284 research outputs found
On plane wave and vortex-like solutions of noncommutative Maxwell-Chern-Simons theory
We investigate the spectrum of the gauge theory with Chern-Simons term on the
noncommutative plane, a modification of the description of the Quantum Hall
fluid recently proposed by Susskind. We find a series of the noncommutative
massive ``plane wave'' solutions with polarization dependent on the magnitude
of the wave-vector. The mass of each branch is fixed by the quantization
condition imposed on the coefficient of the noncommutative Chern-Simons term.
For the radially symmetric ansatz a vortex-like solution is found and
investigated. We derive a nonlinear difference equation describing these
solutions and we find their asymptotic form. These excitations should be
relevant in describing the Quantum Hall transitions between plateaus and the
end transition to the Hall Insulator.Comment: 17 pages, LaTeX (JHEP), 1 figure, added references, version accepted
to JHE
First report of Phytophthora capsici in the Lao PDR
Phytophthora capsici is reported for the first time in the Lao PDR. It was isolated from soil collected from the root zone of wilting red chilli (Capsicum annuum) plants in a polyhouse farm in Paksong district of Champasak province. The wilting chilli plants had typical symptoms of infection by P. capsici including root rot and necrosis of the outer cortex of the stem base. The isolate was identified using morphological and molecular markers. A pathogenicity trial demonstrated that the culture was pathogenic to a local cultivar of chilli seedlings
Supersymmetric codimension-two branes and U(1)_R mediation in 6D gauged supergravity
We construct a consistent supersymmetric action for brane chiral and vector
multiplets in a six-dimensional chiral gauged supergravity. A nonzero brane
tension can be accommodated by allowing for a brane-localized Fayet-Iliopoulos
term proportional to the brane tension. When the brane chiral multiplet is
charged under the bulk U(1)_R, we obtain a nontrivial coupling to the extra
component of the U(1)_R gauge field strength as well as a singular scalar
self-interaction term. Dimensionally reducing to 4D on a football
supersymmetric solution, we discuss the implication of such interactions for
obtaining the U(1)_R D-term in the 4D effective supergravity. By assuming the
bulk gaugino condensates and nonzero brane F- and/or D-term for the uplifting
potential, we have all the moduli stabilized with a vanishing cosmological
constant. The brane scalar with nonzero R charge then gets a soft mass of order
the gravitino mass. The overall sign of the soft mass squared depends on the
sign of the R charge as well as whether the brane F- or D-term dominates.Comment: 28 pages, no figures, version to appear in JHE
F-term uplifting via consistent D-terms
The issue of fine-tuning necessary to achieve satisfactory degree of
hierarchy between moduli masses, the gravitino mass and the scale of the
cosmological constant has been revisited in the context of supergravities with
consistent D-terms. We have studied (extended) racetrack models where
supersymmetry breaking and moduli stabilisation cannot be separated from each
other. We show that even in such cases the realistic hierarchy can be achieved
on the expense of a single fine-tuning. The presence of two condensates changes
the role of the constant term in the superpotential, W_0, and solutions with
small vacuum energy and large gravitino mass can be found even for very small
values of W_0. Models where D-terms are allowed to vanish at finite vevs of
moduli fields - denoted `cancellable' D-terms - and the ones where D-terms may
vanish only at infinite vevs of some moduli - denoted `non-cancellable' -
differ markedly in their properties. It turns out that the tuning with respect
to the Planck scale required in the case of cancellable D-terms is much weaker
than in the case of non-cancellable ones. We have shown that, against
intuition, a vanishing D-term can trigger F-term uplifting of the vacuum energy
due to the stringent constraint it imposes on vacuum expectation values of
charged fields. Finally we note that our models only rely on two dimensionful
parameters: M_P and W_0.Comment: 10 pages, 2 figures, plain Latex, references adde
Supersymmetric codimension-two branes in six-dimensional gauged supergravity
We consider the six-dimensional Salam-Sezgin supergravity in the presence of
codimension-2 branes. In the case that the branes carry only tension, we
provide a way to supersymmetrise them by adding appropriate localised
Fayet-Iliopoulos terms and localised corrections to the Chern-Simons term and
modifying accordingly the fermionic supersymmetry transformations. The
resulting brane action has N=1 supersymmetry (SUSY). We find the axisymmetric
vacua of the system and show that one has unwarped background solutions with
"football"-shaped extra dimensions which always respect N=1 SUSY for any value
of the equal brane tensions, in contrast with the non-supersymmetric brane
action background. Finally, we generically find multiple zero modes of the
gravitino in this background and discuss how one could obtain a single chiral
zero mode present in the low energy spectrum.Comment: 21 pages, no figures, A sign error in the gauge potential at the
lower brane corrected and its consequent effect discusse
Dualities in Quantum Hall System and Noncommutative Chern-Simons Theory
We discuss different dualities of QHE in the framework of the noncommutative
Chern-Simons theory. First, we consider the Morita or T-duality transformation
on the torus which maps the abelian noncommutative CS description of QHE on the
torus into the nonabelian commutative description on the dual torus. It is
argued that the Ruijsenaars integrable many-body system provides the
description of the QHE with finite amount of electrons on the torus. The new
IIB brane picture for the QHE is suggested and applied to Jain and generalized
hierarchies. This picture naturally links 2d -model and 3d CS
description of the QHE. All duality transformations are identified in the brane
setup and can be related with the mirror symmetry and S duality. We suggest a
brane interpretation of the plateu transition in IQHE in which a critical point
is naturally described by WZW model.Comment: 31 pages, 4 figure
Metastable Vacua in Flux Compactifications and Their Phenomenology
In the context of flux compactifications, metastable vacua with a small
positive cosmological constant are obtained by combining a sector where
supersymmetry is broken dynamically with the sector responsible for moduli
stabilization, which is known as the F-uplifting. We analyze this procedure in
a model-independent way and study phenomenological properties of the resulting
vacua.Comment: 21 pages, 19 figures; v2: matches version published in JHE
A Vector Non-abelian Chern-Simons Duality
Abelian Chern-Simons gauge theory is known to possess a `-self-dual'
action where its coupling constant is inverted {\it i.e.} . Here a vector non-abelian duality is found in the
pure non-abelian Chern-Simons action at the classical level. The dimensional
reduction of the dual Chern-Simons action to two-dimensions constitutes a dual
Wess-Zumino-Witten action already given in the literature.Comment: 14+1 pages, LaTeX file, no figures, version to appear in Phys. Rev
de Sitter String Vacua from Kahler Uplifting
We present a new way to construct de Sitter vacua in type IIB flux
compactifications, in which the interplay of the leading perturbative and
non-perturbative effects stabilize all moduli in dS vacua at parametrically
large volume. Here, the closed string fluxes fix the dilaton and the complex
structure moduli while the universal leading perturbative quantum correction to
the Kahler potential together with non-perturbative effects stabilize the
volume Kahler modulus in a dS_4-vacuum. Since the quantum correction is known
exactly and can be kept parametrically small, this construction leads to
calculable and explicitly realized de Sitter vacua of string theory with
spontaneously broken supersymmetry.Comment: 1+21 pages, 5 figures, LaTeX, uses JHEP3 class, v3: conforms with
published versio
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