16,663 research outputs found
Heavy Quarks in Strongly Coupled Non-Conformal Plasmas with Anisotropy
We analysis physical observables of heavy quarks in gravity models describing
strongly coupled non-conformal plasmas with anisotropy via the gauge/gravity
duality. The focus lies on the binding energy of static quark-antiquark -)pairs, the maximum distance (screening distance) of a bound -pair
and the drag force on uniformly moving quarks in the hot plasma. In order to
discover universal behavior in the observables, the computations are worked out
in a two parameter deformation of pure gravity in spacetime with a
black brane which is assumed to be dual to a respective two parameter
deformation of =\,4 supersymmetric Yang-Mills (SYM) theory at
temperature . The deformation is designed to break isotropy and conformal
symmetry and is a solution to equations of motion of a gravity action.Comment: 32 pages, 14 figures, v2: references adde
Entanglement entropy through conformal interfaces in the 2D Ising model
We consider the entanglement entropy for the 2D Ising model at the conformal
fixed point in the presence of interfaces. More precisely, we investigate the
situation where the two subsystems are separated by a defect line that
preserves conformal invariance. Using the replica trick, we compute the
entanglement entropy between the two subsystems. We observe that the entropy,
just like in the case without defects, shows a logarithmic scaling behavior
with respect to the size of the system. Here, the prefactor of the logarithm
depends on the strength of the defect encoded in the transmission coefficient.
We also comment on the supersymmetric case.Comment: 27 pages, 3 figures, v2: additional references and minor correction
Constraints on the Bulk Lorentz Factor of GRB 990123
GRB 990123 was a long, complex gamma-ray burst accompanied by an extremely
bright optical flash. We present the collective constraints on the bulk Lorentz
factor for this burst based on estimates from burst kinematics, synchrotron
spectral decay, prompt radio flash observations, and prompt emission pulse
width. Combination of these constraints leads to an average bulk Lorentz factor
for GRB 990123 of Gamma_0=1000 +/- 100 which implies a baryon loading of
M_jet=8 (+17/-2) x 10^-8 Msolar. We find these constraints to be consistent
with the speculation that the optical light is emission from the reverse shock
component of the external shock. In addition, we find the implied value of
M_jet to be in accordance with theoretical estimates: the baryonic loading is
sufficiently small to allow acceleration of the outflow to Gamma > 100.Comment: 4 pages, 2 postscript figures, to appear in "Gamma-Ray Burst and
Afterglow Astronomy 2001", Woods Hole; 5-9 Nov, 200
Integrative analysis of large-scale biological data sets
We present two novel web-applications for microarray and gene/protein set analysis, ArrayMining.net and TopoGSA. These bioinformatics tools use integrative analysis methods, including ensemble and consensus machine learning techniques, as well as modular combinations of different analysis types, to extract new biological insights from experimental transcriptomics and proteomics data. They enable researchers to combine related algorithms and datasets to increase the robustness and accuracy of statistical analyses and exploit synergies of different computational methods, ranging from statistical learning to optimization and topological network analysis
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