Intense terahertz laser fields on a two-dimensional electron gas with Rashba spin-orbit coupling

The spin-dependent density of states and the density of spin polarization of an InAs-based two-dimensional electron gas with the Rashba spin-orbit coupling under an intense terahertz laser field are investigated by utilizing the Floquet states to solve the time-dependent Schr\"odinger equation. It is found that both densities are strongly affected by the terahertz laser field. Especially a terahertz magnetic moment perpendicular to the external terahertz laser field in the electron gas is induced. This effect can be used to convert terahertz electric signals into terahertz magnetic ones efficiently.Comment: 3 pages, 3 figures, a typo in Fig. 3(b) is correcte

Family Structure, Early Sexual Behavior, and Premarital Births

In this paper, we argue that entry into first sexual intercourse is a key process mediating the effects of family structure on premarital childbearing. We explicate three ways in which onset of sexual activity can mediate effects of family structure on premarital first births. First, the gross association between family structure and premarital birth risks may be due entirely to the effect of family structure on age at first intercourse. Second, the earlier the age at first intercourse, the longer the duration of exposure to the risk of a premarital first birth. Third, an early age at first intercourse may proxy unmeasured individual characteristics correlated with age at onset but uncorrelated with other variables in the model. We develop methods to assess such mediating effects and analyze data from two sources, the 1979-93 National Longitudinal Survey of Youth and the 1988 National Survey of Family Growth. We find that age at first intercourse partially mediates the effect on premarital birth risks of both snapshot measures of family structure at age 14 and a time-varying measure of the number of family transitions, but that significant effects of these variables remain net of age at first intercourse. Delaying age at intercourse by one year reduces the cumulative relative risk of a premarital first birth by a similar amount for both white and black women. For black women, the magnitude of this effect is roughly the same as that of residing in a mother-only family at age 14.

Two Higgs Bi-doublet Left-Right Model With Spontaneous P and CP Violation

A left-right symmetric model with two Higgs bi-doublet is shown to be a consistent model for both spontaneous P and CP violation. The flavor changing neutral currents can be suppressed by the mechanism of approximate global U(1) family symmetry. We calculate the constraints from neural $K$ meson mass difference $\Delta m_K$ and demonstrate that a right-handed gauge boson $W_2$ contribution in box-diagrams with mass well below 1 TeV is allowed due to a cancellation caused by a light charged Higgs boson with a mass range $150 \sim 300$ GeV. The $W_2$ contribution to $\epsilon_K$ can be suppressed from appropriate choice of additional CP phases appearing in the right-handed Cabbibo-Kobayashi-Maskawa matrix. The model is also found to be fully consistent with $B^0$ mass difference $\Delta m_B$, and the mixing-induced CP violation quantity $\sin2\beta_{J/\psi}$, which is usually difficult for the model with only one Higgs bi-doublet. The new physics beyond the standard model can be directly searched at the colliders LHC and ILC.Comment: 25 pages, 6 figures, typos corrected, 1 figure added, published versio

Division and the Giambelli Identity

Given two polynomials f(x) and g(x), we extend the formula expressing the remainder in terms of the roots of these two polynomials to the case where f(x) is a Laurent polynomial. This allows us to give new expressions of a Schur function, which generalize the Giambelli identity.Comment: 9 pages, 1 figur