32,392 research outputs found
A Flexible Implementation of a Matrix Laurent Series-Based 16-Point Fast Fourier and Hartley Transforms
This paper describes a flexible architecture for implementing a new fast
computation of the discrete Fourier and Hartley transforms, which is based on a
matrix Laurent series. The device calculates the transforms based on a single
bit selection operator. The hardware structure and synthesis are presented,
which handled a 16-point fast transform in 65 nsec, with a Xilinx SPARTAN 3E
device.Comment: 4 pages, 4 figures. IEEE VI Southern Programmable Logic Conference
201
Thermal Effects on Photon-Induced Quantum Transport
We theoretically investigate laser induced quantum transport in a two-level
quantum dot attached to electric contacts. Our approach, based on
nonequilibrium Green function technique, allows to include thermal effects on
the photon-induced quantum transport and excitonic coherent dynamics. By
solving a set of coupled integrodifferential equations, involving correlation
and propagator functions, we obtain the photocurrent and the dot occupations as
a function of time. The characteristic coherent Rabi oscillations are found in
both occupations and photocurrent, with two distinct sources of decoherence:
incoherent tunneling and thermal fluctuations. In particular, for increasing
temperature the dot becomes more thermally occupied which shrinks the amplitude
of the Rabi oscillations, due to Pauli blockade. Finally, due to the interplay
between photon and thermal induced electron populations, the photocurrent can
switch sign as time evolves and its stationary value can be maximized by
tunning the laser intensity.Comment: 5 pages, 4 figure
de Broglie-Proca and Bopp-Podolsky massive photon gases in cosmology
We investigate the influence of massive photons on the evolution of the
expanding universe. Two particular models for generalized electrodynamics are
considered, namely de Broglie-Proca and Bopp-Podolsky electrodynamics. We
obtain the equation of state (EOS) for each case using
dispersion relations derived from both theories. The EOS are inputted into the
Friedmann equations of a homogeneous and isotropic space-time to determine the
cosmic scale factor . It is shown that the photon non-null mass does not
significantly alter the result valid for a massless photon
gas; this is true either in de Broglie-Proca's case (where the photon mass
is extremely small) or in Bopp-Podolsky theory (for which is extremely
large).Comment: 8 pages, 2 figures; v2 matches the published versio
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