On Behavior of the Twist-Even Universal Solutions in a-gauge at Low Level in Open String Field Theory

In open string field theory, we performed numerical calculations with the level truncation approximation method in
a-gauge for “double brane” and “ghost brane” solutions in addition to the tachyon vacuum solution in the previous work. These solutions were constructed from one of the solutions in the Siegel gauge at the truncated level 0, 2, and 4, respectively, up to truncated level 20, and their gauge invariants were evaluated for various values of a including a=∞, which corresponds to the Landau gauge. Although these are obtained by restricting the space of string fields to the space spanned by the twist-even universal states, some solutions other than the tachyon vacuum and “double brane” solutions exist at the second lowest truncated level. Here, we evaluate gauge invariants for them and study their behavior. Namely, at the truncated level two, starting from all solutions obtained in a=0 or a=∞ gauge, we construct numerical solutions in various a-gauges by varying the values of a gradually and describe their gauge invariants. Our results might become useful for constructing new physically meaningful solutions at the large truncated level limit.