2,192 research outputs found
Lieb Mode in a Quasi One-Dimensional Bose-Einstein Condensate of Atoms
We calculate the dispersion relation associated with a solitary wave in a
quasi-one-dimensional Bose-Einstein condensate of atoms confined in a harmonic,
cylindrical trap in the limit of weak and strong interactions. In both cases,
the dispersion relation is linear for long wavelength excitations and
terminates at the point where the group velocity vanishes. We also calculate
the dispersion relation of sound waves in both limits of weak and strong
coupling.Comment: 4 pages, 2 ps figures, RevTe
Vortex Rings and Lieb Modes in a Cylindrical Bose-Einstein Condensate
We present a calculation of a solitary wave propagating along a cylindrical
Bose-Einstein trap, which is found to be a hybrid of a one-dimensional (1D)
soliton and a three-dimensional (3D) vortex ring. The calculated
energy-momentum dispersion exhibits characteristics similar to those of a mode
proposed sometime ago by Lieb within a 1D model, as well as some rotonlike
features.Comment: 4 pages, 4 figure
Structures and topological transitions of hydrocarbon films on quasicrystalline surfaces
Lubricants can affect quasicrystalline coatings surfaces by modifying
commensurability of the interfaces. We report results of the first computer
simulation studies of physically adsorbed hydrocarbons on a quasicrystalline
surface: methane, propane, and benzene on decagonal Al-Ni-Co. The grand
canonical Monte Carlo method is employed, using novel Embedded Atom Method
potentials generated from it ab initio calculations, and standard hydrocarbon
interactions. The resulting adsorption isotherms and calculated structures show
the films' evolution from submonolayer to condensation. We discover the
presence and absence of the 5- to 6-fold topological transition, for benzene
and methane, respectively, in agreement with a previsouly formulated
phenomenological rule based on adsorbate-substrate size mismatch.Comment: 5 pages, 5 figure, 1 EPAPS-material.pd
Solitons, solitonic vortices, and vortex rings in a confined Bose-Einstein condensate
Quasi-one-dimensional solitons that may occur in an elongated Bose-Einstein
condensate become unstable at high particle density. We study two basic modes
of instability and the corresponding bifurcations to genuinely
three-dimensional solitary waves such as axisymmetric vortex rings and
non-axisymmetric solitonic vortices. We calculate the profiles of the above
structures and examine their dependence on the velocity of propagation along a
cylindrical trap. At sufficiently high velocity, both the vortex ring and the
solitonic vortex transform into an axisymmetric soliton. We also calculate the
energy-momentum dispersions and show that a Lieb-type mode appears in the
excitation spectrum for all particle densities.Comment: RevTeX 9 pages, 9 figure
A theorem on the absence of phase transitions in one-dimensional growth models with onsite periodic potentials
We rigorously prove that a wide class of one-dimensional growth models with
onsite periodic potential, such as the discrete sine-Gordon model, have no
phase transition at any temperature . The proof relies on the spectral
analysis of the transfer operator associated to the models. We show that this
operator is Hilbert-Schmidt and that its maximum eigenvalue is an analytic
function of temperature.Comment: 6 pages, no figures, submitted to J Phys A: Math Ge
Topological defects and shape of aromatic self-assembled vesicles
We show that the stacking of flat aromatic molecules on a curved surface
results in topological defects. We consider, as an example, spherical vesicles,
self-assembled from molecules with 5- and 6-thiophene cores. We predict that
the symmetry of the molecules influences the number of topological defects and
the resulting equilibrium shape.Comment: accepted as a Letter in the J. Phys. Chem.
News in the classification of WHO 2022 bladder tumors
The fifth-edition of World Health Organization (WHO) Classification of Tumors series for urinary and male genital tract tumors has been published, six years later the fourth-edition. In these years, new treatment approaches have been implemented and new molecular data on urological cancers are known. Morphology remains the groundwork for taxonomy of the urinary tract tumors. However, a molecular approach to classification of urothelial carcinomas and the management of selected neoplasms with new therapeutic modalities such as immunotherapy are emerging. More data are needed for the application of these advances in routine pathology practice and patient management. The 2022 World Health Organization (WHO) Classification of Tumors of the Urinary System and Male Genital Organs represents an update in classification on urinary tract tumors. It also offers new insights with regards to the grading of heterogeneous non-invasive urothelial neoplasms, the definition of inverted neoplasms, the grading of invasive urothelial carcinomas, the diversity of morphological appearance of urothelial carcinomas, the definition of precursor lesions and the lineage of differentiation of the tumors
Effect of spatial variations of superconducting gap on suppression of the transition temperature by impurities
We calculate correction to the critical temperature of a dirty
superconductor, which results from the local variations of the gap function
near impurity sites. This correction is of the order of T_c/E_F and becomes
important for short-coherence length superconductors. It generally reduces a
pair-breaking effect. In s-wave superconductors small amounts of nonmagnetic
impurities can increase the transition temperature.Comment: 5 pages, ReVTE
Probing spectral properties of radio-quiet quasars searched for optical microvariability-II
In the context of AGN unification scheme rapid variability properties play an
important role in understanding any intrinsic differences between sources in
different classes. In this respect any clue based on spectral properties will
be very useful toward understanding the mechanisms responsible for the origin
of rapid small scale optical variations, or microvariability. Here we have
added spectra of 46 radio-quiet quasars (RQQSOs) and Seyfert 1 galaxies to
those of our previous sample of 37 such objects, all of which had been
previously searched for microvariability. We took new optical spectra of 33
objects and obtained 13 others from the literature. Their \hbeta and \mgii
emission lines were carefully fit to determine line widths (FWHM) as well as
equivalent widths (EW) due to the broad emission line components. The line
widths were used to estimate black hole masses and Eddington ratios, .
Both EW and FWHM are anticorrelated with . Nearly all trends were in
agreement with our previous work, although the tendency for sources exhibiting
microvariability to be of lower luminosity was not confirmed. Most importantly,
this whole sample of EW distributions provides no evidence for the hypothesis
that a weak jet component in the radio quiet AGNs is responsible for their
microvariability.Comment: 15 pages, 9 figures, 6 tables, Accepted in MNRAS main journa
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