649,046 research outputs found
Coulombic effects on magnetoconductivity oscillations induced by microwave excitation in multisubband two-dimensional electron systems
We develop a theory of magneto-oscillations in photoconductivity of
multisubband two-dimensional electron systems which takes into account strong
Coulomb interaction between electrons. In the presence of a magnetic field
oriented perpendicular, internal electric fields of fluctuational origin cause
fast drift velocities of electron orbit centers which affect probabilities of
inter-subband scattering and the photoconductivity. For the electron system
formed on the liquid helium surface, internal forces are shown to suppress the
amplitude of magneto-oscillations, and change positions of magnetoconductivity
minima which evolve in zero-resistance states for high radiation power.Comment: 9 pages, 6 figure
Energy losses of fast heavy-ion projectiles in dense hydrogen plasmas
It has been recently shown that the Bethe-Larkin formula for the energy
losses of fast heavy-ion projectiles in dense hydrogen plasmas is corrected by
the electron-ion correlations [Phys. Rev. Lett. \textbf{101}, 075002 (2008)].
We report numerical estimates of this correction based on the values of
obtained by numerical simulations in [Phys. Rev. E \textbf{61},
3470 (2000)]. We also extend this result to the case of projectiles with
dicluster charge distribution. We show that the experimental visibility of the
electron-ion correlation correction is enhanced in the case of dicluster
projectiles with randomly orientated charge centers. Although we consider here
the hydrogen plasmas to make the effect physically more clear, the
generalization to multispecies plasmas is straightforward.Comment: 5 pages, 1 figure. International Conference on Strongly Coupled
Coulomb Systems 2008, Camerino (Italy). To appear in J. Phys.
Jet Methods in Time-Dependent Lagrangian Biomechanics
In this paper we propose the time-dependent generalization of an `ordinary'
autonomous human biomechanics, in which total mechanical + biochemical energy
is not conserved. We introduce a general framework for time-dependent
biomechanics in terms of jet manifolds associated to the extended
musculo-skeletal configuration manifold, called the configuration bundle. We
start with an ordinary configuration manifold of human body motion, given as a
set of its all active degrees of freedom (DOF) for a particular movement. This
is a Riemannian manifold with a material metric tensor given by the total
mass-inertia matrix of the human body segments. This is the base manifold for
standard autonomous biomechanics. To make its time-dependent generalization, we
need to extend it with a real time axis. By this extension, using techniques
from fibre bundles, we defined the biomechanical configuration bundle. On the
biomechanical bundle we define vector-fields, differential forms and affine
connections, as well as the associated jet manifolds. Using the formalism of
jet manifolds of velocities and accelerations, we develop the time-dependent
Lagrangian biomechanics. Its underlying geometric evolution is given by the
Ricci flow equation.
Keywords: Human time-dependent biomechanics, configuration bundle, jet
spaces, Ricci flowComment: 13 pages, 3 figure
Nonlinear Dynamics of Nuclear-Electronic Spin Processes in Ferromagnets
Spin dynamics is considered in ferromagnets consisting of electron and
nuclear subsystems interacting with each other through hyperfine forces. In
addition, the ferromagnetic sample is coupled with a resonance electric
circuit. Under these conditions, spin relaxation from a strongly nonequilibrium
initial state displays several peculiarities absent for the standard set-up in
studying spin relaxation. The main feature of the nonlinear spin dynamics
considered in this communication is the appearance of ultrafast coherent
relaxation, with characteristic relaxation times several orders shorter than
the transverse relaxation time . This type of coherent spin relaxation can
be used for extracting additional information on the intrinsic properties of
ferromagnetic materials and also can be employed for different technical
applications.Comment: 1 file, 4 pages, RevTex, no figure
Microwave-resonance-induced magnetooscillations and vanishing resistance states in multisubband two-dimensional electron systems
The dc magnetoconductivity of the multisubband two-dimensional electron
system formed on the liquid helium surface in the presence of resonant
microwave irradiation is described, and a new mechanism of the negative linear
response conductivity is studied using the self-consistent Born approximation.
Two kinds of scatterers (vapor atoms and capillary wave quanta) are considered.
Besides a conductivity modulation expected near the points, where the
excitation frequency for inter-subband transitions is commensurate with the
cyclotron frequency, a sign-changing correction to the linear conductivity is
shown to appear for usual quasi-elastic inter-subband scattering, if the
collision broadening of Landau levels is much smaller than thermal energy. The
decay heating of the electron system near the commensurability points leads to
magnetooscillations of electron temperature, which are shown to increase the
importance of the sign-changing correction. The line shape of
magnetoconductivity oscillations calculated for wide ranges of temperature and
magnetic field is in a good accordance with experimental observations.Comment: 13 pages, 8 figure
Twist-2 Light-Cone Pion Wave Function
We present an analysis of the existing constraints for the twist-2 light-cone
pion wave function. We find that existing information on the pion wave function
does not exclude the possibility that the pion wave function attains its
asymptotic form. New bounds on the parameters of the pion wave function are
presented.Comment: 7 pages, LaTeX, 1 PS-figure, one reference added, minor changes in
the tex
Energy dependence of cross section of photonuclear reactions on indium isotopes
Experimental isomeric yield ratios for the 113In({\gamma},n)112m,gIn
reactions on the betatron B25/30 bremsstrahlung gamma beam of energy range
12-25 MeV are measured. Effective cross-sections of ({\gamma},n)-reactions with
112mIn and 114mIn isomers output are calculated. The Penfold-Leiss and Tikhonov
methods are applied to solve the Volterra integral equation. The obtained
experimental cross-sections are compared with theoretical calculations using
the TALYS-1.6 code.Comment: 7 pages, 3 figures, 6 table
The role of energy-momentum conservation in emission of Cherenkov gluons
The famous formula for the emission angle of Cherenkov radiation should be
modified when applied to hadronic reactions because of recoil effects. They
impose the upper limit on the energy of the gluon emitted at a given angle.
Also, it leads to essential corrections to the nuclear refractive index value
as determined from the angular position of Cherenkov rings.Comment: 6
- …