10,206 research outputs found
The ultra-compact binary candidate KUV 23182+1007 is a bright quasar
KUV 23182+1007 was identified as a blue object in the Kiso UV Survey in the
1980s. Classification-dispersion spectroscopy showed a featureless continuum
except for a strong emission line in the region of He II 4686 A. This is a
hallmark of the rare AM CVn class of cataclysmic variable star, so we have
obtained a high-S/N blue spectrum of this object to check its classification.
Instead, the spectrum shows a strong quasar-like emission line centred on 4662
A. Comparison with the SDSS quasar template spectra confirms that KUV
23182+1007 is a quasar with a redshift of z = 0.665.Comment: 4 pages, 2 figures, to appear in IBVS. Data are available from
http://www.astro.keele.ac.uk/~jkt
An exact-diagonalization study of rare events in disordered conductors
We determine the statistical properties of wave functions in disordered
quantum systems by exact diagonalization of one-, two- and quasi-one
dimensional tight-binding Hamiltonians. In the quasi-one dimensional case we
find that the tails of the distribution of wave-function amplitudes are
described by the non-linear sigma-model. In two dimensions, the tails of the
distribution function are consistent with a recent prediction based on a direct
optimal fluctuation method.Comment: 13 pages, 5 figure
The influence of self-citation corrections on Egghe's g index
The g index was introduced by Leo Egghe as an improvement of Hirsch's index h
for measuring the overall citation record of a set of articles. It better takes
into account the highly skewed frequency distribution of citations than the h
index. I propose to sharpen this g index by excluding the self-citations. I
have worked out nine practical cases in physics and compare the h and g values
with and without self-citations. As expected, the g index characterizes the
data set better than the h index. The influence of the self-citations appears
to be more significant for the g index than for the h index.Comment: 9 pages, 2 figures, submitted to Scientometric
Localization of non-interacting electrons in thin layered disordered systems
Localization of electronic states in disordered thin layered systems with b
layers is studied within the Anderson model of localization using the
transfer-matrix method and finite-size scaling of the inverse of the smallest
Lyapunov exponent. The results support the one-parameter scaling hypothesis for
disorder strengths W studied and b=1,...,6. The obtained results for the
localization length are in good agreement with both the analytical results of
the self-consistent theory of localization and the numerical scaling studies of
the two-dimensional Anderson model. The localization length near the band
center grows exponentially with b for fixed W but no
localization-delocalization transition takes place.Comment: 6 pages, 5 figure
Two-color QCD with staggered fermions at finite temperature under the influence of a magnetic field
In this paper we investigate the influence of a constant external magnetic
field on the finite-temperature phase structure and the chiral properties of a
simplified lattice model for QCD. We assume an SU(2) gauge symmetry and employ
dynamical staggered fermions of identical mass without rooting, corresponding
to Nf=4 flavors of identical electric charge. For fixed mass (given in lattice
units) the critical temperature is seen to rise with the magnetic field
strength. For three fixed beta-values, selected such that we stay (i) within
the chirally broken phase, (ii) within the transition region or (iii) within
the chirally restored phase, we study the approach to the chiral limit for
various values of the magnetic field. Within the chirally broken (confinement)
phase the chiral condensate is found to increase monotonically with a growing
magnetic field strength. In the chiral limit the increase starts linear in
agreement with a chiral model studied by Shushpanov and Smilga. Within the
chirally restored (deconfinement) phase the chiral condensate tends to zero in
the chiral limit, irrespective of the strength of the magnetic field.Comment: 15 pages, 12 figures; version accepted by Physical Review
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