88 research outputs found
Photoluminescence rings in Corbino disk at quantizing magnetic fields
Spatially resolved photoluminescence of modulation doped AlGaAs/GaAs
heterojunction was investigated in a sample of Corbino disk geometry subject to
strong perpendicular magnetic fields. Significant spatial modulation of the
photoluminescence was observed in form of one or more concentric rings which
travelled across the sample when the magnetic field strength was varied. A
topology of the observed structure excludes the possibility of being a trace of
an external current. The effect is attributed to formation of compressible and
incompressible stripes in a 2DEG density gradient across the sample.Comment: 5 two-column pages, 4 figures (one of them in color
The Akulov-Volkov Lagrangian, Symmetry Currents and Spontaneously Broken Extended Supersymmetry
A generalization of the Akulov-Volkov effective Lagrangian governing the self
interactions of the Nambu-Goldstone fermions associated with spontaneously
broken extended supersymmetry as well as their coupling to matter is presented
and scrutinized. The resulting currents associated with R-symmetry,
supersymmetry and space-time translations are constructed and seen to form a
supermultiplet structure.Comment: 17 pages, LaTeX; Title, abstract and introduction changes, references
adde
Proton polarizability contribution to the hydrogen hyperfine splitting
The contribution of the proton polarizability to the hydrogen hyperfine
splitting is evaluated on the basis of modern experimental and theoretical
results on the proton polarized structure functions. The value of this
correction is equal to 1.4 ppm.Comment: 11 pages, LaTeX2.09, 7 figures, uses linedraw.sty, psfig.sty,
epsf.st
Muonic hydrogen ground state hyperfine splitting
Corrections of orders alpha^5, alpha^6 are calculated in the hyperfine
splitting of the muonic hydrogen ground state. The nuclear structure effects
are taken into account in the one- and two-loop Feynman amplitudes by means of
the proton electromagnetic form factors. The modification of the hyperfine
splitting part of the Breit potential due to the electron vacuum polarization
is considered. Total numerical value of the 1S state hyperfine splitting
182.638 meV in the (mu p) can play the role of proper estimation for the
corresponding experiment with the accuracy 30 ppm.Comment: 18 pages, Talk presented at the 11th Lomonosov Conference on
Elementary Particle Physics, Moscow State University, August 200
Voting 'against all' in postcommunist Russia
Since the early 1990s voters in Russia (and most of the other post-Soviet republics) have been offered
the opportunity to vote ‘against all’ parties and candidates. Increasing numbers have done so. The
evidence of two post-election surveys indicates that ‘against all’ voters are younger than other voters,
more urban and more highly educated. They do not reject liberal democracy, but are critical of the
contemporary practice of Russian politics and find no parties that adequately reflect their views. With
the ending of the ‘against all’ facility in 2006 and other changes in the Russian electoral system under
the Putin presidency, levels of turnout are likely to fall further and the protest vote will seek other
outlets within or outside the parliamentary system
On the Theory of Vibronic Superradiance
The Dicke superradiance on vibronic transitions of impurity crystals is
considered. It is shown that parameters of the superradiance (duration and
intensity of the superradiance pulse and delay times) on each vibronic
transition depend on the strength of coupling of electronic states with the
intramolecular impurity vibration (responsible for the vibronic structure of
the optical spectrum in the form of vibrational replicas of the pure electronic
line) and on the crystal temperature through the Debye-Waller factor of the
lattice vibrations. Theoretical estimates of the ratios of the time delays, as
well as of the superradiance pulse intensities for different vibronic
transitions well agree with the results of experimental observations of
two-color superradiance in the polar dielectric KCl:O2-. In addition, the
theory describes qualitatively correctly the critical temperature dependence of
the superradiance effect.Comment: 8 pages, 1 figur
Retardation and nonstationarity effects on the generation of terahertz radiation by the e-h plasma in a semiconductor
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