36 citations · 106 across the 22 of their papers we have counts for
4 papers · 1 filter
Lacunary matrices
Asma Harcharras, Stefan Neuwirth, Krzysztof Oleszkiewicz
We study unconditional subsequences of the canonical basis e_rc of elementary matrices in the Schatten class S^p. They form the matrix counterpart to Rudin's Lambda(p) sets of inte…
The size of bipartite graphs with girth eight
Stefan Neuwirth
Reiman produced a quadratic inequality for the size of bipartite graphs of girth six. We get its counterpart for girth eight, a cubic inequality. It is optimal in as far as it admi…
The Sidon constant of sets with three elements
Stefan Neuwirth
We solve an elementary extremal problem on trigonometric polynomials and obtain the exact value of the Sidon constant for sets with three elements {n0, n1, n2}: it is \sec(π/ 2n) f…
Cycles and 1-unconditional matrices
Stefan Neuwirth
We characterize the 1-unconditional subsequences of the canonical basis (e_rc) of elementary matrices in the Schatten-von-Neumann class S^p . The set I of couples (r,c) must be the…