133,521 research outputs found
Some peculiarities of burnt birch wood pyrolysis
The results of thermal analysis of sound and burnt birch wood samples were compared. An attempt was made to establish a connection between the type of the TG, DTG and DSC curves and the mechanism of wood pyrolysis. The dependence of the exothermic effect of the pyrolysis process on the oxygen content in the original wood is shown. © 2019 IOP Publishing Ltd. All rights reserved
Strong-coupling effects in the relaxation dynamics of ultracold neutral plasmas
We describe a hybrid molecular dynamics approach for the description of
ultracold neutral plasmas, based on an adiabatic treatment of the electron gas
and a full molecular dynamics simulation of the ions, which allows us to follow
the long-time evolution of the plasma including the effect of the strongly
coupled ion motion. The plasma shows a rather complex relaxation behavior,
connected with temporal as well as spatial oscillations of the ion temperature.
Furthermore, additional laser cooling of the ions during the plasma evolution
drastically modifies the expansion dynamics, so that crystallization of the ion
component can occur in this nonequilibrium system, leading to lattice-like
structures or even long-range order resulting in concentric shells
Quantum-classical transition for an analog of double-slit experiment in complex collisions: Dynamical decoherence in quantum many-body systems
We study coherent superpositions of clockwise and anti-clockwise rotating
intermediate complexes with overlapping resonances formed in bimolecular
chemical reactions. Disintegration of such complexes represents an analog of
famous double-slit experiment. The time for disappearance of the interference
fringes is estimated from heuristic arguments related to fingerprints of
chaotic dynamics of a classical counterpart of the coherently rotating complex.
Validity of this estimate is confirmed numerically for the H+D chemical
reaction. Thus we demonstrate the quantum--classical transition in temporal
behavior of highly excited quantum many-body systems in the absence of external
noise and coupling to an environment.Comment: 5 pages, 2 ps color figures. Accepted for publication in Phys. Rev.
Created-by-current states in long Josephson junctions
Critical curves "critical current - external magnetic field" of long
Josephson junctions with inhomogeneity and variable width are studied. We
demonstrate the existence of the regions of magnetic field where some fluxon
states are stable only, if the external current through the junction is
different from zero. Position and size of such regions depend on length of the
junction, its geometry, parameters of inhomogeneity and form of the junction.
The noncentral (left and right) pure fluxon states are appeared in the
inhomogeneous Josephson junction with increase in the junction length. We
demonstrate new bifurcation points with change in width of the inhomogeneity
and amplitude of the Josephson current through the inhomogeneity.Comment: 7 pages, 8 figure
Chiral symmetry restoration in excited hadrons, quantum fluctuations, and quasiclassics
In this paper, we discuss the transition to the semiclassical regime in
excited hadrons, and consequently, the restoration of chiral symmetry for these
states. We use a generalised Nambu-Jona-Lasinio model with the interaction
between quarks in the form of the instantaneous Lorentz-vector confining
potential. This model is known to provide spontaneous breaking of chiral
symmetry in the vacuum via the standard selfenergy loops for valence quarks. It
has been shown recently that the effective single-quark potential is of the
Lorentz-scalar nature, for the low-lying hadrons, while, for the high-lying
states, it becomes a pure Lorentz vector and hence the model exhibits the
restoration of chiral symmetry. We demonstrate explicitly the quantum nature of
chiral symmetry breaking, the absence of chiral symmetry breaking in the
classical limit as well as the transition to the semiclassical regime for
excited states, where the effect of chiral symmetry breaking becomes only a
small correction to the classical contributions.Comment: RevTeX4, 20 pages, 4 Postscript figures, uses epsfig.sty, typos
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