Titles and Abstracts - 2nd Galileo Xu Guangqi |
Title: Exploring galactic and extragalactic particle accelerators with X-rays, gamma-rays and neutrinos Abstract: I will discuss the potential and prospects of probing galactic and extragalactic cosmic ray accelerators using nonthermal X-rays and high energy gamma rays and neutrinos produced inside or in proximity of these accelerators. Download talk: PDF Title: Observing Black Holes: Quasi-Periodic Oscillations Abstract: Black holes continue to play a profound role in the fundamental description of nature. They occupy a central place in all theories of gravity formulated in various spacetime dimensions, shedding light into the structures and physical consequences of these theories. On the other hand, astronomical observations insistently point to the existence of black holes both in X-ray binary systems and at the centers of most galaxies, including our Milky Way Galaxy. In this talk, I will discuss the current theoretical and observational status of black holes. I will also discuss the theory of {\it Quasi-Periodic Oscillations} around black holes, some new results, challenges and open problems. Title: Pair winds from compact objects with an application to GRB" Abstract: An spherically symmetrical outflowing wind or a fireball consisting of electronpositron pairs, photons, and baryons is considered. We do not assume thermal equilibrium, and include the two-body processes that occur in such plasma: Moller and Bhaba scattering of pairs, Compton scattering, two-photon pair annihilation, two-photon pair production, and pe, pp Coulomb scattering, together with their radiative three-body variants: bremsstrahlung, double Compton scattering, and three-photon pair annihilation, with their inverse processes. We solve the relativistic kinetic Boltzmann equations for distribution functions of pairs, protons, and photons numerically. By the calculating of the timescale of the thermalization we can prove the possibility of using the hydrodynamical approximation (HD). Also the purpose of our investigations is to describe the plasma correctly in all cases, and then the plasma is not in thermal equilibrium and cannot be described in the frame of HD. Download talk: PDF Title: Measuring cosmological parameters with GRBs Abstract: Gamma-Ray Bursts (GRBs) are the brightest sources in the universe, emit mostly in the hard X-ray energy band and have been detected at redshifts up to about 8.1. Thus, they are in principle very powerful probes for cosmology. I shortly review the researches aimed to use GRBs for the measurement of cosmological parameters, which are mainly based on the correlation between spectral peak photon energy and total radiated energy or luminosity. In particular, based on an enriched sample of 115 GRBs, I will provide an update of the analysis by Amati et al. (2008) aimed at extracting information on Omega_M and, to a less extent, on Omega_Lambda, from the Ep,i - Eiso correlation. Download talk: PPT Title: The characteristics of GRB with high energy component in their spectra Download talk: PPTX Title: The application of the BrilLanCe series scintillation detector in the spectrometer of neural particles in the satellite experiment ZINA-NT Download talk: PPTX Title: What determines the Rotational State of a Collapsing Star? Abstract: Black holes have characteristics which are determined by their mass, charge, and rotation. How are these determined in the evolution of a star which collapses to a black hole? While it is generally thought that the net charge of a star is zero, there is less agreement concerning the mass and the rotation rate. Recent efforts to clarify this issue will be summarized. Title: Stationary Einstein-Maxwell Solitons (G.A. Alekseev and V.A. Belinski) Abstract: The new derivation of static equilibrium state for two charged masses in General Relativity is given in the framework of the Inverse Scattering Method in contradistinction to the previous derivation by the Integral Equation Method. This shows that such solution are of solitonic character and represent the particular case of the most general 12-parametric stationary solitonic solution for two rotating charged objects obtained by Alekseev in 1986. It is shown also that an analytical continuation of this solution in the space of arbitrary parameters is possible which means that applicability of the Inverse Scattering Method in presence of electromagnetic field not restricted only to the naked singularities cases. The stability (with respect to a rotation emerged) of the true equilibrium static solution recently obtained by Alekseev and Belinski is demonstrated. Title: Particle Dark Matter in the galactic halo: results from DAMA/LIBRA Abstract: The former DAMA/NaI experiment and the present second generation DAMA/LIBRA (sensitive mass: about 250 kg highly radiopure NaI(Tl)) exploit the model independent Dark Matter annual modulation signature. Both the used target material and the model independent approach assure a wide sensitivity to many Dark Matter candidates and physical scenarios. The experiments have obtained clear evidence for the presence of Dark Matter particles in the galactic halo, with a cumulative 8.9 sigma C.L. in an exposure of 1.17 ton x year collected in 13 independent annual cycles. No other experiment is available whose result can be directly compared in a model independent way with those by DAMA/NaI and DAMA/LIBRA. Implications and perspectives will be addressed. Download talk: PDF Title: The fireshell equations of motion and the P-GRB observational properties Abstract: Within the fireshell model, Gamma-Ray Burst (GRB) light curves are composed by two distinct phenomena: the Proper GRB (P-GRB), emitted when the fireshell becomes transparent, and the extended afterglow, emitted due to the interaction with the CircumBurst Medium (CBM) of the ultrarelativistic baryonic matter shell left over after the transparency point. The peak of the extended afterglow, together with the P-GRB, forms what is usually called the "prompt emission". Such a theoretical framework implies the existence of three GRB classes, as a function of the fireshell baryon loading and of the CBM average density: the "genuine" short GRBs, where the P-GRB is energetically predominant over the extended afterglow, the "long" GRBs, where the extended afterglow is energetically predominant over the P-GRB, and the "disguised" short GRBs, where the extended afterglow, although still energetically predominant, has a peak flux lower than the P-GRB one due to a peculiarly low value of the CBM density, typical of galactic halos. In this talk I will describe the kinematics and dynamics of the fireshell in both the optically thick and the optically thin phase, with special emphasis on the transparency point and on the observational properties of the P-GRB. Such observational properties are crucial for the identification of the P-GRB in the observed GRBs and therefore for their classification in the above recalled three classes. Download talk: PDF Title: Poynting-Robertson effect in black hole spacetimes Abstract: Test particles orbiting black holes with superposed a radiation field suffer for friction-like effects due to the absorbing and consequent re-emitting of radiation. There arise significant modifications to geodesic motion. Details are discussed varying orbital parameters as well as those related to the radiation field. Download talk: PDF Title: Rapid multi-wavelength observations of gamma-ray bursts. Abstract: With the launch of satellites able to provide timely positions, it has been possible to use robotic telescopes to observe the prompt emission and early GRB afterglow. This provides a panchromatic, dynamic view of these events, from the eV to the GeV. Observational aspects, theoretical implications and prospective will be reviewed. Download talk: PPT Title: On Magnetic Fields in Neutron Stars Abstract: We consider an extremely simple model of the neutron stars that includes neutrons, protons and electrons, all treated as degenerate and mostly non-interacting fermions. The charge distribution in the entire configuration is assumed to be globally neutral. The aim of the work is to study the magnetic field induced by the charged distribution when the system is allowed to rotate with constant angular velocity around the axis of symmetry. We present the analyses in the framework of Newtonian theory of gravity and in Einstein theory of gravity. Download talk: PPT Title: MIRAX: a Brazilian-Italian X-Ray Astronomy Mission for GRBs and X-Ray Transients Abstract: MIRAX (Monitor e Imageador de Raios X) is an X-ray astronomy mission being developed primarily at INPE, Brazil. Its main objective is to perform wideband (2-700 keV) imaging (~5 arcmin resolution) spectroscopy of a large sample (2 sr field-of-view) of transient sources and explosive phenomena in the universe. Recently, the participation of Italian institutions, including ICRANet, was discussed and the first steps were taken toward the inclusion of Italian instruments on the MIRAX payload. In this talk I will present the current status of the mission, its main scientific objectives and the preliminary configuration of the instruments and the satellite. Download talk: PPTX Title: On The Correspondence Between Extremal Black Holes and real poles in the ISM for electro-vacuum (V. Belinski, A. Bravetti and H. W. Lee) Abstract: It is shown that (unlike to some statements in the literature) the real poles in the dressing matrix of the Alekseev’s Inverse Scattering Method (ISM) for electro-vacuum does not lead to a principal difficulties but the restriction is that they correspond to the extreme objects. It is shown that solutions of Majumdar-Papapetrou, Perjes-Israel-Wilson and Parker-Ruffini-Wilkins are solitonic solutions but of different type. Interesting algebraic structure for the dressing matrix arise. Title: The class of disguised short bursts: some examples Abstract: Observations of Gamma-ray Bursts (GRBs) put forward in the recent years have revealed, with increasing evidence, that the historical classification between long and short bursts has to be revised. Within the Fireshell scenario, both short and long bursts are cononical bursts, consisting of two different phases.First, a Proper-GRB (P-GRB), that is the emission of photons at the tranparency of the fireshell. Then, the Extended Afterglow, multiwavelenght emission due to the interacion of the baryonic remnants of the fireshell with the CircumBurst Medium (CBM). We discriminate between long and short bursts by the amount of energy stored in the first phase with respect to the second one. This is given by the baryon loading parameter, that quantifies the barionic remnants engulfed by the fireshell. When 10^{-4}<B<10^{-2} we will have a long burst, where the afterglow phase is energetically predominant. When B<10-5 the P-GRB phase is predominant, and we will observe a short burst. Within the Fireshell scenario, we have introduced a third intermediate class: the "disguised" GRBs. They appear like short bursts, because their morphology is characterized by a first, short, hard episode and a following deflated tail, but this last part - coincident with the peak of the afterglow - is energetically predominant. The origin of this peculiar kind of sources is inferred to a very low average density of the environment (of the order of 10-3, compatible with galactic halos). Many analysis have been performed and have been identified some examples of disguised bursts: GRB 970228, GRB 060614, GRB 071227.The study of these bursts within the Amati relation, empirical correlation fulfilled only by long bursts, seems to confirm our hypothesys. Download talk: ODP Title: Black Hole Accretion: How do the variable and outburst sources do it? Abstract: Both from the theoretical arguments and the observational results it has become clear that black hole accretion is complex, and yet, follow a definite pattern. After discussing the theoretical results briefly, I will show that the behavior of several outburst sources as well as the ultra variable source GRS 1915+105 can be explained very well from theoretical understanding of the generalized accretion disks. The interplay between the Keplerian and sub-Keplerian components is very apparent. Occasionally, one component may also be converted to another. We discuss the variation of QPOs and the hysteresis effects in outburst sources and sequence of exhibited variabilities in the most enigmatic black hole known so far, namely, GRS 1915+105. Download talk: PPT Title: Gauge Theory of Gravity with de Sitter Symmetry as a Solution to the Cosmological Constant Problem and the Dark Energy Puzzle Abstract: We propose a solution to the longstanding cosmological constant (CC) problem which is based on the fusion of two existing concepts. The first is the suggestion that the proper description of classical gravitational effects is the gauge theory of gravity in which the connection instead of the metric acts as the dynamical variable. The resulting field equation does not then contain the CC term. This removes the connection between the CC and the quantum vacuum energy, and therefore addresses the old CC problem of why quantum vacuum energy does not gravitate. The CC-equivalent in this approach arises from the constant of integration when reducing the field equation to the Einstein equation. The second is the assumption that the universe obeys de Sitter symmetry, with the observed accelerating expansion as its manifestation. We combine these ideas and identify the constant of integration with the inverse-square of the radius of curvature of the de Sitter space. The origin of dark energy (DE) is therefore associated with the inherent spacetime geometry, with the smallness of DE protected by the symmetry. This addresses the new CC problem, or the DE puzzle. Download talk: PPT Title: Topics in 21cm cosmology Title: Neutron Star Mass and Strong Gravity --- Implications of kHz QPOs Abstract: The recent statistical distributions of measured masses of neutron stars (NSs) in binary pulsar systems are studied, which follow a Gaussian distribution with a mean of 1.4 solar masses. It is found that the mass of fast millisecond pulsar (MSP) generally is bigger than that of slow rotating one, which is consistent with the recycled formation framework of MSPs. If we make the another assumption that the mass of a MSP formed by the accretion induced collapse (AIC) of a white dwarf must be less than 1.35 solar masses, then the portion of the binary MSPs involved in the AICs would be not higher than 20%. Moreover, Ns masses can be also inferred from the kHz QPO frequencies that are belived to be the emission close to the strong gravity regimes. In addition, the possibly existed maximum NS mass is discussed. Download talk: PPT Title: Gedanken and Shining Black Holes Abstract: The accumulating body of experimental information[1] on the characteristics (e.g. associated with relevant spectral, time and space resolutions) of the radiation emission from objects identified as black holes is a compelling reason for the formulation of a realistic theory of the plasmas that can be associated with these objects. In particular, the use of concepts (such as that of viscosity for the transport of angular momentum) and conditions that are suitable for ordinary gases has to be abandoned and the evolution of the appropriate plasma regimes in the entire phase space has to be considered. In the immediate surrounding of rotating black holes three plasma regions [3] are identified: a Buffer Region, a Three-regime Region and a Structured Peripheral Region. In the last region a Composite Disk Structure [2] made of a sequence of plasma rings corresponding to the formation of closed magnetic surfaces (islands) is considered to be present allowing accretion flows to develop intermittently along the relevant separatrices. The intermittence is related to the onset and quenching of ballooning modes (similar to ELMs) resulting from the plasma accumulation between adjacent separatrices. The rings structure, depending on the state of the plasma at the microscopic level: i) may not propagate within the Three-regime Region allowing the onset of a spiral structure with which so called High Frequency Quasi Periodic Oscillations (HFQPOs) are associated; ii) may be allowed to propagate to the outer edge of the Buffer Region where successive rings carrying currents in opposite directions are ejected vertically (in opposite directions) and originate the observed jets; iii) penetrates in the Three-regime Region and is dissipated before reaching the outer edge of the Buffer Region. Three different kind of spectra [2] for the emitted radiation are connected to these regimes. The non linear “Master Equation” describing the composite disk structures [3] is derived and solved in appropriate asymptotic limits. *Sponsored in part by the U.S. Department of Energy. [1] R.A. Remillard and J.E. McClintock, Annu. Rev. A&A 44 49 (2006). [2] B. Coppi, Plasma Phys. Cont. Fus. 51 124007 (8pp) (2009). [3] B. Coppi, MIT (LNS) Report HEP 10/01. To be published in Plasmas in the Laboratory and in the Universe, Editors, G. Bertin et al. (Publ. I.A.P., New York, 2010). Download talk: PDF Title: Relativistic Astrophysics with AGILE Abstract: The AGILE mission is operating in orbit since July 2007. It carries instrumentation allowing to image the sky above 50 MeV and in the hard X-rays (18-60 keV). During the first 2 years AGILE observed the sky through month-long deep and continuous pointings, especially at the Galactic plane. After October 2010 it started a "spinning mode" by which it samples a much wider fraction of sky, with shorter exposure. In this talk I will report about the most recent results achieved by the experiments onboard AGILE in the field of Galactic and Extragalactic Astrophysics. Download talk: PPT Title: Neutrinoless Double Beta Decay Searches Abstract: Neutrinoless double beta decay is one of the most sensitive probes for the regime of physics beyond the standard model. It can provide fundamental information on the character of neutrinos and their absolute mass scale. The present status of experiments searching for neutrinoless double-beta decay (0nuDBD) is reviewed together with the most relevant results. Given the observation of neutrino oscillations and the present knowledge of neutrino masses and mixing parameters, a possibility to observe 0nuDBD at a neutrino mass scale in the range 10-50 meV could actually exist. This is a real challenge faced by a number of new proposed projects. The most important parameters contributing to the experimental sensitivity are outlined. A short discussion on nuclear matrix element calculations is also given. Download talk: PDF Damour Thibault and Lecian Orchidea Maria Title: About the Statistical Properties of Cosmological Billiards Abstract: A remarkable achievement of theoretical cosmology has been the construction, by Belinski, Khalatnikov and Lifshitz (BKL), of a general solution to the 4-dimensional vacuum Einstein equations in the vicinity of a spacelike(``cosmological'') singularity. The description of cosmological singularities in term of billiards in (higher dimensional) Lobatchevsky (or Lorentzian) spaces has recently received a new impetus from the discovery, by Damour, Henneaux and Nicolai, that the billiard chambers corresponding to many interesting physical theories can be identified with the ``Weyl chambers'' of certain (infinite-dimensional) Lorentzian Kac-Moody algebras. The talk will discuss the link between the stochastic properties of the BKL approach, and those of a billiard approach. Our results generalize those of Misner-Chitre and Kirillov-Montani. Download talk: PDF Title: Numerical analysis of an optically thick plasma Abstract: We developed a code to study the evolution of an optically thick plasma composed by photons, electrons, positrons and protons. The particles are treated as two different components: relativistic one (photons, electrons, positrons) and non relativistic one (protons). We found different plasma evolution for different initial spatial distribution of these components. Implications of these results for GRBs, and in particular for P-GRBs will be discussed. Download talk: PDF Title: Wild and Weird Supernovae Abstract: I'll shortly review the status of GRB observations and their possible use as rulers of cosmological parameters. Download talk: PPT Title: Large Scale Structure of the Universe - a powerful probe for fundamental physics Abstract: An overview is given on properties of the LSS using recent sky surveys (SDSS Main and LRG samples). LSS evolves very slowly, thus it contains imprints of physical conditions in the early Universe, as well as processes during its evolution. Present physical experiments are still unable to reproduce conditions in the very early Universe, thus the study of the properties of the LSS yields valuable information for fundamental physics. Download talk 1: PDF and talk 2: PDF Title: Nonlinear evolution of cosmic baryon matter Abstract: I will review the study on the non-evolution of cosmic baryon matter in the regime that the baryon matter is statistically and dynamically decoupling with dark matter. In this regime, the cosmic baryon fluid will be turbulent. The density and velocity fields how typical intermittent behavior like fully developed turbulence in the inertial range. For instance, the vorticity of velocity field increases significantly, and shows the typical features of homogenous and isotropic turbulence. The turbulence of cosmic baryon fluid plays important role to explain various problems related to cosmic baryon fluid. It includes the non-Gaussianity of Ly-alpha transmitted flux fluctuations; turbulent broadening; abnormal scaling; baryon missing in halos etc. A further test on the turbulence scenario with CMB will also be addressed. Download talk: PPT Title: The Italian scientific payload onboard MIRAX Abstract: MIRAX is a small scientific Brazilian mission for X-ray astronomy, due to launch by 2014. Recent scientific cooperation between Italy and Brazil has opened the possibility of a significant Italian contribution to the MIRAX scientific payload. I will present the rationale, the proposed implementation and the expected scientific results of the Italian contibution to MIRAX in the field of Galactic sources and Gamma Ray Bursts. Download talk: PDF Filippi Simonetta and Cherubini Christian Title: Rotating Self-gravitating Systems and Clebsch Theory: the acoustic effective geometry approach Abstract: The Effective geometry formalism, adapted to Clebsch’s potentials theory, is used to derive the perturbation equations of a perfect barotropic Newtonian self-gravitating rotating and compressible fluid coupled with gravitational back-reaction. The analytical case of a uniformly rotating polytrope with index n = 1 is investigated. The geometrical properties of the underlying background four dimensional effective acoustic metric are analyzed focusing in particular on null geodesics as well as on the analog light cone structure. Download talk: PPT Title: The time resolved spectra of Gamma Ray Bursts (Author: F. Frontera, L. Amati et al.) Abstract: I will discuss preliminary results of a systematic investigation devoted to study the time resolved broad-band spectra of the prompt emission of a sample of GRBs. These events were simultaneously detected with the BeppoSAX WFCs and the BATSE instrument aboard CGRO. I will discuss fit results and their implications. Download talk: PPT Title: Earlier star formation in our Milky Way galaxy Title: Validity of thin shell models Abstract: The purpose of this paper is to test the validity of the thin shell formalism. Firstly, we construct a dust thick shell collapsing to a Schwarzschild black hole. From this exact solution, we show that the two sides of the shell satisfy different equations of motion. Moreover, we show that the inner side and the outer side always cross each other right after the formation of the thin shell, causing a breakdown of the model. Secondly, we establish a class of wormholes with non-zero thickness and extremal Reissner-Nordstr\"om exterior. In the thin shell limit, we find that the surface stress-energy tensor contains the contribution of electromagnetic field, which contradicts the treatment in previous literature. Download talk: PPT Title: Star Formation Laws in Galaxies Geralico Andrea and Pompi Francesca Title: Einstein Clusters and Black Holes Abstract: One of the epochal discussions on the existence of Black Holes was centered on the work of Oppenheimer and Snyder, giving the first evidence for the approach to the horizon of a collapsing core and a counterexample given by Einstein himself with what have become to be known as the Einstein clusters. Such clusters can approach an infinite red-shift at their core without forming a horizon. We here expand some previous work by Cocco and Ruffini analyzing the stability of such configurations and we determine as well a new family of Einstein clusters with a Black Hole at their center. Title: The Ultra Relativistic GRBs Download talk: PDF Title: Stationary axisimmetric metrics Download talk: PPT Title: Vacuum Bubbles and Gravity Effects Abstract: The vacuum bubbles in the curved spacetime are analyzed. We classify the true and false vacuum bubbles with the cosmological constants from the minimum of the potential being either positive, zero, or negative. We introduce new type of solutions with Z2 symmetry when the potential has degenerate vacua. Download talk: PPT Title: Nucleation and Dynamics of Vacuum Bubbles of a Self-Gravitating Scalar Field Abstract: The case of a self-gravitating scalar field undergoing the first order phase transition is studied. Particularly the effect of gravity on the nucleation and dynamics of vacuum bubbles is investigated. We also investigate what modifications are induced by the introduction of nonminimal coupling of the scalar field. The possibility of nucleation of false vacuum bubbles within the true vacuum background in the case of a nonminimally coupled scalar field is discussed. Download talk: PPT Title: Tortoise coordinate transformation on apparent horizon of a dynamical black hole Abstract: Thinking of Hawking radiation calculation from a Schwarzschild black hole using Damor-Ruffini method, some key requirements of the tortoise coordinate transformation are pointed out. Extending these requirements to a dynamical black hole, a dynamical tortoise coordinate transformation is proposed. Under this new dynamical tortoise coordinate transformation, Hawking radiation from a Vaidya black hole can be got successfully using Damor-Ruffini method. Moreover, it is found that the radiation should actually originate from the apparent horizon instead of event horizon. Download talk: PDF Title: Cosmological Perturbations and Dark Energy Title: Quantum Noise in the Mirror-Field System: A Field Theoretic Approach Abstract: The field theoretic approach is employed to study quantum noise in the mirrorfield system where the mirror as a reflector is illuminated by a coherent state. Various sources of quantum noises, which are from shot noise and random motion of the mirror due to the radiation pressure fluctuations, are all incorporated consistently with an emphasis on the effects from their correlations. The potential scheme to beat the so-called standard quantum limit is discussed. Download talk: PDF Title: Structure of compact star with dense hadronic matter at the core Abstract: The effect of density dependence of the nuclear symmetry energy on the compact star structure will be discussed in detail together with the strangeness contents in the form of kaon or Hyperons. Download talk: PPTX Title: Primordial magnetic fields by cosmic inflation Abstract: Contrary to the conventional wisdom, we find that it is possible to generate primordial magnetic seed fields via spinodal instibility during cosmic inflation provided that a fast-roll stage is involved before the inflaton entering into the slow-roll phase. Moreover, the primordial magnetic field produced in such a mechanism can be used to constrain the low quadrupole moment of Cosmic Microwave Background. Title: New Gauge Invariance of Gravity and the Fate of Torsion Abstract: If the geometry of spacetime is expressed in Riemann-Cartan spacetime via the gauge fields of translations, the vierbein field $h^\alpha{}_\mu$, and of local Lorentz transformations, the spin connection $ A_{\mu \alpha }{}^ \beta $, there exists a new gauge symmetry which permits shuffling torsion, partially or totally, into the Einstein-Cartan term of the Einstein tensor, and back, via a {\em new multivalued gauge transformation\/}. Torsion can be chosen at will by an arbitrary gauge fixing functional. There are infinitely many equivalent ways of describing the Hilbert-Einstein Lagrangian ${\cal L}\propto R$, for instance Einstein's traditional way in terms of the metric $g_{\mu \nu }=h^ \alpha {}_\mu h_ \alpha {}_ \nu $ and zero torsion, or as a teleparallel spacetime, where $R$ is expressed in terms of the torsion tensor, or any mixture of the two. As far as the gravitational field in the far-zone of a celestial object is concerned, matter composed of spinning particles can be replaced by matter with only orbital angular momentum, without changing the longdistance forces, no matter which of the various new gauge representations is used. Title: Cosmic Microwave Background Anisotropies: Current Status and prospects Abstract: A review is made of the current observational status of Cosmic Microwave Background anisotropies and of their theoretical implications. In particular, I will describe the current constraints on dark matter, inflation, baryonic matter, neutrino mass and curvature achievable from current measurements. I will then move to more "non standard" parameters as variations in fundamental constants and modified gravity theories. I will conclude mentioning the constraints that could be achieved in the very near future by missions as Planck. Download talk: PPTX Mester John and Ferroni Valerio Title: Space and superconducting techniques for General Relativity Download talk: PPT Title: A Bayesian approach to the semi-analytic model of galaxy formation Abstract: Our current understanding of galaxy formation is still at a stage a wide range of physical processes may play a role but exactly how they operate to shape the observed galaxy population is not clear. The problem of galaxy formation is therefore best tackled with a Bayesian-inference based approach, which allows one to constrain theory with data in a statistically rigorous way. The semi-analytic model (SAM) of galaxy formation, which uses multi-parameter parameterizations to describe the underlying physical processes of galaxy formation, provides an important avenue to develop a Bayesian-inference based SAM of galaxy formation. We develop a generalized SAM and a scheme that incorporates such a SAM into the framework of Bayesian inference. With an advanced Markov-Chain Monte-Carlo algorithm and current parallel computations, it is now possible to rigorously sample the posterior distribution of a large number of model parameters. We find that the posterior probability distribution is in general very complex, showing strong degeneracy among some important parameters. Because of the strong covariance of model parameters, some conclusions obtained from early SAMs are not reliable. Our Bayesian inferences from from a number of observational data sets indicate that some new physics is still required in the current model of galaxy formation. Download talk: PDF Title: Solution to Thomas-Fermi equation in the presence of strong magnetic fields Abstract: We study the influence of strong constant magnetic fields on a neutral and compressed system of neutrons, protons and electrons. The size of the system and homogeneous distributions of protons and neutrons at nuclear density are assumed without studying details of gravitational balance and nuclear effects. Instead, using the Thomas-Fermi equation for ultra relativistic electrons with non-vanishing Fermi energy, we exactly obtain analytical solutions for different values of magnetic fields B, much larger 10^(13) Gauss, but smaller than 10^(17) Gauss, giving the electromagnetic structure of the system. The effects of magnetic fields on the Coulomb potential depth at the centre and overcritical electric field near surface are shown. We discuss the up-limit of average magnetic field, whose pressure is necessary for stabilizing the system of degenerate electrons, protons and neutrons in the absence of gravitational field. Download talk: PPT Title: Effects of black holes to inflaton perturbation Abstract: We calculate quantum fluctuations of a free scalar field in the Schwarzschild-de Sitter space-time, adopting the planar metric that is pertinent to the presence of a black hole in an inflationary universe. In a perturbation approach, doing expansion in powers of a small black hole mass, we obtain time evolution of the quantum fluctuations and then derive the scalar power spectrum. Download talk: PPT Title: Symmetries and Singularities Download talk: PDF Pacheco Josè and Kanaan Chadia Title: The energy distribution of gamma-ray bursts revisited Abstract: Since the very first detection of gamma-ray burst (GRBs) by VELA satellites in the late sixties, our knowledge about these objects has dramatically increased both observationally and theoretically. Taking into account the pulse duration, GRBs are classified either as "short" (T90 <2s) or "long" (T90 >2s), where T90 corresponds to the time interval in which 90 % of the total fluence is received. Since most of the events are classified as "long", in the present work only objects of this class will be considered. Using a Monte Carlo technique, we have simulated mock catalogs of GRBs and compare the resulting fluence distributions in different energy bands with those derived from SWIFT data. By a best fit procedure, the parameters defining the (isotropic) energy distribution of GBRs were estimated. Title: Harrison-Zel'dovich primordial spectrum is consistent with observations Abstract: Inflation predicts primordial scalar perturbations with a nearly scale-invariant spectrum and a spectral index approximately unity (the Harrison--Zel'dovich (HZ) spectrum). The first important step for inflationary cosmology is to check the consistency of the HZ primordial spectrum with current observations. Recent analyses have claimed that a HZ primordial spectrum is excluded at more than 99% c.l.. Here we show that the HZ spectrum is only marginally disfavored if one considers a more general reionization scenario. Data from the Planck mission will settle the issue. Download talk: PPT Title: High energetic GRBs and their spectral properties within the fireshell model Abstract: One of the main goals of the fireshell model is to reproduce the observational properties of Gamma Ray Bursts (GRBs) starting from the assumption of a spectral energy distribution of the photons in the comoving frame of the fireshell. This approach represents an attempt to identify the underlying physical process responsible for the energy emission. Each observed instantaneous spectrum is the convolution over the corresponding EquiTemporal Surface (EQTS) of thousands of comoving spectra, duly weighted by their corresponding Lorentz and Doppler factors. Within the fireshell model, for simplicity, a comoving thermal spectrum was assumed and in this way it has been possible to interpret successfully the observational properties of low energetic GRBs (bursts with an isotropic energy Eiso =10^53 ergs); nevertheless, the analysis of higher energetic bursts (Eiso =10^54 ergs) has revealed some discrepancies between the numerical simulations and the observational data. We investigate the possibility of reproducing the observed spectra and light curves of these GRBs by assuming a different comoving spectrum. In particular, we propose a phenomenologically "modified" thermal spectrum: a thermal spectrum characterized by a different asymptotic power-law index in the low energy region. We test this spectrum by comparing the numerical simulations with the observational data of several high energetic bursts: GRB 080319B, GRB 050904 and GRB 990123. Download talk: PDF Title: Understanding the prompt emission of GRBs after Fermi Download talk: PPTX Title: Constraints of initial data for a discrete universe Abstract: Cosmological evolution is considered as the dynamics of a collection of discrete objects. In this approach, averaging is replaced by a mean field description in which each cosmological grain (galaxy or cluster of galaxies) is regarded as a test particle moving in the vacuum field created by all the other galaxies. Issues concerning spatial curvature and initial data in this framework will be discussed. In particular, we present evidence which may imply that spatial sections of the universe are constrained to have a spherical (and hence finite) topology. Download talk: PPT Title: On the relativistic Thomas-Fermi treatment of compressed atoms and compressed nuclear matter cores of stellar dimensions Abstract: Using the recently established scaling laws for the solutions of the relativistic Thomas-Fermi equation we consider the two limiting cases of compressed atoms and compressed nuclear matter cores of stellar dimensions. The Feynman, Metropolis and Teller treatment of compressed atoms is extended to the relativistic regimes. Each atomic configuration is confined by a Wigner-Seitz cell and is characterized by a positive electron Fermi energy. There exists a limiting configuration with a maximum value of the electrons Fermi energy $(E_e^F)_{max}$ reached when the Wigner-Seitz cell radius equals the radius of the nucleus, and it is here expressed analytically in the ultra-relativistic approximation. The results are compared and contrasted to approximate treatments in the literature. Particular attention is given to comparing and contrasting the newly computed configurations of the electrons to the ones obtained by a uniform approximation. Attention is also given to a relativistic evaluation of the exchange Thomas-Fermi-Dirac corrections. These results are particularly significant to study the equation of state for compressed matter under astrophysical conditions. In particular it is shown how this powerful new approach leads to overcome some difficulties present in the Salpeter approximation generally adopted in physics and astrophysics. This treatment is then extrapolated to compressed nuclear matter cores of stellar dimensions with $A\simeq (m_{\rm Planck}/m_n)^3 \sim 10^{57}$ or $M_{core}\sim M_{\odot}$. Again an entire family of equilibrium configurations exist for selected values of the electron Fermi energy varying in the range $0 < E_e^F \leq (E_e^F)_{max}$. Such configurations have electric fields on the core surface, increasing for decreasing values of the electron Fermi energy reaching values much larger than the critical value $E_c = m_e^2c^3/(e\hbar)$ for $E_e^F=0$. We compare and contrast our results with the ones of Thomas-Fermi model in strange stars. Preliminary results on the magnetic fields induced by the elctric fields when the nuclear matter core of stellar dimensions is allowed to rotate with constant angular velocity around the axis of symmetry are illustrated and discussed. Download talk: PPT Title: Sterile neutrino dark matter Abstract: An extension of the Standard Model by three right-handed (sterile) neutrinos with their masses below the electroweak scale allows to explain neutrino oscillations, baryon asymmetry of the Universe, and provides a dark matter candidate. Dark matter made of sterile neutrinos can be warm, cold or mixed and satisfies all existing astrophysical and cosmological bounds. I will overview these bounds and discuss the prospects for future searches. Download talk: PDF Rueda Hernandez Jorge and Pugliese Daniela Title: A general relativistic Thomas-Fermi treatment of neutron star cores Abstract: It is formulated the set of self-consistent ground-state equilibrium equations of a system of degenerate neutrons, protons and electrons in beta equilibrium within the framework of quantum statistics and of the general relativistic field theory for the gravitational, the electromagnetic and the hadronic fields. The hadronic interaction between nucleons is modeled by introducing the sigma, omega and rho fields within the Thomas-Fermi approximation all duly expressed in general relativity. It is demonstrated that, as in the non-interacting case, the minimization procedure of the energy of the configuration brings to the condition of the constancy of the Fermi energy of each particlespecie properly generalized to include the contribution of all fields. Consequences of the new set of the general relativistic equilibrium equations are discussed. Download talk 1: PDF and talk 2: PDF Title: Black holes in GRBs and galactic nuclei Abstract: Black Holes are observed in binary-x-ray sources and in active galactic nuclei. They are also observed during their formation phases in the process of gravitational collapse by the emission of Gamma Ray Bursts (GRBs). Both in the case of binary-x-ray sources and in the case of GRBs the progenitors of Black Holes are formed of baryonic matter. In the case of galactic nuclei an unified picture is proposed explaining at once the galactic halos and the condensation in the galactic cores as originating from dark matter Fermions semi-degenerate. Title: On the origin of high energy gamma-rays from giant radio lobes of Centaurus A. Abstract: Recently Fermi collaboration reported the detection of high energy gamma-ray signal from giant lobes of the radiogalaxy Centaurus A. We discuss the origin of this radiation and the possible radiation mechanisms, including Inverse Compton scattering of electrons, interaction of relativistic protons with the ambient low density plasma, and synchrotron radiation of the secondary electrons produced in p-gamma interactions. Download talk: PPT Title: Pre-inflation matter era and the CMB power spectrum Abstract: We consider the possibility of a pre-inflationary matter era induced by primordial micro black hole remnants. Effects of such epoch on the suppression of low k modes of CMB power spectrum are discussed and computed both analytically and numerically, and compared with the last observational data. Download talk: PDF Title: Methods to measure the solar diameter Abstract: The solar diameter is rock-solid or not? Whatever will be the answer the methods used for its measurements are more and more challenging, and facing new astrophysical and optical problems since the space resolution required is of astrometric quality. A quick overview on different methods is here presented, as well as the problem of the solar limb definition, emerging after the spectrum flash during eclipses. Download talk: PDF Title: SGWB by Cataclysmic Variables Abstract: "On the framework of stochastic gravitational wave background (SGWB) by close binary systems, we investigated the strain spectra of SGWB by cataclysmic variables". Title: Hydrodynamics of the optically thick phase in GRBs Abstract: We study the optically thick phase of GRBs by solving numerically relativistic hydrodynamic equations. By considering various initial distributions of matter we find that during expansion plasma spatial distribution deviate from the simple "frosen radial profile" established by Piran et al. (1993). We outline the consequences of such deviations for observations of GRBs. Download talk: PDF Title: Topics in neutrino astronomy Download talk: PDF Title: Effects of a pre-inflation radiation-dominated epoch to CMB anisotropy Abstract: We consider that the pre-inflation era is radiation-dominated, transiting smoothly to the inflationary era. We work out in detail the dynamics of inflaton fluctuations across the phase transition and the proper choices of initial vacuum states. It is found that this phase transition can suppress long-wavelength quantum fluctuations of inflaton. This may attribute to the large-scale CMB anisotropy a lower power than predicted in the standard $\Lambda$CDM model. In constraining this transitional effect by WMAP anisotropy data, we use the WMAP best-fit scale-invariant $\Lambda$CDM model with the density power spectrum replaced by the one found in this work. We find that the transition occurs at least about $10$ e-folds before the comoving scales comparable to our present horizon size cross the Hubble radius during inflation. Title: Episodic Random Accretion and the Cosmological Evolution of Supermassive Black Hole Spins Abstract: The growth of supermassive black holes (BHs) located at the centers of their host galaxies comes mainly from the accretion of gas, but how to fuel them remains an outstanding unsolved problem in quasar evolution. This issue can be elucidated by quantifying the radiative efficiency parameter (η) as a function of redshift, which also provides constraints on the average spin of the BHs and its possible evolution with time. We derive a formalism to link η with the luminosity density, BH mass density, and duty cycle of quasars, quantities we can estimate from existing quasars, and galaxy survey data. We find that η has a strong cosmological evolution: at z ≈ 2, η ≈ 0.3, and by z ≈ 0 it has decreased by an order of magnitude, to η ≈ 0.03. We interpret this trend as evolution in BH spin, and we appeal to episodic, random accretion as the mechanism for reducing the spin. The observation that the fraction of radio-loud quasars decreases with increasing redshift is inconsistent with the popular notion that BH spin is a critical factor for generating strong radio jets. In agreement with previous studies, we show that the derived history of BH accretion closely follows the cosmic history of star formation, consistent with other evidence that BHs and their host galaxies co-evolve. Title: Dark Matter and Dark Matter Energy Studies from Antarctica Plateau Abstract: Cosmology from Antarctica Plateau The highest peak in Antarctica is unique for modern science. Recent heroic expeditions by Chinese scientists have established the site as the coldest and driest spot on earth. It is also a site of steady air that makes for clear viewing into deep space. Despite all the difficulties, Chinese scientists are determined to build a world-class astronomical observatory at Dome A, Antarctica. Astronomers have already successfully established an automated observatory at the site. Of particular interest, three new 75cm Schmidt telescopes will be installed in Dome A, Antarctica which will provide important data for studying the origins of the Universe and searching for exoplanets. Within the next decades, Dome A, Antarctica will emerge as the best astronomical observatory in the world. It will become our best hope to understand the nature of the vast Universe and a powerhouse to discover new mysterious planets harboring life outside the solar system. In this lecture, Professor Wang will introduce the Kunlun Station of Antarctica, a new platform for modern sciences. Title: Nanotechnology for astrophysics Abstract: In the past three decades, nanotechnology has been widely developed in terms of three fields: material growth (bottom up), nanolithography (top down) and nanocharacterization. These developments have brought great progress in integrated circuits and detectors for modern electronics. In this communication, we will show that these new technologies permit us to explore a novel frontier of scientific research with new generation of electronic devices and innovative experimental methods for astrophysics. LPN/CNRS is a leading French national nanoscience and nanotechnology center with a most advanced setup for nano- and micro-devices fabrication and characterization. In the past years, LPN has been involved in different research projects in astrophysics. We are developing lowpower and ultra-low-noise transistors operating at a temperature below 4.2 K which consists of ultra-low noise HEMTs (High Electron Mobility Transistors) and fully ballistic HEMTs. These transistors will be used for deep cryogenic readouts electronics for deep cryogenic ultra-sensitive detectors, in particular, for the detection of WIMPs. More generally, these transistors can be used for deep cryogenic readouts of various high impedance deep cryogenic detectors. We develop also, submicron Schottky diodes for sub-THz and THz detection and generation. In addition of semiconductor electronic devices, the LPN involves in the development of Hot Electron Bolometer (HEB) matrix by “Observatoire de Paris” for 2.5 THz detection. Download talk: PDF Title: 21CMA: Performance and Prospects Title: Molecular gas and black hole growth in infrared ultra-luminous QSOs Abstract: Based on IRAM 30m observations for 25 infrared ultra-luminous QSOs(IR QSOs) and by comparing with local ULIRGs and high-redshift (sub)mm loud QSOs, we find: 1. The molecular gas content of IR QSOs is in the same range as ULIRGs, implying that there is enough fuel for continuing star formation in the last stage of major wetmerging. 2. Although the star formation rate is high for high-redshift (sub)mm loud QSOs, they are not simple scaled up of local IR QSOs because the ratio of far-infrared luminosity to bolometric luminosity (Lfir/Lbol) is much lower than that of local IR QSOs, which may give hint that the black hole and stellar mass of galaxies grow not coevally. Title: Electron-positron pair oscillation in spatially inhomogeneous electric fields and radiation Abstract: It is known that strong electric fields produce electron and positron pairs from the vacuum, and due to the back-reaction these pairs oscillate back and forth coherently with the alternating electric fields in time. We study this phenomenon in spatially inhomogeneous and bound electric fields by integrating the equations of energymomentum and particle-number conservations and Maxwell equations. The space and time evolutions of the pair-induced electric field, electric charge- and current-densities are calculated. The results show that non-vanishing electric charge-density and the propagation of pair-induced electric fields, differently from the case of homogeneous and unbound electric fields. The space and time variations of pair-induced electric charges and currents emit an electromagnetic radiation. We obtain the narrow spectrum and intensity of this radiation, whose peak $\omega_{\rm peak}$ locates in the region around $5\sim 70$ KeV depending on electric field strengths. We discuss their relevances to both the laboratory experiments for electron and positron pair-productions and the astrophysical observations of compact stars with an electromagnetic structure. Download talk: PPT Title: The evolution of galaxies: central vs satellite Abstract: Galaxies are thought to form within cold dark matter halos. Satellite galaxies were central galaxies associated with the subhalos before their accetion into the host halos. Thus by linking central galaxies with host halos and satellite galaxies with subhalos, at different redshifts, we are able to probe the evolution of galaxies for centrals and satellites separately. Download talk: PPT Title: On the nature of Z-sources: neutron star magnetic field, accretion disk structure and evolution Abstract: Using the data from the Rossi X-Ray Timing Explorer satellite, we investigate the spectral evolution along the Z- and nu-tracks on the hardness-intensity diagrams (HIDs) Z-sources, study their accretion disk structure and evolution, and infer their neutron star surface magnetic field strengths. We find that the disk accretion rate is less on the nu tracks than on the Z-tracks. Along the Z-tracks, at first the disk accretion rate increases on the upper track, and then decreases on the lower track. The disk accretion rate evolves differently on the nu-tracks. The slow variation of the disk accretion rate determines the evolution of the vertical disk structure, with the inner disk thickness proportional to the average disk accretion rate. Along the Z- or nu-tracks, the accretion disk evolves from a slim disk to a standard thin one. Their NS surface magnetic field strengths, derived from the interaction between the magnetosphere and the accretion disk, are on the order of 10^9 G. We also find that the neutron stars in transient Z-sources have surface magnetic field strengths between normal atoll and Z sources. We therefore suggest that the combination of the NS magnetic field strength and accretion rate makes a low mass NS Xray binary appear either as a Z source or an atoll source. Download talk: PDF Title: Fisher Information Content In The Matter Power Spectrum By Wavelet Method Abstract: We use the code “CubeP3M” to do 141 simulations of dark matter density fields. In wavelet space, we construct a non-Gaussian filter in order to separate non- Gaussian structure, which is the result of the non-linear evolution of the universe, from the Gaussian distributions of matter. We find the non-Gaussian feature is more dominant at smaller scales, which is in accordance with the theory of structure formation of the universe. We calculate the power spectra of the Gaussianized and non-Gaussianized density fields, and find that the Gaussianized power spectra is dampened extremely on small scales compared to unfiltered ones. For the Gaussianized cumulative information, we find the plateau in the translinear regime still exists, but is higher than the unfiltered one. We conclude that the wavelet filtering of data can prevent the lose of information in the trans-linear power. |