Chromomagnetic instability in dense quark matter

The results for the Debye and Meissner screening masses of the gluons and the photon in the case of neutral and beta-equilibrated dense two-flavor quark matter are presented. In the limits of the normal phase and the ideal two-flavor color superconducting phase, the screening masses coincide with the known results. Most interestingly, we find that the Meissner screening masses squared can be negative, indicating a plasma-type chromomagnetic instability in dense quark matter.Comment: 5 pages and 2 figures. To appear in Phys. Rev. D; version slightly shortened on request of editor

The gapless 2SC phase

Recent results on the gapless 2SC phase are reviewed. These include: the thermal stability under the constraint of the local charge neutrality condition, the properties at zero and nonzero temperatures, and the color screening properties.Comment: To appear in the proceedings of 6th Conference on Strong and Electroweak Matter 2004 (SEWM04), Helsinki, Finland, 16-19 Jun 2004. Typos correcte

Threshold Regression for Survival Analysis: Modeling Event Times by a Stochastic Process Reaching a Boundary

Many researchers have investigated first hitting times as models for survival data. First hitting times arise naturally in many types of stochastic processes, ranging from Wiener processes to Markov chains. In a survival context, the state of the underlying process represents the strength of an item or the health of an individual. The item fails or the individual experiences a clinical endpoint when the process reaches an adverse threshold state for the first time. The time scale can be calendar time or some other operational measure of degradation or disease progression. In many applications, the process is latent (i.e., unobservable). Threshold regression refers to first-hitting-time models with regression structures that accommodate covariate data. The parameters of the process, threshold state and time scale may depend on the covariates. This paper reviews aspects of this topic and discusses fruitful avenues for future research.Comment: Published at http://dx.doi.org/10.1214/088342306000000330 in the Statistical Science (http://www.imstat.org/sts/) by the Institute of Mathematical Statistics (http://www.imstat.org

Replica study of pinned bubble crystals

In higher Landau levels ($N>1$), the ground state of the two-dimensional electron gas in a strong perpendicular magnetic field evolves from a Wigner crystal for small filling $\nu$ of the partially filled Landau level, into a succession of bubble states with increasing number of guiding centers per bubble as $\nu$ increases, to a modulated stripe state near $\nu =0.5$. In this work, we compute the frequency-dependent longitudinal conductivity $\sigma_{xx}(\omega)$ of the Wigner and bubble crystal states in the presence of disorder. We apply an elastic theory to the crystal states which is characterized by a shear and a bulk modulus. We obtain both moduli from the microscopic time-dependent Hartree-Fock approximation. We then use the replica and Gaussian variational methods to handle the effects of disorder. Within the semiclassical approximation we get the dynamical conductivity as well as the pinning frequency as functions of the Landau level filling factor and compare our results with recent microwave experiments.Comment: 19 pages and 6 eps figure

Specialty Crops and the 2007 Farm Bill: The Potential Role of Farm Savings Accounts

This paper discusses the findings of a research project that examined the potential benefits of establishing farm savings accounts for specialty crop growers1. The primary goal of the project was to determine whether farm savings accounts would provide specialty crop growers with a useful tool for managing financial risk. The project examined how various farm savings account proposals ultimately impacted the benefits that specialty crop growers would receive from the accounts.Agricultural Finance, Crop Production/Industries,

The Paradox of Risk Balancing: Do Risk-reducing Policies Lead to More Risk for Farmers?

The study presents stochastic optimal control/dynamic programming (SOC/DP) to derive the optimal debt level and consumption in farm models concerning two sources of uncertainty: the return on assets and interest rate. The SOC/DP analytic framework is used to analyze the impacts of risk-reducing farm policies on farm’s financial and risk adjustments. The results show the violations of the risk-balancing concept, which theorizes that risk-reducing farm policies may lead to increases in financial leverage, total risk, and the expected returns. Also, this study examines the extent to which the estimates of the optimal debt level are biased when interest rate risk is ignored.Stochastic Optimal Control/Dynamic Programming, Financial Leverage, Uncertainty, Risk Balancing, Agricultural and Food Policy, Risk and Uncertainty,

Vacuum Interpretation for Supergravity M-Branes

A non-local classical duality between the three-block truncated 11D supergravity and the 8D vacuum gravity with two commuting Killing symmetries is established. The supergravity four-form field is generated via an inverse dualisation of the corresponding Killing two-forms in six dimensions. 11D supersymmetry condition is shown to be equivalent to existence of covariantly constant spinors in eight dimensions. Thus any solution to the vacuum Einstein equations in eight dimensions depending on six coordinates and admitting Killing spinors have supersymmetric 11D-supergravity counterparts. Using this duality we derive some new brane solutions to 11D-supergravity including 1/4 supersymmetric intersecting M-branes with a NUT parameter and a dyon solution joining the M2 and M5-branes intersecting at a point.Comment: 4 pages, latex, no figure