K fields, compactons, and thick branes

TL;DR

This paper explores how K fields with non-standard kinetic terms can form compacton domain walls that confine particle propagation and mimic thin branes in higher-dimensional theories, with potential implications for gravity localization.

Contribution

It demonstrates that specific K fields can create finite-thickness branes that confine matter and replicate properties of thin branes, including gravity localization effects.

Findings

Propagation of linear perturbations is suppressed outside the defect.

Inside the defect, perturbations behave normally despite non-standard kinetics.

Gravity localization akin to Randall–Sundrum scenarios is indicated.

Abstract

K fields, that is, fields with a non-standard kinetic term, allow for soliton solutions with compact support, i.e., compactons. Compactons in 1+1 dimensions may give rise to topological defects of the domain wall type and with finite thickness in higher dimensions. Here we demonstrate that, for an appropriately chosen kinetic term, propagation of linear perturbations is completely suppressed outside the topological defect, confining the propagation of particles inside the domain wall. On the other hand, inside the topological defect the propagation of linear perturbations is of the standard type, in spite of the non-standard kinetic term. Consequently, this compacton domain wall may act like a brane of finite thickness which is embedded in a higher dimensional space, but to which matter fields are constrained. In addition, we find strong indications that, when gravity is taken into account, location of gravity in the sense of Randall--Sundrum works for these compacton domain walls. When seen from the bulk, these finite thickness branes, in fact, cannot be distinguished from infinitely thin branes.