| dc.description.abstract | This thesis investigates the non-abelian dynamics of D-Brane systems in String
Theory, specifically focussing on the fate of the open string Tachyon. Starting from
the action of two coincident non-BPS D9-branes, we investigate kink configurations
of the U(2) matrix tachyon field, considering both symmetrised (Str) and
conventional (Tr) prescriptions for the trace over gauge indices of the non-BPS
action. Non-abelian tachyon condensation in the theory with Tr prescription, and
the resulting
fluctuations about the kink profile, are shown to give rise to a theory
of two coincident BPS D8-branes.
Next we investigate magnetic monopole solutions of the non-abelian Dirac-
Born-Infeld (DBI) action describing two coincident non-BPS D9-branes in flat
space. These monopole configurations are singular in the first instance and require
regularization. We discuss a suitable non-abelian ansatz which describes a pointlike
magnetic monopole and show it solves the equations of motion to leading
order in the regularization parameter. Fluctuations are studied and shown to
describe a codimension three BPS D6-brane, a formula is derived for its tension.
Finally, we investigate the dynamics of a pair of coincident D5 branes in the
background of k NS5 branes. We extend Kutasov's original proposal to the nonabelian
case of multiple D-Branes and find that the duality still holds provided
one promotes the radial direction to a matrix valued field associated with a nonabelian
geometric tachyon and a particular parametrization for the transverse
scalar fields is chosen. Analytic and numerical solutions for the pair's equations
of motion are found in certain simplified cases in which the U(2) symmetry is
broken to U(1)
U(1). For certain range of parameters these solutions describe
periodic motion of the centre of mass of the pair bouncing off a finite sized throat
whose minimum size is limited by the D5 branes separation. | en_US |
