12 research outputs found
Fluctuating loops and glassy dynamics of a pinned line in two dimensions
We represent the slow, glassy equilibrium dynamics of a line in a
two-dimensional random potential landscape as driven by an array of
asymptotically independent two-state systems, or loops, fluctuating on all
length scales. The assumption of independence enables a fairly complete
analytic description. We obtain good agreement with Monte Carlo simulations
when the free energy barriers separating the two sides of a loop of size L are
drawn from a distribution whose width and mean scale as L^(1/3), in agreement
with recent results for scaling of such barriers.Comment: 11 pages, 4 Postscript figure
Energy Barriers to Motion of Flux Lines in Random Media
We propose algorithms for determining both lower and upper bounds for the
energy barriers encountered by a flux line in moving through a two-dimensional
random potential. Analytical arguments, supported by numerical simulations,
suggest that these bounds scale with the length of the line as
and , respectively. This provides the first confirmation
of the hypothesis that barriers have the same scaling as the fluctuation in the
free energy. \pacs{PACS numbers: 74.60.Ge, 05.70.Ln, 05.40.+j}Comment: 4 pages Revtex, 2 figures, to appear in PRL 75, 1170 (1995
Continuum limit, Galilean invariance, and solitons in the quantum equivalent of the noisy Burgers equation
A continuum limit of the non-Hermitian spin-1/2 chain, conjectured recently
to belong to the universality class of the noisy Burgers or, equivalently,
Kardar-Parisi-Zhang equation, is obtained and analyzed. The Galilean invariance
of the Burgers equation is explicitly realized in the operator algebra. In the
quasi-classical limit we find nonlinear soliton excitations exhibiting the
dispersion relation with dynamical exponent .Comment: 12 pages, latex, no figure
Fluctuating Loops and Glassy Dynamics of a Pinned Line in Two Dimensions
We represent the slow, glassy equilibrium dynamics of a line in a twodimensional random potential landscape as driven by an array of asymptotically independent two-state systems, or loops, fluctuating on all length scales. The assumption of independence enables a fairly complete analytic description. We obtain good agreement with Monte Carlo simulations when the free energy barriers separating the two sides of a loop of size L are drawn from a distribution whose width and mean scale as L 1=3 , in agreement with recent results for scaling of such barriers. 74.60.Ge, 05.40.+j, 05.70.Ln Typeset using REVT E X Slow dynamics is perhaps the most significant characteristic of the glassy state of matter, affecting essentially all experimental measurements. An intuitively appealing picture, which explains this remarkable slowing down, is that the configuration space of a glass consists of many nearly degenerate free energy minima, separated by high potential barriers [1]. The dynamics is do..
Human monkeypox and smallpox viruses: genomic comparison
AbstractMonkeypox virus (MPV) causes a human disease which resembles smallpox but with a lower person-to-person transmission rate. To determine the genetic relationship between the orthopoxviruses causing these two diseases, we sequenced the 197-kb genome of MPV isolated from a patient during a large human monkeypox outbreak in Zaire in 1996. The nucleotide sequence within the central region of the MPV genome, which encodes essential enzymes and structural proteins, was 96.3% identical with that of variola (smallpox) virus (VAR). In contrast, there were considerable differences between MPV and VAR in the regions encoding virulence and host-range factors near the ends of the genome. Our data indicate that MPV is not the direct ancestor of VAR and is unlikely to naturally acquire all properties of VAR