2,651 research outputs found
Effective-Medium Theory for the Normal State in Orientationally Disordered Fullerides
An effective-medium theory for studying the electronic structure of the
orientationally disordered A3C60 fullerides is developed and applied to study
various normal-state properties. The theory is based on a cluster-Bethe-lattice
method in which the disordered medium is modelled by a three-band Bethe
lattice, into which we embed a molecular cluster whose scattering properties
are treated exactly. Various single-particle properties and the
frequency-dependent conductivity are calculated in this model, and comparison
is made with numerical calculations for disordered lattices, and with
experiment.Comment: 12 pages + 2 figures, REVTeX 3.
Quantum Sturm-Liouville Equation, Quantum Resolvent, Quantum Integrals, and Quantum KdV : the Fast Decrease Case
We construct quantum operators solving the quantum versions of the
Sturm-Liouville equation and the resolvent equation, and show the existence of
conserved currents. The construction depends on the following input data: the
basic quantum field and the regularization .Comment: minor correction
Simulation of truncated normal variables
We provide in this paper simulation algorithms for one-sided and two-sided
truncated normal distributions. These algorithms are then used to simulate
multivariate normal variables with restricted parameter space for any
covariance structure.Comment: This 1992 paper appeared in 1995 in Statistics and Computing and the
gist of it is contained in Monte Carlo Statistical Methods (2004), but I
receive weekly requests for reprints so here it is
Invariant and polynomial identities for higher rank matrices
We exhibit explicit expressions, in terms of components, of discriminants,
determinants, characteristic polynomials and polynomial identities for matrices
of higher rank. We define permutation tensors and in term of them we construct
discriminants and the determinant as the discriminant of order , where
is the dimension of the matrix. The characteristic polynomials and the
Cayley--Hamilton theorem for higher rank matrices are obtained there from
Algebraic Structures of Quantum Projective Field Theory Related to Fusion and Braiding. Hidden Additive Weight
The interaction of various algebraic structures describing fusion, braiding
and group symmetries in quantum projective field theory is an object of an
investigation in the paper. Structures of projective Zamolodchikov al- gebras,
their represntations, spherical correlation functions, correlation characters
and envelopping QPFT-operator algebras, projective \"W-algebras, shift
algebras, braiding admissible QPFT-operator algebras and projective
G-hypermultiplets are explored. It is proved (in the formalism of shift
algebras) that sl(2,C)-primary fields are characterized by their projective
weights and by the hidden additive weight, a hidden quantum number discovered
in the paper (some discussions on this fact and its possible relation to a
hidden 4-dimensional QFT maybe found in the note by S.Bychkov, S.Plotnikov and
D.Juriev, Uspekhi Matem. Nauk 47(3) (1992)[in Russian]). The special attention
is paid to various constructions of projective G-hyper- multiplets
(QPFT-operator algebras with G-symmetries).Comment: AMS-TEX, amsppt style, 16 pages, accepted for a publication in
J.MATH.PHYS. (Typographical errors are excluded
The Response to a Perturbation in the Reflection Amplitude
We apply inverse scattering theory to calculate the functional derivative of
the potential and wave function of a one-dimensional
Schr\"odinger operator with respect to the reflection amplitude .Comment: 16 pages, no figure
On the algebraic structures connected with the linear Poisson brackets of hydrodynamics type
The generalized form of the Kac formula for Verma modules associated with
linear brackets of hydrodynamics type is proposed. Second cohomology groups of
the generalized Virasoro algebras are calculated. Connection of the central
extensions with the problem of quntization of hydrodynamics brackets is
demonstrated
Impurity effects on optical response in a finite band electronic system coupled to phonons
The concepts, which have traditionally been useful in understanding the
effects of the electron--phonon interaction in optical spectroscopy, are based
on insights obtained within the infinite electronic band approximation and no
longer apply in finite band metals. Impurity and phonon contributions to
electron scattering are not additive and the apparent strength of the coupling
to the phonon degrees of freedom is substantially reduced with increased
elastic scattering. The optical mass renormalization changes sign with
increasing frequency and the optical scattering rate never reaches its high
frequency quasiparticle value which itself is also reduced below its infinite
band value
Off-diagonal Interactions, Hund's Rules and Pair-binding in Hubbard Molecules
We have studied the effect of including nearest-neighbor, electron-electron
interactions, in particular the off-diagonal (non density-density) terms, on
the spectra of truncated tetrahedral and icosahedral ``Hubbard molecules,''
focusing on the relevance of these systems to the physics of doped C.
Our perturbation theoretic and exact diagonalization results agree with
previous work in that the density-density term suppresses pair-binding.
However, we find that for the parameter values of interest for the
off-diagonal terms {\em enhance} pair-binding, though not enough to offset the
suppression due to the density-density term. We also find that the critical
interaction strengths for the Hund's rules violating level crossings in
C, C and C are quite insensitive to the
inclusion of these additional interactions.Comment: 20p + 5figs, Revtex 3.0, UIUC preprint P-94-10-08
On the precise connection between the GRW master-equation and master-equations for the description of decoherence
We point out that the celebrated GRW master-equation is invariant under
translations, reflecting the homogeneity of space, thus providing a particular
realization of a general class of translation-covariant Markovian
master-equations. Such master-equations are typically used for the description
of decoherence due to momentum transfers between system and environment.
Building on this analogy we show the exact relationship between the GRW
master-equation and decoherence master-equations, further providing a
collisional decoherence model formally equivalent to the GRW master-equation.
This allows for a direct comparison of order of magnitudes of relevant
parameters. This formal analogy should not lead to confusion on the utterly
different spirit of the two research fields, in particular it has to be
stressed that the decoherence approach does not lead to a solution of the
measurement problem. Building on this analogy however the feasibility of the
extension of spontaneous localization models in order to avoid the infinite
energy growth is discussed. Apart from a particular case considered in the
paper, it appears that the amplification mechanism is generally spoiled by such
modifications.Comment: 9 pages, latex, no figures, to appear on J. Phys.
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