4,602 research outputs found
Crystalline droplets with emergent topological color-charge in many-body systems with sign-changing interactions
We introduce a novel type of self-bound droplet which carries an emergent
color charge. We consider a system of particles hopping on a lattice and
interacting via a commensurately sign-changing potential which is attractive at
a short range. The droplet formation is heralded by spontaneous crystallization
into topologically distinct domains. This endows each droplet with an emergent
color charge governing their mutual interactions: attractive for equal colors
and repulsive otherwise. The number of allowed colors is fixed only by the
discrete spatial symmetries of the sign-changing part of the interaction
potential. With increasing interaction range, the droplets become progressively
more mobile, with their color charge still being energetically protected,
allowing for nontrivial viscous dynamics of the interacting droplet plasmas
formed during cooling. Sign-changing potentials with a short-range attraction
appear quite naturally for light-mediated interactions and we concretely
propose a realization in state-of-the-art experiments with cold atoms in a
multimode optical cavity.Comment: version similar to published, including supplementary material
Phase transitions in ensembles of solitons induced by an optical pumping or a strong electric field
The latest trend in studies of modern electronically and/or optically active
materials is to provoke phase transformations induced by high electric fields
or by short (femtosecond) powerful optical pulses. The systems of choice are
cooperative electronic states whose broken symmetries give rise to topological
defects. For typical quasi-one-dimensional architectures, those are the
microscopic solitons taking from electrons the major roles as carriers of
charge or spin. Because of the long-range ordering, the solitons experience
unusual super-long-range forces leading to a sequence of phase transitions in
their ensembles: the higher-temperature transition of the confinement and the
lower one of aggregation into macroscopic walls. Here we present results of an
extensive numerical modeling for ensembles of both neutral and charged solitons
in both two- and three-dimensional systems. We suggest a specific Monte Carlo
algorithm preserving the number of solitons, which substantially facilitates
the calculations, allows to extend them to the three-dimensional case and to
include the important long-range Coulomb interactions. The results confirm the
first confinement transition, except for a very strong Coulomb repulsion, and
demonstrate a pattern formation at the second transition of aggregation.Comment: 16 pages, 16 figure
What is moving in silica at 1 K? A computer study of the low-temperature anomalies
Though the existence of two-level systems (TLS) is widely accepted to explain
low temperature anomalies in many physical observables, knowledge about their
properties is very rare. For silica which is one of the prototype glass-forming
systems we elucidate the properties of the TLS via computer simulations by
applying a systematic search algorithm. We get specific information in the
configuration space, i.e. about relevant energy scales, the absolute number of
TLS and electric dipole moments. Furthermore important insight about the
real-space realization of the TLS can be obtained. Comparison with experimental
observations is included
Effort and catch estimates for northern and central California marine recreational fisheries, 1981-1986
Nearly 200 species of finfish are taken by the marine recreational fishery along the northern and central California coast. This data report provides estimates of total effort, total catch, and fishery demographics for the years 1981 through 1986 for that fishery. Catch estimate data are presented by number and weight of species, by disposition of the fish caught (e.g. kept or thrown back), by type of access and fishing gear used, and by geographic zone. (311pp.
Phase transitions and pattern formation in ensembles of phase-amplitude solitons in quasi-one-dimensional electronic systems
Most common types of symmetry breaking in quasi-one-dimensional electronic
systems possess a combined manifold of states degenerate with respect to both
the phase and the amplitude sign of the order parameter
. These degrees of freedom can be controlled or accessed
independently via either the spin polarization or the charge densities. To
understand statistical properties and the phase diagram in the course of
cooling under the controlled parameters, we present here an analytical
treatment supported by Monte Carlo simulations for a generic coarse-grained
two-fields model of XY-Ising type. The degeneracies give rise to two coexisting
types of topologically nontrivial configurations: phase vortices and amplitude
kinks -- the solitons. In 2D, 3D states with long-range (or BKT type) orders,
the topological confinement sets in at a temperature which binds
together the kinks and unusual half-integer vortices. At a lower , the
solitons start to aggregate into walls formed as rods of amplitude kinks which
are ultimately terminated by half-integer vortices. With lowering , the
walls multiply passing sequentially across the sample.
The presented results indicate a possible physical realization of a peculiar
system of half-integer vortices with rods of amplitude kinks connecting their
cores. Its experimental realization becomes feasible in view of recent
successes in real space observations and even manipulations of domain walls in
correlated electronic systems
Light-induced quantum droplet phases of lattice bosons in multimode cavities
Multimode optical cavities can be used to implement interatomic interactions
which are highly tunable in strength and range. For bosonic atoms trapped in an
optical lattice, cavity-mediated interactions compete with the short-range
interatomic repulsion, which we study using an extended Bose-Hubbard model.
Already in a single-mode cavity, where the corresponding interaction has an
infinite range, a rich phase diagram has been experimentally observed,
featuring density-wave and supersolid self-organized phases in addition to the
usual superfluid and Mott insulator. Here we show that, for any finite range of
the cavity-mediated interaction, quantum self-bound droplets dominate the
ground state phase diagram. Their size and in turn density is not externally
fixed but rather emerges from the competition between local repulsion and
finite-range attraction. Therefore, the phase diagram becomes very rich,
featuring both compressible superfluid/supersolid as well as incompressible
Mott and density-wave droplets. Additionally, we observe droplets with a
compressible core and incompressible outer shells.Comment: 6 pages, 4 figure
Curvature Correction in the Strutinsky's Method
Mass calculations carried out by Strutinsky's shell correction method are
based on the notion of smooth single particle level density. The smoothing
procedure is always performed using curvature correction. In the presence of
curvature correction a smooth function remains unchanged if smoothing is
applied. Two new curvature correction methods are introduced. The performance
of the standard and new methods are investigated using harmonic oscillator and
realistic potentials.Comment: 4 figures, submitted to Journal of Physics G: Nuclear and Particle
Physic
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