Spectral modeling of type II supernovae. I. Dilution factors

We present substantial extensions to the Monte Carlo radiative transfer code TARDIS to perform spectral synthesis for type II supernovae. By incorporating a non-LTE ionization and excitation treatment for hydrogen, a full account of free-free and bound-free processes, a self-consistent determination of the thermal state and by improving the handling of relativistic effects, the improved code version includes the necessary physics to perform spectral synthesis for type II supernovae to high precision as required for the reliable inference of supernova properties. We demonstrate the capabilities of the extended version of TARDIS by calculating synthetic spectra for the prototypical type II supernova SN1999em and by deriving a new and independent set of dilution factors for the expanding photosphere method. We have investigated in detail the dependence of the dilution factors on photospheric properties and, for the first time, on changes in metallicity. We also compare our results with two previously published sets of dilution factors by Eastman et al. (1996) and by Dessart & Hillier (2005), and discuss the potential sources of the discrepancies between studies.Comment: 16 pages, 12 figures, 2 tables, accepted for publication in A&

Spin-orientation-dependent spatial structure of a magnetic acceptor state in a zincblende semiconductor

The spin orientation of a magnetic dopant in a zincblende semiconductor strongly influences the spatial structure of an acceptor state bound to the dopant. The acceptor state has a roughly oblate shape with the short axis aligned with the dopant's core spin. For a Mn dopant in GaAs the local density of states at a site 8 angstrom away from the dopant can change by as much by 90% when the Mn spin orientation changes. These changes in the local density of states could be probed by scanning tunneling microscopy to infer the magnetic dopant's spin orientation.Comment: 5 pages, 4 figure

Triplet-singlet relaxation in semiconductor single and double quantum dots

We study the triplet-singlet relaxation in two-electron semiconductor quantum dots. Both single dots and vertically coupled double dots are discussed. In our work, the electron-electron Coulomb interaction, which plays an important role in the electronic structure, is included. The spin mixing is caused by spin-orbit coupling which is the key to the triplet-singlet relaxation. We show that the selection rule widely used in the literature is incorrect unless near the crossing/anticrossing point in single quantum dots. The triplet/singlet relaxation in double quantum dots can be markedly changed by varying barrier height, inter-dot distance, external magnetic field and dot size.Comment: 7 pages, 4 figures, PRB in pres

Theory of excitons in cubic III-V semiconductor GaAs, InAs and GaN quantum dots: fine structure and spin relaxation

Exciton fine structures in cubic III-V semiconductor GaAs, InAs and GaN quantum dots are investigated systematically and the exciton spin relaxation in GaN quantum dots is calculated by first setting up the effective exciton Hamiltonian. The electron-hole exchange interaction Hamiltonian, which consists of the long- and short-range parts, is derived within the effective-mass approximation by taking into account the conduction, heavy- and light-hole bands, and especially the split-off band. The scheme applied in this work allows the description of excitons in both the strong and weak confinement regimes. The importance of treating the direct electron-hole Coulomb interaction unperturbatively is demonstrated. We show in our calculation that the light-hole and split-off bands are negligible when considering the exciton fine structure, even for GaN quantum dots, and the short-range exchange interaction is irrelevant when considering the optically active doublet splitting. We point out that the long-range exchange interaction, which is neglected in many previous works, contributes to the energy splitting between the bright and dark states, together with the short-range exchange interaction. Strong dependence of the optically active doublet splitting on the anisotropy of dot shape is reported. Large doublet splittings up to 600 $\mu$eV, and even up to several meV for small dot size with large anisotropy, is shown in GaN quantum dots. The spin relaxation between the lowest two optically active exciton states in GaN quantum dots is calculated, showing a strong dependence on the dot anisotropy. Long exciton spin relaxation time is reported in GaN quantum dots. These findings are in good agreement with the experimental results.Comment: 22+ pages, 16 figures, several typos in the published paper are corrected in re

SU(2)xSU(2) nonlocal quark model with confinement

The nonlocal version of the SU(2)xSU(2) symmetric four-quark interaction of the NJL type is considered. Each of the quark lines contains the form factors. These form factors remove the ultraviolet divergences in quark loops. The additional condition on quark mass function m(p) ensures the absence of the poles in the quark propagator(quark confinement). The constituent quark mass m(0) is expressed thought the cut-off parameter Lambda, m(0)=Lambda=340 MeV in the chiral limit. These parameters are fixed by the experimental value of the weak pion decay and allow us to describe the mass of the light scalar meson, strong decay rho -> pi pi and D/S ratio in the decay a_1 -> rho pi in satisfactory agreement with experimental data.Comment: 8 pages, 1 figure

Topological susceptibility at zero and finite temperature in the Nambu-Jona-Lasinio model

We consider the three flavor Nambu-Jona-Lasinio model with the 't Hooft interaction incorporating the U(1)_A anomaly. In order to set the coupling strength of the 't Hooft term, we employ the topological susceptibility $\chi$ instead of the eta' meson mass. The value for $\chi$ is taken from lattice simulations. We also calculate $\chi$ at finite temperature within the model. Comparing it with the lattice data, we extract information about the behavior of the U(1)_A anomaly at finite temperature. We conclude that within the present framework, the effective restoration of the U(1)_A symmetry does not necessarily take place even at high temperature where the chiral symmetry is restored.Comment: 9 pages, 14 figures, to be published in Phys.Rev.

Spatial structure of Mn-Mn acceptor pairs in GaAs

The local density of states of Mn-Mn pairs in GaAs is mapped with cross-sectional scanning tunneling microscopy and compared with theoretical calculations based on envelope-function and tight-binding models. These measurements and calculations show that the crosslike shape of the Mn-acceptor wavefunction in GaAs persists even at very short Mn-Mn spatial separations. The resilience of the Mn-acceptor wave-function to high doping levels suggests that ferromagnetism in GaMnAs is strongly influenced by impurity-band formation. The envelope-function and tight-binding models predict similarly anisotropic overlaps of the Mn wave-functions for Mn-Mn pairs. This anisotropy implies differing Curie temperatures for Mn $\delta$-doped layers grown on differently oriented substrates.Comment: 4 pages, 4 figure

Interactive Effects of Parents’ Trait Verbal Aggressiveness and Situational Frustration on Parents’ Self‐Reported Anger

Examines the relationship between anger experienced by parents\u27 trait verbal aggressiveness and the frustrations, caused by the interaction with children. What was cited as an ordinary interaction between parents\u27 trait verbal aggressiveness and situational frustration; Process in which the examination was conducted; Exploration of a measure of trait verbal aggressiveness to parents; Discussion based on the results

Interactive Effects of Parents’ Trait Verbal Aggressiveness and Situational Frustration on Parents’ Self‐Reported Anger

Examines the relationship between anger experienced by parents\u27 trait verbal aggressiveness and the frustrations, caused by the interaction with children. What was cited as an ordinary interaction between parents\u27 trait verbal aggressiveness and situational frustration; Process in which the examination was conducted; Exploration of a measure of trait verbal aggressiveness to parents; Discussion based on the results

A Mean Field Approach To The Instanton-Induced Effect Close To The QCD Phase Transition

In the instanton models the chiral phase transition is driven by a transition from random instanton-antiinstanton liquid and correlated instanton-antiinstanton molecules. So far this phenomenon was studied by numerical simulations, while we develop alternative semi-analytic approach. For two massless quark flavors, both instantons and ``molecules" generate specific 4-fermion effective interactions. After those are derived, we determine the temperature dependence of the thermodynamic quantities, the quark condensate and the fraction of molecules using standard mean field method. Using Bethe-Salpeter equation, we calculate T-dependence of mesonic correlation functions.Comment: 26 pages, LaTeX, 6 postscript files of 6 figures in additio