Numerical universal solutions in a-gauge in open string field theory

Abstract

Abstract In bosonic open string field theory, we construct numerical universal solutions in a-gauge corresponding to “double brane” and “ghost brane” solutions in Siegel gauge in addition to the tachyon vacuum solution, and evaluate their gauge invariants, which are energy- and gauge-invariant observables. The a-gauge condition, which contains a real parameter a, was introduced by Asano and Kato. In earlier works it has been applied to find the tachyon vacuum solution with the level truncation method up to level 14. The “double brane” and “ghost brane” solutions were constructed by Kudrna and Schnabl in Siegel gauge, which corresponds to (a = 0)-gauge, up to level 28. Starting from these solutions, by varying a little by little, we have constructed numerical solutions in a-gauge for various values of a including a = ∞ up to level 20. Contrary to naive expectation, the gauge invariants of “double brane” and “ghost brane” solutions in a-gauge seem to be non-constant for a. In particular, although the normalized energy E of the “double brane” solution in a-gauge is approximately two for a ∼ 0, we find that E becomes almost one for 0.5 < a < 1. The gauge-invariant observable behaves similarly. This might imply that the “double brane” solution varies to a single brane solution in such a-gauges.