The angular momentum of a magnetically trapped atomic condensate

For an atomic condensate in an axially symmetric magnetic trap, the sum of the axial components of the orbital angular momentum and the hyperfine spin is conserved. Inside an Ioffe-Pritchard trap (IPT) whose magnetic field (B-field) is not axially symmetric, the difference of the two becomes surprisingly conserved. In this paper we investigate the relationship between the values of the sum/difference angular momentums for an atomic condensate inside a magnetic trap and the associated gauge potential induced by the adiabatic approximation. Our result provides significant new insight into the vorticity of magnetically trapped atomic quantum gases.Comment: 4 pages, 1 figure

Majorana fermions in s-wave noncentrosymmetric superconductor with Rashba and Dresselhaus (110) spin-orbit couplings

The asymmetric spin-orbit (SO) interactions play a crucial role in realizing topological phases in noncentrosymmetric superconductor (NCS).We investigate the edge states and the vortex core states in s-wave NCS with Rashba and Dresselhaus (110) SO couplings by both numerical and analytical methods. In particular, we demonstrate that there exists a novel semimetal phase characterized by the flat Andreev bound states in the phase diagram of the s-wave Dresselhaus NCS which supports the emergence of Majorana fermion (MF). The flat dispersion implies a peak in the density of states which has a clear experimental signature in the tunneling conductance measurements and the MFs proposed here should be experimentally detectable

Resolving SNR 0540-6944 from LMC X-1 with Chandra

We examine the supernova remnant (SNR) 0540-697 in the Large Magellanic Cloud (LMC) using data from the Chandra ACIS. The X-ray emission from this SNR had previously been hidden in the bright emission of nearby X-ray binary LMC X-1; however, new observations with Chandra can finally reveal the SNR's structure and spectrum. We find the SNR to be a thick-shelled structure about 19 pc in diameter, with a brightened northeast region. Spectral results suggest a temperature of 0.31 keV and an X-ray luminosity (0.3-3.0 keV) of 8.4 x 10^33 erg/s. We estimate an age of 12,000-20,000 yr for this SNR, but note that this estimate does not take into account the possibility of cavity expansion or other environmental effects.Comment: 8 pages, 2 GIF figures. Submitted to ApJL. Replaced with minor revisions from referee comment

The effects of surface finish and grain size on the strength of sintered silicon carbide

The effects of surface treatment and microstructure, especially abnormal grain growth, on the strength of sintered SiC were studied. The surfaces of sintered SiC were treated with 400, 800 and 1200 grit diamond wheels. Grain growth was induced by increasing the sintering times at 2050 C. The beta to alpha transformation occurred during the sintering of beta-phase starting materials and was often accompanied by abnormal grain growth. The overall strength distributions were established using Weibull statistics. The strength of the sintered SiC is limited by extrinsic surface flaws in normal-sintered specimens. The finer the surface finish and grain size, the higher the strength. But the strength of abnormal sintering specimens is limited by the abnormally grown large tabular grains. The Weibull modulus increases with decreasing grain size and decreasing grit size for grinding

Cerenkov Line Emission as a Possible Mechanism of X-ray Lines in Gamma-ray Bursts

The recent discoveries of X-ray lines in the afterglows of gamma-ray bursts (GRBs) provide significant clues to the nature of GRB progenitors and central environments. However, the iron line interpretation by fluorescence or recombination mechanism requires a large amount of iron material. We argue that the very strong iron line could be attributed to an alternative mechanism: Cerenkov line emission since relativistic electrons and dense medium exist near GRB sites. Therefore, the broad iron lines are expected, and line intensity will be nearly independent of the iron abundance, the medium with the anomalously high Fe abundance is not required.Comment: 4 pages, revised version accepted for the publication in ApJ

Entanglement and spin squeezing properties for three bosons in two modes

We discuss the canonical form for a pure state of three identical bosons in two modes, and classify its entanglement correlation into two types, the analogous GHZ and the W types as well known in a system of three distinguishable qubits. We have performed a detailed study of two important entanglement measures for such a system, the concurrence $\mathcal{C}$ and the triple entanglement measure $\tau$. We have also calculated explicitly the spin squeezing parameter $\xi$ and the result shows that the W state is the most ``anti-squeezing'' state, for which the spin squeezing parameter cannot be regarded as an entanglement measure.Comment: 7 pages, 6 figures; corrected figure sequence. Thanks to Dr. Han P