1,616 research outputs found
Spectral properties of zero temperature dynamics in a model of a compacting granular column
The compacting of a column of grains has been studied using a one-dimensional
Ising model with long range directed interactions in which down and up spins
represent orientations of the grain having or not having an associated void.
When the column is not shaken (zero 'temperature') the motion becomes highly
constrained and under most circumstances we find that the generator of the
stochastic dynamics assumes an unusual form: many eigenvalues become
degenerate, but the associated multi-dimensional invariant spaces have but a
single eigenvector. There is no spectral expansion and a Jordan form must be
used. Many properties of the dynamics are established here analytically; some
are not. General issues associated with the Jordan form are also taken up.Comment: 34 pages, 4 figures, 3 table
Supersymmetric Model of a 2D Long-Range Bose Liquid
The model Hamiltonian of a two-dimensional Bose liquid (proposed earlier by
Kane, Kivelson, Lee and Zhang as the Hamiltonian which has Jastrow-type
wavefunctions as the ground-state solution), is shown to possess
nonrelativistic supersymmetry. For the special value of the coupling constant
the quantum mechanics described by this Hamiltonian is shown to be
equivalent to the dynamics of (complex) eigenvalues of random Gaussian ensemble
of normal complex matrices. For general , an exact relation between the
equal-time current-current and density-density correlation functions is
obtained, and used to derive an asymptotically exact (at low wavevectors q)
spectrum of single-particle excitations beyond the superfluid ground-state
(realized at low 's). The ground-state at very large is shown
to be of ``Quantum Hexatic" type, possessing long-range orientational order and
quasi-long-range translational order but with zero shear modulus. Possible
scenaria of the ground-state phase transitions as function of are
discussed.Comment: Revtex; 12 pages, 1 Postscript figur
Are you suggesting that’s my hand? The relation between hypnotic suggestibility and the rubber hand illusion
Hypnotic suggestibility (HS) is the ability to respond automatically to suggestions and to experience alterations in perception and behaviour. Hypnotically suggestible participants are also better able to focus and sustain their attention on an experimental stimulus. The present study explores the relation between HS and susceptibility to the rubber hand illusion (RHI). Based on previous research with visual illusions, it was predicted that higher HS would lead to a stronger RHI illusion. Two behavioural output measures of the RHI, an implicit (proprioceptive drift) and an explicit (RHI questionnaire) measure were correlated against HS scores. Hypnotic suggestibility correlated positively with the implicit RHI measure contributing to 30% of the variation. However, there was no relation between HS and the explicit RHI questionnaire measure, or with compliance control items. High hypnotic suggestibility may facilitate, via attentional mechanisms, the multisensory integration of visuoproprioceptive inputs that leads to greater perceptual mislocalisation of a participant’s hand. These results may provide insight into the multisensory brain mechanisms involved in our sense of embodiment
Heavy quark production via leptoquarks at a neutrino factory
The proposed neutrino factory (NF) based on a muon storage ring (MSR) is an
ideal place to look for heavy quark production via neutral current (NC) and
charged current (CC) interactions. In this article, we address the issue of
contribution coming from mediating leptoquarks (LQ) in interactions leading to the production of at a
MSR and investigate the region where LQ interactions are significant in the
near-site experiments.Comment: 12 pages latex, 10 ps figures, uses axocolour.sty, Slightly revised
version to appear in PR
Quantum mechanics with a time-dependent random unitary Hamiltonian: A perturbative study of the nonlinear Keldysh sigma-model
We analyze the perturbative series of the Keldysh-type sigma-model proposed
recently for describing the quantum mechanics with time-dependent Hamiltonians
from the unitary Wigner-Dyson random-matrix ensemble. We observe that vertices
of orders higher than four cancel, which allows us to reduce the calculation of
the energy-diffusion constant to that in a special kind of the matrix \phi^4
model. We further verify that the perturbative four-loop correction to the
energy-diffusion constant in the high-velocity limit cancels, in agreement with
the conjecture of one of the authors.Comment: 27 pages, 15 figures; typos corrected, one reference adde
Stability conditions and positivity of invariants of fibrations
We study three methods that prove the positivity of a natural numerical
invariant associated to parameter families of polarized varieties. All
these methods involve different stability conditions. In dimension 2 we prove
that there is a natural connection between them, related to a yet another
stability condition, the linear stability. Finally we make some speculations
and prove new results in higher dimension.Comment: Final version, to appear in the Springer volume dedicated to Klaus
Hulek on the occasion of his 60-th birthda
Vortex dissipation and level dynamics for the layered superconductors with impurities
We study parametric level statistics of the discretized excitation spectra
inside a moving vortex core in layered superconductors with impurities. The
universal conductivity is evaluated numerically for the various values of
rescaled vortex velocities from the clean case to the dirty limit
case. The random matrix theoretical prediction is verified numerically in the
large regime. On the contrary in the low velocity regime, we observe
which is consistent with the theoretical
result for the super-clean case, where the energy dissipation is due to the
Landau-Zener transition which takes place at the points called ``avoided
crossing''.Comment: 10 pages, 4 figures, REVTeX3.
Statistical analysis and the equivalent of a Thouless energy in lattice QCD Dirac spectra
Random Matrix Theory (RMT) is a powerful statistical tool to model spectral
fluctuations. This approach has also found fruitful application in Quantum
Chromodynamics (QCD). Importantly, RMT provides very efficient means to
separate different scales in the spectral fluctuations. We try to identify the
equivalent of a Thouless energy in complete spectra of the QCD Dirac operator
for staggered fermions from SU(2) lattice gauge theory for different lattice
size and gauge couplings. In disordered systems, the Thouless energy sets the
universal scale for which RMT applies. This relates to recent theoretical
studies which suggest a strong analogy between QCD and disordered systems. The
wealth of data allows us to analyze several statistical measures in the bulk of
the spectrum with high quality. We find deviations which allows us to give an
estimate for this universal scale. Other deviations than these are seen whose
possible origin is discussed. Moreover, we work out higher order correlators as
well, in particular three--point correlation functions.Comment: 24 pages, 24 figures, all included except one figure, missing eps
file available at http://pluto.mpi-hd.mpg.de/~wilke/diff3.eps.gz, revised
version, to appear in PRD, minor modifications and corrected typos, Fig.4
revise
Statistics of Coulomb blockade peak spacings for a partially open dot
We show that randomness of the electron wave functions in a quantum dot
contributes to the fluctuations of the positions of the conductance peaks. This
contribution grows with the conductance of the junctions connecting the dot to
the leads. It becomes comparable with the fluctuations coming from the
randomness of the single particle spectrum in the dot while the Coulomb
blockade peaks are still well-defined. In addition, the fluctuations of the
peak spacings are correlated with the fluctuations of the conductance peak
heights.Comment: 13 pages, 1 figur
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