586 research outputs found
Discrete Symmetries (C,P,T) in Noncommutative Field Theories
In this paper we study the invariance of the noncmmutative gauge theories
under C, P and T transformations. For the noncommutative space (when only the
spatial part of is non-zero) we show that NCQED is Parity invariant.
In addition, we show that under charge conjugation the theory on noncommutative
is transformed to the theory on , so NCQED is a
CP violating theory. The theory remains invariant under time reversal if,
together with proper changes in fields, we also change by .
Hence altogether NCQED is CPT invariant. Moreover we show that the CPT
invariance holds for general noncommutative space-time.Comment: Revtex File, 4 pages, no figures, minor changes from previous verion.
To appear in Phys. Rev. Let
One Loop Renormalizability of Supersymmetric Yang-Mills Theories on Noncommutative Two-Torus
We argue that Yang-Mills theory on noncommutative torus, expressed in the
Fourrier modes, is described by a gauge theory in a usual commutative space,
the gauge group being a generalization of the area-preserving diffeomorphisms
to the noncommutative case. In this way, performing the loop calculation in
this gauge theory in the continuum limit we show that this theory is {\it one
loop renormalizable}, and discuss the UV and IR limits. The moduli space of the
vacua of the noncommutative super Yang-Mills theories in (2+1) dimensions is
discussed.Comment: 16 pp, one figure, v2: One reference added, typos corrected. v3:
minor exchange
Classification of Different Branes at Angles
In this paper, we consider two D-branes rotated with respect to each other,
and argue that in this way one can find brane configurations preserving {1 \f
16} of SUSY. Also we classify different brane configurations preserving {1 \f
2}, {1 \f 4}, {3 \f 16},{1 \f 8}, {1 \f 16} of SUSY.Comment: Tex, 11 page, no figure
More on Mixed Boundary Conditions and D-branes Bound States
In this article, applying different types of boundary conditions; Dirichlet,
Neumann, or Mixed, on open strings we realize various new brane bound states in
string theory. Calculating their interactions with other D-branes, we find
their charge densities and their tension. A novel feature of brane
bound state is its "non-commutative" nature which is manifestly seen both in
the open strings mode expansions and in their scattering off a -brane.
Moreover we study three or more object bound states in string theory language.
Finally we give a M-theoretic picture of these bound states.Comment: Latex file, pages, No Figure
Noncommutative Open String Theories and Their Dualities
The recently found non-critical open string theories is reviewed. These open
strings, noncommutative open string theories (NCOS), arise as consistent
quantum theories describing the low energy theory of D-branes in a background
electric B-field in the critical limit. Focusing on the D3-brane case, we
construct the most general (3+1) NCOS, which is described by four parameters.
We study S and T -dualities of these theories and argue the existence of a
U-duality group.Comment: 10 pages, no figures, The invited talk, presented in the conference
"Brane New World and Noncommutative Geometry", Torino, Villa Gualino,(Italy)
October, 200
Solution Phase Space and Conserved Charges: A General Formulation for Charges Associated with Exact Symmetries
We provide a general formulation for calculating conserved charges for
solutions to generally covariant gravitational theories with possibly other
internal gauge symmetries, in any dimensions and with generic asymptotic
behaviors. These solutions are generically specified by a number of exact
(continuous, global) symmetries and some parameters. We define "parametric
variations" as field perturbations generated by variations of the solution
parameters. Employing the covariant phase space method, we establish that the
set of these solutions (up to pure gauge transformations) form a phase space,
the \emph{solution phase space}, and that the tangent space of this phase space
includes the parametric variations. We then compute conserved charge variations
associated with the exact symmetries of the family of solutions, caused by
parametric variations. Integrating the charge variations over a path in the
solution phase space, we define the conserved charges. In particular, we
revisit "black hole entropy as a conserved charge" and the derivation of the
first law of black hole thermodynamics. We show that the solution phase space
setting enables us to define black hole entropy by an integration over any
compact, codminesion-2, smooth spacelike surface encircling the hole, as well
as to a natural generalization of Wald and Iyer-Wald analysis to cases
involving gauge fields.Comment: 35 pp, no figure
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