6,794 research outputs found
Effective potential for composite operators and for an auxiliary scalar field in a Nambu-Jona-Lasinio model
We derive the effective potentials for composite operators in a
Nambu-Jona-Lasinio (NJL) model at zero and finite temperature and show that in
each case they are equivalent to the corresponding effective potentials based
on an auxiliary scalar field. The both effective potentials could lead to the
same possible spontaneous breaking and restoration of symmetries including
chiral symmetry if the momentum cutoff in the loop integrals is large enough,
and can be transformed to each other when the Schwinger-Dyson (SD) equation of
the dynamical fermion mass from the fermion-antifermion vacuum (or thermal)
condensates is used. The results also generally indicate that two effective
potentials with the same single order parameter but rather different
mathematical expressions can still be considered physically equivalent if the
SD equation corresponding to the extreme value conditions of the two potentials
have the same form.Comment: 7 pages, no figur
Smoking Among Employees at University of Pittsburgh/UPMC
The purpose of this study was to investigate the prevalence of smoking among workers at a major academic medical center including hospitals and other medical and health care facilities. It also was designed to investigate the prevalence of smoking among employees while at the workplace and the amount of time spent doing so. Finally, this study investigates the possible connection between the level of addiction to nicotine and the amount of time spent smoking while at work. The findings in this study may help employers target employees who smoke and assist them in efforts to quit. This study has public health significance because it may improve the health of the employees and those around them, as well as decrease costs and increase productivity. An internet-based survey questionnaire addressing the issues of smoking, demographics, the prevalence of smoking at the workplace, second-hand smoke, and level of dependence to nicotine was distributed via e-mail to employees of a major academic medical center and its affiliated university. The results of this study revealed that 12% of those that responded to the survey are current smokers and half of these individuals smoke at work. Those individuals who have been smoking for a longer period of time seem to be more likely to smoke at work and take more breaks to smoke. Those individuals who have a higher level of dependency to nicotine, according to their score on the Fagerstrom score of nicotine dependency, appear to be more likely to smoke at work, take more breaks to smoke, and have more difficulty refraining from smoking at work for one day than those with lower levels of dependency
Bubble generation in a twisted and bent DNA-like model
The DNA molecule is modeled by a parabola embedded chain with long-range
interactions between twisted base pair dipoles. A mechanism for bubble
generation is presented and investigated in two different configurations. Using
random normally distributed initial conditions to simulate thermal
fluctuations, a relationship between bubble generation, twist and curvature is
established. An analytical approach supports the numerical results.Comment: 7 pages, 8 figures. Accepted for Phys. Rev. E (in press
Optical phonon scattering and theory of magneto-polarons in a quantum cascade laser in a strong magnetic field
We report a theoretical study of the carrier relaxation in a quantum cascade
laser (QCL) subjected to a strong magnetic field. Both the alloy (GaInAs)
disorder effects and the Frohlich interaction are taken into account when the
electron energy differences are tuned to the longitudinal optical (LO) phonon
energy. In the weak electron-phonon coupling regime, a Fermi's golden rule
computation of LO phonon scattering rates shows a very fast non-radiative
relaxation channel for the alloy broadened Landau levels (LL's). In the strong
electron-phonon coupling regime, we use a magneto-polaron formalism and compute
the electron survival probabilities in the upper LL's with including increasing
numbers of LO phonon modes for a large number of alloy disorder configurations.
Our results predict a nonexponential decay of the upper level population once
electrons are injected in this state.Comment: 10 pages, 23 figure
Nuclear spin-lattice relaxation rate in the D+iD superconducting state: implications for CoO superconductor
We calculated the nuclear spin-lattice relaxation rate for the D+iD
superconducting state with impurities. We found that small amount of unitary
impurities quickly produces the residual density of states inside the gap. As a
result, the T-linear behavior in 1/T is observed at low temperatures. Our
results show that the D+iD pairing symmetry of the superconducting state of
NaCoOH O is compatible with recent Co 1/T
experiments of several groups.Comment: 5 pages, 4 figures, minor change
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