117,242 research outputs found
Quantitative -theory for -algebras
Quantitative (or controlled) -theory for -algebras was introduced by Guoliang Yu in his work on the Novikov conjecture for groups with finite asymptotic dimension, and was later expanded into a general theory, with further applications, by Yu together with Hervé Oyono-Oyono. Motivated by investigations of the Baum-Connes conjecture, we will describe an analogous framework of quantitative -theory that applies to algebras of bounded linear operators on subquotients of spaces
On Rearrangement of Items Stored in Stacks
There are stacks, each filled with items, and one empty stack.
Every stack has capacity . A robot arm, in one stack operation (step),
may pop one item from the top of a non-empty stack and subsequently push it
onto a stack not at capacity. In a {\em labeled} problem, all items are
distinguishable and are initially randomly scattered in the stacks. The
items must be rearranged using pop-and-pushs so that in the end, the stack holds items , in that order, from the top to
the bottom for all . In an {\em unlabeled} problem, the
items are of types of each. The goal is to rearrange items so that
items of type are located in the stack for all . In carrying out the rearrangement, a natural question is to find the least
number of required pop-and-pushes.
Our main contributions are: (1) an algorithm for restoring the order of
items stored in an table using only column and row
permutations, and its generalization, and (2) an algorithm with a guaranteed
upper bound of steps for solving both versions of the stack
rearrangement problem when for arbitrary fixed
positive number . In terms of the required number of steps, the labeled and
unlabeled version have lower bounds
and , respectively
Baryon-meson interactions in chiral quark model
Using the resonating group method (RGM), we dynamically study the
baryon-meson interactions in chiral quark model. Some interesting results are
obtained: (1) The Sigma K state has an attractive interaction, which
consequently results in a Sigma K quasibound state. When the channel coupling
of Sigma K and Lambda K is considered, a sharp resonance appears between the
thresholds of these two channels. (2) The interaction of Delta K state with
isospin I=1 is attractive, which can make for a Delta K quasibound state. (3)
When the coupling to the Lambda K* channel is considered, the N phi is found to
be a quasibound state in the extended chiral SU(3) quark model with several MeV
binding energy. (4) The calculated S-, P-, D-, and F-wave KN phase shifts
achieve a considerable improvement in not only the signs but also the
magnitudes in comparison with other's previous quark model study.Comment: 5 pages, 2 figures. Talk given at 3rd Asia Pacific Conference on
Few-Body Problems in Physics (APFB05), Korat, Nakhon Ratchasima, Thailand,
26-30 Jul 200
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