Interplay between spin-density-wave and superconducting states in quasi-one-dimensional conductors

The interference between spin-density-wave and superconducting instabilities in quasi-one-dimensional correlated metals is analyzed using the renormalization group method. At the one-loop level, we show how the interference leads to a continuous crossover from a spin-density-wave state to unconventional superconductivity when deviations from perfect nesting of the Fermi surface exceed a critical value. Singlet pairing between electrons on neighboring stacks is found to be the most favorable symmetry for superconductivity. The consequences of non uniform spin-density-wave pairing on the structure of phase diagram within the crossover region is also discussed.Comment: 10 pages RevTex,4 Figures, submitted to EPJ

Making water policy and water laws democratic: lessons from South Indian states

The present attempt is to propose local people’s involvement in Water Policy and Water Law formulation in Indian sub continent on the growing realization that policies and laws the state governments have so far either visualized or implemented seems remain paper tigers. It examines the existing water laws and its implementation from 3 south Indian states viz., Kerala, Karnataka and Tamil Nadu for this purpose. Analysis shows that water laws mainly are centered on participatory irrigation management and water user associations. Groundwater laws are given lowest emphasis by the state governments where as majority of the Indian population depends upon it especially for domestic use. Indiscriminate sand mining is seen an emerging threat for river hydrological system that has accentuated by income tax rebates and gaps of housing policies. It indicates that the entire process of evolving water policy and laws is devoid of its stakeholders’ participation particularly from the grassroots level. Institutional framework to facilitate local people’s participation like Gram Sabha and Panchayati Raj Institutions are grossly underutilised for this purpose. On this background it examines the recent attempt of Kerala government in facilitating stakeholders’ participation in law formulation in water related Bill, called The Kerala Conservation of Paddy Fields and Wetlands Bill 2007.Length: pp.708-719Water policyWater lawLegislationStakeholders

Immigration Reform and the Earnings of Latino Workers: Do Employer Sanctions Cause Discrimination?

This paper investigates whether employer sanctions for hiring undocumented workers introduced by the 1986 Immigration Reform and Control Act (IRCA) adversely affected the hourly earnings of Latino workers in the southwestern United States. We exploit the staggering of the sanctions and employee verification requirements across sectors to estimate this effect. In particular, IRCA’s employer-sanctions provisions were not extended to agricultural employers until 2 years after their imposition on nonagricultural employers. Hence, Latino agricultural workers provide a control group against which to compare changes in the wages of Latinos in nonagricultural employment. We find substantial pre-post IRCA declines in the hourly earnings of Latino nonagricultural workers relative to Latinos in agriculture. This pattern, however, is considerably stronger for Latino men than Latina women. We do not observe similar intersectoral shifts in relative wages among non-Latino white workers. In fact, the relative wage changes for non-Latino white workers are of the opposite sign. Finally, the pre-post IRCA relative decline in Latino nonagricultural wages reverses the pre-IRCA trend in which the relative earnings of Latino nonagricultural workers had been increasing.

Unbounded entropy in spacetimes with positive cosmological constant

In theories of gravity with a positive cosmological constant, we consider product solutions with flux, of the form (A)dS_p x S^q. Most solutions are shown to be perturbatively unstable, including all uncharged dS_p x S^q spacetimes. For dimensions greater than four, the stable class includes universes whose entropy exceeds that of de Sitter space, in violation of the conjectured "N-bound". Hence, if quantum gravity theories with finite-dimensional Hilbert space exist, the specification of a positive cosmological constant will not suffice to characterize the class of spacetimes they describe.Comment: 25 pages; v2: references adde

Predictions from Star Formation in the Multiverse

We compute trivariate probability distributions in the landscape, scanning simultaneously over the cosmological constant, the primordial density contrast, and spatial curvature. We consider two different measures for regulating the divergences of eternal inflation, and three different models for observers. In one model, observers are assumed to arise in proportion to the entropy produced by stars; in the others, they arise at a fixed time (5 or 10 billion years) after star formation. The star formation rate, which underlies all our observer models, depends sensitively on the three scanning parameters. We employ a recently developed model of star formation in the multiverse, a considerable refinement over previous treatments of the astrophysical and cosmological properties of different pocket universes. For each combination of observer model and measure, we display all single and bivariate probability distributions, both with the remaining parameter(s) held fixed, and marginalized. Our results depend only weakly on the observer model but more strongly on the measure. Using the causal diamond measure, the observed parameter values (or bounds) lie within the central $2\sigma$ of nearly all probability distributions we compute, and always within $3\sigma$. This success is encouraging and rather nontrivial, considering the large size and dimension of the parameter space. The causal patch measure gives similar results as long as curvature is negligible. If curvature dominates, the causal patch leads to a novel runaway: it prefers a negative value of the cosmological constant, with the smallest magnitude available in the landscape.Comment: 68 pages, 19 figure

Revisiting Actor Programming in C++

The actor model of computation has gained significant popularity over the last decade. Its high level of abstraction makes it appealing for concurrent applications in parallel and distributed systems. However, designing a real-world actor framework that subsumes full scalability, strong reliability, and high resource efficiency requires many conceptual and algorithmic additives to the original model. In this paper, we report on designing and building CAF, the "C++ Actor Framework". CAF targets at providing a concurrent and distributed native environment for scaling up to very large, high-performance applications, and equally well down to small constrained systems. We present the key specifications and design concepts---in particular a message-transparent architecture, type-safe message interfaces, and pattern matching facilities---that make native actors a viable approach for many robust, elastic, and highly distributed developments. We demonstrate the feasibility of CAF in three scenarios: first for elastic, upscaling environments, second for including heterogeneous hardware like GPGPUs, and third for distributed runtime systems. Extensive performance evaluations indicate ideal runtime behaviour for up to 64 cores at very low memory footprint, or in the presence of GPUs. In these tests, CAF continuously outperforms the competing actor environments Erlang, Charm++, SalsaLite, Scala, ActorFoundry, and even the OpenMPI.Comment: 33 page