52,393 research outputs found
Enhanced excitonic effects in the energy loss spectra of LiF and Ar at large momentum transfer
It is demonstrated that the bootstrap kernel [\onlinecite{sharma11}] for
finite values of crucially depends upon the matrix character of the
kernel and gives results of the same good quality as in the limit. The bootstrap kernel is further used to study the
electron loss as well as absorption spectra for Si, LiF and Ar for various
values of . The results show that the excitonic effects in LiF and Ar
are enhanced for values of away from the -point. The reason
for this enhancement is the interaction between the exciton and high energy
inter-band electron-hole transitions. This fact is validated by calculating the
absorption spectra under the influence of an external electric field. The
electron energy loss spectra is shown to change dramatically as a function of
The Crystallography of Strange Quark Matter
Cold three-flavor quark matter at large (but not asymptotically large)
densities may exist as a crystalline color superconductor. We explore this
possibility by calculating the gap parameter Delta and free energy Omega(Delta)
for possible crystal structures within a Ginzburg-Landau approximation,
evaluating Omega(Delta) to order Delta^6. We develop a qualitative
understanding of what makes a crystal structure stable, and find two structures
with particularly large values of Delta and the condensation energy, within a
factor of two of those for the CFL phase known to characterize QCD at
asymptotically large densities. The robustness of these phases results in their
being favored over wide ranges of density and though it also implies that the
Ginzburg-Landau approximation is not quantitatively reliable, previous work
suggests that it can be trusted for qualitative comparisons between crystal
structures. We close with a look ahead at the calculations that remain to be
done in order to make contact with observed pulsar glitches and neutron star
cooling.Comment: 6 pages, 3 figures. Contribution to the proceedings of Strangeness in
Quark Matter 2006, UCLA. Talk given by Rishi Sharm
Occultation of compact radio sources by the ion tail of Halley's Comet
Enhancements of scintillations of the compact radio sources PKS 2314+03 and 1827-360 were observed at 103 MHz and 408 MHz during 18-21 December 1985 and on 29 March 1986, respectively, when the plasma tail of Halley's Comet swept across them. At 103 MHz the RMS plasma density variation along the tail was 10 and 3.3/cu cm at 0.12 AU and 0.18 AU, respectively, as measured from the comet's position. At 408 MHz it was 1.9/cu cm at 0.036 AU. Comparison of results of these two sets of observations is presented
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