3,976 research outputs found
Physical condition and spin-resolved exchange correlation kernels in an inhomogeneous many electron system
We first exploit the spin symmetry relation for the exact exchange correlation
kernel in an inhomogeneous many electron system
with arbitrary spin polarization . The physical condition required to
satisfy the specific symmetry relation is derived and examined for simple
ferromagnetic-nonmagnetic structure by taking the electrochemical potential
into account. The condition is then applied to several composite systems useful
in spintronics applications such as the magnetic system with net spin
polarization.Comment: 5 pages, 1 figur
The decline in teen labor force participation
The authors examine the recent decline in teen work activity, offering explanations for both the long secular decline since the late 1970s and the recent acceleration in this decline since 2000. They argue that much of this pattern is due to a significant increase in the rewards to formal education. They also explore the importance of changes to labor demand, crowding out by substitutable workers, the increased work activity of mothers, and increases in wealth.Labor mobility
Explaining the decline in teen labor force participation
Fewer teenagers are participating in the labor force today than at any point since WWII. At just under 44%, teen labor force participation is 15 percentage points below its peak in the late 1970s. Why has there been a long-run secular decline in the work activity of young adults, and why has it sharply accelerated in the last five years?Labor market ; Employees, Training of
Induced local spin-singlet amplitude and pseudogap in high cuprates
In this paper we show that local spin-singlet amplitude with d-wave symmetry,
, can be induced by short-range spin correlations even
in the absence of pairing interactions. Fluctuation theory is formulated to
make connection between pseudogap temperature $T^{*}$, pseudogap size
$\Delta_{pg}$ and . In the present scenario for the
pseudogap, the normal state pseudogap is caused by the induced local
spin-singlet amplitude due to short-range spin correlations, which compete in
the low energy sector with superconducting correlations to make go to
zero near half-filling. Calculated falls from a high value onto the
line and closely follows mean-field N\'{e}el temperature .
The calculated is in good agreement with experimental results. We
propose an experiment in which the present scenario can be critically tested.Comment: 5 pages, 3 figure
Collapse or Swelling Dynamics of Homopolymer Rings: Self-consistent Hartree approach
We investigate by the use of the Martin - Siggia - Rose generating functional
technique and the self - consistent Hartree approximation, the dynamics of the
ring homopolymer collapse (swelling) following an instantaneous change into a
poor (good) solvent conditions.The equation of motion for the time dependent
monomer - to - monomer correlation function is systematically derived. It is
argued that for describing of the coarse - graining process (which neglects the
capillary instability and the coalescence of ``pearls'') the Rouse mode
representation is very helpful, so that the resulting equations of motion can
be simply solved numerically. In the case of the collapse this solution is
analyzed in the framework of the hierarchically crumpled fractal picture, with
crumples of successively growing scale along the chain. The presented numerical
results are in line with the corresponding simple scaling argumentation which
in particular shows that the characteristic collapse time of a segment of
length scales as (where is a bare
friction coefficient and is a depth of quench). In contrast to the
collapse the globule swelling can be seen (in the case that topological effects
are neglected) as a homogeneous expansion of the globule interior. The swelling
of each Rouse mode as well as gyration radius is discussed.Comment: 20 pages, 7 figures, submitted to Phys. Rev.
Pseudogap induced by short-range spin correlations in a doped Mott insulator
We study the evolution of a Mott-Hubbard insulator into a correlated metal
upon doping in the two-dimensional Hubbard model using the Cellular Dynamical
Mean Field Theory. Short-range spin correlations create two additional bands
apart from the familiar Hubbard bands in the spectral function. Even a tiny
doping into this insulator causes a jump of the Fermi energy to one of these
additional bands and an immediate momentum dependent suppression of the
spectral weight at this Fermi energy. The pseudogap is closely tied to the
existence of these bands. This suggests a strong-coupling mechanism that arises
from short-range spin correlations and large scattering rates for the pseudogap
phenomenon seen in several cuprates.Comment: 6 pages, 6 figure
New Insights into Wnt-Lrp5/6-β-Catenin Signaling in Mechanotransduction
Mechanical loading is essential to maintain normal bone metabolism and the balance between bone formation and resorption. The cellular mechanisms that control mechanotransduction are not fully defined, but several key pathways have been identified. We discuss the roles of several components of the Wnt signaling cascade, namely Lrp5, Lrp6, and β-catenin in mechanical loading-induced bone formation. Lrp5 is an important Wnt co-receptor for regulating bone mass and mechanotransduction, and appears to function principally by augmenting bone formation. Lrp6 also regulates bone mass but its action might involve resorption as well as formation. The role of Lrp6 in mechanotransduction is unclear. Studies addressing the role of β-catenin in bone metabolism and mechanotransduction highlight the uncertainties in downstream modulators of Lrp5 and Lrp6. Taken together, these data indicate that mechanical loading might affect bone regulation triggering the canonical Wnt signaling (and perhaps other pathways) not only via Lrp5 but also via Lrp6. Further work is needed to clarify the role of the Wnt signaling pathway in Lrp5 and/or Lrp6-mediated mechanotransduction, which could eventually lead to powerful therapeutic agents that might mimic the anabolic effects of mechanical stimulation
Short-range spin correlations and induced local spin-singlet amplitude in the Hubbard model
In this paper, from the microscopic Hubbard Hamiltonian we extract the local
spin-singlet amplitude due to short-range spin correlations, and quantify its
strength near half-filling. As a first application of the present approach, we
study a problem of the energy dispersion and its d-wave modulation in the
insulating cuprates, SrCuOCl and CaCuOCl.
Without any adjustable parameters, most puzzling issues are naturally and
quantitatively explained within the present approach.Comment: 6 pages, 3 figure
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