2,606 research outputs found
NRG for the bosonic single-impurity Anderson model: Dynamics
The bosonic single-impurity Anderson model (B-SIAM) is studied to understand
the local dynamics of an atomic quantum dot (AQD) coupled to a Bose-Einstein
condensation (BEC) state, which can be implemented to probe the entanglement
and the decoherence of a macroscopic condensate. Our recent approach of the
numerical renormalization group (NRG) calculation for the B-SIAM revealed a
zero-temperature phase diagram, where a Mott phase with local depletion of
normal particles is separated from a BEC phase with enhanced density of the
condensate. As an extension of the previous work, we present the calculations
of the local dynamical quantities of the B-SIAM which reinforce our
understanding of the physics in the Mott and the BEC phases.Comment: 12 pages, 13 figure
PageRank Revisited: On the Relationship between Node Degrees and Node Significances in Different Applications
Does (re-)entering the labour market at advanced ages protect against cognitive decline?:A matching difference-in-differences approach
peer reviewedBACKGROUND: While prolonged labour market participation becomes increasingly important in ageing societies, evidence on the impacts of entering or exiting work beyond age 65 on cognitive functioning is scarce.
METHODS: We use data from two large population-representative data sets from South Korea and the USA to investigate and compare the effects of the labour market (re-)entry and exit by matching employment and other confounder trajectories prior to the exposure. We chose the Korean Longitudinal Study of Aging (N=1872, 2006-2020) for its exceptionally active labour participation in later life and the Health and Retirement Study (N=4070, 2006-2020) for its growing inequality among US older adults in labour participation. We use the matching difference-in-differences (DID) method, which allows us to make causal claims by reducing biases through matching.
RESULTS: We find general positive effects of entering the labour market in South Korea (DID estimate: 0.653, 95% CI 0.167 to 1.133), while in the USA such benefit is not salient (DID estimate: 0.049, 95% CI -0.262 to 0.431). Exiting the late-life labour market leads to cognitive decline in both South Korea (DID estimate: -0.438, 95% CI -0.770 to -0.088) and the USA (DID estimate: -0.432, 95% CI -0.698 to -0.165).
CONCLUSIONS: Findings suggest that Korean participants cognitively benefited from late-life labour market participation, while US participants did not. Differences in participant characteristics and reasons for labour market participation may have led to the differential findings. We found the negative effects of exiting the late-life labour force in both countries
Two-gap and paramagnetic pair-breaking effects on upper critical field of SmFeAsO and SmFeAsOF single crystals
We investigated the temperature dependence of the upper critical field
[] of fluorine-free SmFeAsO and fluorine-doped
SmFeAsOF single crystals by measuring the resistive transition
in low static magnetic fields and in pulsed fields up to 60 T. Both crystals
show that 's along the c axis [] and in an -planar
direction [] exhibit a linear and a sublinear increase,
respectively, with decreasing temperature below the superconducting transition.
's in both directions deviate from the conventional one-gap
Werthamer-Helfand-Hohenberg theoretical prediction at low temperatures. A
two-gap nature and the paramagnetic pair-breaking effect are shown to be
responsible for the temperature-dependent behavior of and
, respectively.Comment: 21 pages, 8 figure
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Benchmarking urine storage and collection conditions for evaluating the female urinary microbiome.
Standardized conditions for collection, preservation and storage of urine for microbiome research have not been established. We aimed to identify the effects of the use of preservative AssayAssure® (AA), and the effects of storage time and temperatures on reproducibility of urine microbiome results. We sequenced the V3-4 segment of the 16S rRNA gene to characterize the bacterial community in the urine of a cohort of women. Each woman provided a single voided urine sample, which was divided into aliquots and stored with and without AA, at three different temperatures (room temperature [RT], 4 °C, or -20 °C), and for various time periods up to 4 days. There were significant microbiome differences in urine specimens stored with and without AA at all temperatures, but the most significant differences were observed in alpha diversity (estimated number of taxa) at RT. Specimens preserved at 4 °C and -20 °C for up to 4 days with or without AA had no significant alpha diversity differences. However, significant alpha diversity differences were observed in samples stored without AA at RT. Generally, there was greater microbiome preservation with AA than without AA at all time points and temperatures, although not all results were statistically significant. Addition of AA preservative, shorter storage times, and colder temperatures are most favorable for urinary microbiome reproducibility
Seismic characterization of fluid migration and Pockmarks formation in the Estremadura Spur, Western Iberian Margin
: A field with more than 30 pockmarks was recently discovered in the Estremadura Spur outer shelf (Lourinhã Monocline). The processing of high-resolution seismic lines permitted the characterization of this pockmark field and of the seismic sequence of the Plio-Quaternary basin where they occur. Results show that this region has been affected by several episodes of fluid migration and fluid escape during the Plio-Quaternary, expressed by the presence of the pockmarks that at the present-time seem to be mainly inactive
Green's function approach to transport through a gate-all-around Si nanowire under impurity scattering
We investigate transport properties of gate-all-around Si nanowires using
non-equilibrium Green's function technique. By taking into account of the
ionized impurity scattering we calculate Green's functions self-consistently
and examine the effects of ionized impurity scattering on electron densities
and currents. For nano-scale Si wires, it is found that, due to the impurity
scattering, the local density of state profiles loose it's interference
oscillations as well as is broaden and shifted. In addition, the impurity
scattering gives rise to a different transconductance as functions of
temperature and impurity scattering strength when compared with the
transconductance without impurity scattering.Comment: 8 pages, 4 figure
Numerical Renormalization Group for Quantum Impurities in a Bosonic Bath
We present a detailed description of the recently proposed numerical
renormalization group method for models of quantum impurities coupled to a
bosonic bath. Specifically, the method is applied to the spin-boson model, both
in the Ohmic and sub-Ohmic cases. We present various results for static as well
as dynamic quantities and discuss details of the numerical implementation,
e.g., the discretization of a bosonic bath with arbitrary continuous spectral
density, the suitable choice of a finite basis in the bosonic Hilbert space,
and questions of convergence w.r.t. truncation parameters. The method is shown
to provide high-accuracy data over the whole range of model parameters and
temperatures, which are in agreement with exact results and other numerical
data from the literature.Comment: 23 pages, 21 figures; three references and one figure adde
Production of photons by the parametric resonance in the dynamical Casimir effect
We calculate the number of photons produced by the parametric resonance in a
cavity with vibrating walls. We consider the case that the frequency of
vibrating wall is which is a generalization of other
works considering only , where is the fundamental-mode
frequency of the electromagnetic field in the cavity. For the calculation of
time-evolution of quantum fields, we introduce a new method which is borrowed
from the time-dependent perturbation theory of the usual quantum mechanics.
This perturbation method makes it possible to calculate the photon number for
any and to observe clearly the effect of the parametric resonance.Comment: 15 pages, RevTeX, no figure
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