33 research outputs found
A holographic perspective on non-relativistic conformal defects
We study defects in non-relativistic conformal field theories. As in the
well-studied case of relativistic conformal defects, we find that a useful tool
to organize correlation functions is the defect operator expansion (dOPE). We
analyze how the dOPE is implemented in theories with a holographic dual,
highlighting some interesting aspects of the operator/state mapping in
non-relativistic holography.Comment: 20 page
On correlation functions of operators dual to classical spinning string states
We explore how to compute, classically at strong coupling, correlation
functions of local operators corresponding to classical spinning string states.
The picture we obtain is of `fattened' Witten diagrams, the evaluation of which
turns out to be surprisingly subtle and requires a modification of the naive
classical action due to a necessary projection onto appropriate wave functions.
We examine string solutions which compute the simplest case of a two-point
function and reproduce the right scaling with the anomalous dimensions
corresponding to the energies of the associated spinning string solutions. We
also describe, under some simplifying assumptions, how the spacetime dependence
of a conformal three-point correlation function arises in this setup.Comment: 27 pages, 3 figures; v2: references and comments added
Chern-Simons diffusion rate in a holographic Yang-Mills theory
Using holography, we compute the Chern-Simons diffusion rate of 4d gauge
theories constructed by wrapping D4-branes on a circle. In the model with
antiperiodic boundary conditions for fermions, we find that it scales like
in the high-temperature phase. With periodic fermions, this scaling
persists at low temperatures. The scaling is reminiscent of 6d hydrodynamic
behavior even at temperatures small compared to compactification scales of the
M5-branes from which the D4-branes descend. We offer a holographic explanation
of this behavior by adding a new entry to the known map between D4 and M5
hydrodynamics, and suggest a field theory explanation based on "deconstruction"
or "fractionization".Comment: 13 pages, misstatement in published version about low temperature
phase removed, main results unaffecte
First Measurement of Antikaon Phase-Space Distributions in Nucleus-Nucleus Collisions at Subthreshold Beam Energies
Differential production cross sections of K and K mesons have been
measured as function of the polar emission angle in Ni+Ni collisions at a beam
energy of 1.93 AGeV. In near-central collisions, the spectral shapes and the
widths of the rapidity distributions of K and K mesons are in agreement
with the assumption of isotropic emission. In non-central collisions, the K
and K rapidity distributions are broader than expected for a single thermal
source. In this case, the polar angle distributions are strongly
forward-backward peaked and the nonisotropic contribution to the total yield is
about one third both for K and K mesons. The K/K ratio is found
to be about 0.03 independent of the centrality of the reaction. This value is
significantly larger than predicted by microscopic transport calculations if
in-medium modifications of K mesons are neglected.Comment: 16 pages, 3 figures, accepted for publication in Physics Letters
Hydrodynamics from charged black branes
We extend the recent work on fluid-gravity correspondence to charged
black-branes by determining the metric duals to arbitrary charged fluid
configuration up to second order in the boundary derivative expansion. We also
derive the energy-momentum tensor and the charge current for these
configurations up to second order in the boundary derivative expansion. We find
a new term in the charge current when there is a bulk Chern-Simons interaction
thus resolving an earlier discrepancy between thermodynamics of charged
rotating black holes and boundary hydrodynamics. We have also confirmed that
all our expressions are covariant under boundary Weyl-transformations as
expected.Comment: 0+ 31 Pages; v2: 0+33 pages, typos corrected and new sections (in
appendix) added; v3:published versio
A Measurement of the Coulomb Dissociation of 8B at 254 MeV/nucleon and the 8B Solar Neutrino Flux
We have measured the Coulomb dissociation of 8B into 7Be and proton at 254
MeV/nucleon using a large-acceptance focusing spectrometer. The astrophysical
S17 factor for the 7Be(p,gamma)8B reaction at E{c.m.} = 0.25-2.78 MeV is
deduced yielding S17(0)=20.6 \pm 1.2 (exp.) \pm 1.0 (theo.) eV-b.
This result agrees with the presently adopted zero-energy S17 factor obtained
in direct-reaction measurements and with the results of other
Coulomb-dissociation studies performed at 46.5 and 51.2 MeV/nucleon.Comment: paper to be published in Phys. Rev. Lett. 3 figures. New Version
fixes formatting problems with the figures only. There are no other change
Transport in holographic superfluids
We construct a slowly varying space-time dependent holographic superfluid and
compute its transport coefficients. Our solution is presented as a series
expansion in inverse powers of the charge of the order parameter. We find that
the shear viscosity associated with the motion of the condensate vanishes. The
diffusion coefficient of the superfluid is continuous across the phase
transition while its third bulk viscosity is found to diverge at the critical
temperature. As was previously shown, the ratio of the shear viscosity of the
normal component to the entropy density is 1/(4 pi). As a consequence of our
analysis we obtain an analytic expression for the backreacted metric near the
phase transition for a particular type of holographic superfluid.Comment: 45 pages + appendice
Cyclin D1 and D3 expression in melanocytic skin lesions
Cyclins, cyclin-dependent kinases, as well as proteins cooperating with them are responsible for cell cycle regulation which is crucial for normal development, injury repair, and tumorigenesis. D-type cyclins regulate G1 cell cycle progression by enhancing the activities of cyclin-dependent kinases, and their expression is frequently altered in tumors. Disturbances in cyclin expression were also reported in melanocytic skin lesions. The objective of the study was to evaluate the expression of cyclins D1 and D3 in common, dysplastic, and malignant melanocytic skin lesions. Forty-eight melanocytic skin lesions including common nevi (10), dysplastic nevi (24), and melanomas (14) were diagnosed by dermoscopy and excised. Expression of cyclin D1 and D3 was detected by immunohistochemistry and quantified as percentage of immunostained cell nuclei in each sample. In normal skin, expression of cyclins D1 and D3 was not detected. The mean percentage of cyclin D1-positive nuclei was 7.75% for melanoma samples, 5% for dysplastic nevi samples, and 0.34% for common nevi samples. For cyclin D3, the respective values were 17.8, 6.4, and 1.8%. Statistically significant differences in cyclin D1 expression were observed between melanomas and common nevi as well as between dysplastic and common nevi (p = 0.0001), but not between melanomas and dysplastic nevi. Cyclin D3 expression revealed significant differences between all investigated lesion types (p = 0.0000). The mean cyclin D1 and D3 scores of melanomas with Breslow thickness <1 mm and >1 mm were not significantly different. G1/S abnormalities are crucial for the progression of malignant melanoma, and enhanced cyclin D1 and D3 expression leading to increased melanocyte proliferation is observed in both melanoma and dysplastic nevi. In histopathologically ambiguous cases, lower cyclin D3 expression in dysplastic nevi can be a diagnostic marker for that lesion type
Measurement of the 92,93,94,100Mo(γ,n) reactions by Coulomb Dissociation
The Coulomb Dissociation (CD) cross sections of the stable isotopes 92,94,100Mo and of the unstable isotope 93Mo were measured at the LAND/R3B setup at GSI Helmholtzzentrum für Schwerionenforschung in Darmstadt, Germany. Experimental data on these isotopes may help to explain the problem of the underproduction of 92,94Mo and 96,98Ru in the models of p-process nucleosynthesis. The CD cross sections obtained for the stable Mo isotopes are in good agreement with experiments performed with real photons, thus validating the method of Coulomb Dissociation. The result for the reaction 93Mo(γ,n) is especially important since the corresponding cross section has not been measured before. A preliminary integral Coulomb Dissociation cross section of the 94Mo(γ,n) reaction is presented. Further analysis will complete the experimental database for the (γ,n) production chain of the p-isotopes of molybdenum