577 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
Gauged M-flation After BICEP2
In view of the recent BICEP2 results [arXiv:1403.3985] which may be
attributed to the observation of B-modes polarization of the CMB with
tensor-to-scalar ratio , we revisit M-flation model.
Gauged M-flation is a string theory motivated inflation model with Matrix
valued scalar inflaton fields in the adjoint representation of a
Yang-Mills theory. In continuation of our previous works, we show that in the
M-flation model induced from a supersymmetric 10d background probed by a stack
of D3-branes, the "effective inflaton" has a double-well Higgs-like
potential, with minima at . We focus on the ,
symmetry-breaking region. We thoroughly examine predictions of the model for
in the region allowed for by the Planck experiment. As
computed in [arXiv:0903.1481], for and we find , which sits in the sweet spot of BICEP2 region for . We find that with
increasing arbitrarily, cannot go beyond . As
varies in the range which is allowed by Planck and could be reached
by the model, varies in the range . Future cosmological
experiments, like the CMBPOL, that confines with can
constrain the model further. Also, in this region of potential, for
, we find that the largest isocurvature mode, which is uncorrelated
with curvature perturbations, has a power spectrum with the amplitude of order
at the end of inflation. We also discuss the range of predictions of
in the hilltop region, .Comment: v1:16 pages, 9 figures; v2: matched the published versio
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