Chiral loop corrections for hadronic properties are considered in a constituent quark model. It is emphasized that the correct implementation of such corrections requires a sum over intermediate hadronic states. The leading non-analytic corrections are very important for baryon magnetic moments and explain the failure of the sum rule (µ Σ + + 2µ Σ −)/µ Λ = −1 predicted by the constituent quark ...

A phenomenological renormalization scheme for hadronic diffraction is proposed, which achieves unitarization without the need for “screening corrections”. Predictions for diffractive photoproduction cross sections at HERA are presented and compared with experimental results. A new interpretation of hard and deep inelastic diffractive data emerges, in which the momentum sum rule is obeyed by the...

We present a general formalism for the evaluation of time-reversal odd parton distributions. This formalism is applied to the evaluation of the two T-odd TMDs allowed at the twist-2 level, i.e., the Sivers and the Boer-Mulders functions. We have performed the calculation for two different models of proton structure: a non relativistic constituent quark model and the MIT bag model. The results o...

We consider the twist-3 gluon contribution to the transverse spin structure function g2.We find that the Burkhardt-Cottingham sum rule is satisfied. The additional nonlocal operators appear in the moments of g2 which were absent in previous analysis of Bukhvostov, Kuraev and Lipatov.

Seymour’s Decomposition Theorem for regular matroids states that any matroid representable over both GF(2) and GF(3) can be obtained from matroids that are graphic, cographic, or isomorphic to R10 by 1-, 2-, and 3-sums. It is hoped that similar characterizations hold for other classes of matroids, notably for the class of near-regular matroids. Suppose that all near-regular matroids can be obta...

Let A be a finite nonempty subset of an additive abelian group G, and let Σ(A) denote the set of all group elements representable as a sum of some subset of A. We prove that |Σ(A)| ≥ |H|+ 1 64 |A \H|2 where H is the stabilizer of Σ(A). Our result implies that Σ(A) = Z/nZ for every set A of units of Z/nZ with |A| ≥ 8√n. This consequence was first proved by Erdős and Heilbronn for n prime, and by...