3 research outputs found
Electrical conductivity of warm neutron star crust in magnetic fields: Neutron-drip regime
We compute the anisotropic electrical conductivity tensor of the inner crust
of a compact star at non-zero temperature by extending a previous work on the
conductivity of the outer crust. The physical scenarios, where such crust is
formed, involve proto-neutron stars born in supernova explosions, binary
neutron star mergers and accreting neutron stars. The temperature-density range
studied covers the transition from a non-degenerate to a highly degenerate
electron gas and assumes that the nuclei form a liquid, i.e., the temperature
is above the melting temperature of the lattice of nuclei. The electronic
transition probabilities include (a) the dynamical screening of electron-ion
interaction in the hard-thermal-loop approximation for the QED plasma, (b) the
correlations of the ionic component in a one-component plasma, and (c) finite
nuclear size effects. The conductivity tensor is obtained from the Boltzmann
kinetic equation in relaxation time approximation accounting for the
anisotropies introduced by a magnetic field. The sensitivity of the results
towards the matter composition of the inner crust is explored by using several
compositions of the inner crust which were obtained using different nuclear
interactions and methods of solving the many-body problem. The standard
deviation of relaxation time and components of the conductivity tensor from the
average are below except close to crust-core transition, where
non-spherical nuclear structures are expected. Our results can be used in
dissipative magneto-hydrodynamics (MHD) simulations of warm compact stars
Kinetic equation approach to graphene in strong external fields
The report presents the results of using the nonperturbative kinetic approach
to describe the excitation of plasma oscillations in a graphene monolayer. As
examples the constant electric field as well as an electric field of short
high-frequency pulses are considered. The dependence of the induced conduction
and polarization currents characteristics on the pulse intensity, pulse
duration, and polarization is investigated. The characteristics of secondary
electromagnetic radiation resulting from the alternating currents is
investigated. The nonlinear response to the external electric field
characterizes graphene as an active medium. Qualitative agreement is obtained
with the existing experimental result of measurements of currents in constant
electric fields and radiation from graphene in the case of excitation by means
of the infrared and optical pulses.Comment: 12 pages, 14 figures, 1 table, version published in Particle
Nonperturbative Kinetic Description of Electron-Hole Excitations in Graphene in a Time Dependent Electric Field of Arbitrary Polarization
On the basis of the well-known kinetic description of e − e + vacuum pair creation in strong electromagnetic fields in D = 3 + 1 QED we construct a nonperturbative kinetic approach to electron-hole excitations in graphene under the action of strong, time-dependent electric fields. We start from the simplest model of low-energy excitations around the Dirac points in the Brillouin zone. The corresponding kinetic equations are analyzed by nonperturbative analytical and numerical methods that allow to avoid difficulties characteristic for the perturbation theory. We consider different models for external fields acting in both, one and two dimensions. In the latter case we discuss the nonlinear interaction of the orthogonal currents in graphene which plays the role of an active nonlinear medium. In particular, this allows to govern the current in one direction by means of the electric field acting in the orthogonal direction. Investigating the polarization current we detected the existence of high frequency damped oscillations in a constant external electric field. When the electric field is abruptly turned off residual inertial oscillations of the polarization current are obtained. Further nonlinear effects are discussed