1,709 research outputs found
Low temperature properties of holographic condensates
In the current work we study various models of holographic superconductors at
low temperature. Generically the zero temperature limit of those models are
solitonic solution with a zero sized horizon. Here we generalized simple
version of those zero temperature solutions to small but non-zero temperature
T. We confine ourselves to cases where near horizon geometry is AdS^4. At a
non-zero temperature a small horizon would form deep inside this AdS^4 which
does not disturb the UV physics. The resulting geometry may be matched with the
zero temperature solution at an intermediate length scale. We understand this
matching from separation of scales by setting up a perturbative expansion in
gauge potential. We have a better analytic control in abelian case and
quantities may be expressed in terms of hypergeometric function. From this we
calculate low temperature behavior of various quatities like entropy, charge
density and specific heat etc. We also calculate various energy gaps associated
with p-wave holographic superconductor to understand the underlying pairing
mechanism. The result deviates significantly from the corresponding weak
coupling BCS counterpart.Comment: 17 Page
Serotonin 2A (5-HT2A) receptor affects cell–matrix adhesion and the formation and maintenance of stress fibers in HEK293 cells
5-HT2A, a G-protein coupled receptor, is widely expressed in the human body, including in the gastrointestinal tract, platelets and the nervous system. It mediates various functions, for e.g. learning, memory, mood regulation, platelet aggregation and vasoconstriction, but its involvement in cell-adhesion remains largely unknown. Here we report a novel role for 5-HT2A in cell–matrix adhesion.
In HEK293 cells, which are loosely adherent, expression and stimulation of human or rat 5-HT2A receptor by agonists such as serotonin or 2,5-dimethoxy-4-iodoamphetamine (DOI) led to a significant increase in adhesion, while inhibition of 5-HT2A by antipsychotics, such as risperidone, olanzapine or chlorpromazine prevented it. 5-HT2A activation gave rise to stress fibers in these cells and was also required for their maintenance. Mechanistically, the 5-HT2A-mediated adhesion was mediated by downstream PKC and Rho signaling. Since 5-HT2A is associated with many disorders such as dementia, depression and schizophrenia, its role in cell–matrix adhesion could have implications for neural circuits
M2-M5 blackfold funnels
We analyze the basic M2-M5 intersection in the supergravity regime using the
blackfold approach. This approach allows us to recover the 1/4-BPS self-dual
string soliton solution of Howe, Lambert and West as a three-funnel solution of
an effective fivebrane worldvolume theory in a new regime, the regime of a
large number of M2 and M5 branes. In addition, it allows us to discuss finite
temperature effects for non-extremal self-dual string soliton solutions and
wormhole solutions interpolating between stacks of M5 and anti-M5 branes. The
purpose of this paper is to exhibit these solutions and their basic properties.Comment: 19 pages, 5 figures, harvmac; typo corrected in equation (3.19
Analytic Approaches to anisotropic Holographic Superfluids
We construct an analytic solution of the Einstein-SU(2)-Yang-Mills system as
the holographic dual of an anisotropic superfluid near its critical point, up
to leading corrections in both the inverse Yang-Mills coupling and a symmetry
breaking order parameter. We have also calculated the ratio of shear viscosity
to entropy density in this background, and shown that the universality of this
ratio is lost in the broken symmetry direction. The ratio displays a scaling
behavior near the critical point with critical exponent , at the
leading order in the double expansion.Comment: 15 pages, typos corrected and references adde
Women’s experiences of receiving care for pelvic organ prolapse: a qualitative study
Background Pelvic organ prolapse is a common urogenital condition affecting 41–50% of women over the age of 40. To achieve early diagnosis and appropriate treatment, it is important that care is sensitive to and meets women’s needs, throughout their patient journey. This study explored women’s experiences of seeking diagnosis and treatment for prolapse and their needs and priorities for improving person-centred care. Methods Twenty-two women receiving prolapse care through urogynaecology services across three purposefully selected NHS UK sites took part in three focus groups and four telephone interviews. A topic guide facilitated discussions about women’s experiences of prolapse, diagnosis, treatment, follow-up, interactions with healthcare professionals, overall service delivery, and ideals for future services to meet their needs. Data were analysed thematically. Results Three themes emerged relating to women’s experiences of a) Evaluating what is normal b) Hobson’s choice of treatment decisions, and c) The trial and error of treatment and technique. Women often delayed seeking help for their symptoms due to lack of awareness, embarrassment and stigma. When presented to GPs, their symptoms were often dismissed and unaddressed until they became more severe. Women reported receiving little or no choice in treatment decisions. Choices were often influenced by health professionals’ preferences which were subtly reflected through the framing of the offer. Women’s embodied knowledge of their condition and treatment was largely unheeded, resulting in decisions that were inconsistent with women’s preferences and needs. Physiotherapy based interventions were reported as helping women regain control over their symptoms and life. A need for greater awareness of prolapse and physiotherapy interventions among women, GPs and consultants was identified alongside greater focus on prevention, early diagnosis and regular follow-up. Greater choice and involvement in treatment decision making was desired. Conclusions As prolapse treatment options expand to include more conservative choices, greater awareness and education is needed among women and professionals about these as a first line treatment and preventive measure, alongside a multi-professional team approach to treatment decision making. Women presenting with prolapse symptoms need to be listened to by the health care team, offered better information about treatment choices, and supported to make a decision that is right for them
Fermion correlators in non-abelian holographic superconductors
We consider fermion correlators in non-abelian holographic superconductors.
The spectral function of the fermions exhibits several interesting features
such as support in displaced Dirac cones and an asymmetric distribution of
normal modes. These features are compared to similar ones observed in angle
resolved photoemission experiments on high T_c superconductors. Along the way
we elucidate some properties of p-wave superconductors in AdS_4 and discuss the
construction of SO(4) superconductors.Comment: 49 pages, 11 figure
Emergent Gauge Fields in Holographic Superconductors
Holographic superconductors have been studied so far in the absence of
dynamical electromagnetic fields, namely in the limit in which they coincide
with holographic superfluids. It is possible, however, to introduce dynamical
gauge fields if a Neumann-type boundary condition is imposed on the
AdS-boundary. In 3+1 dimensions, the dual theory is a 2+1 dimensional CFT whose
spectrum contains a massless gauge field, signaling the emergence of a gauge
symmetry. We study the impact of a dynamical gauge field in vortex
configurations where it is known to significantly affect the energetics and
phase transitions. We calculate the critical magnetic fields H_c1 and H_c2,
obtaining that holographic superconductors are of Type II (H_c1 < H_c2). We
extend the study to 4+1 dimensions where the gauge field does not appear as an
emergent phenomena, but can be introduced, by a proper renormalization, as an
external dynamical field. We also compare our predictions with those arising
from a Ginzburg-Landau theory and identify the generic properties of Abrikosov
vortices in holographic models.Comment: 19 pages, 14 figures, few comments added, version published in JHE
Holographic Superconductors from Einstein-Maxwell-Dilaton Gravity
We construct holographic superconductors from Einstein-Maxwell-dilaton
gravity in 3+1 dimensions with two adjustable couplings and the charge
carried by the scalar field. For the values of and we
consider, there is always a critical temperature at which a second order phase
transition occurs between a hairy black hole and the AdS RN black hole in the
canonical ensemble, which can be identified with the superconducting phase
transition of the dual field theory. We calculate the electric conductivity of
the dual superconductor and find that for the values of and where
is small the dual superconductor has similar properties to the
minimal model, while for the values of and where is
large enough, the electric conductivity of the dual superconductor exhibits
novel properties at low frequencies where it shows a "Drude Peak" in the real
part of the conductivity.Comment: 25 pages, 13 figures; v2, typos corrected; v3, refs added, to appear
in JHE
Analytic study of properties of holographic p-wave superconductors
In this paper, we analytically investigate the properties of p-wave
holographic superconductors in -Schwarzschild background by two
approaches, one based on the Sturm-Liouville eigenvalue problem and the other
based on the matching of the solutions to the field equations near the horizon
and near the asymptotic region. The relation between the critical
temperature and the charge density has been obtained and the dependence of the
expectation value of the condensation operator on the temperature has been
found. Our results are in very good agreement with the existing numerical
results. The critical exponent of the condensation also comes out to be 1/2
which is the universal value in the mean field theory.Comment: Latex, To appear in JHE
p-wave Holographic Superconductors and five-dimensional gauged Supergravity
We explore five-dimensional and
SO(6) gauged supergravities as frameworks for condensed matter applications.
These theories contain charged (dilatonic) black holes and 2-forms which have
non-trivial quantum numbers with respect to U(1) subgroups of SO(6). A question
of interest is whether they also contain black holes with two-form hair with
the required asymptotic to give rise to holographic superconductivity. We first
consider the case, which contains a complex two-form potential
which has U(1) charge . We find that a slight
generalization, where the two-form potential has an arbitrary charge , leads
to a five-dimensional model that exhibits second-order superconducting
transitions of p-wave type where the role of order parameter is played by
, provided . We identify the operator that condenses
in the dual CFT, which is closely related to Super Yang-Mills
theory with chemical potentials. Similar phase transitions between R-charged
black holes and black holes with 2-form hair are found in a generalized version
of the gauged supergravity Lagrangian where the two-forms have
charge .Comment: 35 pages, 14 figure
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