2,400 research outputs found
Quantum Critical Superfluid Flows and Anisotropic Domain Walls
We construct charged anisotropic AdS domain walls as solutions of a
consistent truncation of type IIB string theory. These are a one-parameter
family of solutions that flow to an AdS fixed point in the IR, exhibiting
emergent conformal invariance and quantum criticality. They represent the
zero-temperature limit of the holographic superfluids at finite superfluid
velocity constructed in arXiv:1010.5777. We show that these domain walls exist
only for velocities less than a critical value, agreeing in detail with a
conjecture made there. We also comment about the IR limits of flows with
velocities higher than this critical value, and point out an intriguing
similarity between the phase diagrams of holographic superfluid flows and those
of ordinary superconductors with imbalanced chemical potential.Comment: 11 pages, 3 figures. V2: Very minor corrections. JHEP versio
Type IIB Holographic Superfluid Flows
We construct fully backreacted holographic superfluid flow solutions in a
five-dimensional theory that arises as a consistent truncation of low energy
type IIB string theory. We construct a black hole with scalar and vector hair
in this theory, and study the phase diagram. As expected, the superfluid phase
ceases to exist for high enough superfluid velocity, but we show that the phase
transition between normal and superfluid phases is always second order. We also
analyze the zero temperature limit of these solutions. Interestingly, we find
evidence that the emergent IR conformal symmetry of the zero-temperature domain
wall is broken at high enough velocity.Comment: v3: Published version. Figures 5 and 6 corrected. 24 pages, 7 figure
Sum Rules from an Extra Dimension
Using the gravity side of the AdS/CFT correspondence, we investigate the
analytic properties of thermal retarded Green's functions for scalars,
conserved currents, the stress tensor, and massless fermions. We provide some
results concerning their large and small frequency behavior and their pole
structure. From these results, it is straightforward to prove the validity of
various sum rules on the field theory side of the duality. We introduce a novel
contraction mapping we use to study the large frequency behavior of the Green's
functions.Comment: v2: 23 pages (plus appendix), revised presentation, discussion of
branch cuts moved to appendix, and some minor changes; v1: 24 pages (plus
appendix
The Structure of the Non-SUSY Baryonic Branch of Klebanov-Strassler
We study the two-dimensional space of supergravity solutions corresponding to
non-supersymmetric deformations of the baryonic branch of Klebanov-Strassler.
By combining analytical methods with a numerical survey of the parameter space,
we find that this solution space includes as limits the softly-broken N=1
solutions of Gubser et al. and those of Dymarsky and Kuperstein. We also
identify a one-dimensional family of solutions corresponding to a natural
non-supersymmetric generalisation of Klebanov-Strassler, and one corresponding
to the limit in which supersymmetry is completely absent, even in the far UV.
For almost all of the parameter space we find indications that much of the
structure of the supersymmetric baryonic branch survives.Comment: 29 pages plus appendices, 11 figure
The Many Phases of Holographic Superfluids
We investigate holographic superfluids in AdS_{d+1} with d=3,4 in the
non-backreacted approximation for various masses of the scalar field. In d=3
the phase structure is universal for all the masses that we consider: the
critical temperature decreases as the superfluid velocity increases, and as it
is cranked high enough, the order of the phase transition changes from second
to first. Surprisingly, in d=4 we find that the phase structure is more
intricate. For sufficiently high mass, there is always a second order phase
transition to the normal phase, no matter how high the superfluid velocity. For
some parameters, as we lower the temperature, this transition happens before a
first order transition to a new superconducting phase. Across this first order
transition, the gap in the transverse conductivity jumps from almost zero to
about half its maximum value. We also introduce a double scaling limit where we
can study the phase transitions (semi-)analytically in the large velocity
limit. The results corroborate and complement our numerical results. In d=4,
this approach has the virtue of being fully analytically tractable.Comment: 31 pages, 19 figure
Drag force in a strongly coupled anisotropic plasma
We calculate the drag force experienced by an infinitely massive quark
propagating at constant velocity through an anisotropic, strongly coupled N=4
plasma by means of its gravity dual. We find that the gluon cloud trailing
behind the quark is generally misaligned with the quark velocity, and that the
latter is also misaligned with the force. The drag coefficient can be
larger or smaller than the corresponding isotropic value depending on the
velocity and the direction of motion. In the ultra-relativistic limit we find
that generically . We discuss the conditions under which this
behaviour may extend to more general situations.Comment: 25 pages, 13 figures; v2: minor changes, added reference
Spinal Subdural Haematoma in association with anticoagulant therapy, an unusual presentation: a case report and review of literature
A case of spontaneous, atraumatic subdural haematoma involving thoracic region in a 78-year-old woman on an anticoagulant therapy (Warfarin) for atrial fibrillation presented. This patient initially presented with sudden onset headache and giddiness (signs of increased intracranial pressure) followed by an acute onset neuro-deficit in lower limb. After appropriate investigations she was treated with an emergency surgical decompression of involved spinal segment. Post-operatively the patients had complete neurological recovery
Differential impact of two risk communications on antipsychotic prescribing to people with dementia in Scotland: segmented regression time series analysis 2001-2011
The two risk communications were associated with reductions in antipsychotic use, in ways which were compatible with marked differences in their content and dissemination. Further research is needed to ensure that the content and dissemination of regulatory risk communications is optimal, and to track their impact on intended and unintended outcomes. Although rates are falling, antipsychotic prescribing in dementia in Scotland remains unacceptably hig
Waterpipe smoking in students: Prevalence, risk factors, symptoms of addiction, and smoke intake. Evidence from one British university
Background: Anecdotal reports suggest waterpipe smoking is becoming common in students in western countries. The aim was to examine prevalence, risk factors, symptoms of addiction, and smoke intake.
Methods: This was a cross-sectional survey of students with subsidiary survey of regular waterpipe user and survey of exhaled carbon monoxide (CO) before and after waterpipe smoking in customers of a waterpipe café. 937 students of Birmingham University completed the initial survey with a follow up of 21 regular waterpipe smokers. 63 customers of a waterpipe café near the University completed the study of CO intake.
Results: 355 (37.9%, 95% confidence intervals (CI) 34.8 to 41.1%) students had tried waterpipes,the prevalence of trying rising with duration at University. 75 (8.0%, 95%CI 6.4 to 10.0%) were regular smokers, similar to the prevalence of cigarette smoking (9.4%). Although cigarette smoking was the major risk factor for being a regular waterpipe smoker, odds ratio (95%CI) 2.77 (1.52 to 5.06), 65% of waterpipe smokers did not smoke cigarettes. Seven of 21 (33.3%) regular waterpipe smokers experienced cravings. Nearly all regular waterpipe users thought it less harmful than smoking cigarettes. The mean (standard deviation) rise in CO was 37.4 (25.8)ppm, nearly twice as high as a typical cigarette smoker seeking cessation treatment.
Conclusion: Waterpipe smoking is a common part of student culture in one British university, as in the Middle East and in the United States. It poses a potential threat to public health, with evidence of dependence and high smoke intake
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