Role of Self-Interaction Effects in the Geometry Optimization of Small Metal Clusters

By combining the Self-Interaction Correction (SIC) with pseudopotential perturbation theory, the role of self-interaction errors inherent to the Local Density Approximation (LDA) to Density Functional Theory is estimated in the determination of ground state and low energy isomeric structures of small metallic clusters. Its application to neutral sodium clusters with 8 and 20 atoms shows that the SIC provides sizeable effects in Na_8, leading to a different ordering of the low lying isomeric states compared with ab-initio LDA predictions, whereas for Na_20, the SIC effects are less pronounced, such that a quantitative agreement is achieved between the present method and ab-initio LDA calculations.Comment: RevTeX, 4 pages, 1 figure available from [email protected]

Border Security: A Comprehensive Review of the United States’ Approach to Southwest Border Policy

This paper addresses the effect that the presence of a physical border wall on the southern United States-Mexico border has on deterring unauthorized immigration, illegal drug-trafficking, and countering narco-terrorism. While current techniques and legislation have intended to secure major crossing locations, they have resulted in a redistribution of border route traffic putting more immigrants in fatal danger and increasing demand for coyotes, or human trafficking guides. Not only have the government and media created a public perception of fear in its efforts to protect the homeland through national security, but there have also been negative effects on people on both sides of the border in the process. The impact of political-economic factors of border security and its ties to foreign policy will be considered as well as the relevance of drug violence and immigration perspectives in creating legislation. This paper will seek to describe a more comprehensive and contemporary border policy that utilizes technology and more inclusive policy while still upholding prevention of danger on America’s homeland

Lorentz invariance for mixed neutrinos

We show that a proper field theoretical treatment of mixed (Dirac) neutrinos leads to non-trivial dispersion relations for the flavor states. We analyze such a situation in the framework of the non-linear relativity schemes recently proposed by Magueijo and Smolin. We finally examine the experimental implications of our theoretical proposals by considering the spectrum and the end-point of beta decay in tritium.Comment: 8 pages, 4 figures. Presented at 2nd International Workshop DICE2004: From Decoherence and Emergent Classicality to Emergent Quantum Mechanics, Castello di Piombino, Tuscany, Italy, 1-4 Sep 200

Persistent current magnification in a double quantum-ring system

The electronic transport in a system of two quantum rings side-coupled to a quantum wire is studied via a single-band tunneling tight-binding Hamiltonian. We derived analytical expressions for the conductance, density of states and the persistent current when the rings are threaded by magnetic fluxes. We found a clear manifestation of the presence of bound states in each one of those physical quantities when either the flux difference or the sum of the fluxes are zero or integer multiples of a quantum of flux. These bound states play an important role in the magnification of the persistent current in the rings. We also found that the persistent current keeps a large amplitude even for strong ring-wire coupling.Comment: 15 pages, 10 figures. Submitted to PR

New housing supply: what do we know and how can we learn more?

This paper reviews the literature on new housing supply. The paper starts by summarizing the results of the empirical studies on housing supply, showing that overall these studies reject the hypothesis of a perfectly elastic housing supply and reveal that housing supply is negatively related with financial costs, inflation and sales delay while showing inconclusive results with respect to the construction costs. In addition, we review a recent branch of the literature on housing supply that uses strategic interaction models. There is evidence that the housing market is not well described by the perfect competition model. Thus, a deeper understanding of housing supply can be achieved by considering theoretical models that take into account the strategic interaction between land developers and by using data where the unit of analysis is the land developer.Housing supply; price elasticity of supply, strategic interaction.