21,294 research outputs found
Noncommutative Solitons and Intersecting D-Branes
We construct intersecting D-branes as noncommutative solitons in bosonic and
type II string theory. ``Defect'' branes which are D-branes containing bubbles
of the closed string vacuum play an important role in the construction.Comment: 17 pages, harvmac; published version with added clarification
MAGMO: Coherent magnetic fields in the star forming regions of the Carina-Sagittarius spiral arm tangent
We present the pilot results of the `MAGMO' project, targeted observations of
ground-state hydroxyl masers towards sites of 6.7-GHz methanol maser emission
in the Carina-Sagittarius spiral arm tangent, Galactic longitudes 280 degrees
to 295 degrees. The `MAGMO' project aims to determine if Galactic magnetic
fields can be traced with Zeeman splitting of masers associated with star
formation. Pilot observations of 23 sites of methanol maser emission were made,
with the detection of ground-state hydroxyl masers towards 11 of these and six
additional offset sites. Of these 17 sites, nine are new detections of sites of
1665-MHz maser emission, three of them accompanied by 1667-MHz emission. More
than 70% of the maser features have significant circular polarization, whilst
only ~10% have significant linear polarization (although some features with up
to 100% linear polarization are found). We find 11 Zeeman pairs across six
sites of high-mass star formation with implied magnetic field strengths between
-1.5 mG and +3.8 mG and a median field strength of +1.6 mG. Our measurements of
Zeeman splitting imply that a coherent field orientation is experienced by the
maser sites across a distance of 5.3+/-2.0 kpc within the Carina-Sagittarius
spiral arm tangent.Comment: 19 pages, 13 figures, accepted for publication in MNRA
Laser frequency locking by direct measurement of detuning
We present a new method of laser frequency locking in which the feedback
signal is directly proportional to the detuning from an atomic transition, even
at detunings many times the natural linewidth of the transition. Our method is
a form of sub-Doppler polarization spectroscopy, based on measuring two Stokes
parameters ( and ) of light transmitted through a vapor cell. This
extends the linear capture range of the lock loop by up to an order of
magnitude and provides equivalent or improved frequency discrimination as other
commonly used locking techniques.Comment: 4 pages, 4 figures Revte
Powering process intensification in an oscillatory flow meso-reactor
info:eu-repo/semantics/publishedVersio
Solitons on compact and noncompact spaces in large noncommutativity
We study solutions at the minima of scalar field potentials for Moyal spaces
and torii in the large non-commutativity and interprete these solitons in terms
of non-BPS D-branes of string theory. We derive a mass spectrum formula linking
different D-branes together on quantum torii and suggest that it describes
general systems of D-brane bound states extending the D2-D0 one. Then we
propose a shape for the effective potential approaching these quasi-stable
bound states. We give the gauge symmetries of these systems of branes and show
that they depend on the quantum torii representations.Comment: 25 pages, Latex, 1 figure (use epsfig.sty), corrected formul
RNA Sequencing Reveals Novel Transcripts from Sympathetic Stellate Ganglia During Cardiac Sympathetic Hyperactivity.
Cardiovascular disease is the most prevalent age-related illness worldwide, causing approximately 15 million deaths every year. Hypertension is central in determining cardiovascular risk and is a strong predictive indicator of morbidity and mortality; however, there remains an unmet clinical need for disease-modifying and prophylactic interventions. Enhanced sympathetic activity is a well-established contributor to the pathophysiology of hypertension, however the cellular and molecular changes that increase sympathetic neurotransmission are not known. The aim of this study was to identify key changes in the transcriptome in normotensive and spontaneously hypertensive rats. We validated 15 of our top-scoring genes using qRT-PCR, and network and enrichment analyses suggest that glutamatergic signalling plays a key role in modulating Ca2+ balance within these ganglia. Additionally, phosphodiesterase activity was found to be altered in stellates obtained from the hypertensive rat, suggesting that impaired cyclic nucleotide signalling may contribute to disturbed Ca2+ homeostasis and sympathetic hyperactivity in hypertension. We have also confirmed the presence of these transcripts in human donor stellate samples, suggesting that key genes coupled to neurotransmission are conserved. The data described here may provide novel targets for future interventions aimed at treating sympathetic hyperactivity associated with cardiovascular disease and other dysautonomias
Boundary String Field Theory of the DDbar System
We develop the boundary string field theory approach to tachyon condensation
on the DDbar system. Particular attention is paid to the gauge fields, which
combine with the tachyons in a natural way. We derive the RR-couplings of the
system and express the result in terms of Quillen's superconnection. The result
is related to an index theorem, and is thus shown to be exact.Comment: 38 pages, harvmac. v2: added reference
Tachyons on Dp-branes from Abelian Higgs sphalerons
We consider the Abelian Higgs model in a (p+2)-dimensional space time with
topology M^{p+1} x S^1 as a field theoretical toy model for tachyon
condensation on Dp-branes. The theory has periodic sphaleron solutions with the
normal mode equations resembling Lame-type equations. These equations are
quasi-exactly solvable (QES) for specific choices of the Higgs- to gauge boson
mass ratio and hence a finite number of algebraic normal modes can be computed
explicitely. We calculate the tachyon potential for two different values of the
Higgs- to gauge boson mass ratio and show that in comparison to previously
studied pure scalar field models an exact cancellation between the negative
energy contribution at the minimum of the tachyon potential and the brane
tension is possible for the simplest truncation in the expansion about the
field around the sphaleron. This gives further evidence for the correctness of
Sen's conjecture.Comment: 14 Latex pages including 3 eps-figure
Fivebrane Instantons and couplings in String Theory
We compute the gravitational coupling for IIA string theory on and use string-string duality to deduce the corresponding term for
heterotic string on . The latter is an infinite sum of gravitational
instanton effects which we associate with the effects of Euclidean fivebranes
wrapped on . These fivebranes are the neutral fivebranes or zero size
instantons of heterotic string theory.Comment: 16 pages, harvmac, no figure
Nonlocal, noncommutative picture in quantum mechanics and distinguished canonical maps
Classical nonlinear canonical (Poisson) maps have a distinguished role in
quantum mechanics. They act unitarily on the quantum phase space and generate
-independent quantum canonical maps. It is shown that such maps act in
the noncommutative phase space as dictated by the classical covariance. A
crucial observation made is that under the classical covariance the local
quantum mechanical picture can become nonlocal in the Hilbert space. This
nonlocal picture is made equivalent by the Weyl map to a noncommutative picture
in the phase space formulation of the theory. The connection between the
entanglement and nonlocality of the representation is explored and specific
examples of the generation of entanglement are provided by using such concepts
as the generalized Bell states. That the results have direct application in
generating vacuum soliton configurations in the recently popular scalar field
theories of noncommutative coordinates is also demonstrated.Comment: 14 pages, one figur
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