16 research outputs found
On Stability of the Three 3-brane Model
We show that the Goldberger-Wise mechanism for the three 3-brane scenario proposed by Kogan et al. stabilizes the radion. We find that the system of 3-branes stabilizes in such a way that the loss in the scale factor is insignificant. That is, the negative tension brane chooses to stay close to the visible brane
The Moduli Space of Noncommutative Vortices
The abelian Higgs model on the noncommutative plane admits both BPS vortices
and non-BPS fluxons. After reviewing the properties of these solitons, we
discuss several new aspects of the former. We solve the Bogomoln'yi equations
perturbatively, to all orders in the inverse noncommutivity parameter, and show
that the metric on the moduli space of k vortices reduces to the computation of
the trace of a k-dimensional matrix. In the limit of large noncommutivity, we
present an explicit expression for this metric.Comment: Invited contribution to special issue of J.Math.Phys. on
"Integrability, Topological Solitons and Beyond"; 10 Pages, 1 Figure. v2:
revision of history in introductio
Scalar Solitons on the Fuzzy Sphere
We study scalar solitons on the fuzzy sphere at arbitrary radius and
noncommutativity. We prove that no solitons exist if the radius is below a
certain value. Solitons do exist for radii above a critical value which depends
on the noncommutativity parameter. We construct a family of soliton solutions
which are stable and which converge to solitons on the Moyal plane in an
appropriate limit. These solutions are rotationally symmetric about an axis and
have no allowed deformations. Solitons that describe multiple lumps on the
fuzzy sphere can also be constructed but they are not stable.Comment: 24 pages, 2 figures, typo corrected and stylistic changes. v3:
reference adde
Fuzzy sphere bimodule, ABS construction to the exact soliton solutions
In this paper, we set up the bi-module of the algebra on fuzzy
sphere. Based on the differential operators in moving frame, we generalize the
ABS construction into fuzzy sphere case. The applications of ABS construction
are investigated in various physical systems.Comment: Latex file without figure, 13 page
Dirac-Born-Infeld Action on the Tachyon Kink and Vortex
The tachyon effective field theory describing the dynamics of a non-BPS
D-brane in superstring theory has an infinitely thin but finite tension kink
solution describing a codimension one BPS D-brane. We study the world-volume
theory of massless modes on the kink, and show that the world volume action has
precisely the Dirac-Born-Infeld (DBI) form without any higher derivative
corrections. We generalize this to a vortex solution in the effective field
theory on a brane-antibrane pair. As in the case of the kink, the vortex is
infinitely thin, has finite energy density, and the world-volume action on the
vortex is again given exactly by the DBI action on a BPS D-brane. We also
discuss the coupling of fermions and restoration of supersymmetry and
-symmetry on the world-volume of the kink. Absence of higher derivative
corrections to the DBI action on the soliton implies that all such corrections
are related to higher derivative corrections to the original effective action
on the world-volume of a non-BPS D-brane or brane-antibrane pair.Comment: LaTeX file, 34 pages; references and other minor comments adde
D-Branes on the Conifold and N=1 Gauge/Gravity Dualities
We review extensions of the AdS/CFT correspondence to gauge/ gravity
dualities with N=1 supersymmetry. In particular, we describe the gauge/gravity
dualities that emerge from placing D3-branes at the apex of the conifold. We
consider first the conformal case, with discussions of chiral primary operators
and wrapped D-branes. Next, we break the conformal symmetry by adding a stack
of partially wrapped D5-branes to the system, changing the gauge group and
introducing a logarithmic renormalization group flow. In the gravity dual, the
effect of these wrapped D5-branes is to turn on the flux of 3-form field
strengths. The associated RR 2-form potential breaks the U(1) R-symmetry to
and we study this phenomenon in detail. This extra flux also leads to
deformation of the cone near the apex, which describes the chiral symmetry
breaking and confinement in the dual gauge theory.Comment: Based on I.R.K.'s lectures at the Les Houches Summer School Session
76, ``Gravity, Gauge Theories, and Strings'', August 2001, 42 pages, v2:
clarifications and references adde
Nonperturbative studies of fuzzy spheres in a matrix model with the Chern-Simons term
Fuzzy spheres appear as classical solutions in a matrix model obtained via
dimensional reduction of 3-dimensional Yang-Mills theory with the Chern-Simons
term. Well-defined perturbative expansion around these solutions can be
formulated even for finite matrix size, and in the case of coincident fuzzy
spheres it gives rise to a regularized U() gauge theory on a noncommutative
geometry. Here we study the matrix model nonperturbatively by Monte Carlo
simulation. The system undergoes a first order phase transition as we change
the coefficient () of the Chern-Simons term. In the small
phase, the large properties of the system are qualitatively the same as in
the pure Yang-Mills model (), whereas in the large phase a
single fuzzy sphere emerges dynamically. Various `multi fuzzy spheres' are
observed as meta-stable states, and we argue in particular that the
coincident fuzzy spheres cannot be realized as the true vacuum in this model
even in the large limit. We also perform one-loop calculations of various
observables for arbitrary including . Comparison with our Monte Carlo
data suggests that higher order corrections are suppressed in the large
limit.Comment: Latex 37 pages, 13 figures, discussion on instabilities refined,
references added, typo corrected, the final version to appear in JHE
Noncommutative solitons on Kahler manifolds
We construct a new class of scalar noncommutative multi-solitons on an
arbitrary Kahler manifold by using Berezin's geometric approach to quantization
and its generalization to deformation quantization. We analyze the stability
condition which arises from the leading 1/hbar correction to the soliton energy
and for homogeneous Kahler manifolds obtain that the stable solitons are given
in terms of generalized coherent states. We apply this general formalism to a
number of examples, which include the sphere, hyperbolic plane, torus and
general symmetric bounded domains. As a general feature we notice that on
homogeneous manifolds of positive curvature, solitons tend to attract each
other, while if the curvature is negative they will repel each other.
Applications of these results are discussed.Comment: 26 pages, 3 figures, harvmac; references adde
Noncommutative Fluids
We review the connection between noncommutative gauge theory, matrix models
and fluid mechanical systems. The noncommutative Chern-Simons description of
the quantum Hall effect and bosonization of collective fermion states are used
as specific examples.Comment: To appear in "Seminaire Poincare X", Institut Henri Poincare, Paris;
references adde
Relationship between Vehicle Emissions Laws and Incidence of Suicide by Motor Vehicle Exhaust Gas in Australia, 2001-06: An Ecological Analysis
BACKGROUND: Globally, suicide accounts for 5.2% of deaths among persons aged 15 to 44 years and its incidence is rising. In Australia, suicide rates peaked in 1997 and have been declining since. A substantial part of that decline stems from a plunge in suicides by one particular method: asphyxiation by motor vehicle exhaust gas (MVEG). Although MVEG remains the second most common method of suicide in Australia, its incidence decreased by nearly 70% in the decade to 2006. The extent to which this phenomenon has been driven by national laws in 1986 and 1999 that lowered permissible levels of carbon monoxide (CO) emissions is unknown. The objective of this ecological study was to test the relationship by investigating whether areas of Australia with fewer noxious vehicles per capita experienced lower rates of MVEG suicide. METHODS AND FINDINGS: We merged data on MVEG suicides in Australia (2001-06) with data on the number and age of vehicles in the national fleet, as well as socio-demographic data from the national census. Poisson regression was used to analyse the relationship between the incidence of suicide within two levels of geographical area--postcodes and statistical subdivisions (SSDs)--and the population density of pre-1986 and pre-1999 passenger vehicles in those areas. (There was a mean population of 8,302 persons per postcode in the study dataset and 87,413 persons per SSD.) The annual incidence of MVEG suicides nationwide decreased by 57% (from 2.6 per 100,000 in 2001 to 1.1 in 2006) during the study period; the population density of pre-1986 and pre-1999 vehicles decreased by 55% (from 14.2 per 100 persons in 2001 to 6.4 in 2006) and 26% (from 44.5 per 100 persons in 2001 to 32.9 in 2006), respectively. Area-level regression analysis showed that the suicide rates were significantly and positively correlated with the presence of older vehicles. A percentage point decrease in the population density of pre-1986 vehicles was associated with a 6% decrease (rate ratio [RR] = 1.06; 95% confidence interval [CI] 1.05-1.08) in the incidence of MVEG suicide within postcode areas; a percentage point decrease in the population density of pre-1999 vehicles was associated with a 3% decrease (RR = 1.03; 95% CI 1.02-1.04) in the incidence of MVEG suicide. CONCLUSIONS: Areas of Australia with fewer vehicles predating stringent CO emission laws experience lower rates of MVEG suicide. Although those emission laws were introduced primarily for environmental reasons, countries that lack them may miss the benefits of a serendipitous suicide prevention strategy. Please see later in the article for the Editors' Summary