65,861 research outputs found
Stability analysis of three-dimensional breather solitons in a Bose-Einstein Condensate
We investigate the stability properties of breather soliton trains in a
three-dimensional Bose-Einstein Condensate with Feshbach Resonance Management
of the scattering length. This is done so as to generate both attractive and
repulsive interaction. The condensate is con ned only by a one dimensional
optical lattice and we consider both strong, moderate, and weak con nement. By
strong con nement we mean a situation in which a quasi two dimensional soliton
is created. Moderate con nement admits a fully three dimensional soliton. Weak
con nement allows individual solitons to interact. Stability properties are
investigated by several theoretical methods such as a variational analysis,
treatment of motion in e ective potential wells, and collapse dynamics. Armed
with all the information forthcoming from these methods, we then undertake a
numerical calculation. Our theoretical predictions are fully con rmed, perhaps
to a higher degree than expected. We compare regions of stability in parameter
space obtained from a fully 3D analysis with those from a quasi two-dimensional
treatment, when the dynamics in one direction are frozen. We nd that in the 3D
case the stability region splits into two parts. However, as we tighten the con
nement, one of the islands of stability moves toward higher frequencies and the
lower frequency region becomes more and more like that for quasi 2D. We
demonstrate these solutions in direct numerical simulations and, importantly,
suggest a way of creating robust 3D solitons in experiments in a Bose Einstein
Condensate in a one-dimensional lattice.Comment: 14 pages, 6 figures; accepted to Proc. Roy. Soc. London
Perturbed and Permuted: Signal Integration in Network-Structured Dynamic Systems
Biological systems (among others) may respond to a large variety of distinct
external stimuli, or signals. These perturbations will generally be presented
to the system not singly, but in various combinations, so that a proper
understanding of the system response requires assessment of the degree to which
the effects of one signal modulate the effects of another. This paper develops
a pair of structural metrics for sparse differential equation models of complex
dynamic systems and demonstrates that said metrics correlate with proxies of
the susceptibility of one signal-response to be altered in the context of a
second signal. One of these metrics may be interpreted as a normalized arc
density in the neighborhood of certain influential nodes; this metric appears
to correlate with increased independence of signal response
Polaron Excitations in Doped C60: Effects of Disorders
Effects on C by thermal fluctuations of phonons, misalignment of
C molecules in a crystal, and other intercalated impurities (remaining
C, oxygens, and so on) are simulated by disorder potentials. The
Su-Schrieffer-Heeger--type electron-phonon model for doped C is solved
with gaussian bond disorders and also with site disorders. Sample average is
performed over sufficient number of disorder configurations. The distributions
of bond lengths and electron densities are shown as functions of the disorder
strength and the additional electron number. Stability of polaron excitations
as well as dimerization patterns is studied. Polarons and dimerizations in
lightly doped cases (C) are relatively stable against disorders,
indicated by peak structures in distribution functions. In more heavily doped
cases, the several peaks merge into a single peak, showing the breakdown of
polaron structures as well as the decrease of the dimerization strength.
Possibility of the observation of polaronic lattice distortions and electron
structures in doped C is discussed.Comment: Note: This manusript was accepted for publication in Physical Review
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Optical spectroscopic investigation on the coupling of electronic and magnetic structure in multiferroic hexagonal RMnO3 (R = Gd, Tb, Dy, and Ho) thin films
We investigated the effects of temperature and magnetic field on the
electronic structure of hexagonal RMnO3 (R = Gd, Tb, Dy, and Ho) thin films
using optical spectroscopy. As the magnetic ordering of the system was
disturbed, a systematic change in the electronic structure was commonly
identified in this series. The optical absorption peak near 1.7 eV showed an
unexpectedly large shift of more than 150 meV from 300 K to 15 K, accompanied
by an anomaly of the shift at the Neel temperature. The magnetic field
dependent measurement clearly revealed a sizable shift of the corresponding
peak when a high magnetic field was applied. Our findings indicated strong
coupling between the magnetic ordering and the electronic structure in the
multiferroic hexagonal RMnO3 compounds.Comment: 16 pages including 4 figure
Nonlinear states and dynamics in a synthetic frequency dimension
Recent advances in the study of synthetic dimensions revealed a possibility
to employ the frequency space as an additional degree of freedom which allows
for investigating and exploiting higher-dimensional phenomena in a priori
low-dimensional systems. However, the influence of nonlinear effects on the
synthetic frequency dimensions was studied only under significant restrictions.
In the present paper, we develop a generalized mean-field model for the optical
field envelope inside a single driven-dissipative resonator with quadratic and
cubic nonlinearities, whose frequencies are coupled via an electro-optical
resonant temporal modulation. The leading order equation takes the form of
driven Gross-Pitaevskii equation with a cosine potential. We numerically
investigate the nonlinear dynamics in such microring resonator with a synthetic
frequency dimension in the regime where parametric frequency conversion occurs.
In the case of anomalous dispersion, we find that the presence of
electro-optical mode coupling confines and stabilizes the chaotic modulation
instability region. This leads to the appearance of a novel type of stable
coherent structures which emerge in the synthetic space with restored
translational symmetry, in a region of parameters where conventionally only
chaotic modulation instability states exist. This structure appears in the
center of the synthetic band and, therefore, is referred to as Band Soliton.
Finally, we extend our results to the case of multiple modulation frequencies
with controllable relative phases creating synthetic lattices with nontrivial
geometry. We show that an asymmetric synthetic band leads to the coexistence of
chaotic and coherent states of the electromagnetic field inside the cavity i.e.
dynamics that can be interpreted as chimera-like states. Recently developed
microresonators can open the way to experimentally explore our
findings.Comment: 12 pages, 5 figures; figure 4 and typos correcte
Conceptual design of a nonscaling fixed field alternating gradient accelerator for protons and carbon ions for charged particle therapy
Published by the American Physical Society under the terms of the Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.The conceptual design for a nonscaling fixed field alternating gradient accelerator suitable for charged particle therapy (the use of protons and other light ions to treat some forms of cancer) is described.EPSR
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