ar X iv : m at h / 06 11 35 3 v 2 [ m at h . G N ] 1 6 N ov 2 00 6 SQUARES OF MENGER - BOUNDED GROUPS

ar X iv : m at h / 06 11 35 3 v 1 [ m at h . G N ] 1 2 N ov 2 00 6 SQUARES OF MENGER - BOUNDED GROUPS

Using a portion of the Continuum Hypothesis, we prove that there is a Menger-bounded (also called o-bounded) subgroup of the Baire group Z, whose square is not Menger-bounded. This settles a major open problem concerning boundedness notions for groups, and implies that Menger-bounded groups need not be Scheepers-bounded.

ar X iv : m at h / 06 11 45 2 v 1 [ m at h . A G ] 1 5 N ov 2 00 6 UNIRATIONALITY OF CERTAIN SUPERSINGULAR K 3 SURFACES IN CHARACTERISTIC

We show that every supersingular K3 surface in characteristic 5 with Artin invariant ≤ 3 is unirational.

ar X iv : h ep - l at / 0 11 00 06 v 3 6 N ov 2 00 1 1 Matrix elements of ∆ S = 2 operators with Wilson fermions

ar X iv : m at h / 06 11 38 6 v 1 [ m at h . R A ] 1 3 N ov 2 00 6 Quasi Q n - filiform Lie algebras ∗

In this paper we explicitly determine the derivation algebra, automorphism group of quasi Qn-filiform Lie algebras, and applying some properties of root vector decomposition we obtain their isomorphism theorem. AMS Classification: 17B05; 17B30

ar X iv : m at h / 05 08 14 6 v 4 [ m at h . G N ] 1 6 N ov 2 00 6 THE COMBINATORICS OF THE BAIRE GROUP

We study subgroups of Z which possess group theoretic properties analogous to properties introduced by Menger (1924), Hurewicz (1925), Rothberger (1938), and Scheepers (1996). The studied properties were introduced independently by Kočinac and Okunev. We obtain purely combinatorial characterizations of these properties, and combine them with other techniques to solve several questions of Babink...