1,844 research outputs found
A universe in a global monopole
We investigate brane physics in a universe with an extra dimensional global
monopole and negative bulk cosmological constant. The graviton zero mode is
naturally divergent; we thus invoke a physical cut-off to induce four
dimensional gravity on a brane at the monopole core. Independently, the massive
Kaluza-Klein modes have naturally compactified extra dimensions, inducing a
discrete spectrum. This spectrum remains consistent with four dimensional
gravity on the brane, even for small mass gap. Extra dimensional matter fields
also induce four dimensional matter fields on the brane, with the same
Kaluza-Klein spectrum of excited states. We choose parameters to solve the
hierarchy problem; that is, to induce the observed hierarchy between particle
and Planck scales in the effective four dimensional universe.Comment: 22 pages, 2 eps figures, revte
Gravity of higher-dimensional global defects
Solutions of Einstein's equations are found for global defects in a
higher-dimensional spacetime with a nonzero cosmological constant Lambda. The
defect has a (p-1)-dimensional core (brane) and a `hedgehog' scalar field
configuration in the n extra dimensions. For Lambda = 0 and n > 2, the
solutions are characterized by a flat brane worldsheet and a solid angle
deficit in the extra dimensions. For Lambda > 0, one class of solutions
describes spherical branes in an inflating higher-dimensional universe.
Instantons obtained by a Euclidean continuation of such solutions describe
quantum nucleation of the entire inflating brane-world, or of a spherical brane
in an inflating higher-dimensional universe. For Lambda < 0, one class of
solutions exhibits an exponential warp factor. It is similar to spacetimes
previously discussed by Randall and Sundrum for n = 1 and by Gregory for n = 2.Comment: 18 pages, no figures, uses revte
Mental Health Over Time in a Military Sample: The Impact of Alcohol Use Disorder on Trajectories of Psychopathology After Deployment
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/116086/1/jts22055.pd
Left atrial thrombus resolution in atrial fibrillation or flutter:Results of a prospective study with rivaroxaban (X-TRA) and a retrospective observational registry providing baseline data (CLOT-AF)
BackgroundData on left atrial/left atrial appendage (LA/LAA) thrombus resolution after non–vitamin K antagonist (VKA) oral anticoagulant treatment are scarce. The primary objective of X-TRA was to explore the use of rivaroxaban for the resolution of LA/LAA thrombi in patients with nonvalvular atrial fibrillation (AF) or atrial flutter, with the CLOT-AF registry providing retrospective data after standard-of-care therapy in this setting.MethodsX-TRA was a prospective, single-arm, open-label, multicenter study that investigated rivaroxaban treatment for 6 weeks for LA/LAA thrombus resolution in patients with nonvalvular AF or atrial flutter and LA/LAA thrombus confirmed at baseline on a transesophageal echocardiogram (TEE). CLOT-AF retrospectively collected thrombus-related patient outcome data after standard-of-care anticoagulant treatment for 3 to 12 weeks in patients with nonvalvular AF or atrial flutter who had LA/LAA thrombi on TEE recorded in their medical file.ResultsIn X-TRA, patients were predominantly (95.0%) from Eastern European countries. The adjudicated thrombus resolution rate was 41.5% (22/53 modified intention-to-treat [mITT] patients, 95% CI 28.1%-55.9%) based on central TEE assessments. Resolved or reduced thrombus was evident in 60.4% (32/53 mITT patients, 95% CI 46.0%-73.6%) of patients. In CLOT-AF, the reported thrombus resolution rate was 62.5% (60/96 mITT patients, 95% CI 52.0%-72.2%) and appeared better in Western European countries (34/50; 68.0%) than in Eastern European countries (26/46; 56.5%).ConclusionX-TRA is the first prospective, multicenter study examining LA/LAA thrombus resolution with a non-VKA oral anticoagulant in VKA-naïve patients or in patients with suboptimal VKA therapy. Rivaroxaban could be a potential option for the treatment of LA/LAA thrombi
Galileon Hairs of Dyson Spheres, Vainshtein's Coiffure and Hirsute Bubbles
We study the fields of spherically symmetric thin shell sources, a.k.a. Dyson
spheres, in a {\it fully nonlinear covariant} theory of gravity with the
simplest galileon field. We integrate exactly all the field equations once,
reducing them to first order nonlinear equations. For the simplest galileon,
static solutions come on {\it six} distinct branches. On one, a Dyson sphere
surrounds itself with a galileon hair, which far away looks like a hair of any
Brans-Dicke field. The hair changes below the Vainshtein scale, where the extra
galileon terms dominate the minimal gradients of the field. Their hair looks
more like a fuzz, because the galileon terms are suppressed by the derivative
of the volume determinant. It shuts off the `hair bunching' over the `angular'
2-sphere. Hence the fuzz remains dilute even close to the source. This is
really why the Vainshtein's suppression of the modifications of gravity works
close to the source. On the other five branches, the static solutions are all
{\it singular} far from the source, and shuttered off from asymptotic infinity.
One of them, however, is really the self-accelerating branch, and the
singularity is removed by turning on time dependence. We give examples of
regulated solutions, where the Dyson sphere explodes outward, and its
self-accelerating side is nonsingular. These constructions may open channels
for nonperturbative transitions between branches, which need to be addressed
further to determine phenomenological viability of multi-branch gravities.Comment: 29+1 pages, LaTeX, 2 .pdf figure
Cosmic strings in dilaton gravity
We examine the metric of an isolated self-gravitating abelian-Higgs vortex in
dilatonic gravity for arbitrary coupling of the vortex fields to the dilaton.
We look for solutions in both massless and massive dilaton gravity. We compare
our results to existing metrics for strings in Einstein and Jordan-Brans-Dicke
theory. We explore the generalization of Bogomolnyi arguments for our vortices
and comment on the effects on test particles.Comment: 24 pages plain TEX, 4 figures -- references amended, some additional
comments added, version to appear in journa
Phonon counting and intensity interferometry of a nanomechanical resonator
In optics, the ability to measure individual quanta of light (photons) enables a great many applications, ranging from dynamic imaging within living organisms to secure quantum communication. Pioneering photon counting experiments, such as the intensity interferometry performed by Hanbury Brown and Twiss to measure the angular width of visible stars, have played a critical role in our understanding of the full quantum nature of light. As with matter at the atomic scale, the laws of quantum mechanics also govern the properties of macroscopic mechanical objects, providing fundamental quantum limits to the sensitivity of mechanical sensors and transducers. Current research in cavity optomechanics seeks to use light to explore the quantum properties of mechanical systems ranging in size from kilogram-mass mirrors to nanoscale membranes, as well as to develop technologies for precision sensing and quantum information processing. Here we use an optical probe and single-photon detection to study the acoustic emission and absorption processes in a silicon nanomechanical resonator, and perform a measurement similar to that used by Hanbury Brown and Twiss to measure correlations in the emitted phonons as the resonator undergoes a parametric instability formally equivalent to that of a laser. Owing to the cavity-enhanced coupling of light with mechanical motion, this effective phonon counting technique has a noise equivalent phonon sensitivity of 0.89 ± 0.05. With straightforward improvements to this method, a variety of quantum state engineering tasks using mesoscopic mechanical resonators would be enabled, including the generation and heralding of single-phonon Fock states and the quantum entanglement of remote mechanical elements
Deaf children's understanding of emotions: desires take precedence
Deaf children frequently have trouble understanding other people's emotions. It has been suggested that an impaired theory of mind can account for this. This research focused on the spontaneous use of mental states in explaining other people's emotions by 6- and 10-year-old deaf children as compared to their hearing peers. Within both age-groups deaf children referred to others' beliefs as often as their hearing peers and their references to desires even exceeded those of hearing children. This relative priority for the expression of desires is discussed in terms of possible communicative patterns of deaf children. The specific problems that deaf children meet in their daily communication might explain their abundance of desire-references: plausibly, they give a high priority to stress their own desires and needs unambiguously
Warped compactification on Abelian vortex in six dimensions
We consider the possibility of localizing gravity on a Nielsen-Olesen vortex
in the context of the Abelian Higgs model. The vortex lives in a
six-dimensional space-time with negative bulk cosmological constant. In this
model we find a region of the parameter space leading, simultaneously, to
warped compactification and to regular space-time geometry. A thin defect limit
is studied. Regular solutions describing warped compactifications in the case
of higher winding number are also presented.Comment: LaTeX, 39 pages, 21 figures, final version appeared in Nucl. Phys.
Subthreshold PTSD and PTSD in a prospective‐longitudinal cohort of military personnel: Potential targets for preventive interventions
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/146501/1/da22819_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/146501/2/da22819.pd
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