The minimum rank of a simple graph G over a field F is the smallest possible rank among all real symmetric matrices, over F, whose (i, j)-entry (for i 6= j) is nonzero whenever ij is an edge in G and is zero otherwise. In this paper, the problem of minimum rank of (strict) powers of trees is studied.

let $mathcal {a} $ and $mathcal {b} $ be c$^*$-algebras. assume that $mathcal {a}$ is of real rank zero and unital with unit $i$ and $k>0$ is a real number. it is shown that if $phi:mathcal{a} tomathcal{b}$ is an additive map preserving $|cdot|^k$ for all normal elements; that is, $phi(|a|^k)=|phi(a)|^k $ for all normal elements $ainmathcal a$, $phi(i)$ is a projection, and there exists a posit...

The minimum rank of a simple graph G is the smallest possible rank over all symmetric real matrices A whose nonzero off-diagonal entries correspond to the edges of G. Using the zero forcing number, we prove that the minimum rank of the r-th butterfly network is 1 9 [ (3r + 1)2r+1 − 2(−1)r ] and that this is equal to the rank of its adjacency matrix.

We prove that a number of classes of separable unital C*-algebras are closed under crossed products by finite group actions with the Rokhlin property, including: • AI algebras, AT algebras, and related classes characterized by direct limit decompositions using semiprojective building blocks. • Simple unital AH algebras with slow dimension growth and real rank zero. • C*-algebras with real rank ...

We survey some recent results concerning the use of non-stable K−theoretic methods to efficiently analyse the ideal structure of multiplier algebras for a wide class of C∗algebras having real rank zero and stable rank one. Some applications of these results are delineated, showing a high degree of infiniteness of these objects.