New Bounds for the Mass of Warm Dark Matter Particles Using Results from Fermionic King Model

After reviewing several aspects about the thermodynamics of self-gravitating systems that undergo the evaporation (escape) of their constituents, some recent results obtained in the framework of fermionic King model are applied here to the analysis of galactic halos considering warm dark matter (WDM) particles. According to the present approach, the reported structural parameters of dwarf galaxies are consistent with the existence of a WDM particle with mass in the keV scale. Assuming that the dwarf galaxy Willman 1 belongs to the region III of fermionic King model (whose gravothermal collapse is a continuous phase transition), one obtains the interval 1.2 keV ≤ m ≤ 2.6 keV for the mass of WDM particle. This analysis improves previous estimates by de Vega and co-workers [Astropart. Phys. 46 (2013) 14–22] considering both the quantum degeneration and the incidence of the constituents evaporation. This same analysis evidences that most of galaxies are massive enough to undergo a violent gravothermal collapse (a discontinuous microcanonical phase transition) that leads to the formation of a degenerate core of WDM particles. It is also suggested that quantum-relativistic processes governing the cores of large galaxies (e.g., the formation of supermassive black holes) are somehow related to the gravothermal collapse of the WDM degenerate cores when the total mass of these systems are comparable to the quantum-relativistic characteristic mass Mc=ℏc/G3/2m−2≃1012M⊙ obtained for WDM particles with mass m in the keV scale. The fact that a WDM particle with mass in the keV scale seems to be consistent with the observed properties of dwarf and large galaxies provides a strong support to this dark matter candidate.

Lyapunov spectrum of a relativistic stochastic flow in the Poincaré group

We determine the Lyapunov spectrum and stable manifolds of some stochastic flows on the Poincaré group associated to Dudley's relativistic processes.

SOLUTION TO THE SIGMA PROBLEM OF PULSAR WIND NEBULAE

Pulsar wind nebulae (PWN) provide a unique test-bed for the study of highly relativistic processes right at our astronomical doorstep. In this contribution we will show results from the first 3D RMHD simulations of PWN. Of key interest to our study is the long standing "sigma-problem" that challenges MHD models of Pulsars and their nebulae now for 3 decades. Earlier 2D MHD models were very successful in reproducing the morphology of the inner Crab nebula showing a jet, torus, concentric wisps and a variable knot. However, these models are limited to a purely toroidal field geometry which leads to an exaggerated compression of the termination shock and polar jet — in contrast to the observations. In three dimensions, the toroidal field structure is susceptible to current driven instabilities; hence kink instability and magnetic dissipation govern the dynamics of the nebula flow. This leads to a resolution of the sigma-problem once also the pulsar's obliqueness (striped wind) is taken into account. In addition, we present polarized synchrotron maps constructed from the 3D simulations, showing the wealth of morphological features reproduced in 2D is preserved in the 3D case.

A UNIFYING APPROACH TO RELATIVISTIC DIFFUSIONS AND H-THEOREMS

A new, wide class of relativistic stochastic processes is introduced. All relativistic processes considered so far in the literature (the Relativistic Ornstein–Uhlenbeck Process as well as the Franchi–Le Jan and the Dunkel–Hänggi processes) are members of this class. The stochastic equations of motion and the associated forward Kolmogorov equations are obtained for each process in the class. The corresponding manifestly covariant transport equation is also obtained. In particular, the manifestly covariant equations for the Franchi–Le Jan and the Dunkel–Hänggi processes are derived here for the first time. Finally, the manifestly covariant approach is used to prove a new H-theorem for all processes in the class.

The Big Picture from Radio Waves to Gamma Rays

The conventional paradigm of active galactic nuclei (AGN) holds that they are powered by accretion onto a gravitational engine. In addition, the presence of Doopler-boosted radiation from jets and anisotropic obscuration can create large differences between the observed and intrinsic properties of AGN (Antonucci 1994). The “big picture” of extragalactic radio sources must include observations across the electromagnetic spectrum. Relativistic processes produce radiation with a very wide bandwidth. In addition, much of the energy from AGN is reprocessed, and the opacity is a function of wavelength. Finally, it turns out that only a small fraction of the bolometric luminosity of most AGN is emitted in the traditional radio and optical bands.