1,164 research outputs found
Folding of the Triangular Lattice with Quenched Random Bending Rigidity
We study the problem of folding of the regular triangular lattice in the
presence of a quenched random bending rigidity + or - K and a magnetic field h
(conjugate to the local normal vectors to the triangles). The randomness in the
bending energy can be understood as arising from a prior marking of the lattice
with quenched creases on which folds are favored. We consider three types of
quenched randomness: (1) a ``physical'' randomness where the creases arise from
some prior random folding; (2) a Mattis-like randomness where creases are
domain walls of some quenched spin system; (3) an Edwards-Anderson-like
randomness where the bending energy is + or - K at random independently on each
bond. The corresponding (K,h) phase diagrams are determined in the hexagon
approximation of the cluster variation method. Depending on the type of
randomness, the system shows essentially different behaviors.Comment: uses harvmac (l), epsf, 17 figs included, uuencoded, tar compresse
Universal Power Law in the Noise from a Crumpled Elastic Sheet
Using high-resolution digital recordings, we study the crackling sound
emitted from crumpled sheets of mylar as they are strained. These sheets
possess many of the qualitative features of traditional disordered systems
including frustration and discrete memory. The sound can be resolved into
discrete clicks, emitted during rapid changes in the rough conformation of the
sheet. Observed click energies range over six orders of magnitude. The measured
energy autocorrelation function for the sound is consistent with a stretched
exponential C(t) ~ exp(-(t/T)^{b}) with b = .35. The probability distribution
of click energies has a power law regime p(E) ~ E^{-a} where a = 1. We find the
same power law for a variety of sheet sizes and materials, suggesting that this
p(E) is universal.Comment: 5 pages (revtex), 10 uuencoded postscript figures appended, html
version at http://rainbow.uchicago.edu/~krame
Dissipation and Decoherence in Nanodevices: a Generalized Fermi's Golden Rule
We shall revisit the conventional adiabatic or Markov approximation, which
--contrary to the semiclassical case-- does not preserve the positive-definite
character of the corresponding density matrix, thus leading to highly
non-physical results. To overcome this serious limitation, originally pointed
out and partially solved by Davies and co-workers almost three decades ago, we
shall propose an alternative more general adiabatic procedure, which (i) is
physically justified under the same validity restrictions of the conventional
Markov approach, (ii) in the semiclassical limit reduces to the standard
Fermi's golden rule, and (iii) describes a genuine Lindblad evolution, thus
providing a reliable/robust treatment of energy-dissipation and dephasing
processes in electronic quantum devices. Unlike standard master-equation
formulations, the dependence of our approximation on the specific choice of the
subsystem (that include the common partial trace reduction) does not threaten
positivity, and quantum scattering rates are well defined even in case the
subsystem is infinitely extended/has continuous spectrum.Comment: 6 pages, 0 figure
Dissipation and Decoherence in Nanodevices: a Generalized Fermi's Golden Rule
We shall revisit the conventional adiabatic or Markov approximation, which
--contrary to the semiclassical case-- does not preserve the positive-definite
character of the corresponding density matrix, thus leading to highly
non-physical results. To overcome this serious limitation, originally pointed
out and partially solved by Davies and co-workers almost three decades ago, we
shall propose an alternative more general adiabatic procedure, which (i) is
physically justified under the same validity restrictions of the conventional
Markov approach, (ii) in the semiclassical limit reduces to the standard
Fermi's golden rule, and (iii) describes a genuine Lindblad evolution, thus
providing a reliable/robust treatment of energy-dissipation and dephasing
processes in electronic quantum devices. Unlike standard master-equation
formulations, the dependence of our approximation on the specific choice of the
subsystem (that include the common partial trace reduction) does not threaten
positivity, and quantum scattering rates are well defined even in case the
subsystem is infinitely extended/has continuous spectrum.Comment: 6 pages, 0 figure
Dissipation and Decoherence in Nanodevices: a Generalized Fermi's Golden Rule
We shall revisit the conventional adiabatic or Markov approximation, which
--contrary to the semiclassical case-- does not preserve the positive-definite
character of the corresponding density matrix, thus leading to highly
non-physical results. To overcome this serious limitation, originally pointed
out and partially solved by Davies and co-workers almost three decades ago, we
shall propose an alternative more general adiabatic procedure, which (i) is
physically justified under the same validity restrictions of the conventional
Markov approach, (ii) in the semiclassical limit reduces to the standard
Fermi's golden rule, and (iii) describes a genuine Lindblad evolution, thus
providing a reliable/robust treatment of energy-dissipation and dephasing
processes in electronic quantum devices. Unlike standard master-equation
formulations, the dependence of our approximation on the specific choice of the
subsystem (that include the common partial trace reduction) does not threaten
positivity, and quantum scattering rates are well defined even in case the
subsystem is infinitely extended/has continuous spectrum.Comment: 6 pages, 0 figure
Primary mediastinal liposarcoma: a case report
This is an Open Access article distributed under the terms of the Creative Commons Attribution Licens
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