# Interpreting Numerical Measurements in Fixed Topological Sectors

For quantum field theories with topological sectors, Monte Carlo simulations on fine lattices tend to be obstructed by an extremely long auto-correlation time with respect to the topological charge. Then reliable numerical measurements are feasible only within individual sectors. The challenge is to assemble such restricted measurements in a way that leads to a substantiated approximation to the fully fledged result, which would correspond to the correct sampling over the entire set of configurations. We test an approach for such a topological summation, which was suggested by Brower, Chandrasekharan, Negele and Wiese. Under suitable conditions, energy levels and susceptibilities can be obtained to a good accuracy, as we demonstrate for O(N) models, SU(2) Yang-Mills theory, and for the Schwinger model.

 Comments: 41 pages, LaTex, 12 figures, 10 tables Subjects: High Energy Physics – Lattice (hep-lat); High Energy Physics – Phenomenology (hep-ph) Cite as: arXiv:1603.05630 [hep-lat] (or arXiv:1603.05630v1 [hep-lat] for this version)

# Parton Transverse Momentum and Orbital Angular Momentum Distributions

The quark orbital angular momentum component of proton spin, Lq, can be defined in QCD as the integral of a Wigner phase space distribution weighting the cross product of the quark’s transverse position and momentum. It can also be independently defined from the operator product expansion for the off-forward Compton amplitude in terms of a twist-three generalized parton distribution. We provide an explicit link between the two definitions, connecting them through their dependence on partonic intrinsic transverse momentum. Connecting the definitions provides the key for correlating direct experimental determinations of Lq, and evaluations through Lattice QCD calculations. The direct observation of quark orbital angular momentum does not require transverse spin polarization, but can occur using longitudinally polarized targets.

 Comments: 5 pages, 2 figures Subjects: High Energy Physics – Phenomenology (hep-ph) Cite as: arXiv:1601.06117 [hep-ph] (or arXiv:1601.06117v1 [hep-ph] for this version)

## Postdocs en Guanajuato

La división de Ciencias e Ingenierías de la Universidad de Guanajuato invita a realizar estancias postdoctorales (aplicaciones cuánticas, altas energías, gravitación, física matemática, mecánica estadística, materiales, física médica, etc…)

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