26,392 research outputs found
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 in the left-right twin Higgs model, we choose to give up
the lightest neutral particle of field as a stable dark matter
candidate. Then a new Yukawa interaction for is allowed, which can be
free from the constraint of same-sign top pair production and contribute
sizably to . Considering the constraints from the production rates of
the top pair (), the top decay rates and invariant mass
distribution, we find that this model with such new Yukawa interaction can
explain measured at the Tevatron while satisfying the charge
asymmetry measured at the LHC.Moreover, this model predicts a
strongly correlation between at the LHC and at the
Tevatron, i.e., increases as 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
- …