Studies of highly-boosted top quarks near the TeV scale using jet masses at the LHC

Studies of highly-boosted top quarks produced inclusively in pp collisions at 14 TeV are discussed. The hadronic decays of boosted top quarks was studied in a data-driven approach by analysing shapes of jet-mass distributions. Using Monte Carlo models after a fast detector simulation, it is shown that inclusive production of boosted top quarks can be observed if it has a cross section at least twice larger than the prediction from the approximate next-to-next-to-leading-order (aNNLO) calculation for the ttbar process. The ttbar process with the nominal aNNLO strength can be measured using the masses of jets after a b-tagging.Comment: 11 pages, 5 figure

Zipf Law for Brazilian Cities

This work studies the Zipf Law for cities in Brazil. Data from censuses of 1970, 1980, 1991 and 2000 were used to select a sample containing only cities with 30,000 inhabitants or more. The results show that the population distribution in Brazilian cities does follow a power law similar to the ones found in other countries. Estimates of the power law exponent were found to be 2.22 +/- 0.34 for the 1970 and 1980 censuses, and 2.26 +/- 0.11 for censuses of 1991 and 2000. More accurate results were obtained with the maximum likelihood estimator, showing an exponent equal to 2.41 for 1970 and 2.36 for the other three years.Comment: 12 pages, 6 figures, 3 tables, Elsevier LaTeX, accepted for publication in "Physica A". Correction of minor mistyping (eq. 8

Theory of parity violation in compound nuclear states; one particle aspects

In this work we formulate the reaction theory of parity violation in compound nuclear states using Feshbach's projection operator formalism. We derive in this framework a complete set of terms that contribute to the longitudinal asymmetry measured in experiments with polarized epithermal neutrons. We also discuss the parity violating spreading width resulting from this formalism. We then use the above formalism to derive expressions which hold in the case when the doorway state approximation is introduced. In applying the theory we limit ourselves in this work to the case when the parity violating potential and the strong interaction are one-body. In this approximation, using as the doorway the giant spin-dipole resonance and employing well known optical potentials and a time-reversal even, parity odd one-body interaction we calculate or estimate the terms we derived. In our calculations we explicitly orthogonalize the continuum and bound wave functions. We find the effects of orthogonalization to be very important. Our conclusion is that the present one-body theory cannot explain the average longitudinal asymmetry found in the recent polarized neutron experiments. We also confirm the discrepancy, first pointed out by Auerbach and Bowman, that emerges, between the calculated average asymmetry and the parity violating spreading width, when distant doorways are used in the theory.Comment: 37 pages, REVTEX, 5 figures not included (Postscript, available from the authors

Propagation front of correlations in an interacting Bose gas

We analyze the quench dynamics of a one-dimensional bosonic Mott insulator and focus on the time evolution of density correlations. For these we identify a pronounced propagation front, the velocity of which, once correctly extrapolated at large distances, can serve as a quantitative characteristic of the many-body Hamiltonian. In particular, the velocity allows the weakly interacting regime, which is qualitatively well described by free bosons, to be distinguished from the strongly interacting one, in which pairs of distinct quasiparticles dominate the dynamics. In order to describe the latter case analytically, we introduce a general approximation to solve the Bose-Hubbard Hamiltonian based on the Jordan-Wigner fermionization of auxiliary particles. This approach can also be used to determine the ground-state properties. As a complement to the fermionization approach, we derive explicitly the time-dependent many-body state in the noninteracting limit and compare our results to numerical simulations in the whole range of interactions of the Bose-Hubbard model.Comment: 16 pages, 7 figure

Towards a strong-coupling theory of QCD at finite density

We apply strong-coupling perturbation theory to the QCD lattice Hamiltonian. We begin with naive, nearest-neighbor fermions and subsequently break the doubling symmetry with next-nearest-neighbor terms. The effective Hamiltonian is that of an antiferromagnet with an added kinetic term for baryonic "impurities," reminiscent of the t-J model of high-T_c superconductivity. As a first step, we fix the locations of the baryons and make them static. Following analyses of the t-J model, we apply large-N methods to obtain a phase diagram in the (N_c,N_f) plane at zero temperature and baryon density. Next we study a simplified U(3) toy model, in which we add baryons to the vacuum. We use a coherent state formalism to write a path integral which we analyze with mean field theory, obtaining a phase diagram in the (n_B,T) plane.Comment: Lattice2002(nonzerot) - Parallel talk and poster presented at Lattice 2002, Cambridge, MA, USA, June 2002. 6 pages, 6 EPS figure

Power laws, Pareto distributions and Zipf's law

When the probability of measuring a particular value of some quantity varies inversely as a power of that value, the quantity is said to follow a power law, also known variously as Zipf's law or the Pareto distribution. Power laws appear widely in physics, biology, earth and planetary sciences, economics and finance, computer science, demography and the social sciences. For instance, the distributions of the sizes of cities, earthquakes, solar flares, moon craters, wars and people's personal fortunes all appear to follow power laws. The origin of power-law behaviour has been a topic of debate in the scientific community for more than a century. Here we review some of the empirical evidence for the existence of power-law forms and the theories proposed to explain them.Comment: 28 pages, 16 figures, minor corrections and additions in this versio

Mid-IR continuous-wave fiber-laser-pumped optical parametric oscillators

We review recent developments in continuous-wave mid-infrared optical parametric oscillators pumped by fiber lasers. Such devices are potentially valuable spectroscopic sources providing high output powers and rapid, wide-range tuning in the mid-infrared molecular fingerprint region

Fine Structure Discussion of Parity-Nonconserving Neutron Scattering at Epithermal Energies

The large magnitude and the sign correlation effect in the parity non-conserving resonant scattering of epithermal neutrons from $^{232}$Th is discussed in terms of a non-collective $2p-1h$ local doorway model. General conclusions are drawn as to the probability of finding large parity violation effects in other regions of the periodic table.Comment: 6 pages, Tex. CTP# 2296, to appear in Z. Phys.