63 research outputs found
Reduction of Vector and Axial--Vector Fields in a Bosonized Nambu--Jona--Lasinio Model
We derive the effective action for pseudoscalar mesons by integrating out
vector and axial--vector collective fields in the generating functional of the
bosonized NJL--model. The corresponding modifications of the nonlinear
effective Lagrangian and the bosonized currents, arising at , are
discussed.Comment: 30p. 1 fig. on reques
On the --corrections to decay amplitudes in nonlinear and linear chiral models
The calculations of isotopic amplitudes and their results for the direct
--violating charge asymmetry in decays within the
nonlinear and linear (--model) chiral Lagrangian approach are compared
with each other. It is shown, that the latter, taking into account intermediate
scalar resonances, does not reproduce the --corrections of the nonlinear
approach introduced by Gasser and Leutwyler, being saturated mainly by vector
resonance exchange. The resulting differences concerning the violation
effect are traced in some detail.Comment: 14 page
Can an electric current orient spins in quantum wells?
A longstanding theoretical prediction is the orientation of spins by an
electrical current flowing through low-dimensional carrier systems of
sufficiently low crystallographic symmetry. Here we show by means of terahertz
transmission experiments through two-dimensional hole systems a growing spin
orientation with an increasing current at room temperature.Comment: 5 pages, 2 figure
Pattern Formation in Semiconductors
In semiconductors, nonlinear generation and recombination processes of free carriers and nonlinear charge transport can give rise to non-equilibrium phase transitions. At low temperatures, the basic nonlinearity is due to the autocatalytic generation of free carriers by impact ionization of shallow impurities. The electric field accelerates free electrons, causing an abrupt increase in free carrier density at a critical electric field. In static electric fields, this nonlinearity is known to yield complex filamentary current patterns bound to electric contacts
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