113 research outputs found
The determinants of employment status in Egypt
Egyptian labor market is moving from a period of high overall unemployment to one where unemployment is increasingly concentrated among specific groups whose access to the private-sector labor market is limited. Educated young women are more adversely affected than their male counterparts by the transition to a private-sector-led economy. There is no systematic link between youth unemployment among new entrants and poverty unless it is the head of the household who is unemployed. An economic policy environment that is favorable for labor-intensive, export-oriented industries would help absorb the new entrants into the labor market, and the prospect is particularly good for young female workers. Policymakers should consider a reduction in the female-specific employer mandates (such as the existing provision for a generous maternity leave) that raise the cost of hiring women.Labor market. ,Unemployment. ,Female labor ,Egypt. ,
The determinants of employment status in Egypt
Egyptian labor market is moving from a period of high overall unemployment to one where unemployment is increasingly concentrated among specific groups whose access to the private-sector labor market is limited. Educated young women are more adversely affected than their male counterparts by the transition to a private-sector-led economy. There is no systematic link between youth unemployment among new entrants and poverty unless it is the head of the household who is unemployed. An economic policy environment that is favorable for labor-intensive, export-oriented industries would help absorb the new entrants into the labor market, and the prospect is particularly good for young female workers. Policymakers should consider a reduction in the female-specific employer mandates (such as the existing provision for a generous maternity leave) that raise the cost of hiring women.Labor market. ,Unemployment. ,Female labor ,Egypt. ,
Systematic errors in Gaussian Quantum Monte Carlo and a systematic study of the symmetry projection method
Gaussian Quantum Monte Carlo (GQMC) is a stochastic phase space method for
fermions with positive weights. In the example of the Hubbard model close to
half filling it fails to reproduce all the symmetries of the ground state
leading to systematic errors at low temperatures. In a previous work [Phys.
Rev. B {\bf 72}, 224518 (2005)] we proposed to restore the broken symmetries by
projecting the density matrix obtained from the simulation onto the ground
state symmetry sector. For ground state properties, the accuracy of this method
depends on a {\it large overlap} between the GQMC and exact density matrices.
Thus, the method is not rigorously exact. We present the limits of the approach
by a systematic study of the method for 2 and 3 leg Hubbard ladders for
different fillings and on-site repulsion strengths. We show several indications
that the systematic errors stem from non-vanishing boundary terms in the
partial integration step in the derivation of the Fokker-Planck equation.
Checking for spiking trajectories and slow decaying probability distributions
provides an important test of the reliability of the results. Possible
solutions to avoid boundary terms are discussed. Furthermore we compare results
obtained from two different sampling methods: Reconfiguration of walkers and
the Metropolis algorithm.Comment: 11 pages, 14 figures, revised version, new titl
Systematic errors in Gaussian Quantum Monte Carlo and a systematic study of the symmetry projection method
Gaussian Quantum Monte Carlo (GQMC) is a stochastic phase space method for
fermions with positive weights. In the example of the Hubbard model close to
half filling it fails to reproduce all the symmetries of the ground state
leading to systematic errors at low temperatures. In a previous work [Phys.
Rev. B {\bf 72}, 224518 (2005)] we proposed to restore the broken symmetries by
projecting the density matrix obtained from the simulation onto the ground
state symmetry sector. For ground state properties, the accuracy of this method
depends on a {\it large overlap} between the GQMC and exact density matrices.
Thus, the method is not rigorously exact. We present the limits of the approach
by a systematic study of the method for 2 and 3 leg Hubbard ladders for
different fillings and on-site repulsion strengths. We show several indications
that the systematic errors stem from non-vanishing boundary terms in the
partial integration step in the derivation of the Fokker-Planck equation.
Checking for spiking trajectories and slow decaying probability distributions
provides an important test of the reliability of the results. Possible
solutions to avoid boundary terms are discussed. Furthermore we compare results
obtained from two different sampling methods: Reconfiguration of walkers and
the Metropolis algorithm.Comment: 11 pages, 14 figures, revised version, new titl
Quantum Monte Carlo Loop Algorithm for the t-J Model
We propose a generalization of the Quantum Monte Carlo loop algorithm to the
t-J model by a mapping to three coupled six-vertex models. The autocorrelation
times are reduced by orders of magnitude compared to the conventional local
algorithms. The method is completely ergodic and can be formulated directly in
continuous time. We introduce improved estimators for simulations with a local
sign problem. Some first results of finite temperature simulations are
presented for a t-J chain, a frustrated Heisenberg chain, and t-J ladder
models.Comment: 22 pages, including 12 figures. RevTex v3.0, uses psf.te
Thermodynamics of the half-filled Kondo lattice model around the atomic limit
We present a perturbation theory for studying thermodynamic properties of the
Kondo spin liquid phase of the half-filled Kondo lattice model. The grand
partition function is derived to calculate chemical potential, spin and charge
susceptibilities and specific heat. The treatment is applicable to the model
with strong couplings in any dimensions (one, two and three dimensions). The
chemical potential equals zero at any temperatures, satisfying the requirement
of the particle-hole symmetry. Thermally activated behaviors of the
spin(charge) susceptibility due to the spin(quasiparticle) gap can be seen and
the two-peak structure of the specific heat is obtained. The same treatment to
the periodic Anderson model around atomic limit is also briefly discussed.Comment: 5 pages, 3 figures, to appear in Phys. Rev.
Absence of association between behavior problems in childhood and hypertension in midlife
Background It is known that behavior in childhood is associated with certain physical and mental health problems in midlife. However, there is limited evidence on the role of childhood behavior problems in the development of hypertension in adulthood. The present study aimed to examine whether behavior problems in childhood influenced the risk of hypertension in midlife in the United Kingdom 1958 birth cohort. Methods The 1958 British birth cohort comprised 17,638 individuals born in the first week of March 1958 in the United Kingdom. Behavior problems were assessed at 7, 11, and 16 years of age by parents and teachers. At age 45, blood pressure was measured and hypertension was recorded if blood pressure was ≥140/90 mm Hg or if the participants were informed by their health professionals that they had high blood pressure. Behavioral information was reported according to the Rutter Children's Behaviour Questionnaire (RCBQ) and the Bristol Social Adjustment Guide (BSAG). Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated to examine behavior problems in childhood in relation to hypertension at 45 years of age according to logistic regression analysis, with adjustment for sex, social class in childhood and adulthood, childhood cognition, birth weight, gestational age at birth, body mass index (BMI), smoking, alcohol consumption, and physical activity. Results Behavior problems reported by parents at 7, 11, and 16 years were not associated with hypertension in midlife (OR, 0.93; 95% CI, 0.81, 1.07; OR, 0.95; 95% CI, 0.81, 1.11; OR, 0.98; 95% CI, 0.85, 1.12, respectively). Similarly, teacher-reported behavior problems at 7, 11, and 16 years were not associated with hypertension in midlife (OR, 0.92; 95% CI, 0.72, 1.18; OR, 0.92; 95% CI, 0.84, 1.02; OR, 1.03; 95% CI, 0.92, 1.15, respectively). Further separate analyses showed similar results for males and females. Conclusion There is no association between behavior problems in childhood and hypertension in midlife
Two-orbital SU(N) magnetism with ultracold alkaline-earth atoms
Fermionic alkaline-earth atoms have unique properties that make them
attractive candidates for the realization of novel atomic clocks and degenerate
quantum gases. At the same time, they are attracting considerable theoretical
attention in the context of quantum information processing. Here we demonstrate
that when such atoms are loaded in optical lattices, they can be used as
quantum simulators of unique many-body phenomena. In particular, we show that
the decoupling of the nuclear spin from the electronic angular momentum can be
used to implement many-body systems with an unprecedented degree of symmetry,
characterized by the SU(N) group with N as large as 10. Moreover, the interplay
of the nuclear spin with the electronic degree of freedom provided by a stable
optically excited state allows for the study of spin-orbital physics. Such
systems may provide valuable insights into strongly correlated physics of
transition metal oxides, heavy fermion materials, and spin liquid phases.Comment: 15 pages, 10 figures. V2: extended experimental accessibility and
Kondo sections in the main text (including new Fig. 5b) and in the Methods;
reorganized other parts; added reference
Orbital currents and charge density waves in a generalized Hubbard ladder
We study a generalized Hubbard model on the two-leg ladder at zero
temperature, focusing on a parameter region with staggered flux (SF)/d-density
wave (DDW) order. To guide our numerical calculations, we first investigate the
location of a SF/DDW phase in the phase diagram of the half-filled weakly
interacting ladder using a perturbative renormalization group (RG) and
bosonization approach. For hole doping delta away from half-filling,
finite-size density-matrix renormalization-group (DMRG) calculations are used
to study ladders with up to 200 rungs for intermediate-strength interactions.
In the doped SF/DDW phase, the staggered rung current and the rung electron
density both show periodic spatial oscillations, with characteristic
wavelengths 2/delta and 1/delta, respectively, corresponding to ordering
wavevectors 2k_F and 4k_F for the currents and densities, where 2k_F =
pi(1-delta). The density minima are located at the anti-phase domain walls of
the staggered current. For sufficiently large dopings, SF/DDW order is
suppressed. The rung density modulation also exists in neighboring phases where
currents decay exponentially. We show that most of the DMRG results can be
qualitatively understood from weak-coupling RG/bosonization arguments. However,
while these arguments seem to suggest a crossover from non-decaying
correlations to power-law decay at a length scale of order 1/delta, the DMRG
results are consistent with a true long-range order scenario for the currents
and densities.Comment: 24 pages, 17 figures. Follow-up to cond-mat/0209444. (v2) Some
revisions in text, improved presentation. Minor changes in title, abstract
and reference
Lower cardiorespiratory fitness contributes to increased insulin resistance and fasting glycaemia in middle-aged South Asian compared with European men living in the UK
AIMS/HYPOTHESIS: This study aimed to determine the extent to which increased insulin resistance and fasting glycaemia in South Asian men, compared with white European men, living in the UK, was due to lower cardiorespiratory fitness (maximal oxygen uptake [[Formula: see text]]) and physical activity. METHODS: One hundred South Asian and 100 age- and BMI-matched European men without diagnosed diabetes, aged 40–70 years, had fasted blood taken for measurement of glucose concentration, HOMA-estimated insulin resistance (HOMA(IR)), plus other risk factors, and underwent assessment of physical activity (using accelerometry), [Formula: see text], body size and composition, and demographic and other lifestyle factors. For 13 South Asian and one European man, HbA(1c) levels were >6.5% (>48 mmol/mol), indicating potential undiagnosed diabetes; these men were excluded from the analyses. Linear regression models were used to determine the extent to which body size and composition, fitness and physical activity variables explained differences in HOMA(IR) and fasting glucose between South Asian and European men. RESULTS: HOMA(IR) and fasting glucose were 67% (p < 0.001) and 3% (p < 0.018) higher, respectively, in South Asians than Europeans. Lower [Formula: see text], lower physical activity and greater total adiposity in South Asians individually explained 68% (95% CI 45%, 91%), 29% (11%, 46%) and 52% (30%, 80%), respectively, and together explained 83% (50%, 119%) (all p < 0.001) of the ethnic difference in HOMA(IR). Lower [Formula: see text] and greater total adiposity, respectively, explained 61% (9%, 111%) and 39% (9%, 76%) (combined effect 63% [8%, 115%]; all p < 0.05) of the ethnic difference in fasting glucose. CONCLUSIONS/INTERPRETATION: Lower cardiorespiratory fitness is a key factor associated with the excess insulin resistance and fasting glycaemia in middle-aged South Asian, compared with European, men living in the UK. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s00125-013-2969-y) contains peer-reviewed but unedited supplementary material, which is available to authorised users
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