161 research outputs found
New supersymmetric Wilson loops in ABJ(M) theories
We present two new families of Wilson loop operators in N= 6 supersymmetric
Chern-Simons theory. The first one is defined for an arbitrary contour on the
three dimensional space and it resembles the Zarembo's construction in N=4 SYM.
The second one involves arbitrary curves on the two dimensional sphere. In both
cases one can add certain scalar and fermionic couplings to the Wilson loop so
it preserves at least two supercharges. Some previously known loops, notably
the 1/2 BPS circle, belong to this class, but we point out more special cases
which were not known before. They could provide further tests of the
gauge/gravity correspondence in the ABJ(M) case and interesting observables,
exactly computable by localizationComment: 9 pages, no figure. arXiv admin note: text overlap with
arXiv:0912.3006 by other author
Morita Duality and Noncommutative Wilson Loops in Two Dimensions
We describe a combinatorial approach to the analysis of the shape and
orientation dependence of Wilson loop observables on two-dimensional
noncommutative tori. Morita equivalence is used to map the computation of loop
correlators onto the combinatorics of non-planar graphs. Several
nonperturbative examples of symmetry breaking under area-preserving
diffeomorphisms are thereby presented. Analytic expressions for correlators of
Wilson loops with infinite winding number are also derived and shown to agree
with results from ordinary Yang-Mills theory.Comment: 32 pages, 9 figures; v2: clarifying comments added; Final version to
be published in JHE
Wilson Loops and Area-Preserving Diffeomorphisms in Twisted Noncommutative Gauge Theory
We use twist deformation techniques to analyse the behaviour under
area-preserving diffeomorphisms of quantum averages of Wilson loops in
Yang-Mills theory on the noncommutative plane. We find that while the classical
gauge theory is manifestly twist covariant, the holonomy operators break the
quantum implementation of the twisted symmetry in the usual formal definition
of the twisted quantum field theory. These results are deduced by analysing
general criteria which guarantee twist invariance of noncommutative quantum
field theories. From this a number of general results are also obtained, such
as the twisted symplectic invariance of noncommutative scalar quantum field
theories with polynomial interactions and the existence of a large class of
holonomy operators with both twisted gauge covariance and twisted symplectic
invariance.Comment: 23 page
Lorentz Anomaly and 1+1-Dimensional Radiating Black Holes
The radiation from the black holes of a 1+1-dimensional chiral quantum
gravity model is studied. Most notably, a non-trivial dependence on a
renormalization parameter that characterizes the anomaly relations is uncovered
in an improved semiclassical approximation scheme; this dependence is not
present in the naive semiclassical approximation.Comment: 7 pages, LaTe
Cornwall-Jackiw-Tomboulis effective potential for canonical noncommutative field theories
We apply the Cornwall-Jackiw-Tomboulis (CJT) formalism to the scalar theory in canonical-noncommutative spacetime. We construct the CJT
effective potential and the gap equation for general values of the
noncommutative parameter . We observe that under the
hypothesis of translational invariance, which is assumed in the effective
potential construction, differently from the commutative case
(), the renormalizability of the gap equation is
incompatible with the renormalizability of the effective potential. We argue
that our result, is consistent with previous studies suggesting that a uniform
ordered phase would be inconsistent with the infrared structure of canonical
noncommutative theories.Comment: 15 pages, LaTe
Classical Solutions of the TEK Model and Noncommutative Instantons in Two Dimensions
The twisted Eguchi-Kawai (TEK) model provides a non-perturbative definition
of noncommutative Yang-Mills theory: the continuum limit is approached at large
by performing suitable double scaling limits, in which non-planar
contributions are no longer suppressed. We consider here the two-dimensional
case, trying to recover within this framework the exact results recently
obtained by means of Morita equivalence. We present a rather explicit
construction of classical gauge theories on noncommutative toroidal lattice for
general topological charges. After discussing the limiting procedures to
recover the theory on the noncommutative torus and on the noncommutative plane,
we focus our attention on the classical solutions of the related TEK models. We
solve the equations of motion and we find the configurations having finite
action in the relevant double scaling limits. They can be explicitly described
in terms of twist-eaters and they exactly correspond to the instanton solutions
that are seen to dominate the partition function on the noncommutative torus.
Fluxons on the noncommutative plane are recovered as well. We also discuss how
the highly non-trivial structure of the exact partition function can emerge
from a direct matrix model computation. The quantum consistency of the TEK
formulation is eventually checked by computing Wilson loops in a particular
limit.Comment: 41 pages, JHEP3. Minor corrections, references adde
Chiral Solitons in a Current Coupled Schr\"odinger Equation With Self Interaction
Recently non-topological chiral soliton solutions were obtained in a
derivatively coupled non-linear Schr\"odinger model in 1+1 dimensions. We
extend the analysis to include a more general self-coupling potential (which
includes the previous cases) and find chiral soliton solutions. Interestingly
even the magnitude of the velocity is found to be fixed. Energy and U(1) charge
associated with this non-topological chiral solitons are also obtained.Comment: 8 pages, no figure, to appear in Phys. Rev.
Time-dependent quantum scattering in 2+1 dimensional gravity
The propagation of a localized wave packet in the conical space-time created
by a pointlike massive source in 2+1 dimensional gravity is analyzed. The
scattering amplitude is determined and shown to be finite along the classical
scattering directions due to interference between the scattered and the
transmitted wave functions. The analogy with diffraction theory is emphasized.Comment: 15 pages in LaTeX with 3 PostScript figure
Gauge Theory on Fuzzy S^2 x S^2 and Regularization on Noncommutative R^4
We define U(n) gauge theory on fuzzy S^2_N x S^2_N as a multi-matrix model,
which reduces to ordinary Yang-Mills theory on S^2 x S^2 in the commutative
limit N -> infinity. The model can be used as a regularization of gauge theory
on noncommutative R^4_\theta in a particular scaling limit, which is studied in
detail. We also find topologically non-trivial U(1) solutions, which reduce to
the known "fluxon" solutions in the limit of R^4_\theta, reproducing their full
moduli space. Other solutions which can be interpreted as 2-dimensional branes
are also found. The quantization of the model is defined non-perturbatively in
terms of a path integral which is finite. A gauge-fixed BRST-invariant action
is given as well. Fermions in the fundamental representation of the gauge group
are included using a formulation based on SO(6), by defining a fuzzy Dirac
operator which reduces to the standard Dirac operator on S^2 x S^2 in the
commutative limit. The chirality operator and Weyl spinors are also introduced.Comment: 39 pages. V2-4: References added, typos fixe
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