1,426 research outputs found
Glauber Critical Dynamics: Exact Solution of the Kinetic Gaussian Model
In this paper, we have exactly solved Glauber critical dynamics of the
Gaussian model on three dimensions. Of course, it is much easy to apply to low
dimensional case. The key steps are that we generalize the spin change
mechanism from Glauber's single-spin flipping to single-spin transition and
give a normalized version of the transition probability . We have also
investigated the dynamical critical exponent and found surprisingly that the
dynamical critical exponent is highly universal which refer to that for one-
two- and three-dimensions they have same value independent of spatial
dimensionality in contrast to static (equilibrium) critical exponents.Comment: 9 page
A very fast inference algorithm for finite-dimensional spin glasses: Belief Propagation on the dual lattice
Starting from a Cluster Variational Method, and inspired by the correctness
of the paramagnetic Ansatz (at high temperatures in general, and at any
temperature in the 2D Edwards-Anderson model) we propose a novel message
passing algorithm --- the Dual algorithm --- to estimate the marginal
probabilities of spin glasses on finite dimensional lattices. We show that in a
wide range of temperatures our algorithm compares very well with Monte Carlo
simulations, with the Double Loop algorithm and with exact calculation of the
ground state of 2D systems with bimodal and Gaussian interactions. Moreover it
is usually 100 times faster than other provably convergent methods, as the
Double Loop algorithm.Comment: 23 pages, 12 figures. v2: improved introductio
Solvable Kinetic Gaussian Model in External Field
In this paper, the single-spin transition dynamics is used to investigate the
kinetic Gaussian model in a periodic external field. We first derive the
fundamental dynamic equations, and then treat an isotropic d-dimensional
hypercubic lattice Gaussian spin system with Fourier's transformation method.
We obtain exactly the local magnetization and the equal-time pair correlation
function. The critical characteristics of the dynamical, the complex
susceptibility, and the dynamical response are discussed. The results show that
the time evolution of the dynamical quantities and the dynamical responses of
the system strongly depend on the frequency and the wave vector of the external
field.Comment: 11 page
Scattering phases for meson and baryon resonances on general moving-frame lattices
A proposal by L\"uscher enables one to compute the scattering phases of
elastic two-body systems from the energy levels of the lattice Hamiltonian in a
finite volume. In this work we generalize the formalism to S--, P-- and D--wave
meson and baryon resonances, and general total momenta. Employing nonvanishing
momenta has several advantages, among them making a wider range of energy
levels accessible on a single lattice volume and shifting the level crossing to
smaller values of .Comment: 41 pages, 3 figures. References added, minor edits to text. Version
to be published in Phys. Rev.
Strychnine Intoxication: A Case Report
Strychnine acts as an inhibitor of post-synaptic neuronal inhibition and intoxication leads to distinct clinical manifestations which may culminate in death. Since its commercialization is prohibited in most countries, cases of strychnine intoxication are now rare. We present a case of an elderly patient who voluntarily ingested a white powder thought to be strychnine. He developed myoclonus, startle response, and episodes of generalized muscle contractions accompanied by respiratory arrest in one occasion. Diazepam, valproic acid and supportive treatments were able to control manifestations, however the patient died after 2 days. Our aim is to alert clinicians that, despite its rarity, strychnine intoxication may still be seen in emergency departments, and clinical outcome can be influenced by rapid recognition and timely institution of adequate treatment
Metastable states in the Blume-Emery-Griffiths spin glass model
We study the Blume-Emery-Griffiths spin glass model in presence of an
attractive coupling between real replicas, and evaluate the effective potential
as a function of the density overlap. We find that there is a region, above the
first order transition of the model, where metastable states with a large
density overlap exist. The line where these metastable states appear should
correspond to a purely dynamical transition, with a breaking of ergodicity.
Differently from what happens in p-spin glasses, in this model the dynamical
transition would not be the precursor of a 1-step RSB transition, but
(probably) of a full RSB transition.Comment: RevTeX, 4 pages, 2 fig
Replica Cluster Variational Method: the Replica Symmetric solution for the 2D random bond Ising model
We present and solve the Replica Symmetric equations in the context of the
Replica Cluster Variational Method for the 2D random bond Ising model
(including the 2D Edwards-Anderson spin glass model). First we solve a
linearized version of these equations to obtain the phase diagrams of the model
on the square and triangular lattices. In both cases the spin-glass transition
temperatures and the tricritical point estimations improve largely over the
Bethe predictions. Moreover, we show that this phase diagram is consistent with
the behavior of inference algorithms on single instances of the problem.
Finally, we present a method to consistently find approximate solutions to the
equations in the glassy phase. The method is applied to the triangular lattice
down to T=0, also in the presence of an external field.Comment: 22 pages, 11 figure
Block-Diagonalization and f-electron Effects in Tight-Binding Theory
We extend a tight-binding total energy method to include f-electrons, and
apply it to the study of the structural and elastic properties of a range of
elements from Be to U. We find that the tight-binding parameters are as
accurate and transferable for f-electron systems as they are for d-electron
systems. In both cases we have found it essential to take great care in
constraining the fitting procedure by using a block-diagonalization procedure,
which we describe in detail.Comment: 9 pages, 6 figure
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