666 research outputs found
Over-populated gauge fields on the lattice
We study nonequilibrium dynamics of SU(2) pure gauge theory starting from
initial over-population, where intense classical gauge fields are characterized
by a single momentum scale Q_s. Classical-statistical lattice simulations
indicate a quick evolution towards an approximate scaling behavior with
exponent 3/2 at intermediate times. Remarkably, the value for the scaling
exponent may be understood as arising from the leading O(g^2) contribution in
the presence of a time-dependent background field. The phenomenon is associated
to weak wave turbulence describing an energy cascade towards higher momenta.
This particular aspect is very similar to what is observed for scalar theories,
where an effective cubic interaction arises because of the presence of a
time-dependent Bose condensate.Comment: 15 pages, 4 figure
Real-time effective-action approach to the Anderson quantum dot
The non-equilibrium time evolution of an Anderson quantum dot is
investigated. The quantum dot is coupled between two leads forming a
chemical-potential gradient. We use Kadanoff-Baym dynamic equations within a
non-perturbative resummation of the s-channel bubble chains. The effect of the
resummation leads to the introduction of a frequency-dependent 4-point vertex.
The tunneling to the leads is taken into account exactly. The method allows the
determination of the transient as well as stationary transport through the
quantum dot, and results are compared with different schemes discussed in the
literature (fRG, ISPI, tDMRG and QMC).Comment: 12 pages, 13 figure
Bose condensation far from equilibrium
The formation of Bose condensates far from equilibrium can play an important
role in our understanding of collision experiments of heavy nuclei or for the
evolution of the early universe. In the relativistic quantum world particle
number changing processes can counteract Bose condensation, and there is a
considerable debate about the relevance of this phenomenon in this context. We
show that the involved question of Bose condensation from initial
over-population can be answered for the example of scalar field theories.
Condensate formation occurs as a consequence of an inverse particle cascade
with a universal power-law spectrum. This particle transport towards low
momenta is part of a dual cascade, in which energy is also transfered by weak
wave turbulence towards higher momenta. To highlight the importance of number
changing processes for the subsequent decay of the condensate, we also compare
to non-relativistic theories with exact number conservation. We discuss the
relevance of these results for nonabelian gauge theories.Comment: 4 pages, 5 figures, PRL version, minor change
A rapid and robust assay for detection of S-phase cell cycle progression in plant cells and tissues by using ethynyl deoxyuridine
<p>Abstract</p> <p>Background</p> <p>Progress in plant cell cycle research is highly dependent on reliable methods for detection of cells replicating DNA. Frequency of S-phase cells (cells in DNA synthesis phase) is a basic parameter in studies on the control of cell division cycle and the developmental events of plant cells. Here we extend the microscopy and flow cytometry applications of the recently developed EdU (5-ethynyl-2'-deoxyuridine)-based S-phase assay to various plant species and tissues. We demonstrate that the presented protocols insure the improved preservation of cell and tissue structure and allow significant reduction in assay duration. In comparison with the frequently used detection of bromodeoxyuridine (BrdU) and tritiated-thymidine incorporation, this new methodology offers several advantages as we discuss here.</p> <p>Results</p> <p>Applications of EdU-based S-phase assay in microscopy and flow cytometry are presented by using cultured cells of alfalfa, Arabidopsis, grape, maize, rice and tobacco. We present the advantages of EdU assay as compared to BrdU-based replication assay and demonstrate that EdU assay -which does not require plant cell wall digestion or DNA denaturation steps, offers reduced assay duration and better preservation of cellular, nuclear and chromosomal morphologies. We have also shown that fast and efficient EdU assay can also be an efficient tool for dual parameter flow cytometry analysis and for quantitative assessment of replication in thick root samples of rice.</p> <p>Conclusions</p> <p>In plant cell cycle studies, EdU-based S-phase detection offers a superior alternative to the existing S-phase assays. EdU method is reliable, versatile, fast, simple and non-radioactive and it can be readily applied to many different plant systems.</p
Antibiotic susceptibility profiles of Mycoplasma synoviae strains originating from Central and Eastern Europe
Non-destructive postharvest quality monitoring of different pear and sweet pepper cultivars
Postharvest quality changes of two pear and five sweet pepper varieties during cold storage (2±1 °C and 10±1 °C, respectively) and shelf-life (22±2 °C and 20±1 °C, respectively) by non-destructive optical methods (laser backscattering imaging, chlorophyll fluorescence analysis, surface colour measurement) and texture analysis methods (acoustic impulse-response technique, impact method) were determined and monitored. The rate of the change of âConferenceâ pearsâ Fv/Fm chlorophyll fluorescence parameter was lower than for âBosc kobakâ, referring to the cultivar characteristic and photosynthetically active chlorophyll content related maturity and colour change. Acoustic and impact stiffness decreased during shelf-life, referring clearly to temperature related textural change. Taking into account the seven different measuring wavelengths (650â1064 nm), laser scattering parameters showed significant and cultivar dependent changes versus time during cold storage and shelf-life. The used non-destructive methods were found to be suitable for objective sweet pepper quality determination. Cold storage combined shelf-life resulted in a relatively longer shelf-life, with a lower intensity and rate of quality decrease in time, based upon mass loss, stiffness, surface colour, and chlorophyll fluorescence changes. âGigantâ, âCarmaâ, and âKĂĄrpiaâ cultivars were found to be favourable, but âKaisâ and âKunâ hot pepper samples were really sensitive to quality degradation
Free energy density for mean field perturbation of states of a one-dimensional spin chain
Motivated by recent developments on large deviations in states of the spin
chain, we reconsider the work of Petz, Raggio and Verbeure in 1989 on the
variational expression of free energy density in the presence of a mean field
type perturbation. We extend their results from the product state case to the
Gibbs state case in the setting of translation-invariant interactions of finite
range. In the special case of a locally faithful quantum Markov state, we
clarify the relation between two different kinds of free energy densities (or
pressure functions).Comment: 29 pages, Section 5 added, to appear in Rev. Math. Phy
All Teleportation and Dense Coding Schemes
We establish a one-to-one correspondence between (1) quantum teleportation
schemes, (2) dense coding schemes, (3) orthonormal bases of maximally entangled
vectors, (4) orthonormal bases of unitary operators with respect to the
Hilbert-Schmidt scalar product, and (5) depolarizing operations, whose Kraus
operators can be chosen to be unitary. The teleportation and dense coding
schemes are assumed to be ``tight'' in the sense that all Hilbert spaces
involved have the same finite dimension d, and the classical channel involved
distinguishes d^2 signals. A general construction procedure for orthonormal
bases of unitaries, involving Latin Squares and complex Hadamard Matrices is
also presented.Comment: 21 pages, LaTe
Particle correlations at RHIC from parton coalescence dynamics -- first results
A new dynamical approach that combines covariant parton transport theory with
hadronization channels via parton coalescence and fragmentation is applied to
Au+Au at RHIC. Basic consequences of the simple coalescence formulas, such as
elliptic flow scaling and enhanced proton/pion ratio, turn out to be rather
sensitive to the spacetime aspects of coalescence dynamics.Comment: Contribution to Quark Matter 2004 (January 11-17, 2004, Oakland, CA).
4 pages, 2 EPS figs, IOP style fil
- âŠ