2 N ov 2 00 1 Four - Weight Spin Models and Jones Pairs

Four-weight Spin Models and Jones Pairs

We introduce and discuss Jones pairs. These provide a generalization and a new approach to the four-weight spin models of Bannai and Bannai. We show that each four-weight spin model determines a “dual” pair of association schemes. 1. Jones Pairs The space of k × k matrices acts on itself in three distinct ways: if C ∈ Mk(F), we can define endomorphisms XC , ∆C and YC by XC(M) = CM, ∆C(M) = C ◦M...

N ov 2 00 5 Equiangular lines , mutually unbiased bases , and spin models

We use difference sets to construct interesting sets of lines in complex space. Using (v, k, 1)-difference sets, we obtain k2−k+1 equiangular lines in Ck when k − 1 is a prime power. Using semiregular relative difference sets with parameters (k, n, k, λ) we construct sets of n + 1 mutually unbiased bases in Ck. We show how to construct these difference sets from commutative semifields and that ...

40 0 v 1 2 6 N ov 2 00 2 1 Single Transverse Spin Asymmetry in p ↑ p → πX and ep ↑ → πX

ar X iv : n uc l - ex / 0 41 10 48 v 1 2 4 N ov 2 00 4 Compton Scattering by the Nucleon ⋆

The status of Compton scattering by the nucleon at energies of the first and second resonance is summarized. In addition to a general test of dispersion theories and a precise determination of polarizabilities, the validities of four fundamental sum rules are explored. Recommended averages of experimental values for the electromagnetic polarizabilities and spin-polarizabilities of the nucleon a...

X iv : h ep - t h / 04 11 26 1 v 1 2 9 N ov 2 00 4 Spin bits at two loops

We consider the Super Yang–Mills/spin system map to construct the SU(2) spin bit model at the level of two loops in Yang–Mills perturbation theory. The model describes a spin system with chaining interaction. In the large N limit the model is shown to be reduced to the two loop planar integrable spin chain.