The first Paul Dirac - Lev Landau meeting

29 juin 2015, 09:00 → 30 juin 2015, 19:00 Europe/Paris

Annecy, Haute-Savoie France

Due to new instruments which are being built or planned, astrophysics will experience a huge boost in very high precision measurements in the near future. This will allow to measure relativistic effects on and around the Earth, strong field effects all over our Universe, and to discover new physical and astrophysical systems. It is needed an improved theoretical understanding also leading to new instruments.

The first Paul Dirac–Lev Landau Meeting, a satellite meeting of the French-Russian workshop in theoretical astrophysics, covers the physics of Black Holes and of Neutron Stars, the evolution of very massive stars, Gamma Ray Bursts and Supernovae, accretion disks and jets, Dark Matter, galaxies and the evolution of the Universe, precision measurements in General Relativity and finally the issue of Quantum Theory and General Relativity. There are a lot of unexplained observations and open conceptual questions which can gain from a new unitary approach. The ultimate issue we are going to consider is the physical constituents of matter as well as the physics of strong gravitational and electromagnetic fields, the matter-energy under highest pressures and densities what represents the cutting edge of our understanding of nature.

Poster Dirac-Landau.tiff

lun. 29 juin

1 Welcome Address

2 Why are GRBs as they are?

Transparents Pascal_CV.pdf

3 Coffee Break

4 Novel Kinetic 3DMHD Algorithm for High Performance Parallel Computing Systems

The impressive progress of the kinetic schemes in the solution of gas dynamics problems and the development of effective parallel algorithms for modern high performance parallel computing systems led to the development of advanced methods for the solution of the magnetohydrodynamics problem in the important area of plasma physics. The novel feature of the method is the formulation of the complex Boltzmann-like distribution function of kinetic method with the implementation of electromagnetic interaction terms. The numerical method is based on the explicit schemes. Due to logical simplicity and its efficiency, the algorithm is easily adapted to modern high performance parallel computer systems including hybrid computing systems with graphic processors.

Transparents Chetverushkin_CV.pdf

5 Lunch

6 Gravitational Lensing and GRB Observations

After some historical remarks, observational data on the gravitational lensing are given different types of lensing: strong, weak, and microlensing, discovery of planets around distant stars by microlensing. Lensing is considered with large deviation angles, when light passes close to the gravitational radius of the lens, and formation of weak relativistic rings. Influence of plasma on the gravitational lensing surrounding a gravitating body on lensing is considered. A lensing angle in the uniform plasma depends on the frequency of the electromagnetic wave, due to dispersion properties of plasma. Statistical properties of gamma ray bursts with account of gravitational lensing are discussed, including influence of GRB beaming.

Transparents Bisnovatyi-Kogan_CV.pdf

7 Investigation of the spectral lag -energy of GRBs registered by INTEGRAL

We investigated the dependence of spectral lag on energy band based on 28 bright GRBs detected by the SPI and IBIS/ISGRI instruments on the INTEGRAL observatory. It is found that for simple structured bursts or well separated pulses of multi-pulse bursts the spectral lag can be approximated by the relation t=Alog(E), where A is a positive parameter, which correlates with pulse duration. We have not found any negative lag in simple structured bursts or in well separated pulses. While investigating the time profile of the whole burst negative lag may appear due to different spectral parameters of the pulses.

Transparents Pozanenko_CV.pdf

8 Coffee Break

9 Joint Degree between Russia and France

mar. 30 juin

10 TBC

11 Creation of electron-positron plasma with superstring laser field

We present a short review of recent progress in studying QED effects within the interaction of ultra-relativistic laser pulses with vacuum and e - e + plasma. Current development in laser technologies promises very rapid growth of laser intensities in the near future. Two exawatt class facilities (ELI and XCELS, Russia) in Europe are already in the planning stage. Realization of these projects will make available a laser intensity of ˜ 1026 W/cm2 or even higher. Therefore, discussion of nonlinear optical effects in vacuum are becoming compelling for experimentalists and are currently gaining much attention. We show that, in spite of the fact that the expected field strength is still essentially less than E S = m 2 c 3/ eℏ = 1.32 · 1016 V/cm, the nonlinear vacuum effects will be accessible for observation at the ELI and XCELS facilities. The most promissory effect for observation is pair creation by a laser pulse in vacuum. It is shown, that at intensities ˜ 5 · 1025 W/cm2, creation even of a single pair is accompanied by the development of an avalanche QED cascade. There exists a distinctive feature of the laser-induced cascades, as compared with the air showers arising due primarily to cosmic rays entering the atmosphere. In our case the laser field plays not only the role of a target (similar to a nucleus in the case of air showers) but is also responsible for the acceleration of slow particles. It is shown that the effect of pair creation imposes a natural limit for the attainable laser intensity and, apparently, the field strength E ˜ E S is not accessible for a pair-creating electromagnetic field at all.

Transparents Narozhny_CV.pdf

12 Coffee Break

13 Nucleosynthesis in asymmetric supernovae explosion

The problem of nucleosynthesis is studied within an aspherical supernova explosion model. The detailed yield of the chemical elements was performed as postprocessing step by a tracer particles method. The produced nuclides formed two large-scaled layer-structured bubbles with the sizes comparative to the radius of a stellar core, moving from the center in opposite directions. Each layer contained a particular type of nuclides. The iron- group elements (56Ni) were moving preferentially along the cylindrical axis inside the hot region between the forward and reverse shockwaves. The light elements (12C, 16O, 20Ne, 24Mg) formed a torus-like structure in the equatorial plane. The obtained geometry and chemical composition is consistent with theoretically predicted shock breakout phenomenon and is indirectly supported by some SNe observations.

Transparents Chechetkin_CV.pdf

14 Lunch

15 Hydrodynamics and nucleosynthesis in a PISN model

The results of numerical study of the problem of nucleosynthesis in 100 Msol oxygen stellar core explosion as a pair-instability supernova are presented. The hydrodinamical simulation of supernova model in RZ-geometry is performed with the original numerical code based on a piecewise parabolic method on a local stencil (PPML) with self-gravity and with the equation of state for stellar matter, taking into consideration the creations of electro-positron pairs. Detailed yield of chemical elements is performed as a post-processing step using the tracer particles method. In the report the description of the numerical code and the results of simulation with connection to observations will be presented.

Transparents Popov_CV.pdf

16 Further developments in multidimensional simulations of PISN

According to theoretical models, massive stars with masses within the 100–250 M⊙ range should explode as pair-instability supernovae (PISNe). Since the first stars of the Universe are believed to be very massive, these supernovae should play a significant role in the early stages of its history. But these stars represent the last unobserved population, owing to detection limits of current telescopes. In this work we analyze pair-instability supernovae explosions using various numerical codes. We evolve series of the configurations of oxygen cores to establish a range of masses and initial conditions where this type of explosion is possible. We also study the role of possible instabilities in the propagation of shockwaves during the last stage of the explosion. This investigation could help us to predict the observational properties of PISNe for future space and ground telescopes.

Transparents Baranov_CV.pdf

17 Common French-Russian Lab on Numerical Simulations in Astrophysics