6,612 research outputs found
Small Window Overlaps Are Effective Probes of Replica Symmetry Breaking in 3D Spin Glasses
We compute numerically small window overlaps in the three dimensional Edwards
Anderson spin glass. We show that they behave in the way implied by the Replica
Symmetry Breaking Ansatz, that they do not qualitatively differ from the full
volume overlap and do not tend to a trivial function when increasing the
lattice volume. On the contrary we show they are affected by small finite
volume effects, and are interesting tools for the study of the features of the
spin glass phase.Comment: 9 pages plus 5 figure
1-loop contribution to the dynamical exponents in spin glasses
We evaluate the corrections to the mean field values of the and the
exponents at the first order in the -expansion, for . We find
that both and are decreasing when the space dimension decreases.Comment: 12 pages 3 Postscript figure
Assessment of ultraviolet radiation exposures in photobiological experiments
The interfering effect of ultraviolet (UV) radiation on the natural function of biological processes is wavelength specific and the UV spectrum must be weighted with the action spectrum for the process. The UV spectral irradiance may be measured with calibrated spectroradiometers. Alternatively, the biologically effective UV may be measured with broadband devices. This paper reviews the techniques for assessing biologically effective exposures in photobiological experiments.
UV meters, such as the Robertson-Berger (RB) meter, or passive dosimeters, such as polysulphone, that possess a spectral response approximating the human erythemal response can be used to estimate erythemally effective exposure or actinic exposure due to solar UV. The sensitivity of the RB meter is about 0.56 uW cm-2 and polysulphone can record an exposure of about 2mJ cm-2. For photobiological processes other than erythema these devices are not suitable to determine the exposure. In terms of these applications, a spectrum evaluator consisting of four different types of dosimeter material can be employed to evaluate the UV spectrum of the source. This method can be useful both for solar UV studies and research with UV lamps that possess radiation wavelengths shorter than 295nm. The device can be used to measure exposures where the actinic and erythemal action spectra differ significantly. It can also be used to assess exposure due to low levels of UV (about 0.01uW cm-2) caused by radiation filtered through glasses or plastic
A Numerical Study of Ultrametricity in Finite Dimensional Spin Glasses
We use a constrained Monte Carlo technique to analyze ultrametric features of
a 4 dimensional Edwards-Anderson spin glass with quenched couplings J=\pm 1. We
find that in the large volume limit an ultrametric structure emerges quite
clearly in the overlap of typical equilibrium configurations.Comment: 8 one column pages, latex, 4 figures with epsfig.st
Violation of the Fluctuation Dissipation Theorem in Finite Dimensional Spin Glasses
We study the violation of the fluctuation-dissipation theorem in the three
and four dimensional Gaussian Ising spin glasses using on and off equilibrium
simulations. We have characterized numerically the function X(C) that determine
the violation and we have studied its scaling properties. Moreover we have
computed the function x(C) which characterize the breaking of the replica
symmetry directly from equilibrium simulations. The two functions are
numerically equal and in this way we have established that the conjectured
connection between the violation of fluctuation dissipation theorem in the
off-equilibrium dynamics and the replica symmetry breaking at equilibrium holds
for finite dimensional spin glasses. These results point to a spin glass phase
with spontaneously broken replica symmetry in finite dimensional spin glasses.Comment: 13 pages, 4 figures, also available at
http://chimera.roma1.infn.it/index_papers_complex.htm
Low T Dynamical Properties of Spin Glasses Smoothly Extrapolate to T=0
We compare ground state properties of 3D Ising Spin Glasses with Gaussian
couplings with results from off-equilibrium numerical simulations at non zero
(but low) temperatures. We find that the non-zero temperature properties of the
system smoothly connect to the T=0 behavior, confirming the point of view that
results established at T=0 typically also give relevant information about the
physics of the system.Comment: 14 pages and 4 ps figure
Zero-Temperature Limit of the SUSY-breaking Complexity in Diluted Spin-Glass Models
We study the SUSY-breaking complexity of the Bethe Lattice Spin-Glass in the
zero temperature limit. We consider both the Gaussian and the bimodal
distribution of the coupling constants. For the SUSY breaking
theory yields fields distributions that concentrate on integer values at low
temperatures, at variance with the unbroken SUSY theory. This concentration
takes place both in the quenched as well as in the simpler annealed
formulation.Comment: 4 pages, 2 figure
Effect of cloud on UVA and exposure to humans
The daily autumn and winter UVA exposures and 6-minute UVA irradiance data for a Southern Hemisphere, subtropical site (Toowoomba, Australia, 27.6 S, 151.9 E) are presented. This data is used to quantify the effect of cloud on UVA using an integrated sky-camera and radiation system. Additionally, an estimate of the effect of enhanced UVA exposure on humans is made. The measurement system consisted of broadband visible-infrared and UVA sensors together with a sun tracking, wide-angle video camera. The mean daily June exposure was found to be 409 kJm-2. Under the constraints of the uncertainty of both the UVA measurement system and clear-sky model, one case of enhanced UVA irradiance was found. Three cases of cloud enhancement of daily UVA exposure, approaching clear-sky levels, were also determined using a calculated clear-sky envelope. It was also determined that for a fulltime outdoor worker, the additional UVA exposure could approach approximately that of one third of a full winter's day. For indoor workers with an outside lunch break of noon to 1 pm, the additional UVA exposure was on average 6.9 kJm-2 over three cloud enhanced days. To the authors' knowledge this is the first paper to present some evidence of cloud enhanced UVA human exposure
On the Four-Dimensional Diluted Ising Model
In this letter we show strong numerical evidence that the four dimensional
Diluted Ising Model for a large dilution is not described by the Mean Field
exponents. These results suggest the existence of a new fixed point with
non-gaussian exponents.Comment: 9 pages. compressed ps-file (uufiles
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