5,953 research outputs found
Optimization of quantum cascade laser operation by geometric design of cascade active band in open and closed models
Using the effective mass and rectangular potential approximations, the theory
of electron dynamic conductivity is developed for the plane multilayer
resonance tunnel structure placed into a constant electric field within the
model of open nanosystem, and oscillator forces of quantum transitions within
the model of closed nanosystem. For the experimentally produced quantum cascade
laser with four-barrier active band of separate cascade, it is proven that just
the theory of dynamic conductivity in the model of open cascade most adequately
describes the radiation of high frequency electromagnetic field while the
electrons transport through the resonance tunnel structure driven by a constant
electric field.Comment: 10 pages, 2 figure
Invariants of Triangular Lie Algebras
Triangular Lie algebras are the Lie algebras which can be faithfully
represented by triangular matrices of any finite size over the real/complex
number field. In the paper invariants ('generalized Casimir operators') are
found for three classes of Lie algebras, namely those which are either strictly
or non-strictly triangular, and for so-called special upper triangular Lie
algebras. Algebraic algorithm of [J. Phys. A: Math. Gen., 2006, V.39, 5749;
math-ph/0602046], developed further in [J. Phys. A: Math. Theor., 2007, V.40,
113; math-ph/0606045], is used to determine the invariants. A conjecture of [J.
Phys. A: Math. Gen., 2001, V.34, 9085], concerning the number of independent
invariants and their form, is corroborated.Comment: LaTeX2e, 16 pages; misprints are corrected, some proofs are extende
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