4,904 research outputs found
On the semi-dynamical reflection equation: solutions and structure matrices
Explicit solutions of the non-constant semi-dynamical reflection equation are
constructed, together with suitable parametrizations of their structure
matrices. Considering the semi-dynamical reflection equation with rational
non-constant Arutyunov-Chekhov-Frolov structure matrices, and a specific
meromorphic ansatz, it is found that only two sets of the previously found
constant solutions are extendible to the non-constant case. In order to
simplify future constructions of spin-chain Hamiltonians, a parametrization
procedure is applied explicitly to all elements of the semi-dynamical
reflection equation available. Interesting expressions for `twists' and
R-matrices entering the parametrization procedure are found. In particular,
some expressions for the R-matrices seem to appear here for the first time. In
addition, a new set of consistent structure matrices for the semi-dynamical
reflection equation is obtained.Comment: typos corrected and some comments adde
Emission Line Properties of Seyfert 2 Nuclei
We present a study of the global properties of Joguet's sample of 65 Seyfert
2 galaxies. We use the population synthesis models of our Paper II to derive
`pure' emission-line spectra, and thus explore the statistical properties of
the nuclear nebular components and their relation to the stellar populations.
We find that the emission line clouds suffer substantially more extinction than
the starlight, and confirm the correlations between stellar and nebular
velocity dispersions and between emission line luminosity and velocity
dispersions. Nuclear luminosities correlate with stellar velocity dispersions.
Removing the contribution of young stars to the optical continuum produces a
tighter and steeper relation, , consistent with the
Faber-Jackson law. Emission line ratios indicative of the gas excitation such
as [OIII]/H and [OIII]/[OII] are statistically smaller for Seyferts with
significant star-formation, implying that ionization by massive stars is
responsible for a substantial, and sometimes even a dominant, fraction of the
H and [OII] fluxes. We use our models to constrain the maximum fraction
of the ionizing power that can be generated by a hidden AGN. We correlate this
fraction with classical indicators of AGN photo-ionization: X-ray luminosity
and nebular excitation, but find no significant correlations. Thus, while there
is a strong contribution of starbursts to the excitation of the nuclear nebular
emission in low-luminosity Seyferts, the contribution of the hidden AGN remains
elusive even in hard X-rays. (abridged)Comment: 12 pages, 13 figures. Final version accepted for publication in MNRA
Statistics, distillation, and ordering emergence in a two-dimensional stochastic model of particles in counterflowing streams
In this paper, we proposed a stochastic model which describes two species of
particles moving in counterflow. The model generalizes the theoretical
framework describing the transport in random systems since particles can work
as mobile obstacles, whereas particles of one species move in opposite
direction to the particles of the other species, or they can work as fixed
obstacles remaining in their places during the time evolution. We conducted a
detailed study about the statistics concerning the crossing time of particles,
as well as the effects of the lateral transitions on the time required to the
system reaches a state of complete geographic separation of species. The
spatial effects of jamming were also studied by looking into the deformation of
the concentration of particles in the two-dimensional corridor. Finally, we
observed in our study the formation of patterns of lanes which reach the steady
state regardless the initial conditions used for the evolution. A similar
result is also observed in real experiments involving charged colloids motion
and simulations of pedestrian dynamics based on Langevin equations, when
periodic boundary conditions are considered (particles counterflow in a ring
symmetry). The results obtained through Monte Carlo numerical simulations and
numerical integrations are in good agreement with each other. However,
differently from previous studies, the dynamics considered in this work is not
Newton-based, and therefore, even artificial situations of self-propelled
objects should be studied in this first-principle modeling.Comment: 27 pages, 13 figure
The circumstellar medium of the peculiar supernova SN1997ab
We report the detection of the slow moving wind into which the compact
supernova remnant SN 1997ab is expanding. Echelle spectroscopy provides clear
evidence for a well resolved narrow (Full Width at Zero Intensity, FWZI ~ 180
km/s) P-Cygni profile, both in Ha and Hb, superimposed on the broad emission
lines of this compact supernova remnant. From theoretical arguments we know
that the broad and strong emission lines imply a circumstellar density (n ~
10^7 cm^-3). This, together with our detection, implies a massive and slow
stellar wind experienced by the progenitor star shortly prior to the explosion.Comment: 10 pages, 2 figures, acepted for publication in MNRAS. Uses
referee.sty, psfig.sty and mn.sty. A postscript file can also be retrieved at
http://www.strw.LeidenUniv.nl/~salamanc/latest.htm
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