6,803 research outputs found
The pear-shaped fate of an ice melting front
A fluid-structure interaction problem with the melting of water around a
heated horizontal circular cylinder is analysed with numerical simulations.
Dynamic meshing was used for evolving the flow domain in time as the melting
front extended radially outward from the cylinder; a node shuffle algorithm was
used to retain mesh quality across the significant mesh deformation. We
simulated one case above the density inversion point of water and one case
below, yielding pear-shaped melting fronts due to thermal plumes either rising
or falling from the cylinder, respectively. Results were compared with previous
experimental studies and the melting front profiles matched reasonably well and
melting rates were in agreement. We confirm that natural convection plays a
significant role in the transport of energy as the melt zone increases, and
needs to be considered for accurately modelling phase change under these
conditions.Comment: Accepted for the 12th International Conference on CFD in Oil & Gas,
Metallurgical and Process Industries. SINTEF, Trondheim, Norway. May 30th -
June 1st, 201
The Boltzmann Equation in Classical Yang-Mills Theory
We give a detailed derivation of the Boltzmann equation, and in particular
its collision integral, in classical field theory. We first carry this out in a
scalar theory with both cubic and quartic interactions and subsequently in a
Yang-Mills theory. Our method is not relied on a doubling of the fields, rather
it is based on a diagrammatic approach representing the classical solution to
the problem.Comment: 24 pages, 7 figures; v2: typos corrected, reference added, published
in Eur. Phys. J.
Constituent gluon interpretation of glueballs and gluelumps
Arguments are given that support the interpretation of the lattice QCD
glueball and gluelump spectra in terms of bound states of massless constituent
gluons with helicity-1. In this scheme, the mass hierarchy of the currently
known gluelumps and glueballs is mainly due to the number of constituent gluons
and can be understood within a simple flux tube model. It is also argued that
the lattice QCD glueball should be seen as a four-gluon bound state.
The flux tube model allows for a parameter-free computation of its mass, which
is in good agreement with lattice QCD.Comment: 3 figures, use of package youngta
Relative entropy minimizing noisy non-linear neural network to approximate stochastic processes
A method is provided for designing and training noise-driven recurrent neural
networks as models of stochastic processes. The method unifies and generalizes
two known separate modeling approaches, Echo State Networks (ESN) and Linear
Inverse Modeling (LIM), under the common principle of relative entropy
minimization. The power of the new method is demonstrated on a stochastic
approximation of the El Nino phenomenon studied in climate research
A Connection between Submillimeter Continuum Flux and Separation in Young Binaries
We have made sensitive 800-micron continuum observations of low-mass,
pre-main sequence (PMS) binary stars with projected separations less than 25 AU
in Taurus-Auriga to study disks in the young binary environment. We did not
detect any of the observed binaries, with typical 3-sigma upper limits of about
30 mJy. Combining our observations with previous 1300-micron observations of
PMS Taurus binaries by Beckwith et al. (1990) and others, we find that the
submillimeter fluxes from binaries with projected separations between 1 AU and
50 AU are significantly lower than fluxes from binaries with projected
separations > 50 AU. The submillimeter fluxes from the wider binaries are
consistent with those of PMS single stars. This may indicate lower disk surface
densities and masses in the close binaries. Alternatively, dynamical clearing
of gaps by close binaries is marginally sufficient to lower their submillimeter
fluxes to the observed levels, even without reduction of surface densities
elsewhere in the disks.Comment: 12 pages, uuencoded compressed postscript with figures; Wisconsin
Astrophysics 526; to appear in ApJ Letter
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