141,596 research outputs found
Transition Temperature of a Uniform Imperfect Bose Gas
We calculate the transition temperature of a uniform dilute Bose gas with
repulsive interactions, using a known virial expansion of the equation of
state. We find that the transition temperature is higher than that of an ideal
gas, with a fractional increase K_0(na^3)^{1/6}, where n is the density and a
is the S-wave scattering length, and K_0 is a constant given in the paper. This
disagrees with all existing results, analytical or numerical. It agrees exactly
in magnitude with a result due to Toyoda, but has the opposite sign.Comment: Email correspondence to [email protected] ; 2 pages using REVTe
Convective flow during dendritic growth
A review is presented of the major experimental findings obtained from recent ground-based research conducted under the SPAR program. Measurements of dendritic growth at small supercoolings indicate that below approximately 1.5 K a transition occurs from diffusive control to convective control in succinonitrile, a model system chosen for this study. The key theoretical ideas concerning diffusive and convective heat transport during dendritic growth are discussed, and it is shown that a transition in the transport control should occur when the characteristic length for diffusion becomes larger than the characteristic length for convection. The experimental findings and the theoretical ideas discussed suggest that the Fluid Experiment System could provide appropriate experimental diagnostics for flow field visualization and quantification of the fluid dynamical effects presented here
Recommended from our members
Implication of Sialidases in Salmonella Infection: Genome Release of Sialidase Knockout Strains from Salmonella enterica Serovar Typhimurium LT2.
Sialidases, which are widely distributed in nature, cleave the α-ketosidic bond of terminal sialic acid residue. These emerging virulence factors degrade the host glycan. We report here the release of seven sialidase and one sialic acid transporter deletion in Salmonella enterica serovar Typhimurium strain LT2, which are important in cellular invasion during infection
Gamma-Rays Produced in Cosmic-Ray Interactions and the TeV-band Spectrum of RX J1713.7-3946
We employ the Monte Carlo particle collision code DPMJET3.04 to determine the
multiplicity spectra of various secondary particles (in addition to 's)
with 's as the final decay state, that are produced in cosmic-ray
('s and 's) interactions with the interstellar medium. We derive an
easy-to-use -ray production matrix for cosmic rays with energies up to
about 10 PeV. This -ray production matrix is applied to the GeV excess
in diffuse Galactic -rays observed by EGRET, and we conclude the
non- decay components are insufficient to explain the GeV excess,
although they have contributed a different spectrum from the -decay
component. We also test the hypothesis that the TeV-band -ray emission
of the shell-type SNR RX J1713.7-3946 observed with HESS is caused by hadronic
cosmic rays which are accelerated by a cosmic-ray modified shock. By the
statistics, we find a continuously softening spectrum is strongly
preferred, in contrast to expectations. A hardening spectrum has about 1%
probability to explain the HESS data, but then only if a hard cutoff at 50-100
TeV is imposed on the particle spectrum.Comment: 3 pages; 4 figures; Contribution to the First GLAST Symposium,
Standord, 200
Universality and itinerant ferromagnetism in rotating strongly interacting Fermi gases
We analytically determine the properties of three interacting fermions in a
harmonic trap subject to an external rotation. Thermodynamic quantities such as
the entropy and energy are calculated from the third order quantum virial
expansion. By parameterizing the solutions in the rotating frame we find that
the energy and entropy are universal for all rotations in the strongly
interacting regime. Additionally, we find that rotation suppresses the onset of
itinerant ferromagnetism in strongly interacting repulsive three-body systems.Comment: 5 pages with 3 figure
Localization Transition in Incommensurate non-Hermitian Systems
A class of one-dimensional lattice models with incommensurate complex
potential is found
to exhibit localization transition at . This
transition from extended to localized states manifests in the behavior of the
complex eigenspectum. In the extended phase, states with real eigenenergies
have finite measure and this measure goes to zero in the localized phase.
Furthermore, all extended states exhibit real spectrum provided . Another novel feature of the system is the fact that the
imaginary part of the spectrum is sensitive to the boundary conditions {\it
only at the onset to localization}
- …