42,469 research outputs found
Interatomic collisions in two-dimensional and quasi-two-dimensional confinements with spin-orbit coupling
We investigate the low-energy scattering and bound states of two
two-component fermionic atoms in pure two-dimensional (2D) and quasi-2D
confinements with Rashba spin-orbit coupling (SOC). We find that the SOC
qualitatively changes the behavior of the 2D scattering amplitude in the
low-energy limit. For quasi-2D systems we obtain the analytic expression for
the effective-2D scattering amplitude and the algebraic equations for the
two-atom bound state energy. Based on these results, we further derive the
effective 2D interaction potential between two ultracold atoms in the quasi-2D
confinement with Rashba SOC. These results are crucial for the control of the
2D effective physics in quasi-2D geometry via the confinement intensity and the
atomic three-dimensional scattering length.Comment: 13pages, 5 figure
Coexistence of Antiferromagnetism and Triplet Superconductivity
The authors discuss the possibility of coexistence of antiferromagnetism and
triplet superconductivity as a particular example of a broad class of systems
where the interplay of magnetism and superconductivity is important. This paper
focuses on the case of quasi-one-dimensional metals, where it is known
experimentally that antiferromagnetism is in close proximity to triplet
superconductivity in the temperature versus pressure phase diagram. Over a
narrow range of pressures, the authors propose an intermediate non-uniform
phase consisting of alternating insulating antiferromagnetic and triplet
superonducting stripes.Comment: 9 pages, 3 figures. 2004 Conference of Magnetism and Magnetic
Material
The supersymmetric affine Yangian
The affine Yangian of is known to be isomorphic to , the -algebra that characterizes the bosonic higher spin --
CFT duality. In this paper we propose defining relations of the Yangian that
are relevant for the superconformal version of . Our construction is based on the observation that the superconformal algebra contains two commuting
bosonic algebras, and that the additional generators
transform in bi-minimal representations with respect to these two algebras. The
corresponding affine Yangian can therefore be built up from two affine Yangians
of by adding in generators that transform appropriately.Comment: 35 pages, 5 figure
The structural, mechanical, electronic, optical and thermodynamic properties of t-XAs (X Si, Ge and Sn) by first-principles calculations
The structural, mechanical, electronic, optical and thermodynamic properties
of the t-XAs (X Si, Ge and Sn) with
tetragonal structure have been investigated by first principles calculations.
Our calculated results show that these compounds are mechanically and
dynamically stable. By the study of elastic anisotropy, it is found that the
anisotropic of the t-SnAs is stronger than that
of t-SiAs and
t-GeAs. The band structures and density of states
show that the t-XAs (Si, Ge and Sn) are
semiconductors with narrow band gaps. Based on the analyses of electron density
difference, in t-XAs As atoms get electrons, X
atoms lose electrons. The calculated static dielectric constants,
, are 15.5, 20.0 and 15.1 eV for
t-XAs (X Si, Ge and Sn), respectively. The
Dulong-Petit limit of t-XAs is about 10 J
molK. The thermodynamic stability successively
decreases from t-SiAs to
t-GeAs to t-SnAs.Comment: 14 pages, 10 figures, 6 table
Coexistence of Spin Density Wave and Triplet Superconductivity
We discuss the possibility of coexistence of spin density wave
(antiferromagnetism) and triplet superconductivity as a particular example of a
broad class of systems where the interplay of magnetism and superconductivity
is important. We focus on the case of quasi-one-dimensional metals, where it is
known experimentally that antiferromagnetism is in close proximity to triplet
superconductivity in the temperature versus pressure phase diagram. Over a
narrow range of pressures, we propose an intermediate non-uniform phase
consisting of alternating antiferromagnetic and triplet superconducting
stripes. Within the non-uniform phase there are also changes between two and
three dimensional behavior.Comment: Revtex4, 4 pages, 5 figure
A comprehensive analysis of Swift/XRT data: I. Apparent spectral evolution of GRB X-ray tails
An early steep decay component following the prompt GRBs is commonly observed
in {\em Swift} XRT light curves, which is regarded as the tail emission of the
prompt gamma-rays. Prompted by the observed strong spectral evolution in the
tails of GRBs 060218 and 060614, we present a systematic time-resolved spectral
analysis for the {\em Swift} GRB tails detected between 2005 February and 2007
January. We select a sample of 44 tails that are bright enough to perform
time-resolved spectral analyses. Among them 11 tails are smooth and without
superimposing significant flares, and their spectra have no significant
temporal evolution. We suggest that these tails are dominated by the curvature
effect of the prompt gamma-rays due to delay of propagation of photons from
large angles with respect to the line of sight . More interestingly, 33 tails
show clear hard-to-soft spectral evolution, with 16 of them being smooth tails
directly following the prompt GRBs,while the others being superimposed with
large flares. We focus on the 16 clean, smooth tails and consider three toy
models to interpret the spectral evolution. The curvature effect of a
structured jet and a model invoking superposition of the curvature effect tail
and a putative underlying soft emission component cannot explain all the data.
The third model, which invokes an evolving exponential spectrum, seems to
reproduce both the lightcurve and the spectral evolution of all the bursts,
including GRBs 060218 and 060614. More detailed physical models are called for
to understand the apparent evolution effect.Comment: 13 pages in emulateapj style,6 figures, 1 table, expanded version,
matched to published version, ApJ, 2007, in press. This is the first paper of
a series. Paper II see arXiv:0705.1373 (ApJ,2007, in press
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