Schwinger Pair Production at Finite Temperature and Novel Astrophysical Probes of Millicharged Fermions

Abstract

Schwinger pair production is a non-perturbative and non-linear phenomenon in Quantum Electrodynamics. It is equally interesting to theoretical and experimental physics because of the necessity of strong electric field required to study it. Many theoretical models have been developed to explain and extend the result for the number of pair produced from Scalar QED and QED vacuum. We use Worldline Instanton method to find vacuum decay rate for scalar QED and QED vacuum in presence of constant Electric field and constant Electric field parallel to the Magnetic field at zero temperature in weak field approximation and weak coupling limit. We thus verify results obtained by other theoretical methods for these field configurations. We extend the result to finite temperature case i.e. we give an analytical expression for Scalar QED and QED vacuum decay rate in presence of constant Electric field and constant Electric field parallel to the magnetic field at some non-zero temperature in weak field approximation and weak coupling limit.

Schwinger pair production of electron-positron pairs requires a constant electric field of the order of $10^{18}V/m$. This huge electric field is not achieved in laboratory till now. Some of the astronomical objects like Magnetars do produce an electric field of the order of $10^{14}V/m$. Many extensions of the standard model generically give rise to hypothetical Millicharged particles. These are particles with fractional electric charges. Millicharged particles are interesting from the viewpoint of charge quantization and they are viable dark matter candidate too.

Schwinger pair production of the Millicharged particle is possible in the Magnetar environment and affect the magnetic field evolution of magnetar. We provide a novel, model-independent constraints on these hypothetical particles based on Energy loss argument and Magnetic field evolution argument. We also show the effect of millicharged particles on the braking index of the magnetar.