15,032 research outputs found
Apparent Clustering of Intermediate-redshift Galaxies as a Probe of Dark Energy
We show the apparent redshift-space clustering of galaxies in redshift range
of 0.2--0.4 provides surprisingly useful constraints on dark energy component
in the universe, because of the right balance between the density of objects
and the survey depth. We apply Fisher matrix analysis to the the Luminous Red
Galaxies (LRGs) in the Sloan Digital Sky Survey (SDSS), as a concrete example.
Possible degeneracies in the evolution of the equation of state (EOS) and the
other cosmological parameters are clarified.Comment: 5 pages, 3 figures, Phys.Rev.Lett., replaced with the accepted
versio
Optical generation of hybrid entangled state via entangling single-photon-added coherent state
We propose a feasible scheme to realize the optical entanglement of
single-photon-added coherent state (SPACS) and show that, besides the Sanders
entangled coherent state, the entangled SPACS also leads to new forms of hybrid
entanglement of quantum Fock state and classical coherent state. We probe the
essential difference of two types of hybrid entangled state (HES). This HES
provides a novel link between the discrete- and the continuous-variable
entanglement in a natural way.Comment: 6 pages, 2 figure
Progress in thin film GaAs solar cells
Solar cells using polycrystalline films of gallium arsenid
Compton Heating of the Intergalactic Medium by the Hard X-ray Background
High-resolution hydrodynamics simulations of the Ly-alpha forest in cold dark
matter dominated cosmologies appear to predict line widths that are
substantially narrower than those observed. Here we point out that Compton
heating of the intergalactic gas by the hard X-ray background (XRB), an effect
neglected in all previous investigations, may help to resolve this discrepancy.
The rate of gain in thermal energy by Compton scattering will dominate over the
energy input from hydrogen photoionization if the XRB energy density is
0.2x/ times higher than the energy density of the UV background at a
given epoch, where x is the hydrogen neutral fraction in units of 1e-6 and
is the mean X-ray photon energy in units of m_ec^2. The numerical
integration of the time-dependent rate equations shows that the intergalactic
medium approaches a temperature of about 1.5e4 K at z>3 in popular models for
the redshift evolution of the extragalactic background radiation. The
importance of Compton heating can be tested experimentally by measuring the
Ly-alpha line-width distribution as a function of redshift, thus the
Lyman-alpha forest may provide a useful probe of the evolution of the XRB at
high redshifts.Comment: LaTeX, 10 pages, 2 figures, final version to be published in the Ap
CD4+ T-cell responses to Epstein-Barr virus nuclear antigen EBNA1 in Chinese populations are highly focused on novel C-terminal domain-derived epitopes
Epstein-Barr virus nuclear antigen EBNA1, the one viral protein uniformly expressed in nasopharyngeal carcinoma (NPC), represents a prime target for T-cell-based immunotherapy. However, little is known about the EBNA1 epitopes, particularly CD4 epitopes, presented by HLA alleles in Chinese people, the group at highest risk for NPC. We analyzed the CD4 T-cell responses to EBNA1 in 78 healthy Chinese donors and found marked focusing on a small number of epitopes in the EBNA1 C-terminal region, including a DP5- restricted epitope that was recognized by almost half of the donors tested and elicited responses able to recognize EBNA1-expressing, DP5-positive target cells
Giant Conductance Oscillations In Mesoscopic Andreev Interferometers
We analyze the electrical conductance of a two-dimensional, phase
coherent structure in contact with two superconductors, which is known to be an
oscillatory function of the phase difference between the
superconductors. It is predicted that for a metallic sample, the amplitude of
oscillation is enhanced by placing a normal barrier at the interface and that,
by tuning the strength of the barrier, can be orders of magnitude greater than
values observed in recent experiments. Giant oscillations can also be obtained
without a barrier, provided a crucial sum rule is broken. This can be achieved
by disorder induced normal scattering. In the absence of zero phase
inter-channel scattering, the conductance possesses a zero phase minimum.Comment: 4 pages of Revtex, 6 figures available on reques
Relativistic Hartree-Fock-Bogoliubov theory with Density Dependent Meson-Nucleon Couplings
Relativistic Hartree-Fock-Bogoliubov (RHFB) theory with density-dependent
meson-nucleon couplings is presented. The integro-differential RHFB equations
are solved by expanding the different components of the quasi-particle spinors
in the complete set of eigen-solutions of the Dirac equations with Woods-Saxon
potentials. Using the finite-range Gogny force D1S as an effective interaction
in the pairing channel, systematic RHFB calculations are performed for Sn
isotopes and N=82 isotones. It is demonstrated that an appropriate description
of both mean field and pairing effects can be obtained within RHFB theory with
finite range Gogny pairing forces. Better systematics are also found in the
regions from the stable to the neutron-rich side with the inclusion of Fock
terms, especially in the presence of -tensor couplings.Comment: 11 pages, 2 tables and 4 figure
Time-Resolved Intraband Relaxation of Strongly-Confined Electrons and Holes in Colloidal PbSe Nanocrystals
The relaxation of strongly-confined electrons and holes between 1P and 1S
levels in colloidal PbSe nanocrystals has been time-resolved using femtosecond
transient absorption spectroscopy. In contrast to II-VI and III-V semiconductor
nanocrystals, both electrons and holes are strongly confined in PbSe
nanocrystals. Despite the large electron and hole energy level spacings (at
least 12 times the optical phonon energy), we consistently observe picosecond
time-scale relaxation. Existing theories of carrier relaxation cannot account
for these experimental results. Mechanisms that could possibly circumvent the
phonon bottleneck in IV-VI quantum dots are discussed
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