Matrix model, noncommutative gauge theory and the tachyon potential

The D2 brane-anti-D2-brane system is described in the framework of BFSS Mat rix model and noncommutative (NC) gauge theory. The physical spectrum of fi elds is found by appropriate gauge fixing. The exact tachyon potential is c omputed in terms of these variables and an exact description of tachyon con densation provided. We exhibit multiple vortex production with increasing t opological charge and interpret this as gradual conversion of the brane-ant ibrane system to DO branes. The entire analysis is carried out using the kn own Hamiltonian of the Matrix model, which is equivalent to the Hamiltonian of the NC gauge theory. We identify the supersymmetric ground state of thi s Hamiltonian with the tachyonic vacuum; Sen's conjecture about the latter follows simply from this identification. We also find two types of closed s tring excitations, solitonic (a la Dijkgraaf, Verlinde and Verlinde) as wel l as perturbative, around the tachyonic vacuum. (C) 2001 Elsevier Science B .V. All rights reserved.