Covariant transport equation and gravito-conductivity in generic stationary spacetimes

TL;DR

This paper derives a covariant transport equation for particle flux in stationary spacetimes, analyzing gravito-conductivity near horizons and connecting relativistic results to classical gravitational transport models.

Contribution

It introduces a new near detailed balance solution to the relativistic Boltzmann equation with a novel collision term, and constructs an explicit covariant transport equation applicable to generic stationary spacetimes.

Findings

Gravito-conductivity diverges near the horizon in Rindler and Kerr spacetimes.

Results match non-relativistic gravitational transport in the weak field limit.

Transport tensors depend on integral functions of chemical potential and relativistic coldness.

Abstract

We find a near detailed balance solution to the relativistic Boltzmann equation under the relaxation time approximation with a collision term which differs from the Anderson-Witting model and is dependent on the stationary observer. Using this new solution, we construct an explicit covariant transport equation for the particle flux in response to the generalized temperature and chemical potential gradients in generic stationary spacetimes, with the transport tensors characterized by some integral functions in the chemical potential and the relativistic coldness. To illustrate the application of the transport equation we study probe systems in Rindler and Kerr spacetimes and analyze the asymptotic properties of the gravito-conductivity tensor in the near horizon limit. It turns out that both the longitudinal and lateral parts (if present) of the gravito-conductivity tend to be divergent in the near horizon limit. In the weak field limit, our results coincide with with the non-relativistic gravitational transport equation which follows from the direct application of the Drude model.