1,706 research outputs found
Spontaneous symmetry emergence as a source of new class of phase transitions
Spontaneous symmetry breaking in systems with symmetry is core-stone
phenomenon accompanying second-order phase transitions. Here, we predict an
opposite phenomenon, namely, spontaneous symmetry emergence in a system without
symmetry. On the example of two coupled oscillators interacting
non-symmetrically with a set of oscillators whose frequencies uniformly fill a
finite frequency range, we demonstrate that the system state can acquire
symmetry, which is not inherent to the system Hamiltonian. The symmetry
emergence manifests in the change of the system dynamics, which can be
interpreted as a new class of phase transitions
BLR kinematics and Black Hole Mass in Markarian 6
We present results of the optical spectral and photometric observations of
the nucleus of Markarian 6 made with the 2.6-m Shajn telescope at the Crimean
Astrophysical Observatory. The continuum and emission Balmer line intensities
varied more than by a factor of two during 1992-2008. The lag between the
continuum and Hbeta emission line flux variations is 21.1+-1.9 days. For the
Halpha line the lag is about 27 days but its uncertainty is much larger. We use
Monte-Carlo simulation of the random time series to check the effect of our
data sampling on the lag uncertainties and we compare our simulation results
with those obtained by random subset selection (RSS) method of Peterson et al.
(1998). The lag in the high-velocity wings are shorter than in the line core in
accordance with the virial motions. However, the lag is slightly larger in the
blue wing than in the red wing. This is a signature of the infall gas motion.
Probably the BLR kinematic in the Mrk 6 nucleus is a combination of the
Keplerian and infall motions. The velocity-delay dependence is similar for
individual observational seasons. The measurements of the Hbeta line width in
combination with the reverberation lag permits us to determine the black hole
mass, M_BH=(1.8+-0.2)x10^8 M_sun. This result is consistent with the AGN
scaling relationships between the BLR radius and the optical continuum
luminosity (R_BLR is proportional to L^0.5) as well as with the black-hole
mass-luminosity relationship (M_BH-L) under the Eddington luminosity ratio for
Mrk 6 to be L_bol/L_Edd ~ 0.01.Comment: 17 pages, 10 figures, accepted for publication in MNRA
Phase transition at exceptional point in Hermitian systems
Exceptional point (EP) is a spectral singularity in non-Hermitian systems.
The passing over the EP leads to a phase transition which endows the system
with unconventional features that find a wide range of applications. However,
the need of using the dissipation and amplification limits the possible
applications of systems with the EP. In this work, the concept of phase
transitions at the EP is expanded to Hermitian systems which are free from
dissipation and amplification. It is considered a composite Hermitian system
including both two coupled subsystems and their environment consisting only of
several tens degrees of freedom such that the energy can return from the
environment to the subsystems. It is shown that the dynamics of such a
Hermitian system demonstrates a clear phase transition. It occurs at the
critical coupling strength between subsystems corresponding to the EP in the
non-Hermitian system. This phase transition manifests itself even in the
non-Markovian regime of the system dynamics in which collapses and revivals of
the energy occur. A photonic circuit is proposed for observing the EP phase
transition in systems free from dissipation and amplification. The obtained
results extend the range of practical applications of the EP phenomena to
Hermitian systems.Comment: 16 pages, 8 figure
Self-consistent description of relaxation processes in systems with ultra- and deep-strong coupling
An ultra-strong coupling regime takes place in a compound system when a
coupling strength between the subsystems exceeds one tenth of the system
eigenfrequency. It transforms into a deep-strong coupling regime when the
coupling strength exceeds the system eigenfrequency. In these regimes, there
are difficulties with description of relaxation processes without explicit
considering of environment degrees of freedom. To correctly evaluate the
relaxation rates, it is necessary to consider the interaction of the system
with its environment taking into account the counter-rotating wave and
diamagnetic terms. We develop a self-consistent theory for calculation of the
relaxation rates in the systems, in which the coupling strength is of the order
of the system eigenfrequency. We demonstrate that the increase in the coupling
strength can lead to a significant decrease in the relaxation rates. In
particular, we show that for frequency-independent density of states of the
environment, the relaxation rates decrease exponentially with the increase in
the coupling strength. This fact can be used to suppress losses by tuning the
strength coupling and the environment states
Functional Tetrahedron Equation
We describe a scheme of constructing classical integrable models in
2+1-dimensional discrete space-time, based on the functional tetrahedron
equation - equation that makes manifest the symmetries of a model in local
form. We construct a very general "block-matrix model" together with its
algebro-geometric solutions, study its various particular cases, and also
present a remarkably simple scheme of quantization for one of those cases.Comment: LaTeX, 16 page
Variability of Fe II Emission Features in the Seyfert 1 Galaxy NGC 5548
We study the low-contrast Fe II emission blends in the ultraviolet
(1250--2200A) and optical (4000--6000A) spectra of the Seyfert 1 galaxy NGC
5548 and show that these features vary in flux and that these variations are
correlated with those of the optical continuum. The amplitude of variability of
the optical Fe II emission is 50% - 75% that of Hbeta and the ultraviolet Fe II
emission varies with an even larger amplitude than Hbeta. However, accurate
measurement of the flux in these blends proves to be very difficult even using
excellent Fe II templates to fit the spectra. We are able to constrain only
weakly the optical Fe II emission-line response timescale to a value less than
several weeks; this upper limit exceeds all the reliably measured emission-line
lags in this source so it is not particularly meaningful. Nevertheless, the
fact that the optical Fe II and continuum flux variations are correlated
indicates that line fluorescence in a photoionized plasma, rather than
collisional excitation, is responsible for the Fe II emission. The iron
emission templates are available upon request.Comment: 34 pages including 12 figures and 2 tables. Accepted for publication
by ApJ (tentatively in vol. 626 June 10, 2005
Higher order glass-transition singularities in colloidal systems with attractive interactions
The transition from a liquid to a glass in colloidal suspensions of particles
interacting through a hard core plus an attractive square-well potential is
studied within the mode-coupling-theory framework. When the width of the
attractive potential is much shorter than the hard-core diameter, a reentrant
behavior of the liquid-glass line, and a glass-glass-transition line are found
in the temperature-density plane of the model. For small well-width values, the
glass-glass-transition line terminates in a third order bifurcation point, i.e.
in a A_3 (cusp) singularity. On increasing the square-well width, the
glass-glass line disappears, giving rise to a fourth order A_4 (swallow-tail)
singularity at a critical well width. Close to the A_3 and A_4 singularities
the decay of the density correlators shows stretching of huge dynamical
windows, in particular logarithmic time dependence.Comment: 19 pages, 12 figures, Phys. Rev. E, in prin
Reverberation Mapping Results from MDM Observatory
We present results from a multi-month reverberation mapping campaign
undertaken primarily at MDM Observatory with supporting observations from
around the world. We measure broad line region (BLR) radii and black hole
masses for six objects. A velocity-resolved analysis of the H_beta response
shows the presence of diverse kinematic signatures in the BLR.Comment: To appear in the Proceedings of the IAU Symposium No. 267:
Co-Evolution of Central Black Holes and Galaxies, Rio de Janeiro, 200
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