1,914 research outputs found
Improved Magnetic Information Storage using Return-Point Memory
The traditional magnetic storage mechanisms (both analog and digital) apply
an external field signal H(t) to a hysteretic magnetic material, and read the
remanent magnetization M(t), which is (roughly) proportional to H(t). We
propose a new analog method of recovering the signal from the magnetic
material, making use of the shape of the hysteresis loop M(H). The field H,
``stored'' in a region with N domains or particles, can be recovered with
fluctuations of order 1/N using the new method - much superior to the 1/sqrt{N}
fluctuations in traditional analog storage.Comment: 9 pages, 15 figure
Multicanonical Methods vs. Molecular Dynamics vs. Monte Carlo: Comparison for Lennard-Jones Glasses
We applied a multicanonical algorithm (entropic sampling) to a
two-dimensional and a three-dimensional Lennard-Jones system with
quasicrystalline and glassy ground states. Focusing on the ability of the
algorithm to locate low lying energy states, we compared the results of the
multicanonical simulations with standard Monte Carlo simulated annealing and
molecular dynamics methods. We find slight benefits to using entropic sampling
in small systems (less than 80 particles), which disappear with larger systems.
This is disappointing as the multicanonical methods are designed to surmount
energy barriers to relaxation. We analyze this failure theoretically, and show
(1) the multicanonical method is reduced in the thermodynamic limit (large
systems) to an effective Monte Carlo simulated annealing with a random
temperature vs. time, and (2) the multicanonical method gets trapped by
unphysical entropy barriers in the same metastable states whose energy barriers
trap the traditional quenches. The performance of Monte Carlo and molecular
dynamics quenches were remarkably similar.Comment: 12 pages, 6 figures, REVTEX, epsf.st
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