Speaker
Description
We revisit the identity-based solutions for tachyon condensation in
open bosonic string field theory (SFT) from the viewpoint of the
sine-square deformation (SSD). We show that the open string system with
SSD exhibits decoupling of the left and right moving modes and so it
behaves like a system with a periodic boundary condition. With a method
developed by Ishibashi and Tada, we construct pairs of Virasoro
generators in this system, which represent symmetries for a closed
string system. Moreover, we find that the modified BRST operator in the
open SFT at the identity-based tachyon vacuum decomposes to holomorphic
and antiholomorphic parts, and these reflect closed string symmetries in
the open SFT. On the basis of SSD and these decomposed operators, we
construct holomorphic and antiholomorphic continuous Virasoro algebras
at the tachyon vacuum. These results imply that it is possible to
formulate a pure closed string theory in terms of the open SFT at the
identity-based tachyon vacuum
