Temperature effects on microwave-induced resistivity oscillations and zero resistance states in 2D electron systems

In this work we address theoretically a key issue concerning microwave-induced longitudinal resistivity oscillations and zero resistance states, as is tempoerature. In order to explain the strong temperature dependence of the longitudinal resistivity and the thermally activated transport in 2DEG, we have developed a microscopic model based on the damping suffered by the microwave-driven electronic orbit dynamics by interactions with the lattice ions yielding acoustic phonons. Recent experimental results show a reduction in the amplitude of the longitudinal resistivity oscillations and a breakdown of zero resistance states as the radiation intensity increases. In order to explain it we have included in our model the electron heating due to large microwave intensities and its effect on the longitudinal resistivity.Comment: 4 pages and 4 figures. Accepted in Phys Rev

Top quark forward-backward asymmetry and charge asymmetry in left-right twin Higgs model

In order to explain the Tevatron anomaly of the top quark forward-backward asymmetry $A_{FB}^t$ in the left-right twin Higgs model, we choose to give up the lightest neutral particle of $\hat{h}$ field as a stable dark matter candidate. Then a new Yukawa interaction for $\hat{h}$ is allowed, which can be free from the constraint of same-sign top pair production and contribute sizably to $A_{FB}^t$. Considering the constraints from the production rates of the top pair ($t\bar t$), the top decay rates and $t\bar{t}$ invariant mass distribution, we find that this model with such new Yukawa interaction can explain $A_{FB}^t$ measured at the Tevatron while satisfying the charge asymmetry $A_{C}^t$ measured at the LHC.Moreover, this model predicts a strongly correlation between $A_{C}^t$ at the LHC and $A_{FB}^t$ at the Tevatron, i.e., $A_{C}^t$ increases as $A_{FB}^t$ increases.Comment: 17 pages, 9 figures; matches the published versio

Post-purchase Counseling and Default Resolutions among Low- and Moderate-Income Borrowers

The rise of delinquencies and foreclosures in a softening housing market calls for systematic studies of default behavior and efforts to minimize the default risks. Using a sample of residential mortgages made to low- to moderate-income borrowers, this paper empirically examines the impact of a proactive post-purchase counseling service on moderately delinquent mortgages. It demonstrates that well-timed, situation-appropriate counseling, even over the phone, effectively increases the curing probability of delinquent borrowers. The findings hold even after accounting for unobserved heterogeneity among borrowers and the endogeneity problem. Many other factors, such as home equity, local economic conditions, and borrower and loan characteristics, also impact the transition of delinquencies.

Neighborhood Subprime Lending and the Performance of Community Reinvestment Mortgages

This study analyzes the spillover effect of the spatial concentration of subprime lending on the performance of recently originated community reinvestment mortgages targeting low- to moderate-income borrowers. The level of subprime lending in a census tract is found to be a significant predictor of the default and prepayment probability of the community reinvestment loans in the same neighborhoods. The results suggest that the concentration of subprime lending and the resulting clusters of foreclosed properties reduce neighborhood property values and increase price volatility. The lowered property values and the increased volatility increase the default probability of borrowers holding any loan product, including community reinvestment mortgages. This study provides new evidence concerning the negative impacts of the concentration of subprime lending in certain neighborhoods.

Spherical to deformed shape transition in the nucleon-pair shell model

A study of the shape transition from spherical to axially deformed nuclei in the even Ce isotopes using the nucleon-pair approximation of the shell model is reported. As long as the structure of the dominant collective pairs is determined using a microscopic framework appropriate to deformed nuclei, the model is able to produce a shape transition. However, the resulting transition is too rapid, with nuclei that should be transitional being fairly well deformed, perhaps reflecting the need to maintain several pairs with each angular momentum.Comment: 7 pages, 5 figure