7,668 research outputs found
Wigner distributions and quark orbital angular momentum
We discuss the quark phase-space or Wigner distributions of the nucleon which
combine in a single picture all the information contained in the generalized
parton distributions and the transverse-momentum dependent parton
distributions. In particular, we present results for the distribution of
unpolarized quarks in a longitudinally polarized nucleon obtained in a
light-front constituent quark model. We show how the quark orbital angular
momentum can be extracted from the Wigner distributions and compare it with
alternative definitions.Comment: 8 pages, 2 figures, 1 table, contribution to the proceedings of the
QCD Evolution workshop 2012, May 14-17, JLa
Final State Interactions and the Transverse Structure of the Pion
In the factorized picture of semi-inclusive deep inelastic scattering the
naive time reversal-odd parton distributions exist by virtue of the gauge link
which is intrinsic to their definition. The link structure describes
initial/final-state interactions of the active parton due to soft gluon
exchanges with the target remnant. Though these interactions are
non-perturbative, calculations of final-state interaction have been performed
in a perturbative one-gluon approximation. We include higher-order
contributions by applying non-perturbative eikonal methods to calculate the
Boer-Mulders function of the pion. Using this framework we explore under what
conditions the Boer-Mulders function can be described in terms of factorization
of final state interactions and a spatial distortion.Comment: 13 pages, 5 figures; Proceedings of the workshop, "Recent Advances in
Perturbative QCD and Hadronic Physics" ECT*, Trento (Italy), in Honor of
Anatoli V. Efremov on the occasion of his 75th Birthday, to appear in Mod.
Phys. Lett.
The determination of the natural modes of vibration of the saturn sa-5 and sa-8 vehicles final summary report
Natural modes of vibration of Saturn I SA-5 and SA-8 launch vehicle
International Aspects of the Great Depression and the Crisis of 2007: Similarities, Differences, and Lessons
We focus on two international aspects of the Great Depression--financial crises and international trade—and try to discern lessons for the current economic crisis. Both downturns featured global banking crises which were generated by boom-slump macroeconomic cycles. During both crises, world trade collapsed faster than world incomes and the trade decline was highly synchronized across countries. In the Depression, income losses and rises in trade barriers explain trade’s collapse. Due to vertical specialization and more intense trade in durables today’s trade collapse is due to uncertainty and small shocks to trade costs hitting international supply chains. So far, the global economy has avoided the global trade wars and banking collapses of the Depression perhaps due to improved policy. Even so, the global economy remains susceptible to large shocks due to financial innovation and technological change as recent events illustrate.Great Depression, Crisis of 2007
Dilaton Brane Cosmology with Second Order String Corrections and the Cosmological Constant
We consider, in five dimensions, the effective action from heterotic string
which includes quantum gravity corrections up to (a')^2. The expansion, in the
string frame, is in terms of |a'R|, where R is the scalar curvature and uses
the third order Euler density, next to the Gauss-Bonnet term. For a positive
tension brane and infinite extra dimension, the logarithmic class of solutions
is less dependent from fine-tuning problems than in previous formulations. More
importantly, the model suggests that in the full non-perturbative formulation,
the string scale can be much lower than the effective Planck mass, without the
string coupling to be vanishingly small. Also a less severe fine-tuning of the
brane tension in needed.Comment: 19 pages, 5 figures LaTeX. Accepted for publication in IJMP
Trade Booms, Trade Busts, and Trade Costs
What has driven trade booms and trade busts in the past and present? We derive a micro-founded measure of trade frictions from leading trade theories and use it to gauge the importance of bilateral trade costs in determining international trade flows. We construct a new balanced sample of bilateral trade flows for 130 country pairs across the Americas, Asia, Europe, and Oceania for the period from 1870 to 2000 and demonstrate an overriding role for declining trade costs in the pre-World War I trade boom. In contrast, for the post-World War II trade boom we identify changes in output as the dominant force. Finally, the entirety of the interwar trade bust is explained by increases in trade costs.
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