301,164 research outputs found
What can gauge-gravity duality teach us about condensed matter physics?
I discuss the impact of gauge-gravity duality on our understanding of two
classes of systems: conformal quantum matter and compressible quantum matter.
The first conformal class includes systems, such as the boson Hubbard model
in two spatial dimensions, which display quantum critical points described by
conformal field theories. Questions associated with non-zero temperature
dynamics and transport are difficult to answer using conventional field
theoretic methods. I argue that many of these can be addressed systematically
using gauge-gravity duality, and discuss the prospects for reliable computation
of low frequency correlations.
Compressible quantum matter is characterized by the smooth dependence of the
charge density, associated with a global U(1) symmetry, upon a chemical
potential. Familiar examples are solids, superfluids, and Fermi liquids, but
there are more exotic possibilities involving deconfined phases of gauge fields
in the presence of Fermi surfaces. I survey the compressible systems studied
using gauge-gravity duality, and discuss their relationship to the condensed
matter classification of such states. The gravity methods offer hope of a
deeper understanding of exotic and strongly-coupled compressible quantum
states.Comment: 34 pages, 11 figures + 16 pages of Supplementary Material with 4
figures; to appear in Annual Reviews of Condensed Matter Physics; (v2) add a
figure, and clarifications; (v3) final version; (v4) small correction
Universe Models with a Variable Cosmological "Constant" and a "Big Bounce"
We present a rich class of exact solutions which contains radiation-dominated
and matter-dominated models for the early and late universe. They include a
variable cosmological ``constant'' which is derived from a higher dimension and
manifests itself in spacetime as an energy density for the vacuum. This is in
agreement with observational data and is compatible with extensions of general
relativity to string and membrane theory. Our solutions are also typified by a
non-singular ``big bounce'' (as opposed to a singular big bang), where matter
is created as in inflationary cosmology.Comment: 17 pages, 2 figures, AASTEX. To appear in Ap
On the capture probabilities of resonance rotation for Mercury
Capture probabilities of resonance rotation for Mercur
Thermal and tidal effect on the libration of Mercury
Thermal and tidal effect on Mercury libratio
Level Densities by Particle-Number Reprojection Monte Carlo Methods
A particle-number reprojection method is applied in the framework of the
shell model Monte Carlo approach to calculate level densities for a family of
nuclei using Monte Carlo sampling for a single nucleus. In particular we can
also calculate level densities of odd-even and odd-odd nuclei despite a new
sign problem introduced by the projection on an odd number of particles. The
method is applied to level densities in the iron region using the complete
-shell. The single-particle level density parameter and the
backshift parameter are extracted by fitting the microscopically
calculated level densities to the backshifted Bethe formula. We find good
agreement with experimental level densities with no adjustable parameters in
the microscopic calculations. The parameter is found to vary smoothly with
mass and does not show odd-even effects. The calculated backshift parameter
displays an odd-even staggering effect versus mass and is in better
agreement with the experimental data than are the empirical values.Comment: To be published in the proceedings of the Tenth International
Symposium on Capture Gamma-Ray Spectroscopy and Related Topics, S. Wender,
ed., AIP Conference Proceedings (2000
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