9,122 research outputs found
The effect of hydrogen sulphide on ammonium bisulphite when used as an oxygen scavenger in aqueous solutions
Peer reviewedPostprin
Near-Infrared Variability in the 2MASS Calibration Fields: A Search for Planetary Transit Candidates
The 2MASS photometric calibration observations cover ~6 square degrees on the
sky in 35 "calibration fields" each sampled in nominal photometric conditions
between 562 and 3692 times during the four years of the 2MASS mission. We
compile a catalog of variables from the calibration observations to search for
M dwarfs transited by extra-solar planets. We present our methods for measuring
periodic and non-periodic flux variability. From 7554 sources with apparent Ks
magnitudes between 5.6 and 16.1, we identify 247 variables, including
extragalactic variables and 23 periodic variables. We have discovered three M
dwarf eclipsing systems, including two candidates for transiting extrasolar
planets.Comment: The Astrophysical Journal Supplement, in press; figures compresse
Metal-superconductor transition at zero temperature: A case of unusual scaling
An effective field theory is derived for the normal metal-to-superconductor
quantum phase transition at T=0. The critical behavior is determined exactly
for all dimensions d>2. Although the critical exponents \beta and \nu do not
exist, the usual scaling relations, properly reinterpreted, still hold. A
complete scaling description of the transition is given, and the physics
underlying the unusual critical behavior is discussed. Quenched disorder leads
to anomalously strong T_c-fluctuations which are shown to explain the
experimentally observed broadening of the transition in low-T_c thin films.Comment: 4 pp., no figs, final version as publishe
Spanning Trees in Random Satisfiability Problems
Working with tree graphs is always easier than with loopy ones and spanning
trees are the closest tree-like structures to a given graph. We find a
correspondence between the solutions of random K-satisfiability problem and
those of spanning trees in the associated factor graph. We introduce a modified
survey propagation algorithm which returns null edges of the factor graph and
helps us to find satisfiable spanning trees. This allows us to study
organization of satisfiable spanning trees in the space spanned by spanning
trees.Comment: 12 pages, 5 figures, published versio
Possible triplet superconductivity in MOSFETs
A theory that predicts a spin-triplet, even-parity superconducting ground
state in two-dimensional electron systems is re-analyzed in the light of recent
experiments showing a possible insulator-to-conductor transition in such
systems. It is shown that the observations are consistent with such an exotic
superconductivity mechanism, and predictions are made for experiments that
would further corroborate or refute this proposal.Comment: 4 pp., REVTeX, psfig, 1 eps fig, final version as publishe
Phase diagram of glassy systems in an external field
We study the mean-field phase diagram of glassy systems in a field pointing
in the direction of a metastable state. We find competition among a
``magnetized'' and a ``disordered'' phase, that are separated by a coexistence
line as in ordinary first order phase transitions. The coexistence line
terminates in a critical point, which in principle can be observed in numerical
simulations of glassy models.Comment: 4 pages, 5 figure
Tricritical Points in Random Combinatorics: the (2+p)-SAT case
The (2+p)-Satisfiability (SAT) problem interpolates between different classes
of complexity theory and is believed to be of basic interest in understanding
the onset of typical case complexity in random combinatorics. In this paper, a
tricritical point in the phase diagram of the random -SAT problem is
analytically computed using the replica approach and found to lie in the range
. These bounds on are in agreement with previous
numerical simulations and rigorous results.Comment: 7 pages, 1 figure, RevTeX, to appear in J.Phys.
Numerical study of a short-range p-spin glass model in three dimensions
In this work we study numerically a short range p-spin glass model in three
dimensions. The behaviour of the model appears to be remarkably different from
mean field predictions. In fact it shares some features typical of models with
full replica-symmetry breaking (FRSB). Nevertheless, we believe that the
transition that we study is intrinsically different from the FRSB and basically
due to non-perturbative contributions. We study both the statics and the
dynamics of the system which seem to confirm our conjectures.Comment: 20 pages, 15 figure
Quantum critical behavior of itinerant ferromagnets
The quantum ferromagnetic transition of itinerant electrons is considered. We
give a pedagogical review of recent results which show that zero-temperature
soft modes that are commonly neglected, invalidate the standard
Landau-Ginzburg-Wilson description of this transition. If these modes are taken
into account, then the resulting order parameter field theory is nonlocal in
space and time. Nevertheless, for both disordered and clean systems the
critical behavior has been exactly determined for spatial dimensions d>2 and
d>1, respectively. The critical exponents characterizing the
paramagnetic-to-ferromagnetic transition are dimensionality dependent, and
substantially different from both mean-field critical exponents, and from the
classical Heisenberg exponents that characterize the transition at finite
temperatures. Our results should be easily observable, particularly those for
the disordered case, and experiments to check our predictions are proposed.Comment: 11pp., REVTeX, 6 eps figures, Santa Barbara Conf. Proceedings, final
version as publishe
Quantum Metal--Superconductor Transition: A Local Field Theory Approach
The zero temperature, or quantum, metal-superconductor phase transition is
studied in disordered systems in dimension greater than two. A effective local
field theory is developed that keeps all soft modes or fluctuations explicitly.
A simple renormalization group analysis is used to exactly determine the
quantum critical behavior at this transition.Comment: 6 page
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