114 research outputs found
Band Distributions for Quantum Chaos on the Torus
Band distributions (BDs) are introduced describing quantization in a toral
phase space. A BD is the uniform average of an eigenstate phase-space
probability distribution over a band of toral boundary conditions. A general
explicit expression for the Wigner BD is obtained. It is shown that the Wigner
functions for {\em all} of the band eigenstates can be reproduced from the
Wigner BD. Also, BDs are shown to be closer to classical distributions than
eigenstate distributions. Generalized BDs, associated with sets of adjacent
bands, are used to extend in a natural way the Chern-index characterization of
the classical-quantum correspondence on the torus to arbitrary rational values
of the scaled Planck constant.Comment: 12 REVTEX page
The heavy baryons in the nonperturbative string approach
We present some piloting calculations of the short-range correlation
coefficients for the light and heavy baryons and masses of the doubly heavy
baryons and () in the framework of the
simple approximation within the nonperturbative QCD approach.Comment: 21 pages; to appear in Phys. Atom. Nuc
Wigner Functions and Separability for Finite Systems
A discussion of discrete Wigner functions in phase space related to mutually
unbiased bases is presented. This approach requires mathematical assumptions
which limits it to systems with density matrices defined on complex Hilbert
spaces of dimension p^n where p is a prime number. With this limitation it is
possible to define a phase space and Wigner functions in close analogy to the
continuous case. That is, we use a phase space that is a direct sum of n
two-dimensional vector spaces each containing p^2 points. This is in contrast
to the more usual choice of a two-dimensional phase space containing p^(2n)
points. A useful aspect of this approach is that we can relate complete
separability of density matrices and their Wigner functions in a natural way.
We discuss this in detail for bipartite systems and present the generalization
to arbitrary numbers of subsystems when p is odd. Special attention is required
for two qubits (p=2) and our technique fails to establish the separability
property for more than two qubits.Comment: Some misprints have been corrected and a proof of the separability of
the A matrices has been adde
Multicomplementary operators via finite Fourier transform
A complete set of d+1 mutually unbiased bases exists in a Hilbert spaces of
dimension d, whenever d is a power of a prime. We discuss a simple construction
of d+1 disjoint classes (each one having d-1 commuting operators) such that the
corresponding eigenstates form sets of unbiased bases. Such a construction
works properly for prime dimension. We investigate an alternative construction
in which the real numbers that label the classes are replaced by a finite field
having d elements. One of these classes is diagonal, and can be mapped to
cyclic operators by means of the finite Fourier transform, which allows one to
understand complementarity in a similar way as for the position-momentum pair
in standard quantum mechanics. The relevant examples of two and three qubits
and two qutrits are discussed in detail.Comment: 15 pages, no figure
Heavy Baryon Specroscopy from the Lattice
The results of an exploratory lattice study of heavy baryon spectroscopy are
presented. We have computed the full spectrum of the eight baryons containing a
single heavy quark, on a lattice at , using an
-improved fermion action. We discuss the lattice baryon operators and
give a method for isolating the contributions of the spin doublets
, and to the correlation
function of the relevant operator. We compare our results with the available
experimental data and find good agreement in both the charm and the beauty
sectors, despite the long extrapolation in the heavy quark mass needed in the
latter case. We also predict the masses of several undiscovered baryons. We
compute the \Lambda-\mbox{pseudoscalar meson} and mass
splittings. Our results, which have errors in the range , are in good
agreement with the experimental numbers. For the mass
splitting, we find results considerably smaller than the experimental values
for both the charm and the beauty baryons, although in the latter case the
experimental results are still preliminary. This is also the case for the
lattice results for the hyperfine splitting for the heavy mesons.Comment: 31 pages LaTex, with postscript figures include
Observation of Two Narrow States Decaying into and
We report the first observation of two narrow charmed strange baryons
decaying to and , respectively, using data from
the CLEO II detector at CESR. We interpret the observed signals as the
and , the symmetric partners
of the well-established antisymmetric and .
The mass differences and
are measured to be and
, respectively.Comment: 11 pages, postscript file also available through
http://w4.lns.cornell.edu/public/CLN
Particle Content of the Nonlinear Sigma Model with Theta-Term: a Lattice Model Investigation
Using new as well as known results on dimerized quantum spin chains with
frustration, we are able to infer some properties on the low-energy spectrum of
the O(3) Nonlinear Sigma Model with a topological theta-term. In particular,
for sufficiently strong coupling, we find a range of values of theta where a
singlet bound state is stable under the triplet continuum. On the basis of
these results, we propose a new renormalization group flow diagram for the
Nonlinear Sigma Model with theta-term.Comment: 10 pages, 5 figures .eps, iopart format, submitted to JSTA
SU(3) Predictions for Weak Decays of Doubly Heavy Baryons -- including SU(3) breaking terms
We find expressions for the weak decay amplitudes of baryons containing two b
quarks (or one b and one c quark -- many relationship are the same) in terms of
unknown reduced matrix elements. This project was originally motivated by the
request of the FNAL Run II b Physics Workshop organizers for a guide to
experimentalists in their search for as yet unobserved hadrons. We include an
analysis of linear SU(3) breaking terms in addition to relationships generated
by unbroken SU(3) symmetry, and relate these to expressions in terms of the
complete set of possible reduced matrix elements.Comment: 49 page
Percolation thresholds in chemical disordered excitable media
The behavior of chemical waves advancing through a disordered excitable medium is investigated in terms of percolation theory and autowave properties in the framework of the light-sensitive Belousov-Zhabotinsky reaction. By controlling the number of sites with a given illumination, different percolation thresholds for propagation are observed, which depend on the relative wave transmittances of the two-state medium considered
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