4,401 research outputs found
Equilibrium glassy phase in a polydisperse hard sphere system
The phase diagram of a polydisperse hard sphere system is examined by
numerical minimization of a discretized form of the Ramakrishnan-Yussouff free
energy functional. Crystalline and glassy local minima of the free energy are
located and the phase diagram in the density-polydispersity plane is mapped out
by comparing the free energies of different local minima. The crystalline phase
disappears and the glass becomes the equilibrium phase beyond a "terminal"
value of the polydispersity. A crystal to glass transition is also observed as
the density is increased at high polydispersity. The phase diagram obtained in
our study is qualitatively similar to that of hard spheres in a quenched random
potential.Comment: 4 pages, 4 figure
Laser induced reentrant freezing in two-dimensional attractive colloidal systems
The effects of an externally applied one-dimensional periodic potential on
the freezing/melting behaviour of two-dimensional systems of colloidal
particles with a short-range attractive interaction are studied using Monte
Carlo simulations. In such systems, incommensuration results when the
periodicity of the external potential does not match the length-scale at which
the minimum of the attractive potential occurs. To study the effects of this
incommensuration, we consider two different models for the system. Our
simulations for both these models show the phenomenon of reentrant freezing as
the strength of the periodic potential is varied. Our simulations also show
that different exotic phases can form when the strength of the periodic
potential is high, depending on the length-scale at which the minimum of the
attractive pair-potential occurs.Comment: 24 pages (including figures) in preprint forma
Theoretical studies of the atomic transitions in boron-like ions: Mg VIII, Si X and S XII
In this paper, we have carried out the calculations of the weighted
oscillator strengths and the transition probabilities for a few low-lying
transitions of boron-like ions: Mg VIII, Si X and S XII which are
astrophysically important, particularly, in the atmospheres of the solar
corona. We have employed an all-order relativistic many-body theory called the
relativistic coupled-cluster theory to calculate very precisely these atomic
quantities of astrophysical interest. We have reported for the first time the
transition probabilities for some forbidden transitions which are unavailable
in the literature; either theoretically or experimentally. We also discuss the
physical effects associated with these transitions. Our data can be used for
the identification of spectral lines arising from the coronal atmospheres of
Sun and Sun-like stars having an extended corona.Comment: 8 pages, 4 table
Accurate estimations of circumstellar and interstellar lines of quadruply ionized vanadium using the coupled cluster approach
Accurate {\it ab initio} calculations have been carried out to study the
valence electron removal energies and oscillator strengths of astrophysically
important electromagnetic transitions of quadruply ionized vanadium, .
Many important electron correlations are considered to all-orders using the
relativistic coupled-cluster theory. Calculated ionization potentials and fine
structure splittings are compared with the experimental values, wherever
available. To our knowledge, oscillator strengths of electric dipole
transitions are predicted for the first time for most of the transitions. The
transitions span in the range of ultraviolet, visible and near infrared regions
and are important for astrophysical observations.Comment: Submitted in Astrophysical
Deconfinement and the Hagedorn Transition in String Theory
Superseded and extended in hep-th/0105110 and hep-th/0208112.Comment: Superseded and extended in hep-th/0105110 and hep-th/020811
XML Reconstruction View Selection in XML Databases: Complexity Analysis and Approximation Scheme
Query evaluation in an XML database requires reconstructing XML subtrees
rooted at nodes found by an XML query. Since XML subtree reconstruction can be
expensive, one approach to improve query response time is to use reconstruction
views - materialized XML subtrees of an XML document, whose nodes are
frequently accessed by XML queries. For this approach to be efficient, the
principal requirement is a framework for view selection. In this work, we are
the first to formalize and study the problem of XML reconstruction view
selection. The input is a tree , in which every node has a size
and profit , and the size limitation . The target is to find a subset
of subtrees rooted at nodes respectively such that
, and is maximal.
Furthermore, there is no overlap between any two subtrees selected in the
solution. We prove that this problem is NP-hard and present a fully
polynomial-time approximation scheme (FPTAS) as a solution
Spectrum of One-Dimensional Anharmonic Oscillators
We use a power-series expansion to calculate the eigenvalues of anharmonic
oscillators bounded by two infinite walls. We show that for large finite values
of the separation of the walls, the calculated eigenvalues are of the same high
accuracy as the values recently obtained for the unbounded case by the
inner-product quantization method. We also apply our method to the Morse
potential. The eigenvalues obtained in this case are in excellent agreement
with the exact values for the unbounded Morse potential.Comment: 11 pages, 5 figures, 4 tables; there are changes to match the version
published in Can. J. Phy
Laser-induced freezing in 2-d colloids
Dielectric colloid particles prefer occupying the intensity maxima of an applied stationary interference pattern of laser beams. A 2-d system of colloidal liquid freezes to form a triangular lattice structure when the external laser modulation is in 1-d and the period of the intensity maxima is commensurate to that of the triangular lattice. In this article we review our recent simulation results on this phenomenon of laser-induced freezing
On rational solution of the state equation of a finite automaton
We prove that the necessary and sufficient condition for the state equation of a finite automaton M to have a rational solution is that the lexicographical Gödel numbers of the strings belonging to each of the end-sets of M form an ultimately periodic set. A method of determining the existence of a rational solution of the state equation is also given
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