The tropicalization of the entropic barrier

TL;DR

This paper explores the tropicalization of the entropic barrier's central path, revealing it as a piecewise linear curve with potential exponential complexity in the problem's dimension.

Contribution

It establishes the tropicalization of the entropic central path and links it to the tropicalization of the logarithmic central path, highlighting its complexity.

Findings

Tropicalization results in a piecewise linear curve.

Number of linear segments can be exponential.

Connects entropic barrier with tropical geometry.

Abstract

The entropic barrier, studied by Bubeck and Eldan (Proc. Mach. Learn. Research, 2015), is a self-concordant barrier with asymptotically optimal self-concordance parameter. In this paper, we study the tropicalization of the central path associated with the entropic barrier, i.e., the logarithmic limit of this central path for a parametric family of linear programs defined over the field of Puiseux series. Our main result is that the tropicalization of the entropic central path is a piecewise linear curve which coincides with the tropicalization of the logarithmic central path studied by Allamigeon et al. (SIAM J. Applied Alg. Geom., 2018). One consequence is that the number of linear pieces in the tropical entropic central path can be exponential in the dimension and the number of inequalities defining the linear program.