Let X be a homogeneous tree of degree q + 1 (2 ≤ q ≤ ∞) and let ψ : X × X → C be a function for which ψ(x, y) only depend on the distance between x, y ∈ X. Our main result gives a necessary and sufficient condition for such a function to be a Schur multiplier on X×X. Moreover, we find a closed expression for the Schur norm ‖ψ‖S of ψ. As applications, we obtain a closed expression for the comple...

We characterize the set of diagonals of the unitary orbit of a self-adjoint operator with a finite spectrum. Our result extends the Schur-Horn theorem from a finite dimensional setting to an infinite dimensional Hilbert space, analogous to Kadison’s theorem for orthogonal projections [17, 18], and the second author’s result for operators with three point spectrum [16].

Each finite p-perfect group G (p a prime) has a universal central p-extension coming from the p part of its Schur multiplier. Serre gave a StiefelWhitney class approach to analyzing spin covers of alternating groups (p = 2) aimed at geometric covering space problems that included their regular realization for the Inverse Galois Problem. A special case of a general result is that any finite simp...

Each finite p-perfect group G (p a prime) has a universal central p-extension coming from the p part of its Schur multiplier. Serre gave a StiefelWhitney class approach to analyzing spin covers of alternating groups (p = 2) aimed at geometric covering space problems that included their regular realization for the Inverse Galois Problem. A special case of a general result is that any finite simp...

R. C. Buck fl] has shown that if a regular matrix sums every subsequence of a sequence x, then x is convergent. I. J. Maddox [4] improved Buck's theorem by showing that if a non-Schur matrix sums every subsequence of a sequence x, then x is convergent. Actually Maddox proved a stronger result: If x is divergent and A sums every subsequence of x, then A is a Schur matrix, i.e., It should be rema...

We introduce the notion of the cutting strip of an outside decomposition of a skew shape, and show that cutting strips are in one-to-one correspondence with outside decompositions for a given skew shape. Outside decompositions are introduced by Hamel and Goulden and are used to give an identity for the skew Schur function that unifies the determinantal expressions for the skew Schur functions i...

and Applied Analysis 3 a splitting procedure of the box of reflection coefficients, new conditions for the Schur stability are given. The application of Theorem 1.2 for determining the stability of polynomials with multilinear coefficients yield conservative results. In 8, 9 sufficient conditions are given for ensuring that the image of a multilinear function over the box Q is a convex polygon ...

In this note we prove a generalization of the Frobenius-Schur theorem for finite groups for the case of semisimple Hopf algebra over an algebraically closed field of characteristic 0. A similar result holds in characteristic p > 2 if the Hopf algebra is also cosemisimple. In fact we show a more general version for any finite-dimensional semisimple algebra with an involution; this more general r...

Thus if all primes are colored with k colors, then there exist arbitrarily long monochromatic arithmetic progressions. This is a van der Waerden-type [9] theorem for primes. (The well-known van der Waerden theorem states that for any m-coloring of all positive integers, there exist arbitrarily long monochromatic arithmetic progressions.) On the other hand, Schur’s theorem [7] is another importa...

Thus if all primes are colored with k colors, then there exist arbitrarily long monochromatic arithmetic progressions. This is a van der Waerden-type [9] theorem for primes. (The well-known van der Waerden theorem states that for any k-coloring of all positive integers, there exist arbitrarily long monochromatic arithmetic progressions.) On the other hand, Schur’s theorem [7] is another famous ...