Large BCFT moduli in open string field theory

TL;DR

This paper analytically relates the BCFT modulus to the boundary marginal field coefficient in open string field theory, revealing a non-one-to-one correspondence and the limitations of using the coefficient as a global coordinate.

Contribution

It provides an explicit analytical relation between BCFT moduli and string field theory parameters, showing the non-injective nature of this mapping.

Findings

The relation between BCFT modulus and marginal field coefficient is not one-to-one.

The BCFT moduli space is fully covered by the solution.

The marginal field coefficient is not a good global coordinate.

Abstract

We use the recently constructed solution for marginal deformations by one of the authors, to analytically relate the BCFT modulus (lambda_BCFT) to the coefficient of the boundary marginal field in the solution (lambda_SFT). We explicitly find that the relation is not one to one and the same value of lambda_SFT corresponds to a pair of different lambda_BCFT 's: a "small" one, and a "large" one. The BCFT moduli space is fully covered, but the coefficient of the marginal field in the solution is not a good global coordinate on such a space.