Speaker
Description
We study the influence of positrons on the outer crusts of neutron
stars and the interiors of white dwarfs, introducing them as a novel
component in both the composition of matter and in transport
processes. We solve a system of coupled Boltzmann kinetic equations
for the electron and positron distribution functions in the
relaxation-time approximation, taking into account electron–ion,
positron–ion, and electron–positron collisions. The relevant
scattering matrix elements are calculated from one-plasmon exchange
diagrams, with in-medium polarization tensors derived within the
hard–thermal–loop effective theory. Numerical results are obtained
for matter composed of carbon, iron and helium nuclei. We find that the conductivity
rises with temperature, following a power law $\sigma \propto T^4$
in the semi-degenerate regime and $\sigma \propto T$ in the
nondegenerate regime, due to the intense creation of thermal
electron–positron pairs and the resulting collisions among
them. These results highlight the importance of including positrons
in the transport properties of heated, dense astrophysical plasmas.