1,795,943 research outputs found
Two dimensional foam rheology with viscous drag
We formulate and apply a continuum model that incorporates elasticity, yield
stress, plasticity and viscous drag. It is motivated by the two-dimensional
foam rheology experiments of Debregeas et al. [G. Debregeas, H. Tabuteau, and
J.-M. di Meglio, Phys. Rev. Lett. 87, 178305 (2001)] and Wang et al [Y. Wang,
K. Krishan, and M. Dennin, Phys. Rev. E 73, 031401 (2006)], and is successful
in exhibiting their principal features an exponentially decaying velocity
profile and strain localisation. Transient effects are also identified.Comment: accepted version (to appear in PRL). Some parts of the paper have
been rewritten (mainly introduction and final discussion
Yang-Lee Zeros of the Triangular Ising Antiferromagnets
Using both the exact enumeration method (microcanonical transfer matrix) for
a small system (L = 9) and the Wang-Landau Monte Carlo algorithm for large
systems to L = 30, we obtain the exact and approximate densities of states
g(M,E), as a function of magnetization M and exchange energy E, for the
triangular-lattice Ising model. Based on the density of states g(M,E), we
investigate the phase transition properties of Yang-Lee zeros for the
triangular Ising antiferromagnets and obtain the magnetic exponents at various
temperatures
Weighted Hamiltonian stationary Lagrangian submanifolds and generalized Lagrangian mean curvature flows in toric almost Calabi-Yau manifolds
In this paper we generalize examples of Hamiltonian stationary Lagrangian
submanifolds constructed by Lee and Wang in to toric almost
Calabi-Yau manifolds. We construct examples of weighted Hamiltonian stationary
Lagrangian submanifolds in toric almost Calabi-Yau manifolds and solutions of
generalized Lagrangian mean curvature flows starting from these examples. We
allow these flows to have some singularities and topological changes.Comment: 16 page
The elementary symmetric functions of a reciprocal polynomial sequence
Erd\"{o}s and Niven proved in 1946 that for any positive integers and
, there are at most finitely many integers for which at least one of the
elementary symmetric functions of are
integers. Recently, Wang and Hong refined this result by showing that if , then none of the elementary symmetric functions of is an integer for any positive integers and . Let be a
polynomial of degree at least and of nonnegative integer coefficients. In
this paper, we show that none of the elementary symmetric functions of is an integer except for with being
an integer and .Comment: 4 pages. To appear in Comptes Rendus Mathematiqu
Axisymmetric circumstellar interaction in supernovae
Multiwavelength observations of Type II supernovae have shown evidence for
the interaction of supernovae with the dense slow winds from the red supergiant
progenitor stars. Observations of planetary nebulae and the nebula around SN
1987A show that the slow winds from extended stars frequently have an axisymme-
tric structure with a high density in the equatorial plane. We have carried out
numerical calculations of the interaction of a supernova with such an axisymme-
tric density distribution. For small values of the angular density gradient at
the pole, the asymmetry in the interaction shell is greater than, but close to,
that expected from purely radial motion. If the angular density gradient is
above a moderate value, the flow qualitatively changes and a protrusion emerges
along the axis. For a power-law supernova density profile, the flow approaches
a self-similar state in which the protrusion length is times the radius
of the main shell. The critical density gradient is larger for steeper density
profiles of the ejecta. Most of our calculations are axisymmetric, but we have
carried out a 3-dimensional calculation to show that the protrusion is not a
numerical artifact along the symmetry axis. For typical supernova parameters,
the protrusions take several years to develop. The appearance of the
shell with protrusions is similar to that observed in VLBI radio images of the
remnant 41.9 +58 in M82 and, possibly, of SN 1986J. We also considered the
possibility of asymmetric ejecta and found that it had a relatively small
effect on the asymmetry of the interaction region.Comment: 22 page postscript file (gzipped and uuencoded), 10 gzipped
postscript figures may be retrieved from
ftp://www.astro.su.se/pub/supernova/blc96_asym/ Submitted to Ap
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