Strings from tachyons: the<i>c</i>= 1 matrix reloaded

Abstract

We propose a new interpretation of the c=1 matrix model as the world-line\ntheory of N unstable D-particles, in which the hermitian matrix is provided by\nthe non- abelian open string tachyon. For D-particles in 1+1-d string theory,\nwe find a direct quantitative match between the closed string emission due to a\nrolling tachyon and that due to a rolling eigenvalue in the matrix model. We\nexplain the origin of the double-scaling limit, and interpret it as an extreme\nrepresentative of a large equivalence class of dual theories. Finally, we\ndefine a concrete decoupling limit of unstable D-particles in IIB string theory\nthat reduces to the c=1 matrix model, suggesting that 1+1-d string theory\nrepresents the near-horizon limit of an ultra-dense gas of IIB D-particles.\n