Frobenius and multiplicities

Multiplicities and Reduction Numbers

Let (R,m) be a Cohen–Macaulay local ring and let I be an ideal. There are at least five algebras built on I whose multiplicity data affect the reduction number r(I) of the ideal. We introduce techniques from the Rees algebra theory of modules to produce estimates for r(I), for classes of ideals of dimension one and two. Previous cases of such estimates were derived for ideals of dimension zero.

Multidiameters and Multiplicities

The k-diameter of a graph 0 is the largest pairwise minimum distance of a set of k vertices in 0, i.e., the best possible distance of a code of size k in 0. A k-diameter for some k is called a multidiameter of the graph. We study the function N (k,1, D), the largest size of a graph of degree at most1 and kdiameter D. The graphical analogues of the Gilbert bound and the Hamming bound in coding t...

Eigenfamilies, Characters and Multiplicities

Weighted Frobenius-Perron and Koopman operators

Eigenvalues, Multiplicities and Graphs

For a given graph, there is a natural question of the possible lists of multiplicities for the eigenvalues among the spectra of Hermitian matrices with that graph (no constraint is placed upon the diagonal entries of the matrices by the graph). Here, we survey some of what is known about this question and include some new information about it. There is a natural focus upon the case in which the...