193 research outputs found
U(1) Instantons on AdS_4 and the Uplift to Exact Supergravity Solutions
We consider self-duality equation of U(1) gauge fields on Euclidean AdS_4
space, and find a simple finite action solution. With a suitable ansatz, we are
able to embed this solution into the 10d supergravity background of AdS_4\times
CP^3. Further, we show that the solution can be uplifted to an exact solution
in 11d supergravity background of AdS_4\times SE_7.Comment: 12 pages, a comment on boundary conditions and refs. adde
Universality and exactness of Schrodinger geometries in string and M-theory
We propose an organizing principle for classifying and constructing
Schrodinger-invariant solutions within string theory and M-theory, based on the
idea that such solutions represent nonlinear completions of linearized vector
and graviton Kaluza-Klein excitations of AdS compactifications. A crucial
simplification, derived from the symmetry of AdS, is that the nonlinearities
appear only quadratically. Accordingly, every AdS vacuum admits infinite
families of Schrodinger deformations parameterized by the dynamical exponent z.
We exhibit the ease of finding these solutions by presenting three new
constructions: two from M5 branes, both wrapped and extended, and one from the
D1-D5 (and S-dual F1-NS5) system. From the boundary perspective, perturbing a
CFT by a null vector operator can lead to nonzero beta-functions for spin-2
operators; however, symmetry restricts them to be at most quadratic in
couplings. This point of view also allows us to easily prove nonrenormalization
theorems: for any Sch(z) solution of two-derivative supergravity constructed in
the above manner, z is uncorrected to all orders in higher derivative
corrections if the deforming KK mode lies in a short multiplet of an AdS
supergroup. Furthermore, we find infinite classes of 1/4 BPS solutions with
4-,5- and 7-dimensional Schrodinger symmetry that are exact.Comment: 31 pages, plus appendices; v2, minor corrections, added refs, slight
change in interpretation in section 2.3, new Schrodinger and Lifshitz
solutions included; v3, clarifications in sections 2 and 3 regarding
existence of solutions and multi-trace operator
The Boundary Multiplet of N=4 SU(2)xU(1) Gauged Supergravity on Asymptotically-AdS_5
We consider N=4 SU(2)xU(1) gauged supergravity on asymptotically-AdS_5
backgrounds. By a near-boundary analysis we determine the boundary-dominant
components of the bulk fields from their partially gauge-fixed field equations.
Subdominant components are projected out in the boundary limit and we find a
reduced set of boundary fields, constituting the N=2 Weyl multiplet. The
residual bulk symmetries are found to act on the boundary fields as
four-dimensional diffeomorphisms, N=2 supersymmetry and (super-)Weyl
transformations. This shows that the on-shell N=4 supergravity multiplet yields
the N=2 Weyl multiplet on the boundary with the appropriate local N=2
superconformal transformations. Building on these results we use the AdS/CFT
conjecture to calculate the Weyl anomaly of the dual four-dimensional
superconformal field theories in a generic bosonic N=2 conformal supergravity
background.Comment: 23 pages; to appear in JHE
Reappraisal of Vipera aspis Venom Neurotoxicity
BACKGROUND: The variation of venom composition with geography is an important aspect of intraspecific variability in the Vipera genus, although causes of this variability remain unclear. The diversity of snake venom is important both for our understanding of venomous snake evolution and for the preparation of relevant antivenoms to treat envenomations. A geographic intraspecific variation in snake venom composition was recently reported for Vipera aspis aspis venom in France. Since 1992, cases of human envenomation after Vipera aspis aspis bites in south-east France involving unexpected neurological signs were regularly reported. The presence of genes encoding PLA(2) neurotoxins in the Vaa snake genome led us to investigate any neurological symptom associated with snake bites in other regions of France and in neighboring countries. In parallel, we used several approaches to characterize the venom PLA(2) composition of the snakes captured in the same areas. [br/]
METHODOLOGY/PRINCIPAL FINDINGS: We conducted an epidemiological survey of snake bites in various regions of France. In parallel, we carried out the analysis of the genes and the transcripts encoding venom PLA(2)s. We used SELDI technology to study the diversity of PLA(2) in various venom samples. Neurological signs (mainly cranial nerve disturbances) were reported after snake bites in three regions of France: Languedoc-Roussillon, Midi-Pyrénées and Provence-Alpes-CÎte d'Azur. Genomes of Vipera aspis snakes from south-east France were shown to contain ammodytoxin isoforms never described in the genome of Vipera aspis from other French regions. Surprisingly, transcripts encoding venom neurotoxic PLA(2)s were found in snakes of Massif Central region. Accordingly, SELDI analysis of PLA(2) venom composition confirmed the existence of population of neurotoxic Vipera aspis snakes in the west part of the Massif Central mountains. [br/]
CONCLUSIONS/SIGNIFICANCE: The association of epidemiological studies to genetic, biochemical and immunochemical analyses of snake venoms allowed a good evaluation of the potential neurotoxicity of snake bites. A correlation was found between the expression of neurological symptoms in humans and the intensity of the cross-reaction of venoms with anti-ammodytoxin antibodies, which is correlated with the level of neurotoxin (vaspin and/or ammodytoxin) expression in the venom. The origin of the two recently identified neurotoxic snake populations is discussed according to venom PLA(2) genome and transcriptome data
Holography for chiral scale-invariant models
Deformation of any d-dimensional conformal field theory by a constant null
source for a vector operator of dimension (d + z -1) is exactly marginal with
respect to anisotropic scale invariance, of dynamical exponent z. The
holographic duals to such deformations are AdS plane waves, with z=2 being the
Schrodinger geometry. In this paper we explore holography for such chiral
scale-invariant models. The special case of z=0 can be realized with gravity
coupled to a scalar, and is of particular interest since it is related to a
Lifshitz theory with dynamical exponent two upon dimensional reduction. We show
however that the corresponding reduction of the dual field theory is along a
null circle, and thus the Lifshitz theory arises upon discrete light cone
quantization of an anisotropic scale invariant field theory.Comment: 62 pages; v2, published version, minor improvements and references
adde
Signs and symptoms of acute mania: a factor analysis
<p>Abstract</p> <p>Background</p> <p>The major diagnostic classifications consider mania as a uni-dimensional illness. Factor analytic studies of acute mania are fewer compared to schizophrenia and depression. Evidence from factor analysis suggests more categories or subtypes than what is included in the classification systems. Studies have found that these factors can predict differences in treatment response and prognosis.</p> <p>Methods</p> <p>The sample included 131 patients consecutively admitted to an acute psychiatry unit over a period of one year. It included 76 (58%) males. The mean age was 44.05 years (SD = 15.6). Patients met International Classification of Diseases-10 (ICD-10) clinical diagnostic criteria for a manic episode. Patients with a diagnosis of mixed bipolar affective disorder were excluded. Participants were evaluated using the Young Mania Rating Scale (YMRS). Exploratory factor analysis (principal component analysis) was carried out and factors with an eigenvalue > 1 were retained. The significance level for interpretation of factor loadings was 0.40. The unrotated component matrix identified five factors. Oblique rotation was then carried out to identify three factors which were clinically meaningful.</p> <p>Results</p> <p>Unrotated principal component analysis extracted five factors. These five factors explained 65.36% of the total variance. Oblique rotation extracted 3 factors. Factor 1 corresponding to 'irritable mania' had significant loadings of irritability, increased motor activity/energy and disruptive aggressive behaviour. Factor 2 corresponding to 'elated mania' had significant loadings of elevated mood, language abnormalities/thought disorder, increased sexual interest and poor insight. Factor 3 corresponding to 'psychotic mania' had significant loadings of abnormalities in thought content, appearance, poor sleep and speech abnormalities.</p> <p>Conclusions</p> <p>Our findings identified three clinically meaningful factors corresponding to 'elated mania', 'irritable mania' and 'psychotic mania'. These findings support the multidimensional nature of manic symptoms. Further evidence is needed to support the existence of corresponding clinical subtypes.</p
Doping the holographic Mott insulator
Mott insulators form because of strong electron repulsions, being at the
heart of strongly correlated electron physics. Conventionally these are
understood as classical "traffic jams" of electrons described by a short-ranged
entangled product ground state. Exploiting the holographic duality, which maps
the physics of densely entangled matter onto gravitational black hole physics,
we show how Mott-insulators can be constructed departing from entangled
non-Fermi liquid metallic states, such as the strange metals found in cuprate
superconductors. These "entangled Mott insulators" have traits in common with
the "classical" Mott insulators, such as the formation of Mott gap in the
optical conductivity, super-exchange-like interactions, and form "stripes" when
doped. They also exhibit new properties: the ordering wave vectors are detached
from the number of electrons in the unit cell, and the DC resistivity diverges
algebraically instead of exponentially as function of temperature. These
results may shed light on the mysterious ordering phenomena observed in
underdoped cuprates.Comment: 27 pages, 9 figures. Accepted in Nature Physic
Holography for Einstein-Maxwell-dilaton theories from generalized dimensional reduction
We show that a class of Einstein-Maxwell-Dilaton (EMD) theories are related
to higher dimensional AdS-Maxwell gravity via a dimensional reduction over
compact Einstein spaces combined with continuation in the dimension of the
compact space to non-integral values (`generalized dimensional reduction').
This relates (fairly complicated) black hole solutions of EMD theories to
simple black hole/brane solutions of AdS-Maxwell gravity and explains their
properties. The generalized dimensional reduction is used to infer the
holographic dictionary and the hydrodynamic behavior for this class of theories
from those of AdS. As a specific example, we analyze the case of a black brane
carrying a wave whose universal sector is described by gravity coupled to a
Maxwell field and two neutral scalars. At thermal equilibrium and finite
chemical potential the two operators dual to the bulk scalar fields acquire
expectation values characterizing the breaking of conformal and generalized
conformal invariance. We compute holographically the first order transport
coefficients (conductivity, shear and bulk viscosity) for this system.Comment: v2, Important additions: (1) discussion of the entropy current, (2)
postulated zeta/eta bound is generically violated. Some comments and
references added, typos corrected. 50 page
Holographic renormalization and supersymmetry
Holographic renormalization is a systematic procedure for regulating
divergences in observables in asymptotically locally AdS spacetimes. For dual
boundary field theories which are supersymmetric it is natural to ask whether
this defines a supersymmetric renormalization scheme. Recent results in
localization have brought this question into sharp focus: rigid supersymmetry
on a curved boundary requires specific geometric structures, and general
arguments imply that BPS observables, such as the partition function, are
invariant under certain deformations of these structures. One can then ask if
the dual holographic observables are similarly invariant. We study this
question in minimal N = 2 gauged supergravity in four and five dimensions. In
four dimensions we show that holographic renormalization precisely reproduces
the expected field theory results. In five dimensions we find that no choice of
standard holographic counterterms is compatible with supersymmetry, which leads
us to introduce novel finite boundary terms. For a class of solutions
satisfying certain topological assumptions we provide some independent tests of
these new boundary terms, in particular showing that they reproduce the
expected VEVs of conserved charges.Comment: 70 pages; corrected typo
A Single Argonaute Gene Participates in Exogenous and Endogenous RNAi and Controls Cellular Functions in the Basal Fungus Mucor circinelloides
The mechanism of RNAi is well described in metazoans where it plays a role in diverse cellular functions. However, although different classes of endogenous small RNAs (esRNAs) have been identified in fungi, their biological roles are poorly described due, in part, to the lack of phenotype of mutants affected in the biogenesis of these esRNAs. Argonaute proteins are one of the key components of the RNAi pathways, in which different members of this protein family participate in the biogenesis of a wide repertoire of esRNAs molecules. Here we identified three argonaute genes of the fungus Mucor circinelloides and investigated their participation in exogenous and endogenous RNAi. We found that only one of the ago genes, ago-1, is involved in RNAi during vegetative growth and is required for both transgene-induced RNA silencing and the accumulation of distinct classes of esRNAs derived from exons (ex-siRNAs). Classes I and II ex-siRNAs bind to Ago-1 to control mRNA accumulation of the target protein coding genes. Class III ex-siRNAs do not specifically bind to Ago-1, but requires this protein for their production, revealing the complexity of the biogenesis pathways of ex-siRNAs. We also show that ago-1 is involved in the response to environmental signals, since vegetative development and autolysis induced by nutritional stress are affected in ago-1(-) M. circinelloides mutants. Our results demonstrate that a single Ago protein participates in the production of different classes of esRNAs that are generated through different pathways. They also highlight the role of ex-siRNAs in the regulation of endogenous genes in fungi and expand the range of biological functions modulated by RNAi
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