Fundamental strings and NS5-branes from unstable D-branes in supergravity

Abstract

By using the non-supersymmetric p -brane solutions delocalized in arbitrary number of transverse directions in type II supergravities, we show how they can be regarded as interpolating solutions between unstable D p -branes (a non-BPS D-brane or a pair of coincident D-brane–anti-D-brane) and fundamental strings and also between unstable D p -branes and NS5-branes. We also show that some of these solutions can be regarded as interpolating solutions between NS5/ NS ¯ 5 and D p -branes (for p ⩽ 5 ). This gives a closed string description of the tachyon condensation and lends support to the conjecture that the open string theory on unstable D-branes at the tachyonic vacuum has soliton solutions describing not only the lower-dimensional BPS D-branes, but also the fundamental strings as well as the NS5-branes.