Fast CP Violation

$B$ flavor tagging will be extensively studied at the asymmetric $B$ factories due to its importance in CP asymmetry measurements. The primary tagging modes are the semileptonic decays of the $b$ (lepton tag), or the hadronic $b \to c (\to s)$ decays (kaon tag). We suggest that looking for time dependent CP asymmetries in events where one $B$ is tagged leptonically and the other one is tagged with a kaon could result in an early detection of CP violation. Although in the Standard Model these asymmetries are expected to be small, $\sim 1$, they could be measured with about the same amount of data as in the ``gold-plated'' decay $B_d \to \psi K_S$. In the presence of physics beyond the Standard Model, these asymmetries could be as large as $\sim 5$, and the first CP violation signal in the $B$ system may show up in these events. We give explicit examples of new physics scenarios where this occurs.Comment: 9 pages, revtex, no figures. Discussion of new physics effects on CP violation with two lepton tags expanded. Factors of 2 correcte

CP Asymmetry in B_d --> phi K_S: Standard Model Pollution

The difference in the time dependent CP asymmetries between the modes $B --> psi K_S$ and $B --> phi K_S$ is a clean signal for physics beyond the Standard Model. This interpretation could fail if there is a large enhancement of the matrix element of the $b --> u ubar s$ operator between the $B_d$ initial state and the $phi K_S$ final state. We argue against this possibility and propose some experimental tests that could shed light on the situation.Comment: 9 pages, Revte

N-body decomposition of bipartite networks

In this paper, we present a method to project co-authorship networks, that accounts in detail for the geometrical structure of scientists collaborations. By restricting the scope to 3-body interactions, we focus on the number of triangles in the system, and show the importance of multi-scientists (more than 2) collaborations in the social network. This motivates the introduction of generalized networks, where basic connections are not binary, but involve arbitrary number of components. We focus on the 3-body case, and study numerically the percolation transition.Comment: 5 pages, submitted to PR

Fractal dimensions of the Q-state Potts model for the complete and external hulls

Fortuin-Kastelyn clusters in the critical $Q$-state Potts model are conformally invariant fractals. We obtain simulation results for the fractal dimension of the complete and external (accessible) hulls for Q=1, 2, 3, and 4, on clusters that wrap around a cylindrical system. We find excellent agreement between these results and theoretical predictions. We also obtain the probability distributions of the hull lengths and maximal heights of the clusters in this geometry and provide a conjecture for their form.Comment: 9 pages 4 figure

Constraining the CKM Parameters using CP Violation in semi-leptonic B Decays

We discuss the usefulness of the CP violating semi-leptonic asymmetry a_{SL} not only as a signal of new physics, but also as a tool in constraining the CKM parameters. We show that this technique could yield useful results in the first years of running at the B factories. We present the analysis graphically in terms of M_{12}, the dispersive part of the B-Bbar mixing amplitude. This is complementary to the usual unitarity triangle representation and often allows a cleaner interpretation of the data.Comment: 15 pages REVTEX, 7 figure

The Dynamics of Two Coupled Rigid Bodies

In this paper we derive a Poisson bracket on the phase space so(3)^*x so(3)^*x SO(3) such that the dynamics of two three- dimensional rigid bodies coupled by a ball and socket joint can be written as a Hamiltonian system

Confined Harmonically Interacting Spin-Polarized Fermions in a Magnetic Field: Thermodynamics

We investigate the combined influence of a magnetic field and a harmonic interparticle interaction on the thermodynamic properties of a finite number of spin polarized fermions in a confiment potential. This study is an extension using our path integral approach of symmetrized density matrices for identical particles. The thermodynamical properties are calculated for a three dimensional model of N harmonically interacting spin polarized fermions in a parabolic potential well in the presence of a magnetic field. The free energy and the internal energy are obtained for a limited number of particles. Deviations from the thermodynamical limit become negligible for about 100 or more particles, but even for a smaller number of fermions present in the well, scaling relations similar to those of the continuum approximation to the density of states are already satisfied.Comment: 7 pages REVTEX and 8 postscript figures, accepted in Phys. Rev.

Density and Pair Correlation Function of Confined Identical Particles: the Bose-Einstein Case

Two basic correlation functions are calculated for a model of $N$ harmonically interacting identical particles in a parabolic potential well. The density and the pair correlation function of the model are investigated for the boson case. The dependence of these static response properties on the complete range of the temperature and of the number of particles is obtained. The calculation technique is based on the path integral approach of symmetrized density matrices for identical particles in a parabolic confining well.Comment: 8 pages (REVTEX) + 6 figures (postscript

Marijuana and Youth

This paper contains the first estimates of the price sensitivity of the prevalence of youth marijuana use. Survey data on marijuana use by high school seniors from the Monitoring the Future Project are combined with data on marijuana prices and potency from the Drug Enforcement Administration Office of Intelligence or Intelligence Division. Our estimates of the price elasticity of annual marijuana participation range from 0.06 to 0.47, while those for thirty day participation range from 0.002 to 0.69. These estimates clearly imply that changes in the real, quality adjusted price of marijuana contributed significantly to the trends in youth marijuana use between 1982 and 1998, particularly during the contraction in use from 1982 to 1992. Similarly, changes in youth perceptions of the harms associated with regular marijuana use had a substantial impact on both the contraction in use during the 1982 though 1992 period and the subsequent expansion in use after 1992. These findings underscore the usefulness of considering price in addition to more traditional determinants in any analysis of marijuana consumption decisions made by youths.

Optimization of robustness of scale-free network to random and targeted attacks

The scale-fee networks, having connectivity distribution $P(k)\sim k^{-\alpha}$ (where $k$ is the site connectivity), is very resilient to random failures but fragile to intentional attack. The purpose of this paper is to find the network design guideline which can make the robustness of the network to both random failures and intentional attack maximum while keeping the average connectivity per node constant. We find that when $=3$ the robustness of the scale-free networks reach its maximum value if the minimal connectivity $m=1$, but when is larger than four, the networks will become more robust to random failures and targeted attacks as the minimal connectivity $m$ gets larger