973 research outputs found
Nature of fault planes in solid neutron star matter
The properties of tectonic earthquake sources are compared with those deduced
here for fault planes in solid neutron-star matter. The conclusion that
neutron-star matter cannot exhibit brittle fracture at any temperature or
magnetic field is significant for current theories of pulsar glitches, and of
the anomalous X-ray pulsars and soft-gamma repeaters.Comment: 5 AAS LaTeX pages 1 eps figur
Tricritical Phenomena at the Cerium Transition
The isostructural transition in the
CeLaTh system is measured as a function of La alloying
using specific heat, magnetic susceptibility, resistivity, thermal
expansivity/striction measurements. A line of discontinuous transitions, as
indicated by the change in volume, decreases exponentially from 118 K to close
to zero with increasing La doping and the transition changes from being
first-order to continuous at a critical concentration . At the tricritical point, the coefficient of the linear term in the
specific heat and the magnetic susceptibility start to increase
rapidly near = 0.14 and gradually approaches large values at =0.35
signifying that a heavy Fermi-liquid state evolves at large doping. Near ,
the Wilson ratio, , has a value of 3.0, signifying the presence of
magnetic fluctuations. Also, the low-temperature resistivity shows that the
character of the low-temperature Fermi-liquid is changing
On the correlation between fragility and stretching in glassforming liquids
We study the pressure and temperature dependences of the dielectric
relaxation of two molecular glassforming liquids, dibutyl phtalate and
m-toluidine. We focus on two characteristics of the slowing down of relaxation,
the fragility associated with the temperature dependence and the stretching
characterizing the relaxation function. We combine our data with data from the
literature to revisit the proposed correlation between these two quantities. We
do this in light of constraints that we suggest to put on the search for
empirical correlations among properties of glassformers. In particular, argue
that a meaningful correlation is to be looked for between stretching and
isochoric fragility, as both seem to be constant under isochronic conditions
and thereby reflect the intrinsic effect of temperature
Complete pressure dependent phase diagrams for SrFe2As2 and BaFe2As2
The temperature dependent electrical resistivity of single crystalline
SrFe2As2 and BaFe2As2 has been measured in a liquid medium, modified Bridgman
anvil cell for pressures in excess of 75 kbar. These data allow for the
determination of the pressure dependence of the higher temperature, structural
/ antiferromagnetic phase transitions as well as the lower temperature
superconducting phase transition. For both compounds the ambient pressure,
higher temperature structural / antiferromagnetic phase transition can be fully
suppressed with a dome-like region of zero resistivity found to be centered
about its critical pressure. Indeed, qualitatively, the temperature dependence
of the resistivity curves closest to the critical pressures are the closest to
linear, consistent with possible quantum criticality. For pressures
significantly higher than the critical pressure the zero resistivity state is
suppressed and the low temperature resistivity curves asymptotically approach a
universal, low temperature manifold. These results are consistent with the
hypothesis that correlations / fluctuations associated with the
ambient-pressure, high-temperature, tetragonal phase have to be brought to low
enough temperature to allow superconductivity, but if too fully suppressed can
lead to the loss of the superconducting state
Positive-Operator-Valued Time Observable in Quantum Mechanics
We examine the longstanding problem of introducing a time observable in
Quantum Mechanics; using the formalism of positive-operator-valued measures we
show how to define such an observable in a natural way and we discuss some
consequences.Comment: 13 pages, LaTeX, no figures. Some minor changes, expanded the
bibliography (now it is bigger than the one in the published version),
changed the title and the style for publication on the International Journal
of Theoretical Physic
Density scaling and quasiuniversality of flow-event statistics for athermal plastic flows
Athermal plastic flows were simulated for the Kob-Andersen binary
Lennard-Jones system and its repulsive version in which the sign of the
attractive terms is changed to a plus. Properties evaluated from simulations at
different densities include the distributions of energy drops, stress drops,
and strain intervals between the flow events. By reference to hidden scale
invariance we show that simulations at a single density in conjunction with an
equilibrium-liquid simulation at the same density allows one to predict the
plastic flow-event properties at other densities. We furthermore demonstrate
quasiuniversality of the flow-event statistics
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