2,662 research outputs found
Chemical Enrichment at High Redshifts
We have tried to understand the recent observations related to metallicity in
Ly forest clouds in the framework of the two component model suggested
by Chiba & Nath (1997). We find that even if the mini-halos were chemically
enriched by an earlier generation of stars, to have [C/H] -2.5, the
number of C IV lines with column density , contributed by the
mini-halos, at the redshift of 3, would be only about 10% of the total number
of lines, for a chemical enrichment rate of in the galaxies.
Recently reported absence of heavy element lines associated with most of the Ly
lines with H I column density between and by Lu et al (1998), if correct, gives an upper limit on [C/H]=-3.7,
not only in the mini-halos, but also in the outer parts of galactic halos. This
is consistent with the results of numerical simulations, according to which,
the chemical elements associated with the Ly clouds are formed in situ
in clouds, rather than in an earlier generation of stars. However, the mean
value of for the column density ratio of C IV and H I,
determined by Cowie and Songaila (1998) for low Lyman alpha optical depths,
implies an abundance of [C/H] =-2.5 in mini-halos as well as in most of the
region in galactic halos, presumably enriched by an earlier generation of
stars. The redshift and column density distribution of C IV has been shown to
be in reasonable agreement with the observations.Comment: 23 pages, 6 figures, To appear in Astrophysical Journa
New Shape Invariant Potentials in Supersymmetric Quantum Mechanics
Quantum mechanical potentials satisfying the property of shape invariance are
well known to be algebraically solvable. Using a scaling ansatz for the change
of parameters, we obtain a large class of new shape invariant potentials which
are reflectionless and possess an infinite number of bound states. They can be
viewed as q-deformations of the single soliton solution corresponding to the
Rosen-Morse potential. Explicit expressions for energy eigenvalues,
eigenfunctions and transmission coefficients are given. Included in our
potentials as a special case is the self-similar potential recently discussed
by Shabat and Spiridonov.Comment: 8pages, Te
New supersymmetric partners for the associated Lame potentials
We obtain exact solutions of the one-dimensional Schrodinger equation for
some families of associated Lame potentials with arbitrary energy through a
suitable ansatz, which may be appropriately extended for other such a families.
The formalism of supersymmetric quantum mechanics is used to generate new
exactly solvable potentials.Comment: 8 pages, 2 figures, submitted on 24 November 2004 to Phys. Lett.
Center and representations of infinitesimal Hecke algebras of sl_2
In this paper, we compute the center of the infinitesimal Hecke algebras Hz
associated to sl_2 ; then using nontriviality of the center, we study
representations of these algebras in the framework of the BGG category O. We
also discuss central elements in infinitesimal Hecke algebras over gl(n) and
sp(2n) for all n. We end by proving an analogue of the theorem of Duflo for Hz.Comment: Final form, to appear in "Communications in Algebra"; 35 pages, laTe
Intermediate-statistics quantum bracket, coherent state, oscillator, and representation of angular momentum (su(2)) algebra
In this paper, we first discuss the general properties of an
intermediate-statistics quantum bracket, ,
which corresponds to intermediate statistics in which the maximum occupation
number of one quantum state is an arbitrary integer, . A further study of
the operator realization of intermediate statistics is given. We construct the
intermediate-statistics coherent state. An intermediate-statistics oscillator
is constructed, which returns to bosonic and fermionic oscillators respectively
when and . The energy spectrum of such an
intermediate-statistics oscillator is calculated. Finally, we discuss the
intermediate-statistics representation of angular momentum () algebra.
Moreover, a further study of the operator realization of intermediate
statistics is given in the Appendix.Comment: 12 pages, no figures. Revte
Periodic Solutions of Nonlinear Equations Obtained by Linear Superposition
We show that a type of linear superposition principle works for several
nonlinear differential equations. Using this approach, we find periodic
solutions of the Kadomtsev-Petviashvili (KP) equation, the nonlinear
Schrodinger (NLS) equation, the model, the sine-Gordon
equation and the Boussinesq equation by making appropriate linear
superpositions of known periodic solutions. This unusual procedure for
generating solutions is successful as a consequence of some powerful, recently
discovered, cyclic identities satisfied by the Jacobi elliptic functions.Comment: 19 pages, 4 figure
Linear Superposition in Nonlinear Equations
Even though the KdV and modified KdV equations are nonlinear, we show that
suitable linear combinations of known periodic solutions involving Jacobi
elliptic functions yield a large class of additional solutions. This procedure
works by virtue of some remarkable new identities satisfied by the elliptic
functions.Comment: 7 pages, 1 figur
Goethite on Mars - A laboratory study of physically and chemically bound water in ferric oxides
Thermogravimetric study of physically and chemically bound water in ferric oxides of limonite with application to goethite on Mar
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