1,098 research outputs found
A Comparative Note on Tunneling in AdS and in its Boundary Matrix Dual
For charged black hole, within the grand canonical ensemble, the decay rate
from thermal AdS to the black hole at a fixed high temperature increases with
the chemical potential. We check that this feature is well captured by a
phenomenological matrix model expected to describe its strongly coupled dual.
This comparison is made by explicitly constructing the kink and bounce
solutions around the de-confinement transition and evaluating the matrix model
effective potential on the solutions.Comment: 1+12 pages, 9 figure
Non-equilibrium Dynamics of O(N) Nonlinear Sigma models: a Large-N approach
We study the time evolution of the mass gap of the O(N) non-linear sigma
model in 2+1 dimensions due to a time-dependent coupling in the large-
limit. Using the Schwinger-Keldysh approach, we derive a set of equations at
large which determine the time dependent gap in terms of the coupling.
These equations lead to a criterion for the breakdown of adiabaticity for slow
variation of the coupling leading to a Kibble-Zurek scaling law. We describe a
self-consistent numerical procedure to solve these large- equations and
provide explicit numerical solutions for a coupling which starts deep in the
gapped phase at early times and approaches the zero temperature equilibrium
critical point in a linear fashion. We demonstrate that for such a
protocol there is a value of the coupling where the gap
function vanishes, possibly indicating a dynamical instability. We study the
dependence of on both the rate of change of the coupling and
the initial temperature. We also verify, by studying the evolution of the mass
gap subsequent to a sudden change in , that the model does not display
thermalization within a finite time interval and discuss the implications
of this observation for its conjectured gravitational dual as a higher spin
theory in .Comment: 22 pages, 9 figures. Typos corrected, references rearranged and
added.v3 : sections rearranged, abstract modified, comment about Kibble-Zurek
scaling correcte
Supersymmetric Electromagnetic Waves on Giants and Dual-Giants
We set up the BPS equations for a D3-brane moving in AdS_5 \times S^5 which
preserves two supercharges and with all bosonic fields turned on in the
world-volume theory. By solving these, we find generalizations of Mikhailov
giants and wobbling dual-giants that include electromagnetic waves propagating
on their world-volume. For these giants (dual-giants) we show that the BPS
field strength is the real part of the pull-back of a holomorphic 2-form in the
ambient space C^3 (C^{1,2}) onto the world-volume.Comment: 18 page
Genetic Variants Associated with Arsenic Susceptibility: Study of Purine Nucleoside Phosphorylase, Arsenic (+3) Methyltransferase, and Glutathione S-Transferase Omega Genes
BACKGROUND: Individual variability in arsenic metabolism may underlie individual susceptibility
toward arsenic-induced skin lesions and skin cancer. Metabolism of arsenic proceeds through
sequential reduction and oxidative methylation being mediated by the following genes: purine
nucleoside phosphorylase (PNP), arsenic (+3) methyltransferase (As3MT), glutathione S-transferase
omega 1 (GSTO1), and omega 2 (GSTO2). PNP functions as arsenate reductase; As3MT methylates
inorganic arsenic and its metabolites; and both GSTO1 and GSTO2 reduce the metabolites.
Alteration in functions of these gene products may lead to arsenic-specific disease manifestations.
OBJECTIVES: To find any probable association between arsenicism and the exonic single nucleotide
polymorphisms (SNPs) of the above-mentioned arsenic-metabolizing genes, we screened all the
exons in those genes in an arsenic-exposed population.
METHODS: Using polymerase chain reaction restriction fragment length polymorphism analysis, we
screened the exons in 25 cases (individuals with arsenic-induced skin lesions) and 25 controls (individuals
without arsenic-induced skin lesions), both groups drinking similar arsenic-contaminated
water. The exonic SNPs identified were further genotyped in a total of 428 genetically unrelated
individuals (229 cases and 199 controls) for association study.
RESULTS: Among four candidate genes, PNP, As3MT, GSTO1, and GSTO2, we found that distribution
of three exonic polymorphisms, His20His, Gly51Ser, and Pro57Pro of PNP, was associated
with arsenicism. Genotypes having the minor alleles were significantly overrepresented in the case
group: odds ratio (OR) = 1.69 [95% confidence interval (CI), 1.08â2.66] for His20His; OR = 1.66
[95% CI, 1.04â2.64] for Gly51Ser; and OR = 1.67 [95% CI, 1.05â2.66] for Pro57Pro.
CONCLUSIONS: The results indicate that the three PNP variants render individuals susceptible
toward developing arsenic-induced skin lesions.
KEY WORDS: arsenic, As3MT, GSTO1, GSTO2, PNP, skin lesion, susceptibility. Environ Health
Perspect 116:501â505 (2008). doi:10.1289/ehp.10581 available via http://dx.doi.org/ [Online
14 January 2008
Thermal quenches in N=2* plasmas
We exploit gauge/gravity duality to study `thermal quenches' in a plasma of
the strongly coupled N=2* gauge theory. Specifically, we consider the response
of an initial thermal equilibrium state of the theory under variations of the
bosonic or fermionic mass, to leading order in m/T<<1. When the masses are made
to vary in time, novel new counterterms must be introduced to renormalize the
boundary theory. We consider transitions the conformal super-Yang-Mills theory
to the mass deformed gauge theory and also the reverse transitions. By
construction, these transitions are controlled by a characteristic time scale
\calt and we show how the response of the system depends on the ratio of this
time scale to the thermal time scale 1/T. The response shows interesting
scaling behaviour both in the limit of fast quenches with T\calt<<1 and slow
quenches with T\calt>>1. In the limit that T\calt\to\infty, we observe the
expected adiabatic response. For fast quenches, the relaxation to the final
equilibrium is controlled by the lowest quasinormal mode of the bulk scalar
dual to the quenched operator. For slow quenches, the system relaxes with a
(nearly) adiabatic response that is governed entirely by the late time profile
of the mass. We describe new renormalization scheme ambiguities in defining
gauge invariant observables for the theory with time dependant couplings.Comment: 78 pages, 17 figure
M-Branes and Metastable States
We study a supersymmetry breaking deformation of the M-theory background
found in arXiv:hep-th/0012011. The supersymmetric solution is a warped product
of R^{2,1} and the 8-dimensional Stenzel space, which is a higher dimensional
generalization of the deformed conifold. At the bottom of the warped throat
there is a 4-sphere threaded by \tilde{M} units of 4-form flux. The dual
(2+1)-dimensional theory has a discrete spectrum of bound states. We add p
anti-M2 branes at a point on the 4-sphere, and show that they blow up into an
M5-brane wrapping a 3-sphere at a fixed azimuthal angle on the 4-sphere. This
supersymmetry breaking state turns out to be metastable for p / \tilde{M} <
0.054. We find a smooth O(3)-symmetric Euclidean bounce solution in the
M5-brane world volume theory that describes the decay of the false vacuum.
Calculation of the Euclidean action shows that the metastable state is
extremely long-lived. We also describe the corresponding metastable states and
their decay in the type IIA background obtained by reduction along one of the
spatial directions of R^{2,1}.Comment: 33 pages, 5 figures; v2 note adde
Risk factors for severe outcomes in patients with systemic vasculitis & COVIDâ19: a biânational registryâbased cohort study
OBJECTIVE: COVID-19 is a novel infectious disease with a broad spectrum of clinical severity. Patients with systemic vasculitis have an increased risk of serious infections and so may be at risk of severe outcomes following COVID-19. It is important to establish the risk factors for severe COVID-19 outcomes in these patients, including the impact of immunosuppressive therapies. METHODS: A multi-centre cohort was developed through the participation of centres affiliated with national UK and Ireland vasculitis registries. Clinical characteristics and outcomes were described. Logistic regression was used to evaluate associations between potential risk factors and severe COVID-19 outcome, defined as a requirement for advanced oxygen therapy, invasive ventilation, or death. RESULTS: Sixty-five cases of patients with systemic vasculitis who developed COVID-19 were reported (median age 70 years, 49% female) of whom 25 (38%) experienced a severe outcome. Most cases (55/65, 85%) had ANCA-associated vasculitis (AAV). Almost all patients required hospitalization (59/65, 91%), 7 patients (11%) were admitted to intensive care and 18 patients (28%) died. Background glucocorticoid therapy was associated with severe outcome (adjusted odds ratio [aOR] 3.7 (1.1-14.9, p=0.047)) as was comorbid respiratory disease (aOR 7.5 (1.9-38.2, p=0.006)). Vasculitis disease activity and non-glucocorticoid immunosuppression were not associated with severe outcome. CONCLUSION: In patients with systemic vasculitis, glucocorticoid use at presentation and comorbid respiratory disease were associated with severe outcomes in COVID-19. These data can inform clinical decision making relating to risk of severe COVID-19 in this vulnerable patient group
Thermodynamics of Large N Gauge Theories with Chemical Potentials in a 1/D Expansion
In order to understand thermodynamical properties of N D-branes with chemical
potentials associated with R-symmetry charges, we study a one dimensional large
N gauge theory (bosonic BFSS type model) as a first step. This model is
obtained through a dimensional reduction of a 1+D dimensional SU(N) Yang-Mills
theory and we use a 1/D expansion to investigate the phase structure. We find
three phases in the \mu-T plane. We also show that all the adjoint scalars
condense at large D and obtain a mass dynamically. This dynamical mass protects
our model from the usual perturbative instability of massless scalars in a
non-zero chemical potential. We find that the system is at least meta-stable
for arbitrary large values of the chemical potentials in D \to \infty limit. We
also explore the existence of similar condensation in higher dimensional gauge
theories in a high temperature limit. In 2 and 3 dimensions, the condensation
always happens as in one dimensional case. On the other hand, if the dimension
is higher than 4, there is a critical chemical potential and the condensation
happens only if the chemical potentials are below it.Comment: 37 pages, 4 figures; v2: minor corrections, references added; v3:
minor corrections, to appear in JHE
Trauma history and depression predict incomplete adherence to antiretroviral therapies in a low income country.
As antiretroviral therapy (ART) for HIV becomes increasingly available in low and middle income countries (LMICs), understanding reasons for lack of adherence is critical to stemming the tide of infections and improving health. Understanding the effect of psychosocial experiences and mental health symptomatology on ART adherence can help maximize the benefit of expanded ART programs by indicating types of services, which could be offered in combination with HIV care. The Coping with HIV/AIDS in Tanzania (CHAT) study is a longitudinal cohort study in the Kilimanjaro Region that included randomly selected HIV-infected (HIV+) participants from two local hospital-based HIV clinics and four free-standing voluntary HIV counselling and testing sites. Baseline data were collected in 2008 and 2009; this paper used data from 36 month follow-up interviews (Nâ=â468). Regression analyses were used to predict factors associated with incomplete self-reported adherence to ART. INCOMPLETE ART ADHERENCE WAS SIGNIFICANTLY MORE LIKELY TO BE REPORTED AMONGST PARTICIPANTS WHO EXPERIENCED A GREATER NUMBER OF CHILDHOOD TRAUMATIC EVENTS: sexual abuse prior to puberty and the death in childhood of an immediate family member not from suicide or homicide were significantly more likely in the non-adherent group and other negative childhood events trended toward being more likely. Those with incomplete adherence had higher depressive symptom severity and post-traumatic stress disorder (PTSD). In multivariable analyses, childhood trauma, depression, and financial sacrifice remained associated with incomplete adherence.\ud
This is the first study to examine the effect of childhood trauma, depression and PTSD on HIV medication adherence in a low income country facing a significant burden of HIV. Allocating spending on HIV/AIDS toward integrating mental health services with HIV care is essential to the creation of systems that enhance medication adherence and maximize the potential of expanded antiretroviral access to improve health and reduce new infections
QCD with Chemical Potential in a Small Hyperspherical Box
To leading order in perturbation theory, we solve QCD, defined on a small
three sphere in the large N and Nf limit, at finite chemical potential and map
out the phase diagram in the (mu,T) plane. The action of QCD is complex in the
presence of a non-zero quark chemical potential which results in the sign
problem for lattice simulations. In the large N theory, which at low
temperatures becomes a conventional unitary matrix model with a complex action,
we find that the dominant contribution to the functional integral comes from
complexified gauge field configurations. For this reason the eigenvalues of the
Polyakov line lie off the unit circle on a contour in the complex plane. We
find at low temperatures that as mu passes one of the quark energy levels there
is a third-order Gross-Witten transition from a confined to a deconfined phase
and back again giving rise to a rich phase structure. We compare a range of
physical observables in the large N theory to those calculated numerically in
the theory with N=3. In the latter case there are no genuine phase transitions
in a finite volume but nevertheless the observables are remarkably similar to
the large N theory.Comment: 44 pages, 18 figures, jhep3 format. Small corrections and
clarifications added in v3. Conclusions cleaned up. Published versio
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