Opportunistic Interference Management for Multicarrier systems

We study opportunistic interference management when there is bursty interference in parallel 2-user linear deterministic interference channels. A degraded message set communication problem is formulated to exploit the burstiness of interference in M subcarriers allocated to each user. We focus on symmetric rate requirements based on the number of interfered subcarriers rather than the exact set of interfered subcarriers. Inner bounds are obtained using erasure coding, signal-scale alignment and Han-Kobayashi coding strategy. Tight outer bounds for a variety of regimes are obtained using the El Gamal-Costa injective interference channel bounds and a sliding window subset entropy inequality. The result demonstrates an application of techniques from multilevel diversity coding to interference channels. We also conjecture outer bounds indicating the sub-optimality of erasure coding across subcarriers in certain regimes.Comment: 8 pages, 5 figures, a shorter version of this work will appear in the proceedings of ISIT 201

Harnessing Bursty Interference in Multicarrier Systems with Feedback

We study parallel symmetric 2-user interference channels when the interference is bursty and feedback is available from the respective receivers. Presence of interference in each subcarrier is modeled as a memoryless Bernoulli random state. The states across subcarriers are drawn from an arbitrary joint distribution with the same marginal probability for each subcarrier and instantiated i.i.d. over time. For the linear deterministic setup, we give a complete characterization of the capacity region. For the setup with Gaussian noise, we give outer bounds and a tight generalized degrees of freedom characterization. We propose a novel helping mechanism which enables subcarriers in very strong interference regime to help in recovering interfered signals for subcarriers in strong and weak interference regimes. Depending on the interference and burstiness regime, the inner bounds either employ the proposed helping mechanism to code across subcarriers or treat the subcarriers separately. The outer bounds demonstrate a connection to a subset entropy inequality by Madiman and Tetali.Comment: A shorter version of this work will appear in the proceedings of ISIT 201

Vacuum structure and effective potential at finite temperature: a variational approach

We compute the effective potential for $\phi^4$ theory with a squeezed coherent state type of construct for the ground state. The method essentially consists in optimising the basis at zero and finite temperatures. The gap equation becomes identical to resumming the infinite series of daisy and super daisy graphs while the effective potential includes multiloop effects and agrees with that obtained through composite operator formalism at finite temperature.Comment: 15 pages, Revtex, No figures, to appear in Jou. of Phys.G(Nucl. and Part. Phys.

Theory of thermal conductivity in extended-ss state superconductors: application to ferropnictides

Within a two-band model for the recently discovered ferropnictide materials, we calculate the thermal conductivity assuming general superconducting states of $A_{1g}$ ("s-wave") symmetry, considering both currently popular isotropic "sign-changing" $s$ states and states with strong anisotropy, including those which manifest nodes or deep minima of the order parameter. We consider both intra- and interband disorder scattering effects, and show that in situations where a low-temperature linear-$T$ exists in the thermal conductivity, it is not always "universal" as in d-wave superconductors. We discuss the conditions under which such a term can disappear, as well as how it can be induced by a magnetic field. We compare our results to several recent experiments.Comment: 13 page

Determinants of Meats Purchase Behavior by Ethnic Groups

Farmers and food companies need to assess their production and marketing strategies for nurturing business opportunities that will arise from the simultaneous increase in population and income of Hispanics in the United States. Previous studies on demand for meat products have not received much attention on the determinants of meats purchase behavior by Hispanics in relation to other ethnic groups. This study investigates the impact of ethnicity and the determinants of meats purchase behavior in the U.S. by using single Probit equations. The analyzed data comes from the U.S. Consumer Expenditure Survey. The results indicate that ethnicity plays an important role in the purchase behavior of meat products, as well as household size and income.consumer behavior, marketing, food demand, Hispanic food, hispanic food market, Latin foods, comida latina, alimentos, ethnic foods, Agribusiness, Consumer/Household Economics, Demand and Price Analysis, Food Consumption/Nutrition/Food Safety, Industrial Organization, Marketing, D01, D03, D12, L14, L66, M31, M37,

The Effects of Public Debt on Labor Demand in the United States

The relationship between appreciation of the exchange rate and employment is investigated in the period 1980-2008 for the United States. Previous literature has found a negative relationship, studying as channels of transmission the role of exports, substitution of factors of production, terms of trade, openness, and productivity. This study endeavors to shed some light on the role of government debt on determining the level of employment through the exchange rate. The mechanism of transmission is defined. The model is derived from a standard Cobb Douglas production function having government debt affecting the growth of productivity. Exchange rate appreciations and increasing public debt were found to be detrimental to employment.Unemployment rate, government, budget deficit, exchange rate, trade deficit, FDI, Financial Economics, International Development, Labor and Human Capital, Political Economy, Public Economics, F31, J01, E24, E62,

Spin Polarization via Electron Tunneling through an Indirect-Gap Semiconductor Barrier

We study the spin dependent tunneling of electrons through a zinc-blende semiconductor with the indirect X (or D) minimum serving as the tunneling barrier. The basic difference between tunneling through the G vs. the X barrier is the linear-k spin-orbit splitting of the two spin bands at the X point, as opposed to the k3 Dresselhaus splitting at the G point. The linear coefficient of the spin splitting b at the X point is computed for several semiconductors using density-functional theory and the transport characteristics are calculated using the barrier tunneling model. We show that both the transmission coefficient as well as the spin polarization can be large, suggesting the potential application of these materials as spin filters.Comment: 9 page