Participants

 

Belinski Vladimir

ICRA ( International Center for Relativistic Astrophisics )
belinski@icra.it
Coauthors:
M. V. Barkov and G.S. Bisnovatyi-Kogan,
Institute of Cosmic Research (IKI), Moscow, Russia
An exact General Relativity solution for the Motion and Intersections of Self-Gravitating Shells in the Field of a Massive Black Hole

      It is found the complete exact solution in the General Relativity for the intersection process of two massive selfgravitating spherically symmetric shells (in general with tangential pressure). It is shown how one can calculate all shellOs parameters after intersection in terms of the parameters before the intersection. The solution was applied to the analysis of matter ejection effect from stellar clusters. Also it is shown that the motion of two intersecting shells in general reveal a chaotic behaviour.

 

Bianco Carlo Luciano

ICRA ( International Center for Relativistic Astrophisics )
Dept of Fisica
Università degli Studi di Roma "La Sapienza"
P.le Aldo Moro, 5 - 00185 Roma, Italia

bianco@icra.it
The equitemporal surfaces in GRB afterglows

      

 

Bini Donato

Istituto per Applicazioni del Calcolo “M. Picone”, 
via del Policlinico, 137, I-00161, Roma
- Italy
binid@icra.it
On the Fermi work on a gravitating charge

      Test particle motion as well as Maxwell equations are discussed in the frame of an accelerated observer using Fermi coordinates.

 

Chardonnet Pascal


chardonnet@icra.it
The gamma ray bursts: a new window on cosmology ?

      

 

Filippi Simonetta

University Campus Biomed. of Rome, 
Via E. Longoni, 83, Rome, ITALY
filippi@icra.it
Galactic models with rotation and vorticity

      

 

Fraschetti Federico


fraschetti@icra.it
GRB 980425/SN 1998 bw association within EMBH model

      

 

Geralico Andrea

Dipartimento di Fisica - Università di Lecce
INFN,
Sezione di Lecce, 
Via Arnesano, CP 193, I-73100 Lecce, Italy

ICRA ( International Center for Relativistic Astrophisics )
P.le della Repubblica, 10
65100 Pescara, Italia
geralico@icra.it
On the charge in Reissner-Nordström geometry

      The interaction of a Reissner-Nordström black hole with charged test particle is studied together with the lines of force of their electric fields.
The electric properties of the black hole horizon are discussed in detail and used to explain the expulsion of the lines of force from the horizon as the hole becomes extreme.
The particle backreaction is also taken into account, studying the effect of general static perturbations of the hole following the pioneering approach of Zerilli.

 

Gurzadyan Vahe

ICRA ( International Center for Relativistic Astrophisics )
P.le della Repubblica, 10
65100 Pescara, Italia
gurzadyan@icra.it
Department of Theoretical Physics
Yerevan Physics institute,
Yerevan 375036, Armenia
Ellipticity analysis of CMB maps

      I review the recent studies of Boomerang and WMAP CMB maps which revealed ellipticity of anisotropies independent on the temperature threshold. The algorithms of the study of anisotropy areas are discussed. The ellipticity is detected at scales both smaller and larger than the horizon at the large scattering epoch. If this effect is due to geodesic mixing and hence due to non precisely zero curvature of the hyperbolic Universe, it can be related with the low multipole anomaly detected by WMAP.

 

Bi Hong-Guang

dept of phys.
univ. of arizona,
Tucson, AZ 85721 USA
peterbi@att.net
The formation of the first objects from the primordial gas: the log-normal model

We study the baryonic gas clouds (the IGM) in the universe before the reionization with the lognormal model which is shown to be dynamcially legitimate in describing the fluctuation evolution in quasilinear as well as nonlinear regimes in recent years. The probability distribution function of the mass field in the LN model is long tailed and so plays an important role in rare events, such as the formation of the first generation of baryonic objects. We calculate density and velocity distributions of the IGM at very high spatial resolutions, and simulate the distributions at resolution of 0.15 kpc from z=7 to 15 in the LCDM cosmological model. We performed a statistics of the hydrogen clouds including column densities, clumping factors, sizes, masses, and spatial number density etc. One of our goals is to identify which hydrogen clouds are going to collapse. By inspecting the mass density profile and the velocity profile of clouds, we found that the velocity outflow significantly postpones the collapsing process in less massive clouds, in spite of their masses are larger than the Jeans mass. Consequently, only massive (> 10^5 M_sun) clouds can form objects at higher redshift, and less massive (10^4-10^5) collapsed objects are formed later.
For example, although the mass fraction in clouds with sizes larger than the Jeans length is already larger than 1 at z=15, there is only a tiny fraction of mass (10^{-8}) in the clouds which are collapsed at that time. If all the ionizing photons, and the 10^{-2} metallicity observed at low redshift are produced by the first 1% mass of collapsed baryonic clouds, the majority of those first generation objects would not happen until z=10.

 

Jantzen Robert

Dept. of Mathematical Sciences
Villanova University, 
Villanova, PA 19085 - USA
jantzen@icra.it
Fermi Time and the Square Root of 2

      By examining the geodesic equation in a Fermi coordinate system using the gravitoelectromagnetic splitting, rewritten as a relative acceleration equation, one sees that the special property of the speed of light as a constant solution is transferred to the coordinate speed $\sqrt{2}$ for the approximation of the Fermi coordinates when using the coordinate time instead of the Fermi coordinate observer proper time. However, examining the exact Fermi coordinates in Rindler spacetime for uniform acceleration along a fixed direction, one sees that this is an artifact of the limitations of the Fermi coordinate approximation, frozen in at the lowest order of the approximation, and when higher order terms become important one sees that it is really the speed of light which is the important speed.

 

Liu Ji-Ren

Center for astrophysics
University of Science and technology of C hina
Hefei, Anhui, 230026
P.R.China
liujr@mail.ustc.edu.cn
Using Scale-Scale Correlation to Detect SZ effect in WMAP

Rencently WMAP observation had provided CMB data with high quanlity, such data excited interest on additional anisotropy, SZ effects is such a candidate. It's contribution to CMB had been debated.
Here we use SSC of  the difference in Q and W band of WMAP data to show a definite signal not from CMB, noise, mask or foreground like synchrotron/free-free/dust emisssion, so SZ is very likey the contributor. Also we show SZ indeed had such SSC with simulation.

 

Lattanzi Massimiliano

ICRA ( International Center for Relativistic Astrophisics )
Dept of Fisica
Università degli Studi di Roma "La Sapienza"
P.le Aldo Moro, 5 - 00185 Roma, Italia
lattanzi@icra.it
Neutrino asymmetry and cosmological parameters estimation

      The recent analysis of the cosmic microwave background data carried out by the WMAP team seems to show that the sum of the neutrino masses is <0.7 eV. However, this result is not model-independent, depending on precise assumptions on the cosmological model. We study how this result is modified when the assumption of perfect lepton symmetry is dropped out.

 

Fang Li-Zhi

dept of phys.
univ. of arizona,
Tucson, AZ 85721, USA
fanglz@physics.arizona.edu
The discrepancy between the large scale structures of baryon gas and dark matter in the universe

      I will present the investigation on the relationship between the mass and velocity fields of the intergalactic medium (IGM) and dark matter.
Although the evolution of the IGM is dynamically governed by the gravity of the underlying dark matter field, many statistical properties of the IGM
inevitably decouple from those of the dark matter once the nonlinearity of the dynamical equations and the stochastic nature of the field is considered. Many features of cosmic large scales structurtes can be explained with this discrepancy.

 

Feng Long-Long

Purple Mountain Observatory
2 Beijing, Xi Lu
Nanjing, Jiangsu, 210008
P.R.China
fengll@ustc.edu.cn
A Hybrid Cosmological Hydrodynamic/N-body Code Based on a Weighted Essentially Non-Oscillatory Scheme
I will present a newly developed cosmological hydrodynamics code based on weighted essentially non-oscillatory (WENO) schemes for hyperbolic conservation laws.
WENO is a higher order accurate finite difference scheme designed for problems with piecewise smooth solutions containing discontinuities, and has been successfully applied for problems involving both shocks and complicated smooth solution structures.
We couple hydrodynamics based on the WENO scheme with standard Poisson solver - particle-mesh (PM) algorithm for evolving the self-gravitating system. The third order low storage total variation diminishing (TVD) Runge-Kutta scheme has been used for the time integration of the system. To test accuracy and convergence rate of the code, we subject it to a number of typical tests including the Sod shock tube in multidimensions, the Sedov blast wave and formation of the Zeldovich pancake. These tests validate the WENO hydrodynamics with fast convergence rate and high accuracy. We also evolve a low density flat cosmological model ($\Lambda$CDM) to explore the validity of the code in practical simulations.

 

Ruffini Remo

ICRA ( International Center for Relativistic Astrophisics )
Dept of Fisica
Università degli Studi di Roma "La Sapienza"
P.le Aldo Moro, 5 - 00185 Roma, Italia

Ruffini@icra.it
Gamma Ray Bursts

 

Xiang Shou-Ping

Center for astrophysics
University of Science and technology of China
Hefei, Anhui, 230026
P.R.China
spxiang@ustc.edu.cn

 

Xia Xiao-Yang

National Astronomical Observatories,
A20 Datun Road, Chaoyang
Beijing 100012 P.R. China
xyxia@ns.bao.ac.cn
Properties of Ultra-Luminous Infrared Galxies

      We study the properties of hot gaseous halos in 10 nearby ultraluminous IRAS galaxies observed with the ACIS instrument on board Chandra.
For all sample
galaxies, diffuse soft X-ray emissions are found within ~10 kpc of the central region; their spectra are well fitted by a MEKAL model plus emission lines from alpha-elements and other ions. The temperature of the hot gas is about 0.7 keV and metallicity is about 1 solar.
Outside the central region, extended hot gaseous halos are found for nine out of the ten ULIRGs. Most spectra of these extended halos can be fitted with a MEKAL model with a temperature of about 0.6 keV and a low metallicity (~ 0.1 solar). We discuss the implications of our results on the origin of X-ray halos in elliptical galaxies and the feedback processes associated with starbursts.

 

Xue She-Sheng 

ICRA ( International Center for Relativistic Astrophisics )
Dept. of Fisica
Università degli Studi di Roma "La Sapienza"
P.le Aldo Moro, 5 - 00185 Roma, Italia

xue@icra.it
On the dynamical formation of the Dyadosphere

     We describe electron-positron pairs creation around an electrically charged star core collapsing to an electromagnetic black hole (EMBH), as well as pairs annihilation into photons. We use the kinetic Vlasov equation formalism for the pairs and photons and show that a regime of plasma oscillations is established around the core. As a byproduct of our analysis we can provide an estimate for the thermalization time scale.

 

Jing Yi-Ping

Shanghai Astr. Observatory
Shanghai, 200030
P.R.China
jingmpa2000@yahoo.com
Simulating the structure formation in the Universe
In this talk I present the current status of the research activities at the Partner Group of MPA in Shanghai Astronomical Observatory. The backbone for our research is high resolution simulations. With these simulations, we have discovered a tight relation between the inner radius of dark matter halos and the mass within the inner radius. Based on this finding, we have developed a recipe for predicting the concentration parameter of dark matter halos from their mass accretion history. This prescription has been demonstrated to be significantly more accurate than the previous empirical formula, and can be applied to many research subjects in cosmology. We have also implemented the semi-analytical modeling of galaxy formation into our simulations. Because the subhalos are well resolved, the dynamical merger of galaxies, which is a key process to drive the evolution of galaxies, can be reliably followed in our simulations. Our model, for the first time, can reproduce very well the luminosity functions of galaxies in the five wavebands of the SDSS observation. I also present our recent measurement for the luminosity dependence of the pairwise velocity dispersion of galaxies in the 2dF Galaxy Redshift Survey, and demonstrate that the statistic is an important input for the galaxy formation models, including the halo occupation models. In collaboration with the University of Toronto, we have already started our campaign for a new sample of giant simulations, which aims at cosmological simulations of 8 billion particles and individual halo simulations of 100 million particles. These simulations will be more accurate than ever to predict how the structures have developed in our Universe.

 

Deng Zu-Gan

Dept. of Physics,
Graduate School,
P.O.Box 3908,
Beijing, 100039
P.R. China
zugan_deng@yahoo.co
m
The formation of Bulge in Late-type Galaxies

The dynamical evolution of super star clusters (SSCs) moving in the background of a dark matter halo has been investigated as a possible event responsible for the formation of bulges in late-type spirals.
The underlying physical processes include sinking of SSCs due to the dynamical friction and stripping of SSCs on their way to
the center. Based on the assumption of a universal density profile for the dark matter halo, and an isothermal model for the SSCs, our simulations have yielded bulges that are similar in many aspects to the observational ones.
In particular, the derived
surface density profiles can be well fitted by an exponential structure with nuclear cusps, which is consistent with HST observations.The preliminary simulations with the Burkert density profile yield very instructive predictions on the bulge formation, which is surely worth further investigating.