5,473 research outputs found
Perturbation study of the conductance through a finite Hubbard chain
Transport through a Hubbard chain of size N (=1,2,3,...) connected to
reservoirs is studied at T = 0 in an electron-hole symmetric case based on the
second-order perturbation theory in U. The result shows a typical even-odd
property corresponding to a Kondo or Mott-Hubbard physics. In this report,
specifically, we study the dependence of the conductance on the coupling
between the chain and reservoirs, which was not examined in detail in our
previous report [Phy. Rev. B 59, 12240 (1999)].Comment: 2 pages, LaTeX, submitted to LT22 (Physica B
Transmission probability through small interacting systems: application to a series of quantum dots
We apply a theory for the transmission probability of small interacting
systems, which was formulated based on the Kubo formalism in our previous
study, to a series of quantum dots described by the N-impurity Anderson model.
In this report, we present the transmission pobability for the system of N=2
calculated using the order self-energy and vertex corrections.
Particularly, we examine the features in the two typical parameter regions,
, where the Kondo effect or the inter-dot correlation
dominates. Here, is the inter-dot transfer and is the level
broadening caused by the coupling with the noninteracting leads.Comment: 2 pages, 2 figures: proccedings of LT23 (Hiroshima, August, 2002
Kondo screening of a high-spin Nagaoka state in a triangular quantum dot
We study transport through a triangle triple quantum dot connected to two
noninteracting leads using the numerical renormalization group (NRG). The
triangle has a high-spin ground state of S=1 caused by a Nagaoka
ferromagnetism, when it is isolated and has one extra electron introduced into
a half-filling. The results show that the conduction electrons screen the local
moment via two separate stages with different energy scales. The half of the
S=1 is screened first by one of the channel degrees, and then at very low
temperature the remaining half is fully screened to form a Kondo singlet. The
transport is determined by two phase shifts for quasi-particles with even and
odd parities, and then a two-terminal conductance in the series configuration
is suppressed , while plateau of a four-terminal
parallel conductance reaches a Unitary limit value of two conducting modes.Comment: 2pages, 2figures: fig1 is revised to show a narrow dip found in the
series conductanc
The Mass Distribution of SDSS J1004+4112 Revisited
We present a strong lens analysis of SDSS J1004+4112, a unique quasar lens
produced by a massive cluster of galaxies at z=0.68, using a newly developed
software for gravitational lensing. We find that our parametric mass model well
reproduces all observations including the positions of quasar images as well as
those of multiply imaged galaxies with measured spectroscopic redshifts, time
delays between quasar images, and the positions of faint central images. The
predicted large total magnification of \mu ~ 70 suggests that the lens system
is indeed a useful site for studying the fine structure of a distant quasar and
its host galaxy. The dark halo component is found to be unimodal centered on
the brightest cluster galaxy and the Chandra X-ray surface brightness profile.
In addition, the orientation of the halo component is quite consistent with
those of the brightest cluster galaxy and member galaxy distribution, implying
that the lensing cluster is a relaxed system. The radial profile of the
best-fit mass model is in good agreement with a mass profile inferred from the
X-ray observation. While the inner radial slope of the dark halo component is
consistent with being -1, a clear dependence of the predicted A-D time delay on
the slope indicates that an additional time delay measurement will improve
constraints on the mass model.Comment: 9 pages, 5 figures, accepted for publication in PASJ. The lens
software presented in the paper available at
http://www.slac.stanford.edu/~oguri/glafic
Self-Calibrated Cluster Counts as a Probe of Primordial Non-Gaussianity
We show that the ability to probe primordial non-Gaussianity with cluster
counts is drastically improved by adding the excess variance of counts which
contains information on the clustering. The conflicting dependences of changing
the mass threshold and including primordial non-Gaussianity on the mass
function and biasing indicate that the self-calibrated cluster counts well
break the degeneracy between primordial non-Gaussianity and the observable-mass
relation. Based on the Fisher matrix analysis, we show that the count variance
improves constraints on f_NL by more than an order of magnitude. It exhibits
little degeneracy with dark energy equation of state. We forecast that upcoming
Hyper Suprime-cam cluster surveys and Dark Energy Survey will constrain
primordial non-Gaussianity at the level \sigma(f_NL) \sim 8, which is
competitive with forecasted constraints from next-generation cosmic microwave
background experiments.Comment: 4 pages, 3 figures, accepted for publication in PR
Is There a Quad Problem among Optical Gravitational Lenses?
Most of optical gravitational lenses recently discovered in the Sloan Digital
Sky Survey Quasar Lens Search (SQLS) have two-images rather than four-images,
in marked contrast to radio lenses for which the fraction of four-image lenses
(quad fraction) is quite high. We revisit the quad fraction among optical
lenses by taking the selection function of the SQLS into account. We find that
the current observed quad fraction in the SQLS is indeed lower than, but
consistent with, the prediction of our theoretical model. The low quad fraction
among optical lenses, together with the high quad fraction among radio lenses,
implies that the quasar optical luminosity function has a relatively shallow
faint end slope.Comment: 9 pages, 4 figures, invited contribution to appear in New Journal of
Physics (Focus on Gravitational Lensing
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