608 research outputs found
World Volume Noncommutativity versus Target Space Noncommutativity
It is known that the noncommutativity of D-brane coordinate is responsible
for describing the higher-dimensional D-branes in terms of more fundamental
ones such as D-particles or D-instantons, while considering a noncommutative
torus as a target space is conjectured to be equivalent to introducing the
background antisymmetric tensor field in matrix models. In the present paper we
clarify the dual nature of both descriptions. Namely the noncommutativity of
conjugate momenta of the D-brane coordinates realizes the target space
structure, whereas noncommutativity of the coordinates themselves realizes
world volume structure. We explicitly construct a boundary state for the
Dirichlet boundary condition where the string boundary is adhered to the
D-brane on the noncommutative torus. There are non-trivial relations between
the parameters appeared in the algebra of the coordinates and that of the
momenta.Comment: 17 pages, LaTex, no figure
New Covariant Gauges in String Field Theory
A single-parameter family of covariant gauge fixing conditions in bosonic
string field theory is proposed. It is a natural string field counterpart of
the covariant gauge in the conventional gauge theory, which includes the Landau
gauge as well as the Feynman (Siegel) gauge as special cases. The action in the
Landau gauge is largely simplified in such a way that numerous component fields
have no derivatives in their kinetic terms and appear in at most quadratic in
the vertex.Comment: 24 page
Supersymmetric extended string field theory in NS^n sector and NS^{n-1}-R sector
We construct a class of quadratic gauge invariant actions for extended string
fields defined on the tensor product of open superstring state space for
multiple open string Neveu-Schwarz (NS) sectors with or without one Ramond (R)
sector. The basic idea is the same as for the bosonic extended string field
theory developed by the authors [arXiv:1309.3850]. The theory for NS^n sector
and NS^{n-1}-R sector contains general n-th rank tensor fields and (n-1)-th
rank spinor-tensor fields in the massless spectrum respectively. In principle,
consistent gauge invariant actions for any generic type of 10-dimensional
massive or massless tensor or spinor-tensor fields can be extracted from the
theory. We discuss some simple examples of bosonic and fermionic massless
actions.Comment: 25 page
Topological Matrix Model
Starting from the primal principle based on the noncommutative nature of
(9+1)-dimensional spacetime, we construct a topologically twisted version of
the supersymmetric reduced model with a certain modification. Our formulation
automatically provides extra 1+1 dimensions, thereby the dimensions of
spacetime are promoted to 10+2. With a suitable gauge choice, we can reduce the
model with (10+2)-dimensional spacetime to the one with (9+1)-dimensions and
thus we regard this gauge as the light-cone gauge. It is suggested that the
model so obtained would describe the light-cone F-theory. From this viewpoint
we argue the relation of the reduced model to the matrix model of M-theory and
the SL(2,Z) symmetry of type IIB string theory. We also discuss the general
covariance of the matrix model in a broken phase, and make some comments on the
background independence.Comment: 18 pages, LaTeX, no figures, minor corrections and modifications,
references adde
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