1,026 research outputs found
The wake of a quark moving through a strongly-coupled supersymmetric Yang-Mills plasma
The energy density wake produced by a heavy quark moving through a strongly
coupled N=4 supersymmetric Yang-Mills plasma is computed using gauge/string
duality.Comment: 4 pages, typos fixe
Jets in strongly-coupled N = 4 super Yang-Mills theory
We study jets of massless particles in N=4 super Yang-Mills using the AdS/CFT
correspondence both at zero and finite temperature. We set up an initial state
corresponding to a highly energetic quark/anti-quark pair and follow its time
evolution into two jets. At finite temperature the jets stop after traveling a
finite distance, whereas at zero temperature they travel and spread forever. We
map out the corresponding baryon number charge density and identify the generic
late time behavior of the jets as well as features that depend crucially on the
initial conditions.Comment: 21 pages, 12 figures. Added discussion regarding string profiles in
more than one spatial dimension. Refs adde
Shining a Gluon Beam Through Quark-Gluon Plasma
We compute the energy density radiated by a quark undergoing circular motion
in strongly coupled supersymmetric Yang-Mills plasma. If it
were in vacuum, this quark would radiate a beam of strongly coupled radiation
whose angular distribution has been characterized and is very similar to that
of synchrotron radiation produced by an electron in circular motion in
electrodynamics. Here, we watch this beam of gluons getting quenched by the
strongly coupled plasma. We find that a beam of gluons of momenta is attenuated rapidly, over a distance in
a plasma with temperature . As the beam propagates through the plasma at the
speed of light, it sheds trailing sound waves with momenta .
Presumably these sound waves would thermalize in the plasma if they were not
hit soon after their production by the next pulse of gluons from the
lighthouse-like rotating quark. At larger and larger , the trailing sound
wave becomes less and less prominent. The outward going beam of gluon radiation
itself shows no tendency to spread in angle or to shift toward larger
wavelengths, even as it is completely attenuated. In this regard, the behavior
of the beam of gluons that we analyze is reminiscent of the behavior of jets
produced in heavy ion collisions at the LHC that lose a significant fraction of
their energy without appreciable change in their angular distribution or their
momentum distribution as they plow through the strongly coupled quark-gluon
plasma produced in these collisions.Comment: 16 pages, 4 figure
Fluctuation, dissipation, and thermalization in non-equilibrium AdS_5 black hole geometries
We give a simple recipe for computing dissipation and fluctuations
(commutator and anti-commutator correlation functions) for non-equilibrium
black hole geometries. The recipe formulates Hawking radiation as an initial
value problem, and is suitable for numerical work. We show how to package the
fluctuation and dissipation near the event horizon into correlators on the
stretched horizon. These horizon correlators determine the bulk and boundary
field theory correlation functions. In addition, the horizon correlators are
the components of a horizon effective action which provides a quantum
generalization of the membrane paradigm. In equilibrium, the analysis
reproduces previous results on the Brownian motion of a heavy quark. Out of
equilibrium, Wigner transforms of commutator and anti-commutator correlation
functions obey a fluctuation-dissipation relation at high frequency.Comment: 28 pages, 6 figure
Dobutamine stress MRI in pulmonary hypertension: relationships between stress pulmonary artery relative area change, RV performance, and 10-year survival
In pulmonary hypertension (PH), right ventricular (RV) performance determines survival. Pulmonary artery (PA) stiffening is an important biomechanical event in PH and also predicts survival based on the PA relative area change (RAC) measured at rest using magnetic resonance imaging (MRI). In this exploratory study, we sought to generate novel hypotheses regarding the influence of stress RAC on PH prognosis and the interaction between PA stiffening, RV performance and survival. Fifteen PH patients underwent dobutamine stress-MRI (ds-MRI) and right heart catheterization. RACREST, RACSTRESS, and ΔRAC (RAC STRESS – RAC REST) were correlated against resting invasive hemodynamics and ds-MRI data regarding RV performance and RV-PA coupling efficiency (n’vv [RV stroke volume/RV end-systolic volume]). The impact of RAC, RV data, and n’vv on ten-year survival were determined using Kaplan–Meier analysis. PH patients with a low ΔRAC (<−2.6%) had a worse long-term survival (log-rank P = 0.045, HR for death = 4.46 [95% CI = 1.08–24.5]) than those with ΔRAC ≥ −2.6%. Given the small sample, these data should be interpreted with caution; however, low ΔRAC was associated with an increase in stress diastolic PA area indicating proximal PA stiffening. Associations of borderline significance were observed between low RACSTRESS and low n’vvSTRESS, Δη’VV, and ΔRVEF. Further studies are required to validate the potential prognostic impact of ΔRAC and the biomechanics potentially connecting low ΔRAC to shorter survival. Such studies may facilitate development of novel PH therapies targeted to the proximal PA
The stress-energy tensor of a quark moving through a strongly-coupled N=4 supersymmetric Yang-Mills plasma: comparing hydrodynamics and AdS/CFT
The stress-energy tensor of a quark moving through a strongly coupled N=4
supersymmetric Yang-Mills plasma is evaluated using gauge/string duality. The
accuracy with which the resulting wake, in position space, is reproduced by
hydrodynamics is examined. Remarkable agreement is found between hydrodynamics
and the complete result down to distances less than 2/T away from the quark. In
performing the gravitational analysis, we use a relatively simple formulation
of the bulk to boundary problem in which the linearized Einstein field
equations are fully decoupled. Our analysis easily generalizes to other sources
in the bulk.Comment: 29 page
Thermalization from gauge/gravity duality: Evolution of singularities in unequal time correlators
We consider a gauge/gravity dual model of thermalization which consists of a
collapsing thin matter shell in asymptotically Anti-de Sitter space. A central
aspect of our model is to consider a shell moving at finite velocity as
determined by its equation of motion, rather than a quasi-static approximation
as considered previously in the literature. By applying a divergence matching
method, we obtain the evolution of singularities in the retarded unequal time
correlator , which probes different stages of the thermalization. We
find that the number of singularities decreases from a finite number to zero as
the gauge theory thermalizes. This may be interpreted as a sign of decoherence.
Moreover, in a second part of the paper, we show explicitly that the thermal
correlator is characterized by the existence of singularities in the complex
time plane. By studying a quasi-static state, we show the singularities at real
times originate from contributions of normal modes. We also investigate the
possibility of obtaining complex singularities from contributions of
quasi-normal modes.Comment: 35 pages, 4 figure
Discovery of a Role for Rab3b in Habituation and Cocaine Induced Locomotor Activation in Mice Using Heterogeneous Functional Genomic Analysis
Substance use disorders are prevalent and present a tremendous societal cost but the mechanisms underlying addiction behavior are poorly understood and few biological treatments exist. One strategy to identify novel molecular mechanisms of addiction is through functional genomic experimentation. However, results from individual experiments are often noisy. To address this problem, the convergent analysis of multiple genomic experiments can discern signal from these studies. In the present study, we examine genetic loci that modulate the locomotor response to cocaine identified in the recombinant inbred (BXD RI) genetic reference population. We then applied the GeneWeaver software system for heterogeneous functional genomic analysis to integrate and aggregate multiple studies of addiction genomics, resulting in the identification o
The Gluonic Field of a Heavy Quark in Conformal Field Theories at Strong Coupling
We determine the gluonic field configuration sourced by a heavy quark
undergoing arbitrary motion in N=4 super-Yang-Mills at strong coupling and
large number of colors. More specifically, we compute the expectation value of
the operator tr[F^2+...] in the presence of such a quark, by means of the
AdS/CFT correspondence. Our results for this observable show that signals
propagate without temporal broadening, just as was found for the expectation
value of the energy density in recent work by Hatta et al. We attempt to shed
some additional light on the origin of this feature, and propose a different
interpretation for its physical significance. As an application of our general
results, we examine when the quark undergoes oscillatory motion,
uniform circular motion, and uniform acceleration. Via the AdS/CFT
correspondence, all of our results are pertinent to any conformal field theory
in 3+1 dimensions with a dual gravity formulation.Comment: 1+38 pages, 16 eps figures; v2: completed affiliation; v3: corrected
typo, version to appear in JHE
QTL and systems genetics analysis of mouse grooming and behavioral responses to novelty in an open field
International audienceThe open field is a classic test used to assess exploratory behavior, anxiety, and locomotor activity in rodents. Here we mapped quantitative trait loci (QTLs) underlying behaviors displayed in an open field, using a panel of 53 BXD recombinant inbred mouse strains with deep replication (10 per strain and sex). The use of these strains permits the integration and comparison of data obtained in different laboratories, and also offers the possibility to study trait covariance by exploiting powerful bioinformatics tools and resources. We quantified behavioral traits during 20 min test sessions including (1) percent time spent and distance travelled near the wall (thigmotaxis), (2) leaning against the wall, (3) rearing, (4) jumping, (5) grooming duration, (6) grooming frequency, (7) locomotion, and (8) defecation. All traits exhibit moderate heritability making them amenable to genetic analysis. We identified a significant QTL on chromosome M.m. 4 at ~104 Mb that modulates grooming duration in both males and females (LRS values of ~18, explaining 25% and 14% of the variance, respectively) and a suggestive QTL modulating locomotion that maps to the same locus. Bioinformatic analysis indicates Disabled 1 (Dab1, a key protein in the reelin signaling pathway) as a particularly strong candidate gene modulating these behaviors. We also found two highly suggestive QTLs for a sex by strain interaction for grooming duration on chromosomes 13 and 17. In addition, we identified a pairwise epistatic interaction between loci on chromosomes 12 at 36-37 Mb and 14 at 34-36 Mb that influences rearing frequency in males
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