2,516 research outputs found

### Zero Forcing Sets and Bipartite Circulants

In this paper we introduce a class of regular bipartite graphs whose
biadjacency matrices are circulant matrices and we describe some of their
properties. Notably, we compute upper and lower bounds for the zero forcing
number for such a graph based only on the parameters that describe its
biadjacency matrix. The main results of the paper characterize the bipartite
circulant graphs that achieve equality in the lower bound.Comment: 22 pages, 13 figure

### On the t-Term Rank of a Matrix

For t a positive integer, the t-term rank of a (0,1)-matrix A is defined to
be the largest number of 1s in A with at most one 1 in each column and at most
t 1s in each row. Thus the 1-term rank is the ordinary term rank. We generalize
some basic results for the term rank to the t-term rank, including a formula
for the maximum term rank over a nonempty class of (0,1)-matrices with the the
same row sum and column sum vectors. We also show the surprising result that in
such a class there exists a matrix which realizes all of the maximum terms
ranks between 1 and t.Comment: 18 page

### Cyclic Matching Sequencibility of Graphs

We define the cyclic matching sequencibility of a graph to be the largest
integer $d$ such that there exists a cyclic ordering of its edges so that every
$d$ consecutive edges in the cyclic ordering form a matching. We show that the
cyclic matching sequencibility of $K_{2m}$ and $K_{2m+1}$ equal $m-1$

### Spectral arbitrariness for trees fails spectacularly

If $G$ is a graph and $\mathbf{m}$ is an ordered multiplicity list which is
realizable by at least one symmetric matrix with graph $G$, what can we say
about the eigenvalues of all such realizing matrices for $\mathbf{m}$? It has
sometimes been tempting to expect, especially in the case that $G$ is a tree,
that any spacing of the multiple eigenvalues should be realizable. In 2004,
however, F. Barioli and S. Fallat produced the first counterexample: a tree on
16 vertices and an ordered multiplicity list for which every realizing set of
eigenvalues obeys a nontrivial linear constraint.
We extend this by giving an infinite family of trees and ordered multiplicity
lists whose sets of realizing eigenvalues are very highly constrained, with at
most 5 degrees of freedom, regardless of the size of the tree in this family.
In particular, we give the first examples of multiplicity lists for a tree
which impose nontrivial nonlinear eigenvalue constraints and produce an ordered
multiplicity list which is achieved by a unique set of eigenvalues, up to
shifting and scaling.Comment: 45 page

### Glueball production in radiative J/psi, Upsilon decays

Using a bound-state model of weakly bound gluons for glueballs made of two
gluons and a natural generalization of the perturbative QCD formalism for
exclusive hadronic processes, we present results for glueball production in
radiative J/psi, Upsilon decays into several possible glueball states,
including L \not= 0 ones. We perform a detailed phenomenological analysis,
presenting results for the more favored experimental candidates and for decay
angular distributions.Comment: RevTeX4, 26 pages, 11 eps figure

### FAPRI 2000 U.S. Agricultural Outlook

Crop Production/Industries, Livestock Production/Industries,

### Enhanced stability of layered phases in parallel hard-spherocylinders due to the addition of hard spheres

There is increasing evidence that entropy can induce microphase separation in
binary fluid mixtures interacting through hard particle potentials. One such
phase consists of alternating two dimensional liquid-like layers of rods and
spheres. We study the transition from a uniform miscible state to this ordered
state using computer simulations and compare results to experiments and theory.
We conclude that (1) there is stable entropy driven microphase separation in
mixtures of parallel rods and spheres, (2) adding spheres smaller then the rod
length decreases the total volume fraction needed for the formation of a
layered phase, therefore small spheres effectively stabilize the layered phase;
the opposite is true for large spheres and (3) the degree of this stabilization
increases with increasing rod length.Comment: 11 pages, 9 figures. Submitted to Phys. Rev. E. See related website
http://www.elsie.brandeis.ed

### A surveillance system for monitoring, public reporting, and improving minority access to cancer clinical trials

The Institute of Medicine (IOM) has recommended that each person with cancer should have access to clinical trials, which have been associated with improving care quality and disparities. With no effective enrollment monitoring system, patterns of trial enrollment remain unclear

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