2,895 research outputs found
Sigma-drop in galaxies and the sigma-metallicity degeneracy
In some galaxies, the central velocity dispersion, sigma, is depressed with
respect to the surroundings. This sigma-drop phenomenon may have different
physical origins, bearing information about the internal dynamics of the host
galaxy. In this article, we stress the importance also of observational
artifacts due to the sigma-metallicity degeneracy: when a spectrum of a
population is compared with a template of miss-matched metallicity, the
velocity dispersion may be wrongly estimated. A sigma-drop may appear in place
of a metallicity peak. The discussion is illustrated using VLT/FORS spectra of
diffuse elliptical galaxies. Some of the sigma-drop galaxies reported in the
literature may be analysis artifacts.Comment: (1) Observatoire de Lyon, France (2) University of Sofia, Bulgaria
(3) Ghent University, Belgium 4 pages, 3 figures. Proceeding at Galactic &
Stellar Dynamics conference, Strasbourg 2008, To appear in Astronomische
Nachrichte
Observing Quantum Tunneling in Perturbation Series
We apply Borel resummation method to the conventional perturbation series of
ground state energy in a metastable potential, . We observe
numerically that the discontinuity of Borel transform reproduces the imaginary
part of energy eigenvalue, i.e., total decay width due to the quantum
tunneling. The agreement with the exact numerical value is remarkable in the
whole tunneling regime 0.Comment: 12 pages, 2 figures. Phyzzx, Tables.tex, The final version to appear
in Phys. Lett.
Effective potential in three-dimensional O(N) models
We consider the effective potential in three-dimensional models with O(N)
symmetry. For generic values of N, and in particular for the physically
interesting cases N=0,1,2,3, we determine the six-point and eight-point
renormalized coupling constants which parametrize its small-field expansion.
These estimates are obtained from the analysis of their -expansion,
taking into account the exact results in one and zero dimensions, and, for the
Ising model (i.e. N=1), the accurate high-temperature estimates in two
dimensions. They are compared with the available results from other approaches.
We also obtain corresponding estimates for the two-dimensional O() models.Comment: 22 pages, revtex, 2 fig
Four-point renormalized coupling constant and Callan-Symanzik beta-function in O(N) models
We investigate some issues concerning the zero-momentum four-point
renormalized coupling constant g in the symmetric phase of O(N) models, and the
corresponding Callan-Symanzik beta-function. In the framework of the 1/N
expansion we show that the Callan- Symanzik beta-function is non-analytic at
its zero, i.e. at the fixed-point value g^* of g. This fact calls for a check
of the actual accuracy of the determination of g^* from the resummation of the
d=3 perturbative g-expansion, which is usually performed assuming analyticity
of the beta-function. Two alternative approaches are exploited. We extend the
\epsilon-expansion of g^* to O(\epsilon^4). Quite accurate estimates of g^* are
then obtained by an analysis exploiting the analytic behavior of g^* as
function of d and the known values of g^* for lower-dimensional O(N) models,
i.e. for d=2,1,0. Accurate estimates of g^* are also obtained by a reanalysis
of the strong-coupling expansion of lattice N-vector models allowing for the
leading confluent singularity. The agreement among the g-, \epsilon-, and
strong-coupling expansion results is good for all N. However, at N=0,1,
\epsilon- and strong-coupling expansion favor values of g^* which are sligthly
lower than those obtained by the resummation of the g-expansion assuming
analyticity in the Callan-Symanzik beta-function.Comment: 35 pages (3 figs), added Ref. for GRT, some estimates are revised,
other minor change
Multi-Instantons and Exact Results III: Unified Description of the Resonances of Even and Odd Anharmonic Oscillators
This is the third article in a series of three papers on the resonance energy
levels of anharmonic oscillators. Whereas the first two papers mainly dealt
with double-well potentials and modifications thereof [see J. Zinn-Justin and
U. D. Jentschura, Ann. Phys. (N.Y.) 313 (2004), pp. 197 and 269], we here focus
on simple even and odd anharmonic oscillators for arbitrary magnitude and
complex phase of the coupling parameter. A unification is achieved by the use
of PT-symmetry inspired dispersion relations and generalized quantization
conditions that include instanton configurations. Higher-order formulas are
provided for the oscillators of degrees 3 to 8, which lead to subleading
corrections to the leading factorial growth of the perturbative coefficients
describing the resonance energies. Numerical results are provided, and
higher-order terms are found to be numerically significant. The resonances are
described by generalized expansions involving intertwined non-analytic
exponentials, logarithmic terms and power series. Finally, we summarize
spectral properties and dispersion relations of anharmonic oscillators, and
their interconnections. The purpose is to look at one of the classic problems
of quantum theory from a new perspective, through which we gain systematic
access to the phenomenologically significant higher-order terms.Comment: 51 pages, LaTeX, Latin2 font
The Hydrogen Atom in Strong Electric Fields: Summation of the Weak Field Series Expansion
The order dependent mapping method, its convergence has recently been proven
for the energy eigenvalue of the anharmonic oscillator, is applied to re-sum
the standard perturbation series for Stark effect of the hydrogen atom. We
perform a numerical experiment up to the fiftieth order of the perturbation
expansion. A simple mapping suggested by the analytic structure and the strong
field behavior gives an excellent agreement with the exact value for an
intermediate range of the electric field, . The imaginary
part of the energy (the decay width) as well as the real part of the energy is
reproduced from the standard perturbation series.Comment: 14 pages, 8 figure
New approach to Borel summation of divergent series and critical exponent estimates for an N-vector cubic model in three dimensions from five-loop \epsilon expansions
A new approach to summation of divergent field-theoretical series is
suggested. It is based on the Borel transformation combined with a conformal
mapping and does not imply the exact asymptotic parameters to be known. The
method is tested on functions expanded in their asymptotic power series. It is
applied to estimating the critical exponent values for an N-vector field model,
describing magnetic and structural phase transitions in cubic and tetragonal
crystals, from five-loop \epsilon expansions.Comment: 9 pages, LaTeX, 3 PostScript figure
STEllar Content and Kinematics from high resolution galactic spectra via Maximum A Posteriori
We introduce STECKMAP (STEllar Content and Kinematics via Maximum A
Posteriori), a method to recover the kinematical properties of a galaxy
simultaneously with its stellar content from integrated light spectra. It is an
extension of STECMAP (astro-ph/0505209) to the general case where the velocity
distribution of the underlying stars is also unknown.
%and can be used as is for the analysis of large sets of data. The
reconstructions of the stellar age distribution, the age-metallicity relation,
and the Line-Of-Sight Velocity Distribution (LOSVD) are all non-parametric,
i.e. no specific shape is assumed. The only a propri we use are positivity and
the requirement that the solution is smooth enough. The smoothness parameter
can be set by GCV according to the level of noise in the data in order to avoid
overinterpretation. We use single stellar populations (SSP) from PEGASE-HR
(R=10000, lambda lambda = 4000-6800 Angstrom, Le Borgne et al. 2004) to test
the method through realistic simulations. Non-Gaussianities in LOSVDs are
reliably recovered with SNR as low as 20 per 0.2 Angstrom pixel. It turns out
that the recovery of the stellar content is not degraded by the simultaneous
recovery of the kinematic distribution, so that the resolution in age and error
estimates given in Ocvirk et al. 2005 remain appropriate when used with
STECKMAP. We also explore the case of age-dependent kinematics (i.e. when each
stellar component has its own LOSVD). We separate the bulge and disk components
of an idealized simplified spiral galaxy in integrated light from high quality
pseudo data (SNR=100 per pixel, R=10000), and constrain the kinematics (mean
projected velocity, projected velocity dispersion) and age of both components.Comment: 12 pages, 6 figures, accepted for publication in MNRA
Effects of acute exposure to dispersed oil and burned oil residue on long-term survival, growth, and reproductive development in polar cod (Boreogadus saida)
Accepted manuscript version, licensed CC BY-NC-ND 4.0. Published version available at https://doi.org/10.1016/j.marenvres.2018.09.005.The present study investigates the potential long-term physiological effects on maturing polar cod (Boreogadus saida), an Arctic key species, after an acute exposure (48 h) to environmentally realistic concentrations of either mechanically dispersed oil (MDO), chemically dispersed oil (CDO) or burned oil residues (BO) (N = 58–60 per treatment). Following exposure, fish were monitored in a common tank supplied with clean water for a seven-month period coinciding with the period of reproductive development. Females exposed to BO residues were more frequently found in an earlier phase of gonadal maturation compared to unexposed females while no effects of different oil spill response (OSR) actions were seen in the reproductive development of males. Mechanically and chemically dispersed oil induced a transient short-term reduction in growth in the first week post-exposure. Overall, no significant long-term effects of exposure were seen in growth or mortality. Ultimately, this study provides information for the assessment of population consequences of different OSR actions as part of a net environmental benefit analysis
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