26,490 research outputs found
Out of Equilibrium Solutions in the -Hamiltonian Mean Field model
Out of equilibrium magnetised solutions of the -Hamiltonian Mean Field
(-HMF) model are build using an ensemble of integrable uncoupled pendula.
Using these solutions we display an out-of equilibrium phase transition using a
specific reduced set of the magnetised solutions
Numerical calculation of the combinatorial entropy of partially ordered ice
Using a one-parameter case as an example, we demonstrate that multicanonical
simulations allow for accurate estimates of the residual combinatorial entropy
of partially ordered ice. For the considered case corrections to an
(approximate) analytical formula are found to be small, never exceeding 0.5%.
The method allows one as well to calculate combinatorial entropies for many
other systems.Comment: Extended version: 7 pages, 10 figures (v1 is letter-type version
Scientific, institutional and personal rivalries among Soviet geographers in the late Stalin era
Scientific, institutional and personal rivalries between three key centres of geographical research and scholarship (the Academy of Sciences Institute of Geography and the Faculties of Geography at Moscow and Leningrad State Universities) are surveyed for the period from 1945 to the early 1950s. It is argued that the debates and rivalries between members of the three institutions appear to have been motivated by a variety of scientific, ideological, institutional and personal factors, but that genuine scientific disagreements were at least as important as political and ideological factors in influencing the course of the debates and in determining their final outcome
Geometry and topology of knotted ring polymers in an array of obstacles
We study knotted polymers in equilibrium with an array of obstacles which
models confinement in a gel or immersion in a melt. We find a crossover in both
the geometrical and the topological behavior of the polymer. When the polymers'
radius of gyration, , and that of the region containing the knot,
, are small compared to the distance b between the obstacles, the knot
is weakly localised and scales as in a good solvent with an amplitude
that depends on knot type. In an intermediate regime where ,
the geometry of the polymer becomes branched. When exceeds b, the
knot delocalises and becomes also branched. In this regime, is
independent of knot type. We discuss the implications of this behavior for gel
electrophoresis experiments on knotted DNA in weak fields.Comment: 4 pages, 6 figure
On the minimization of Dirichlet eigenvalues of the Laplace operator
We study the variational problem \inf \{\lambda_k(\Omega): \Omega\
\textup{open in}\ \R^m,\ |\Omega| < \infty, \ \h(\partial \Omega) \le 1 \},
where is the 'th eigenvalue of the Dirichlet Laplacian
acting in , \h(\partial \Omega) is the - dimensional
Hausdorff measure of the boundary of , and is the Lebesgue
measure of . If , and , then there exists a convex
minimiser . If , and if is a minimiser,
then is also a
minimiser, and is connected. Upper bounds are
obtained for the number of components of . It is shown that if
, and then has at most components.
Furthermore is connected in the following cases : (i) (ii) and (iii) and (iv) and
. Finally, upper bounds on the number of components are obtained for
minimisers for other constraints such as the Lebesgue measure and the torsional
rigidity.Comment: 16 page
Thermodynamics of two lattice ice models in three dimensions
In a recent paper we introduced two Potts-like models in three dimensions,
which share the following properties: (A) One of the ice rules is always
fulfilled (in particular also at infinite temperature). (B) Both ice rules hold
for groundstate configurations. This allowed for an efficient calculation of
the residual entropy of ice I (ordinary ice) by means of multicanonical
simulations. Here we present the thermodynamics of these models. Despite their
similarities with Potts models, no sign of a disorder-order phase transition is
found.Comment: 5 pages, 7 figure
Applicability of ERTS-1 to Montana geology
The author has identified the following significant results. Late autumn imagery provides the advantages of topographic shadow enhancement and low cloud cover. Mapping of rock units was done locally with good results for alluvium, basin fill, volcanics, inclined Paleozoic and Mesozoic beds, and host strata of bentonite beds. Folds, intrusive domes, and even dip directions were mapped where differential erosion was significant. However, mapping was not possible for belt strata, was difficult for granite, and was hindered by conifers compared to grass cover. Expansion of local mapping required geologic control and encountered significant areas unmappable from ERTS imagery. Annotation of lineaments provided much new geologic data. By extrapolating test site comparisons, it is inferred that 27 percent of some 1200 lineaments mapped from western Montana represent unknown faults. The remainder appear to be localized mainly by undiscovered faults and sets of minor faults or joints
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