609 research outputs found
Spin diffusion at finite electric and magnetic fields
Spin transport properties at finite electric and magnetic fields are studied
by using the generalized semiclassical Boltzmann equation. It is found that the
spin diffusion equation for non-equilibrium spin density and spin currents
involves a number of length scales that explicitly depend on the electric and
magnetic fields. The set of macroscopic equations can be used to address a
broad range of the spin transport problems in magnetic multilayers as well as
in semiconductor heterostructure. A specific example of spin injection into
semiconductors at arbitrary electric and magnetic fields is illustrated
Quantum Entanglement of Excitons in Coupled Quantum Dots
Optically-controlled exciton dynamics in coupled quantum dots is studied. We
show that the maximally entangled Bell states and Greenberger-Horne-Zeilinger
(GHZ) states can be robustly generated by manipulating the system parameters to
be at the avoided crossings in the eigenenergy spectrum. The analysis of
population transfer is systematically carried out using a dressed-state
picture. In addition to the quantum dot configuration that have been discussed
by Quiroga and Johnson [Phys. Rev. Lett. \QTR{bf}{83}, 2270 (1999)], we show
that the GHZ states also may be produced in a ray of three quantum dots with a
shorter generation time.Comment: 16 pages, 7 figures, to appear in Phys. Rev.
Star and Planet Formation with ALMA: an Overview
Submillimeter observations with ALMA will be the essential next step in our
understanding of how stars and planets form. Key projects range from detailed
imaging of the collapse of pre-stellar cores and measuring the accretion rate
of matter onto deeply embedded protostars, to unravelling the chemistry and
dynamics of high-mass star-forming clusters and high-spatial resolution studies
of protoplanetary disks down to the 1 AU scale.Comment: Invited review, 8 pages, 5 figures; to appear in the proceedings of
"Science with ALMA: a New Era for Astrophysics". Astrophysics & Space
Science, in pres
The composition of the protosolar disk and the formation conditions for comets
Conditions in the protosolar nebula have left their mark in the composition
of cometary volatiles, thought to be some of the most pristine material in the
solar system. Cometary compositions represent the end point of processing that
began in the parent molecular cloud core and continued through the collapse of
that core to form the protosun and the solar nebula, and finally during the
evolution of the solar nebula itself as the cometary bodies were accreting.
Disentangling the effects of the various epochs on the final composition of a
comet is complicated. But comets are not the only source of information about
the solar nebula. Protostellar disks around young stars similar to the protosun
provide a way of investigating the evolution of disks similar to the solar
nebula while they are in the process of evolving to form their own solar
systems. In this way we can learn about the physical and chemical conditions
under which comets formed, and about the types of dynamical processing that
shaped the solar system we see today.
This paper summarizes some recent contributions to our understanding of both
cometary volatiles and the composition, structure and evolution of protostellar
disks.Comment: To appear in Space Science Reviews. The final publication is
available at Springer via http://dx.doi.org/10.1007/s11214-015-0167-
Quantum theory of two-photon interference
In this paper, we study two-photon interference with the approach of photon
quantum theory, with specific attention to the two-photon interference
experiment carried out by Milena D'Angelo et al. (Phys. Rev. Lett 87:013602,
2001). We find the theoretical result is accordance with experiment data.Comment: arXiv admin note: substanital text overlap with arXiv:1011.3593, and
with arXiv:quant-ph/0408001, arXiv:quant-ph/0103035 by other author
The PHENIX Experiment at RHIC
The physics emphases of the PHENIX collaboration and the design and current
status of the PHENIX detector are discussed. The plan of the collaboration for
making the most effective use of the available luminosity in the first years of
RHIC operation is also presented.Comment: 5 pages, 1 figure. Further details of the PHENIX physics program
available at http://www.rhic.bnl.gov/phenix
Dynamical symmetry breaking in a 2D electron gas with a spectral node
We study a disordered 2D electron gas with a spectral node in a vicinity of
the node. After identifying the fundamental dynamical symmetries of this
system, the spontaneous breaking of the latter by a Grassmann field is studied
within a nonlinear sigma model approach. This allows us to reduce the average
two-particle Green's function to a diffusion propagator with a random diffusion
coefficient. The latter has non-degenerate saddle points and is treated by the
conventional self-consistent Born approximation. This leads to a renormalized
chemical potential and a renormalized diffusion coefficient, where the DC
conductivity increases linearly with the density of quasiparticles. Applied to
the special case of Dirac fermions, our approach provides a comprehensive
description of the minimal conductivity at the Dirac node as well as for the
V-shape conductivity inside the bands.Comment: 13 pages, 4 figures, extended versio
Gene Ă dietary pattern interactions in obesity: Analysis of up to 68 317 adults of European ancestry
Obesity is highly heritable. Genetic variants showing robust associations with obesity traits have been identified through genome-wide association studies. We investigated whether a composite score representing healthy diet modifies associations of these variants with obesity traits. Totally, 32 body mass index (BMI)- and 14 waist-hip ratio (WHR)-associated single nucleotide polymorphisms were genotyped, and genetic risk scores (GRS) were calculated in 18 cohorts of European ancestry (n = 68 317). Diet score was calculated based on self-reported intakes of whole grains, fish, fruits, vegetables, nuts/seeds (favorable) and red/processed meats, sweets, sugar-sweetened beverages and fried potatoes (unfavorable). Multivariable adjusted, linear regression within each cohort followed by inverse variance-weighted, fixed-effects meta-analysis was used to characterize: (a) associations of each GR
Genome-wide association meta-analysis of fish and EPA+DHA consumption in 17 US and European cohorts
Background: Regular fish and omega-3 consumption may have several health benefits and are recommended by major dietary guidelines. Yet, their intakes remain remarkably variable both within and across populations, which could partly owe to genetic influences. Objective: To identify common genetic variants that influence fish and dietary eicosapentaenoic acid plus docosahexaenoic acid (EPA+DHA) consumption. Design: We conducted genome-wide association (GWA) meta-analysis of fish (n = 86, 467) and EPA +DHA (n = 62, 265) consumption in 17 cohorts of European descent from the CHARGE (Cohorts for Heart and Aging Research in Genomic Epidemiology) Consortium Nutrition Working Group. Results from cohort-specific GWA analyses (additive model) for fish and EPA+DHA consumption were adjusted for age, sex, energy intake, and population stratification, and meta-analyzed separately using fixed-effect meta-analysis with inverse variance weights (METAL software). Additionally, heritability was estimated in 2 cohorts. Results: Heritability estimates for fish and EPA+DHA consumption ranged from 0.13
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