A New Real Tachyon Vacuum Solution in Cubic Superstring Field Theory

We study a real tachyon vacuum solution in cubic superstring field theory that avoids square roots and phantom terms. Using this new solution, we evaluate the vacuum energy and obtain a result consistent with Sen’s conjecture. Additionally, we demonstrate that the equation of motion, when contracted with the solution itself, is satisfied.

💡 Research Summary

The paper addresses the long‑standing problem of constructing an analytic tachyon vacuum solution in the modified cubic superstring field theory (MCSFT) that is both real and free of the technical complications that have plagued earlier constructions. Schnabl’s original solution, while real, contains a singular “phantom term” and square‑root factors of the form (\sqrt{1+K}). These features make the evaluation of the action cumbersome and obscure the physical interpretation, especially when one attempts to enforce reality through similarity transformations.

Starting from the non‑real but simple solution originally proposed by Gorbachev, \