369,720 research outputs found
Gravitational Lensing and Anisotropies of CBR on the Small Angular Scales
We investigate the effect of gravitational lensing, produced by linear
density perturbations, for anisotropies of the Cosmic Background Radiation
(CBR) on scales of arcminutes. In calculations, a flat universe ()
and the Harrison-Zel'dovich spectrum () are assumed. The numerical results
show that on scales of a few arcminutes, gravitational lensing produces only
negligible anisotropies in the temperature of the CBR. Our conclusion disagrees
with that of Cay\'{o}n {\it et al.} who argue that the amplification of on scales may even be larger than 100\%.Comment: Accepted by MNRAS. 16 pages, 2 figures, tarred, compressed and
uuencoded Postscript file
Rotating Superconductors and the Frame-independent London Equation
A frame-independent, thermodynamically exact London equation is presented,
which is especially valid for rotating superconductors. A direct result is the
unexpectedly high accuracy () for the usual expression of the
London moment.Comment: 4 pages, 0 figure
Witnessing a Poincar\'e recurrence with Mathematica
The often elusive Poincar\'e recurrence can be witnessed in a completely
separable system. For such systems, the problem of recurrence reduces to the
classic mathematical problem of simultaneous Diophantine approximation of
multiple numbers. The latter problem then can be somewhat satisfactorily solved
by using the famous Lenstra-Lenstra-Lov\'{a}sz (LLL) algorithm, which is
implemented in the Mathematica built-in function \verb"LatticeReduce". The
procedure is illustrated with a harmonic chain. The incredibly large recurrence
times are obtained exactly. They follow the expected scaling law very well.Comment: 8 pages, 5 figure
A random matrix definition of the boson peak
The density of vibrational states for glasses and jammed solids exhibits
universal features, including an excess of modes above the Debye prediction
known as the boson peak located at a frequency . We show that the
eigenvector statistics for boson peak modes are universal, and develop a new
definition of the boson peak based on this universality that displays the
previously observed characteristic scaling . We
identify a large new class of random matrices that obey a generalized global
tranlational invariance constraint and demonstrate that members of this class
also have a boson peak with precisely the same universal eigenvector
statistics. We denote this class as boson peak random matrices, and conjecture
it comprises a new universality class. We characterize the eigenvector
statistics as a function of coordination number, and find that one member of
this new class reproduces the scaling of with coordination number
that is observed near the jamming transition.Comment: 6 pages, 4 figures, Supplementary Figures available at
https://mmanning.expressions.syr.edu/epl2015
Phonon-Assisted Gain in a Semiconductor Double Quantum Dot Maser
We develop a microscopic model for the recently demonstrated double quantum
dot (DQD) maser. In characterizing the gain of this device we find that, in
addition to the direct stimulated emission of photons, there is a large
contribution from the simultaneous emission of a photon and a phonon, i.e., the
phonon sideband. We show that this phonon-assisted gain typically dominates the
overall gain which leads to masing. Recent experimental data are well fit with
our model.Comment: v1: 6 pgs, 2 figures; v2: 6 pgs, 3 figures, added Fig 2b and Fig. 3b,
modified main text; v3: 6+ pgs, 3 figures, modified main tex
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