3,183 research outputs found
Semiclassical analysis of defect sine-Gordon theory
The classical sine-Gordon model is a two-dimensional integrable field theory,
with particle like solutions the so-called solitons. Using its integrability
one can define its quantum version without the process of canonical
quantization. This bootstrap method uses the fundamental propterties of the
model and its quantum features in order to restrict the structure of the
scattering matrix as far as possible. The classical model can be extended with
integrable discontinuities, purely transmitting jump-defects. Then the quantum
version of the extended model can be determined via the bootstrap method again.
But the outcoming quantum theory contains the so-called CDD uncertainity. The
aim of this article is to carry throw the semiclassical approximation in both
the classical and the quantum side of the defect sine-Gordon theory. The CDD
ambiguity can be restricted by comparing the two results. The relation between
the classical and quantum parameters as well as the resoncances appeared in the
spectrum are other objectives
Some aspects of mathematical and chemical modeling of complex chemical processes
Some theoretical questions involved in the mathematical modeling of the kinetics of complex chemical process are discussed. The analysis is carried out for the homogeneous oxidation of ethylbenzene in the liquid phase. Particular attention is given to the determination of the general characteristics of chemical systems from an analysis of mathematical models developed on the basis of linear algebra
Electronic and structural properties of alkali doped SWNT
Comprehensive experiments on structural and transport properties of alkali intercalated
single walled carbon nanotubes (SWNT) are presented. The increasing electron density was
measured as a shift of the Drude-edge in optical reflectivity in-situ with progressive doping. In
saturation-doped samples the Drude-edge shifts into the visible (to 25,000 - 30,000 cm— 1 for potassium
and rubidium doped samples) and the samples have a golden-brown color, similar to stage I
graphite. X-ray diffraction reveals a crystalline rope structure with expanded lattice constant, similar
to results of Duclaux et al. The change in the low temperature divergence of the resistivity after
degassing at high temperature and high vacuum and after K-doping is studied in-situ
The Plasma Structure of the Cygnus Loop from the Northeastern Rim to the Southwestern Rim
The Cygnus Loop was observed from the northeast to the southwest with
XMM-Newton. We divided the observed region into two parts, the north path and
the south path, and studied the X-ray spectra along two paths. The spectra can
be well fitted either by a one-component non-equilibrium ionization (NEI) model
or by a two-component NEI model. The rim regions can be well fitted by a
one-component model with relatively low \kTe whose metal abundances are
sub-solar (0.1--0.2). The major part of the paths requires a two-component
model. Due to projection effects, we concluded that the low kTe (about 0.2 keV)
component surrounds the high kTe (about 0.6 keV) component, with the latter
having relatively high metal abundances (about 5 times solar). Since the Cygnus
Loop is thought to originate in a cavity explosion, the low-kTe component
originates from the cavity wall while the high-kTe component originates from
the ejecta. The flux of the cavity wall component shows a large variation along
our path. We found it to be very thin in the south-west region, suggesting a
blowout along our line of sight. The metal distribution inside the ejecta shows
non-uniformity, depending on the element. O, Ne and Mg are relatively more
abundant in the outer region while Si, S and Fe are concentrated in the inner
region, with all metals showing strong asymmetry. This observational evidence
implies an asymmetric explosion of the progenitor star. The abundance of the
ejecta also indicates the progenitor star to be about 15 M_sun.Comment: 24 pages, 9 figures, Astrophysical Journal in pres
Ordered low-temperature structure in K4C60 detected by infrared spectroscopy
Infrared spectra of a K4C60 single-phase thin film have been measured between
room temperature and 20 K. At low temperatures, the two high-frequency T1u
modes appear as triplets, indicating a static D2h crystal-field stabilized
Jahn-Teller distortion of the (C60)4- anions. The T1u(4) mode changes into the
known doublet above 250 K, a pattern which could have three origins: a dynamic
Jahn-Teller effect, static disorder between "staggered" anions, or a phase
transition from an orientationally-ordered phase to one where molecular motion
is significant.Comment: 4 pages, 2 figures submitted to Phys. Rev.
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