61,108 research outputs found
Event-by-event simulation of the Hanbury Brown-Twiss experiment with coherent light
We present a computer simulation model for the Hanbury Brown-Twiss experiment
that is entirely particle-based and reproduces the results of wave theory. The
model is solely based on experimental facts, satisfies Einstein's criterion of
local causality and does not require knowledge of the solution of a wave
equation. The simulation model is fully consistent with earlier work and
provides another demonstration that it is possible to give a particle-only
description of wave phenomena, rendering the concept of wave-particle duality
superfluous.Comment: Submitted to Commmun. Comput. Phy
Nonclassical effects in two-photon interference experiments: event-by-event simulations
It is shown that both the visibility predicted for
two-photon interference experiments with two independent
sources\textcolor{black}{, like the Hanbury Brown-Twiss experiment,} and the
visibility predicted for two-photon interference experiments
with a parametric down-conversion source\textcolor{black}{, like the
Ghosh-Mandel experiment,} can be explained \textcolor{black}{by a discrete
event simulation. This simulation approach reproduces the statistical
distributions of wave theory not by requiring the knowledge of the solution of
the wave equation of the whole system but by generating detection events
one-by-one according to an unknown distribution.} There is thus no need to
invoke quantum theory to explain the so-called nonclassical effects in the
interference of signal and idler photons in parametric down conversion. Hence,
a revision of the commonly accepted criterion of the nonclassical nature of
light\textcolor{black}{, ,} is called for.Comment: arXiv admin note: substantial text overlap with arXiv:1208.2368,
arXiv:1006.172
Highly nonlinear contact interaction and dynamic energy dissipation by forest of carbon nanotubes
Mechanical response and energy dissipation of an array of carbon nanotubes under high-strain rate deformation was studied using a simple drop-ball test with the measurement of the dynamic force between the ball and forest of nanotubes. This convenient process allows extracting force–displacement curves and evaluating dissipated energy by the nanotubes. The contact force exhibits a strongly nonlinear dependence on displacement being fundamentally different than the Hertz law. The forest of vertically aligned nanotubes may be used as a strongly nonlinear spring in discrete systems for monitoring signal propagation speed, and as a microstructure for localized energy absorption
Data analysis of Einstein-Podolsky-Rosen-Bohm laboratory experiments
Data sets produced by three different Einstein-Podolsky-Rosen-Bohm (EPRB)
experiments are tested against the hypothesis that the statistics of this data
is described by quantum theory. Although these experiments generate data that
violate Bell inequalities for suitable choices of the time-coincidence window,
the analysis shows that it is highly unlikely that these data sets are
compatible with the quantum theoretical description of the EPRB experiment,
suggesting that the popular statements that EPRB experiments agree with quantum
theory lack a solid scientific basis and that more precise experiments are
called for.Comment: arXiv admin note: substantial text overlap with arXiv:1112.262
Accidental Peccei-Quinn Symmetry from Discrete Flavour Symmetry and Pati-Salam
We show how an accidental Peccei-Quinn (PQ) symmetry can arise from a
discrete family symmetry combined with a discrete flavour symmetry , in a realistic Pati-Salam unified theory
of flavour. Imposing only these discrete flavour symmetries, the axion solution
to the strong problem is protected from PQ-breaking operators to the
required degree. A QCD axion arises from a linear combination of
triplet flavons, which are also responsible for fermion flavour structures due
to their vacuum alignments. We find that the requirement of an accidental PQ
symmetry arising from a discrete flavour symmetry constrains the form of the
Yukawa matrices, providing a link between flavour and the strong
problem. Our model predicts specific flavour-violating couplings of the
flavourful axion and thus puts a strong limit on the axion scale from kaon
decays.Comment: 14 pages, 2 figure
Finite-temperature charge transport in the one-dimensional Hubbard model
We study the charge conductivity of the one-dimensional repulsive Hubbard
model at finite temperature using the method of dynamical quantum typicality,
focusing at half filling. This numerical approach allows us to obtain current
autocorrelation functions from systems with as many as 18 sites, way beyond the
range of standard exact diagonalization. Our data clearly suggest that the
charge Drude weight vanishes with a power law as a function of system size. The
low-frequency dependence of the conductivity is consistent with a finite dc
value and thus with diffusion, despite large finite-size effects. Furthermore,
we consider the mass-imbalanced Hubbard model for which the charge Drude weight
decays exponentially with system size, as expected for a non-integrable model.
We analyze the conductivity and diffusion constant as a function of the mass
imbalance and we observe that the conductivity of the lighter component
decreases exponentially fast with the mass-imbalance ratio. While in the
extreme limit of immobile heavy particles, the Falicov-Kimball model, there is
an effective Anderson-localization mechanism leading to a vanishing
conductivity of the lighter species, we resolve finite conductivities for an
inverse mass ratio of .Comment: 13 pages, 11 figure
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