14,273 research outputs found
Whose Schools Are Failing?
Persistent school segregation does not mean just that children of dierent racial and ethnic backgrounds attend dierent schools, but that their schools are also unequal in their students' performance. This study documents nationally the extent of disparities in student performance between schools attended by whites and Asians compared to blacks, Hispanics, and Native Americans. The analysis shows that a focus solely on schools at the bottom of the distribution as in No Child Left Behind would only modestly reduce the wide disparities between groups
Single-particle dynamics of the Anderson model: a two-self-energy description within the numerical renormalization group approach
Single-particle dynamics of the Anderson impurity model are studied using
both the numerical renormalization group (NRG) method and the local moment
approach (LMA). It is shown that a 'two-self-energy' description of dynamics
inherent to the LMA, as well as a conventional 'single-self-energy'
description, arise within NRG; each yielding correctly the same local
single-particle spectrum. Explicit NRG results are obtained for the broken
symmetry spectral constituents arising in a two-self-energy description, and
the total spectrum. These are also compared to analytical results obtained from
the LMA as implemented in practice. Very good agreement between the two is
found, essentially on all relevant energy scales from the high-energy Hubbard
satellites to the low-energy Kondo resonance.Comment: 12 pages, 6 figure
Spectral scaling and quantum critical behaviour in the pseudogap Anderson model
The pseudogap Anderson impurity model provides a classic example of an
essentially local quantum phase transition. Here we study its single-particle
dynamics in the vicinity of the symmetric quantum critical point (QCP)
separating generalized Fermi liquid and local moment phases, via the local
moment approach. Both phases are shown to be characterized by a low-energy
scale that vanishes at the QCP; and the universal scaling spectra, on all
energy scales, are obtained analytically. The spectrum precisely at the QCP is
also obtained; its form showing clearly the non-Fermi liquid, interacting
nature of the fixed point.Comment: 7 pages, 2 figure
The Dynamics of Food Deprivation and Overall Health: Evidence from the Canadian National Population Health Survey
The paper explores whether the responses to food deprivation questions on the longitudinal Canadian National Population Health Survey help explain the links between socio-economic status and health. Transitions in food deprivation status are correlated with changes in health status. While health transitions are correlated with changes in food deprivation status, there is little evidence that change in food deprivation status leads changes in health status but some evidence that change in health status leads change in food deprivation status.Food insecurity; Granger causality
Quantum phase transition in capacitively coupled double quantum dots
We investigate two equivalent, capacitively coupled semiconducting quantum
dots, each coupled to its own lead, in a regime where there are two electrons
on the double dot. With increasing interdot coupling a rich range of behavior
is uncovered: first a crossover from spin- to charge-Kondo physics, via an
intermediate SU(4) state with entangled spin and charge degrees of freedom;
followed by a quantum phase transition of Kosterlitz-Thouless type to a
non-Fermi liquid `charge-ordered' phase with finite residual entropy and
anomalous transport properties. Physical arguments and numerical
renormalization group methods are employed to obtain a detailed understanding
of the problem.Comment: 4 pages, 3 figure
Dynamics of capacitively coupled double quantum dots
We consider a double dot system of equivalent, capacitively coupled
semiconducting quantum dots, each coupled to its own lead, in a regime where
there are two electrons on the double dot. Employing the numerical
renormalization group, we focus here on single-particle dynamics and the
zero-bias conductance, considering in particular the rich range of behaviour
arising as the interdot coupling is progressively increased through the strong
coupling (SC) phase, from the spin-Kondo regime, across the SU(4) point to the
charge-Kondo regime; and then towards and through the quantum phase transition
to a charge-ordered (CO) phase. We first consider the two-self-energy
description required to describe the broken symmetry CO phase, and implications
thereof for the non-Fermi liquid nature of this phase. Numerical results for
single-particle dynamics on all frequency scales are then considered, with
particular emphasis on universality and scaling of low-energy dynamics
throughout the SC phase. The role of symmetry breaking perturbations is also
briefly discussed.Comment: 14 pages, 6 figure
The Dynamics of Food Deprivation and Overall Health: Evidence from the Canadian National Population Health Survey
The paper explores whether the responses to food deprivation questions on the longitudinal Canadian National Population Health Survey help explain the links between socio-economic status and health. Transitions in food deprivation status are correlated with changes in health status. While health transitions are correlated with changes in food deprivation status, there is little evidence that change in food deprivation status leads changes in health status but some evidence that change in health status leads change in food deprivation status.Food insecurity; Granger causality; NPHS
Measuring the Lifetime of Trapped Sleptons Using the General Purpose LHC Detectors
In supergravity where the gravitino is the lightest supersymmetric particle
(LSP), the next-to-lightest supersymmetric particle (NLSP) decays to the
gravitino with a naturally long lifetime (10^4 - 10^8). However, cosmological
constraints favour charged sleptons with lifetimes below a year as the natural
NLSP candidate. For this scenario we report a method to accurately determine
the slepton lifetime and SUSY cross-section from observation of the decays of
sleptons trapped in the material comprising the main detector (ATLAS, CMS). A
measurement of the lifetime to 5% is possible after 3 years at nominal
luminosity and running conditions. This method is sensitive to the
cosmologically preferred stau lifetime of ~37 days and does not require the use
of ancillary trapping volumes
Magnetic properties of the Anderson model: a local moment approach
We develop a local moment approach to static properties of the symmetric
Anderson model in the presence of a magnetic field, focussing in particular on
the strong coupling Kondo regime. The approach is innately simple and
physically transparent; but is found to give good agreement, for essentially
all field strengths, with exact results for the Wilson ratio, impurity
magnetization, spin susceptibility and related properties.Comment: 7 pages, 3 postscript figues. Latex 2e using the epl.cls Europhysics
Letters macro packag
- …