Gauge Fields and Fermions in Tachyon Effective Field Theories

TL;DR

This paper extends tachyon effective field theories for unstable D-branes by incorporating gauge fields and fermions, analyzing their spectra, and establishing solvability of complex models, revealing insights into gauge excitations and bose-fermi degeneracy.

Contribution

It introduces gauge and fermion couplings into tachyon models, explores their spectra, and demonstrates solvability of models with higher-derivative kinetic terms, advancing understanding of brane dynamics.

Findings

Massless gauge fields and infinite massive gauge modes on branes.

Absence of continuum spectrum suggests no conventional gauge excitations in the stable vacuum.

Fermions localize correctly, showing bose-fermi degeneracy at the massless level.

Abstract

In this paper we incorporate gauge fields into the tachyon field theory models for unstable D-branes in bosonic and in Type II string theories. The chosen couplings yield massless gauge fields and an infinite set of equally spaced massive gauge fields on codimension one branes. A lack of a continuum spectrum is taken as evidence that the stable tachyon vacuum does not support conventional gauge excitations. For the bosonic string model we find two possible solvable couplings, one closely related to Born-Infeld forms and the other allowing a detailed comparison to the open string modes on bosonic D-branes. We also show how to include fermions in the type II model. They localize correctly on stable codimension one branes resulting in bose-fermi degeneracy at the massless level. Finally, we establish the solvability of a large class of models that include kinetic terms with more than two derivatives.