Testing Closed String Field Theory with Marginal Fields

TL;DR

This paper investigates the validity of level expansion in closed string field theory by testing the quartic vertex through potential flatness in marginal directions, combining infinite and finite-level computations.

Contribution

It provides a numerical validation of the quartic vertex in closed string field theory using a novel combination of level expansion techniques.

Findings

Quartic vertex contributions are comparable or smaller than level four fields.

Level expansion can effectively test the quartic vertex.

Numerical results support the consistency of the quartic vertex.

Abstract

We study the feasibility of level expansion and test the quartic vertex of closed string field theory by checking the flatness of the potential in marginal directions. The tests, which work out correctly, require the cancellation of two contributions: one from an infinite-level computation with the cubic vertex and the other from a finite-level computation with the quartic vertex. The numerical results suggest that the quartic vertex contributions are comparable or smaller than those of level four fields.