compactified Kaluza-Klein model, where, after the introduction of a 5D matter tensor, the simultaneous reduction of matter and geometry is performed. We present two main results: the KK tower of huge massive modes is removed and an extra source term, coming from the external tensor, is recognized. The model looks like a consistent modified gravity theory in presence of matter and therefore dark energy scenarios can be faced. We discuss some isotropic solutions of the model, placing emphasis on those providing an accelerated expansion.

Montani Giovanni

Institute: University of Rome “Sapienza”

Title: MHD Features of Stellar Accretion Disks

Abstract: We present a discussion on the accretion disk configurations around compact magnetized stars, as described in a two-dimensional MHD framework. The problem of balancing the azimuthal Lorentz force, acting on the electrons, is properly addressed, both in terms of a non-zero Nernst coefficient, as well as when the resistivity of the plasma in the disk is taken into account. The morphology of the accretion mechanism in the linear regime and the phenomenological implications of the model are eventually analyzed.

Patricelli Barbara

Institute: University of Rome “Sapienza”

Pizzi Marco

Institute: University of Rome “Sapienza”

Title: Shell intersection: neutral and charged case

Abstract: We firstly describe the dynamics of two neutral spherical shells with tangential pressure in the field of a central Schwarzschild black hole (Barkov-Belinski-Bisnovati-Kogan model)determining the motion of the shell after the crossing. Then we generalize the problem to the charged shell case in the field of a central Reissner-Nordstrom source. We solve the problem of determining the motion of the two shells after the intersection by solving the related Einstein-Maxwell equations and by requiring a physical continuity condition on the shells velocities. We consider also four applications: post-Newtonian and ultra-relativistic approximations, a test-shell case, and the ejection mechanism of one shell.

Qadir Asghar

Institute: National University of Sciences and Technology, Pakistan

Quevedo Cubillos Hernando

Institute: ICRANet

Title: On the structure of spacetimes with quadrupole moment

Abstract: We analyze the simplest static generalization of Schwarzschild's metric which includes an additional parameter representing a quadrupole moment. In the Newtonian limit the solution represents a point mass so that this type of quadrupole is pure relativistic. It is shown that the presence of the quadrupole completely changes the structure of spacetime and, in particular, several naked singularities appear, one of them situated on the horizon. The effects associated to repulsive gravity near the naked singularities are also discussed.

Rangel Lemos Luis Juracy

Institute: University of Rome “Sapienza”

Title: The relevance of pp interactions in GRB scenarium

Abstract: In this work we study the production of pions and electromagnetic energy from pp collisions. We analyse the work of Fermi 1950, in which he used a statistical approach of the interaction, then we compare it with the data obtained with two Monte Carlo codes, SIBYLL and PITHIA. The new telescopes working in the high energy domain could give us better data, although they do not have yet a good accuracy in the MeV-GeV energy range; for example, the Fermi telescope detected more than 100 photons in the energy range >100 MeV from GRB 080916C. The data of the pp interaction show that the radiation spectrum from the collision has a peak around the rest mass of pions (135 MeV). We are investigating the possibility of high energy photons of GRBs be produced from pp interactions process.

Rotondo Michael

Institute: University of Rome “Sapienza”

Title: On the gravitational and electrodynamical stability of massive nuclear density cores

Abstract: We present a unified treatment of nuclear density cores recovering the classic results for neutral atoms with heavy nuclei having a mass number A~ 10^2-10^6 and extrapolating these results to massive nuclear density cores with A ~ (mPlanck/mn)^3 ~ 10^{57}. The treatment consists of solving the relativistic Thomas-Fermi equation describing a system of Nn neutrons, Np protons and Ne electrons in beta equilibrium with Np=Ne. The Np protons are distributed at a constant density within a spherical core of radius Rc. A new island of stability is found for A>A¯ = 0.039*(Np/A)^{1/2}*{mPlanck/mn)^3. The Coulomb repulsion, screened by relativistic electrons, is balanced by the gravitational self-interaction of the core. In analogy to heavy nuclei they present, near their surface, an overcritical electric field. The relation between A and Np is generalized to an arbitrary value of the mass number, and the phenomenological relations for A< 1.5 * 10^{2} are obtained as a limiting case.

Rueda Hernandez Jorge Armando

Institute: University of Rome “Sapienza”

Ruffini Remo

Institute: University of Rome “Sapienza” and ICRANet

Sigismondi Costantino

Institution: University of Rome “Sapienza”

Title: Astronomy in China and Europe around 1600

Abstract: Around 1600 in Europe observational and theoretical astronomy undergo a tremendous boost thanks to Tycho Brahe and his new instruments, Kepler's interpretations and finding of elliptical heliocentric orbits. Copernicus and Clavius criticized the model of Ptolemy and its parameters, with observations of lunar (1500) and solar (1567) eclipses and Aldebaran occultation (1497). Kepler found the elliptical orbit of Mars, and the bisection of the Ptolemaic eccentricity, using the data of Tycho Brahe. Pinhole solar telescopes (built in catholic cathedrals by Cassini 1655 and Bianchini 1702) measured accurately the eccentricity of Earth's orbit according to Kepler's bisection. Jesuits Fathers, in particular Christopher Clavius and after Matteo Ricci, were deeply involved with euclidean geometry, cartography and the reformation of Gregorian Calendar (1582), and they were perfect to transfer european knowledges fitting them to chinese need of their calendar's reformation. Chinese calendar is luni-solar as well as the perpetual calculations of Easter's sunday (spring equinox+full moon). From 1598 (Matteo Ricci first contact with China) to 1774 (Clement XIV suppression of Jesuits) the interaction between chinese and european scientists, through translations and technology transfer, was a very fruitful duty carried by Jesuit Fathers.

Siutsou Ivan

Institute: University of Rome “Sapienza”

Title: On the gravitational origin of the Pioneer Anomaly

Abstract: From Doppler tracking data and data on circular motion of astronomical objects we obtain a metric of the Pioneer Anomaly. The metric obtained gives a solution for the problem of the manifest absence of anomaly acceleration in the orbits of the outer planets and extra-Pluto objects of the Solar system. However, it turns out that the corresponding energy-momentum tensor of matter generating such a gravitational field in GR violates energy dominance conditions, and light deflection in such a space-time deviates from that in Schwarzschild field far beyond the experimental errors. This fact strongly suggests a non-gravitational origin of the Pioneer Anomaly.

Vereshchagin Gregory

Institute: ICRANet

Title: Relaxation time constants in mildly relativistic plasma

Xue She-Sheng

Institute: ICRANet

Title: Regularization and quantization of Einstein-Cartan theory

Abstract: We study regularization and quantization of Einstein-Cartan theory for describing the dynamics of 4-dimensional Euclidean manifold discretized as a 4-simplices complex. Tetrad field e_\mu(x) and spin-connection field \omega_\mu(x) are assigned to each 1-simplex. Applying the torsion-free Cartan structure equation to each 2-simplex, we discuss parallel transports and construct a diffeomorphism and {\it local} gauge-invariant regularization of Einstein-Cartan action. The {\it global} holonomy of field \omega_\mu(x) along a large loop in the 4-simplices complex is also presented. Quantization is defined by a bounded Euclidean partition function with the measure of SO(4)-group valued \omega_\mu(x) fields and Grassmann anticommuting e_\mu(x) fields over the 4-simplices complex. In the 2-dimensional case (2-simplices complex), we calculate: (i) system's entropy and free-energy, being proportional to its surface; (ii) the average of regularized Einstein-Cartan action, implying that the Planck length sets the scale for the minimal distance between two space-time points.