15,884 research outputs found
Quantum critical superconductors in string theory and M-theory
We construct zero-temperature solutions of supergravity theories in five and
four dimensions which interpolate between two copies of anti-de Sitter space,
one of which preserves an abelian gauge symmetry while the other breaks it.
These domain wall solutions can be lifted to solutions of type IIB string
theory and eleven-dimensional supergravity. They describe quantum critical
behavior and emergent relativistic conformal symmetry in a superfluid or
superconducting state of a strongly coupled dual gauge theory. We include
computations of frequency-dependent conductivities which exhibit power law
scaling in the infrared, with exponents determined by irrelevant perturbations
to the symmetry-breaking anti-de Sitter background.Comment: 5 pages, 3 figures. v2: References slightly improved, mentioned F^F
constrain
Bulk viscosity of strongly coupled plasmas with holographic duals
We explain a method for computing the bulk viscosity of strongly coupled
thermal plasmas dual to supergravity backgrounds supported by one scalar field.
Whereas earlier investigations required the computation of the leading
dissipative term in the dispersion relation for sound waves, our method
requires only the leading frequency dependence of an appropriate Green's
function in the low-frequency limit. With a scalar potential chosen to mimic
the equation of state of QCD, we observe a slight violation of the lower bound
on the ratio of the bulk and shear viscosities conjectured in arXiv:0708.3459.Comment: 33 pages, 3 figure
Gluon energy loss in the gauge-string duality
We estimate the stopping length of an energetic gluon in a thermal plasma of
strongly coupled N=4 super-Yang-Mills theory by representing the gluon as a
doubled string rising up out of the horizon.Comment: 33 pages, 8 figures. v2: minor improvement
On the dimensional dependence of duality groups for massive p-forms
We study the soldering formalism in the context of abelian p-form theories.
We develop further the fusion process of massless antisymmetric tensors of
different ranks into a massive p-form and establish its duality properties. To
illustrate the formalism we consider two situations. First the soldering mass
generation mechanism is compared with the Higgs and Julia-Toulouse mechanisms
for mass generation due to condensation of electric and magnetic topological
defects. We show that the soldering mechanism interpolates between them for
even dimensional spacetimes, in this way confirming the Higgs/Julia-Toulouse
duality proposed by Quevedo and Trugenberger \cite{QT} a few years ago. Next,
soldering is applied to the study of duality group classification of the
massive forms. We show a dichotomy controlled by the parity of the operator
defining the symplectic structure of the theory and find their explicit
actions.Comment: Reference [8] has been properly place
DNA-psoralen: single-molecule experiments and first principles calculations
The authors measure the persistence and contour lengths of DNA-psoralen
complexes, as a function of psoralen concentration, for intercalated and
crosslinked complexes. In both cases, the persistence length monotonically
increases until a certain critical concentration is reached, above which it
abruptly decreases and remains approximately constant. The contour length of
the complexes exhibits no such discontinuous behavior. By fitting the relative
increase of the contour length to the neighbor exclusion model, we obtain the
exclusion number and the intrinsic intercalating constant of the psoralen-DNA
interaction. Ab initio calculations are employed in order to provide an
atomistic picture of these experimental findings.Comment: 9 pages, 4 figures in re-print format 3 pages, 4 figures in the
published versio
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