137,916 research outputs found
Superconducting pairing of interacting electrons: implications from the two-impurity Anderson model
We study the non-local superconducting pairing of two interacting Anderson
impurities, which has an instability near the quantum critical point from the
competition between the Kondo effect and an antiferromagnetic inter-impurity
spin exchange interaction. As revealed by the dynamics over the whole energy
range, the superconducting pairing fluctuations acquire considerable strength
from an energy scale much higher than the characteristic spin fluctuation scale
while the low energy behaviors follow those of the staggered spin
susceptibility. We argue that the glue to the superconducting pairing is not
the spin fluctuations, but rather the effective Coulomb interaction. On the
other hand, critical spin fluctuations in the vicinity of quantum criticality
are also crucial to a superconducting pairing instability, by preventing a
Fermi liquid fixed point being reached to keep the superconducting pairing
fluctuations finite at low energies. A superconducting order, to reduce the
accumulated entropy carried by the critical degrees of freedom, may arise
favorably from this instability.Comment: 6 pages, 2 figure
Performance Evaluation of Distributed-Antenna Communications Systems Using Beam-Hopping
Digital beamforming (DBF) techniques are capable of improving the performance of communications systems significantly. However, if the transmitted signals are conflicted with strong interference, especially, in the direction of the transmitted beams , these directional jamming signals will severely degrade the system performance. In order to efficiently mitigate the interference of the directional jammers, in this contribution a beam-hopping (BH) communications scheme is proposed. In the proposed BH communications scheme, only one pair of the beams is used for transmission and it hops from one to the next according to an assigned BH pattern. In this contribution a range of expressions in terms of the average SINR performance have been derived, when both the uplink and downlink are considered. The average SINR performance of the proposed BH scheme and that of the conventional single-beam (SB) as well as multiple-beam (MB) assisted beam-processing schemes have been investigated. Our analysis and results show that the proposed BH scheme is capable of efficiently combating the directional jamming, with the aid of utilizing the directional gain of the beams generated by both the transmitter and the receiver. Furthermore, the BH scheme is capable of reducing the intercept probability of the communications. Therefore, the proposed BH scheme is suitable for communications, when several distributed antenna arrays are available around a mobile
Analytical modeling of open-Circuit air-Gap field distributions in multisegment and multilayer interior permanent-magnet machines
We present a simple lumped magnetic circuit model for interior permanent-magnet (IPM) machines with multisegment and multilayer permanent magnets. We derived analytically the open-circuit air-gap field distribution, average air-gap flux density, and leakage fluxes. To verify the developed models and analytical method, we adopted finite-element analysis (FEA). We show that for prototype machines, the errors between the FEA and analytically predicted results are 1% for multisegment IPM machines and 2% for multilayer IPM machines. By utilizing the developed lumped magnetic circuit models, the IPM machines can be optimized for maximum fundamental and minimum total harmonic distortion of the air-gap flux density distribution
Calculating Biological Behaviors of Epigenetic States in Phage lambda Life Cycle
Gene regulatory network of lambda phage is one the best studied model systems
in molecular biology. More 50 years of experimental study has provided a
tremendous amount of data at all levels: physics, chemistry, DNA, protein, and
function. However, its stability and robustness for both wild type and mutants
has been a notorious theoretical/mathematical problem. In this paper we report
our successful calculation on the properties of this gene regulatory network.
We believe it is of its first kind. Our success is of course built upon
numerous previous theoretical attempts, but following 3 features make our
modeling uniqu:
1) A new modeling method particular suitable for stability and robustness
study;
2) Paying a close attention to the well-known difference of in vivo and in
vitro;
3) Allowing more important role for noise and stochastic effect to play.
The last two points have been discussed by two of us (Ao and Yin,
cond-mat/0307747), which we believe would be enough to make some of previous
theoretical attempts successful, too. We hope the present work would stimulate
a further interest in the emerging field of gene regulatory network.Comment: 16 pages, 3 figures, 1 tabl
Description of Charged Particle Pseudorapidity Distributions in Pb+Pb Collisions with Tsallis Thermodynamics
The centrality dependence of pseudorapidity distributions for charged
particles produced in Au+Au collisions at GeV and 200 GeV
at RHIC, and in Pb+Pb collisions at TeV at LHC are
investigated in the fireball model, assuming that the rapidity axis is
populated with fireballs following one distribution function. We assume that
the particles in the fireball fulfill the Tsallis distribution. The theoretical
results are compared with the experimental measurements and a good agreement is
found. Using these results, the pseudorapidity distributions of charged
particles produced in Pb+Pb central collisions at TeV and
10 TeV are predicted.Comment: 9 pages, 8 figure
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