2,778 research outputs found
Age Dating of Globular Clusters Using UBV(RI) Main-sequence Photometry in the Two-color Diagram: Age of NGC 6397
I propose and apply a method for deriving ages of the metal-poor globular
clusters (GCs) in a distance-independent way, which is based on age indicator
related to the main sequence in the two-color diagrams with U-B index. Age of
the metal-poor GC NGC 6397 has been estimated, using Yale isochrones of
Demarque et al. (1996), to be close to 16 Gyr provided the cluster metallicity
is near [Fe/H]=-2.0.Comment: 2 pages, 1 figure, uses IAU207_pasp.sty (included). To be published
in the Proceedings of the IAU Symposium 207, "Extragalactic Star Clusters",
eds. E.K. Grebel, D. Geisler and D. Minnit
Nonlinear Quantum Coherence Effects in Driven Mesoscopic Systems
In these pedagogical notes the diffuson-cooperon perturbation theory of weak
localization and mesoscopic phenomena is extended to describe non-equilibrium
and nonlinear effects in quantum disordered systems. It is shown how such
perturbation theory works in the time and frequency domain for essentially
nonlinear phenomena. Examples of quantum rectification in a mesoscopic ring and
the dynamic localization in quantum dots are discussed in detail.Comment: 36 pages, 21 figures, Proceedings of LXXXI Les Houches School on
"Nanoscopic quantum transport", Les Houches, France, June 28-July 30, 200
Spectral Statistics at the Anderson Transition: Multifractality of Wave Functions and the Violation of the Normalization Sum Rule
The statistics of energy levels of electrons in a random potential is
considered in the critical energy window near the mobility edge. It is shown
that the multifractality of critical wave functions results in the violation of
the normalization sum rule in the thermodynamic limit and leads to the
quasi-Poisson linear term in the level number variance. The slope of the linear
term is equal to the sum rule deficiency which is expressed in terms of the
fractal dimension D(2).Comment: Proceedings of the Correlated Fermions and Transport in Mesoscopic
Systems Moriond Conference, Les Arcs, 1996. 10 pages REVTEX, one figur
Second-Parameter Globular Clusters in the Milky Way and in M33 as Tracers of Mass Loss from M31 in the Early Epoch?
I suggest that the bulk of the "young", second-parameter globular clusters
(SPGCs) observed in the outer halo of our Galaxy and recently found in other
massive spiral of the Local Group (LG), M33, may have originated due to mass
outflow from M31 and subsequent accretion of gas on the Galaxy and M33 in the
early epoch.Comment: 2 pages, no figures, uses IAU207_pasp.sty. To be published in the
Proceedings of the IAU Symposium 207, "Extragalactic Star Clusters", eds.
E.K. Grebel, D. Geisler and D. Minnit
Large-scale distribution of quasars in deep pencil-beam surveys
We have used integral two-point spatial correlation function and its second
derivative to analyze the distribution of quasars in three very deep surveys
published in the literature. Statistically significant ()
correlations were found at scales of Mpc in all of the
analyzed surveys. We have used the friends-of-friends cluster analysis to show
that these correlations can be explained by the presence of relatively small
quasar clusters (3-6 objects) which may possibly belong to larger structures
such as Large Quasar Groups found in the bigger surveys. The sizes of these
clusters along the redshift direction and distances between them are similar to
those for structures found recently in studies of CIV absorption systems. These
results present further evidence for the existence of large-scale structures at
redshifts .Comment: 5 pages, 2 figures, LaTeX (uses mn.sty), submitted to MNRAS, also
available at http://astro.nmsu.edu/~akravtso/publications.htm
Random matrix representations of critical statistics
We consider two random matrix ensembles which are relevant for describing
critical spectral statistics in systems with multifractal eigenfunction
statistics. One of them is the Gaussian non-invariant ensemble which
eigenfunction statistics is multifractal, while the other is the invariant
random matrix ensemble with a shallow, log-square confinement potential. We
demonstrate a close correspondence between the spectral as well as eigenfuncton
statistics of these random matrix ensembles and those of the random
tight-binding Hamiltonian in the point of the Anderson localization transition
in three dimensions. Finally we present a simple field theory in 1+1 dimensions
which reproduces level statistics of both of these random matrix models and the
classical Wigner-Dyson spectral statistics in the framework of the unified
formalism of Luttinger liquid. We show that the (equal-time) density
correlations in both random matrix models correspond to the finite-temperature
density correlations of the Luttinger liquid. We show that spectral
correlations in the invariant ensemble with log-square confinement correspond
to a Luttinger liquid in the 1+1 curved space-time with the event horizon,
similar to the phonon density correlations in the sonic analogy of Hawking
radiation in black holes.Comment: 21 pages, 4 figures, Chapter in the Handbook on Random Matrix Theor
Self-Induced Formaton of Metal-Rich Globulars in Bulges?
Taken together, key latest observations assume that (i) old metal-rich
globular cluster populations (MRGCPs) in bulges were able to form due to
essentially increased, self(internally)-induced star formation rate (SFR) in
the hosts, while galaxy merging played an additional role; (ii) massive star
cluster populations (MSCPs) in irregulars may be young, less prominent
counterparts of the old MRGCPs in spheroids.Comment: 1 page, no figures, poster presenrted at JD06, IUA General Assembly,
Sydney, July 17, 2003, to appear in Highlights of Astronom
Metal-Rich Globular Clusters: an Unaccounted Factor Responsible for Their Formation?
Presently unaccounted but quite probable "chemical factor" may be responsible
for the formation of old metal-rich globular clusters (MRGCs) in spheroids, as
well as of their conterparts, young (intermediate-age) massive star clusters
(MSCs) in irregulars. Their formation presumably occurs at the same stage of
the host galaxies' chemical evolution and is related to the essentially
increased SF activity in the hosts around the same metallicity, Zsol/3
([Fe/H]~-0.5). It is achieved very soon in massive spheroids, later in
lower-mass spheroids, and (much) more later in irregulars.Comment: 2 pages, 1 figure; to be published in the proceedings of the
conference "Globular Clusters - Guides to Galaxies", held in Concepcion,
Chile, March 200
Dephasing and Dynamic Localization in Quantum Dots
The effects of dynamic localization in a solid-state system -- a quantum dot
-- are considered. The theory of weak dynamic localization is developed for
non-interacting electrons in a closed quantum dot under arbitrary
time-dependent perturbation and its equivalence to the theory of weak Anderson
localization is demonstrated. The dephasing due to inelastic electron
scattering is shown to destroy the dynamic localization in a closed quantum dot
leading to the classical energy absorption at times much greater than the
inelastic scattering time. Finally a realistic case of a dot weakly connected
to leads is studied and it is shown that the dynamic localization may lead to a
drastic change of the shape of the Coulomb blockade peak in the dc conductance
vs the gate voltage.Comment: 24 pages, 7 figures, Proceeding of the NATO Conference "Fundamental
Problems of Mesoscopic Physics: Interaction and Decoherence.", Granada
(Spain
Random matrix theory: Wigner-Dyson statistics and beyond. (Lecture notes of a course given at SISSA (Trieste, Italy))
This is a course on Random Matrix Theory which includes traditional as well
as advanced topics presented with an extensive use of classical logarithmic
plasma analogy and that of the quantum systems of one-dimensional interacting
fermions with inverse square interaction (Calogero-Sutherland model). Certain
non-invariant random matrix ensembles are also considered with the emphasis on
the eigenfunction statistics in them. The course can also be viewed as
introduction to theory of localization where the (non-invariant) random matrix
ensembles play a role of the toy models to illustrate functional methods based
on super-vector/super-matrix representations.Comment: TeX, 27 page
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