Electric field of a pointlike charge in a strong magnetic field and ground state of a hydrogenlike atom

TL;DR

This paper investigates how a strong magnetic field modifies the Coulomb potential of a point charge, revealing a Yukawa-like short-range component, anisotropic long-range behavior, and implications for hydrogenlike atoms and neutron star surfaces.

Contribution

It demonstrates the vacuum polarization effects in strong magnetic fields, deriving a modified potential with a Yukawa component and showing the non-infinite ground-state energy of hydrogenlike atoms in such conditions.

Findings

Short-range Yukawa-like potential component identified.

Anisotropic Coulomb law with slower decay along magnetic field.

Ground-state energy of hydrogenlike atom remains finite at infinite magnetic field.

Abstract

In an external constant magnetic field, so strong that the electron Larmour length is much shorter than its Compton length, we consider the modification of the Coulomb potential of a point charge owing to the vacuum polarization. We establish a short-range component of the static interaction in the Larmour scale, expressed as a Yukawa-like law, and reveal the corresponding "photon mass" parameter. The electrostatic force regains its long-range character in the Compton scale: the tail of the potential follows an anisotropic Coulomb law, decreasing away from the charge slower along the magnetic field and faster across. In the infinite-magnetic-field limit the potential is confined to an infinitely thin string passing though the charge parallel to the external field. This is the first evidence for dimensional reduction in the photon sector of quantum electrodynamics. The one-dimensional form of the potential on the string is derived that includes a delta-function centered in the charge. The nonrelativistic ground-state energy of a hydrogenlike atom is found with its use and shown not to be infinite in the infinite-field limit, contrary to what was commonly accepted before, when the vacuum polarization had been ignored. These results may be useful for studying properties of matter at the surface of extremely magnetized neutron stars.