11,536 research outputs found
Semiclassical Inequivalence of Polygonalized Billiards
Polygonalization of any smooth billiard boundary can be carried out in
several ways. We show here that the semiclassical description depends on the
polygonalization process and the results can be inequivalent. We also establish
that generalized tangent-polygons are closest to the corresponding smooth
billiard and for de Broglie wavelengths larger than the average length of the
edges, the two are semiclassically equivalent.Comment: revtex, 4 ps figure
The Complex Time WKB Approximation And Particle Production
The complex time WKB (CWKB) approximation has been an effective technique to
understand particle production in curved as well as in flat spacetime. Earlier
we obtained the standard results on particle production in time dependent gauge
in various curved spacetime. In the present work we generalize the technique of
CWKB to the equivalent problems in space dependent gauge. Using CWKB, we first
obtain the gauge invariant result for particle production in Minkowski
spacetime in strong electric field. We then carry out particle production in
de-Sitter spacetime in space dependent gauge and obtain the same result that we
obtained earlier in time dependent gauge. The results obtained for de-Sitter
spacetime has a obvious extension to particle production in black hole
spacetime. It is found that the origin of Planckian spectrum is due to repeated
reflections between the turning points. As mentioned earlier, it is now
explicitly shown that particle production is accompanied by rotation of
currents.Comment: 12 pages, Revte
Comparative study of the centrosymmetric and non-centrosymmetric superconducting phases of Re3W using muon-spin spectroscopy and heat capacity measurements
We compare the low-temperature electronic properties of the centrosymmetric
(CS) and non-centrosymmetric (NCS) phases of Re3W using muon-spin spectroscopy
and heat capacity measurements. The zero-field muSR results indicate that
time-reversal symmetry is preserved for both structures of Re3W.
Transverse-field muon spin rotation has been used to study the temperature
dependence of the penetration depth lambda(T) in the mixed state. For both
phases of Re3W, lambda(T) can be explained using a single-gap s-wave BCS model.
The magnetic penetration depth at zero temperature, lambda(0), is 164(7) and
418(6) nm for the centrosymmetric and the non-centrosymmetric phases of Re3W
respectively. Low-temperature specific heat data also provide evidence for an
s-wave gap-symmetry for the two phases of Re3W. Both the muSR and heat capacity
data show that the CS material has a higher Tc and a larger superconducting gap
Delta(0) at 0 K than the NCS compound. The ratio Delta(0)/kBTc indicates that
both phases of Re3W should be considered as strong-coupling superconductors.Comment: 7 pages, to appear in Physical Review
Power loss in open cavity diodes and a modified Child Langmuir Law
Diodes used in most high power devices are inherently open. It is shown that
under such circumstances, there is a loss of electromagnetic radiation leading
to a lower critical current as compared to closed diodes. The power loss can be
incorporated in the standard Child-Langmuir framework by introducing an
effective potential. The modified Child-Langmuir law can be used to predict the
maximum power loss for a given plate separation and potential difference as
well as the maximum transmitted current for this power loss. The effectiveness
of the theory is tested numerically.Comment: revtex4, 11 figure
- …