A Note on the Tachyon State in Vacuum String Field Theory

Abstract

We re-examine the recent proposal of Rastelli, Sen and Zwiebach on the tachyon fluctuation of the vacuum string field theory representing a D25 brane, originally considered by Hata and Kawano. We show that the tachyon state satisfies the linearized equations of motion on-shell in the strong sense thereby allowing us to calculate the ratio of energy density to the tension of the D-brane to be $E_c/T_{25}\simeq \pi^2/3[1/16(ln2)^3]\simeq 0.62$. Our proof relies on a careful handling of the limits ($n\to\infty$) involved in the conformal theory description of the sliver and tachyon states. We conjecture that the sliver state represents a single D25 brane.