Uncertanties in Air-showers from Small-x pQCD Mini-Jets

To investigate uncertainties in air shower simulations caused by the small-x regime, a model including leading-twist hard pQCD plus soft processes was built, which are separated by an energy dependent transverse momentum cut-off. We provide a fit of the cut-off to the total pp cross section for different PDFs using the eikonal formalism and show that for modern PDF sets there is only a small uncertainty in the mini-jet cross section, and hence in the final-state multiplicity and the number of produced muons.Comment: 4 pages, 2 figures, contribution to QM2005 proceedings, revised version after referee comment

U.S. Unemployment Duration: Has Long Become Longer or Short Become Shorter?

The U.S. labor market has been experiencing unprecedented high average unemployment duration. The shift in the unemployment duration distribution can be traced back to the early nineties. In this study, censored quantile regression methods are employed to analyze the changes in the U.S. unemployment duration distribution. We explore the decomposition method proposed by Machado and Mata (2005) to disentangle the contribution of the changes generated by the covariate distribution and by the conditional distribution. The data used in this inquiry are taken from the nationally representative Displaced Worker Surveys of 1988 and 1998. We provide evidence that the change in the unemployment duration distribution is mainly produced by the opposing effects of a sharp rise in job-to-job transition rates and an increased sensitivity of unemployment duration to unemployment rates. Compositional changes in the labor force played a limited role. We rationalize our findings by arguing that improved screening technology is likely to be the relevant underlying mechanism at work.Quantile Regression, Duration Analysis, Unemployment Duration, Counterfactual Decomposition.

The role of local and global strangeness neutrality at the inhomogeneous freeze-out in relativistic heavy ion collisions

The decoupling surface in relativistic heavy-ion collisions may not be homogeneous. Rather, inhomogeneities should form when a rapid transition from high to low entropy density occurs. We analyze the hadron "chemistry" from high-energy heavy-ion reactions for the presence of such density inhomogeneities. We show that due to the non-linear dependence of the particle densities on the temperature and baryon-chemical potential such inhomogeneities should be visible even in the integrated, inclusive abundances. We analyze experimental data from Pb+Pb collisions at CERN-SPS and Au+Au collisions at BNL-RHIC to determine the amplitude of inhomogeneities and the role of local and global strangeness neutrality.Comment: 8 pages, 6 figures, To appear in proceedings of the workshop on 'Particle Correlations and Femtoscopy' September 9-11, 2006, Sao Paulo, Brazi

Coined Quantum Walks as Quantum Markov Chains

We analyze the equivalence between discrete-time coined quantum walks and Szegedy's quantum walks. We characterize a class of flip-flop coined models with generalized Grover coin on a graph $\Gamma$ that can be directly converted into Szegedy's model on the subdivision graph of $\Gamma$ and we describe a method to convert one model into the other. This method improves previous results in literature that need to use the staggered model and the concept of line graph, which are avoided here.Comment: 10 pages, 4 fig