String field theory at large B-field and non-commutative geometry

In the search for the exact minimum of the tachyon potential in the Witten' s cubic string field theory we try to learn as much as possible from the st ring field theory in the large B-field background. We offer a simple altern ative proof of the Witten's factorization, carry out the analysis of string field equations also for the non-commutative torus and find some novel rel ations to the algebraic K-theory. We note an intriguing relation between Ch ern-Simons and Chern classes of two non-commutative bundles. Finally we obs erve a certain pattern which enables us to make a plausible conjecture abou t the exact form of the minimum.