1,882 research outputs found
Dynamical screening in hot systems away from (chemical) equilibrium
Within the Closed Time Path Formalism of Thermal Field Theory we calculate
the hard photon emission rate as well as the collisional energy-loss rate for a
quark-gluon plasma away from chemical equilibrium. Mass singularities are shown
to be dynamically screened within HTL-resummed perturbation theory also away
from equilibrium. Additional (pinch) singularities are absent and well defined
results are obtained.Comment: Talk given at the Japanese Workshop on Thermal Quantum Field Theories
and their Applications, Kyoto, Japan, 25.-27. August 1999, 6 page
Dynamical screening away from equilibrium: hard photon production and collisional energy loss
We investigate the production rate for hard real photons and the collisional
energy loss in the quark-gluon plasma away from chemical equilibrium. Applying
the Hard-Thermal-Loop resummation scheme away from equilibrium, we can show
that Landau damping provides dynamical screening for both fermion and boson
exchange present in the two quantities.Comment: 5 pages RevTeX, 2 figures, remarks for clarification and one
reference added, typos correcte
Simulation of inhomogeneous distributions of ultracold atoms in an optical lattice via a massively parallel implementation of nonequilibrium strong-coupling perturbation theory
We present a nonequilibrium strong-coupling approach to inhomogeneous systems
of ultracold atoms in optical lattices. We demonstrate its application to the
Mott-insulating phase of a two-dimensional Fermi-Hubbard model in the presence
of a trap potential. Since the theory is formulated self-consistently, the
numerical implementation relies on a massively parallel evaluation of the
self-energy and the Green's function at each lattice site, employing thousands
of CPUs. While the computation of the self-energy is straightforward to
parallelize, the evaluation of the Green's function requires the inversion of a
large sparse matrix, with . As a crucial ingredient,
our solution heavily relies on the smallness of the hopping as compared to the
interaction strength and yields a widely scalable realization of a rapidly
converging iterative algorithm which evaluates all elements of the Green's
function. Results are validated by comparing with the homogeneous case via the
local-density approximation. These calculations also show that the
local-density approximation is valid in non-equilibrium setups without mass
transport.Comment: 14 pages, 9 figure
A Slavnov-Taylor identity and equality of damping rates for static transverse and longitudinal gluons in hot QCD
A Slavnov-Taylor identity is derived for the gluon polarization tensor in hot
QCD. We evaluate its implications for damping of gluonic modes in the plasma.
Applying the identity to next to the leading order in hard-thermal-loop
resummed perturbation theory, we derive the expected equality of damping rates
for static transverse and longitudinal (soft) gluons. This is of interest also
in view of deviating recent reports of based
on a direct calculation of .Comment: 13 pages, 1 figure, LaTe
Photon and Dilepton Production from Hot Out-Off-Equilibrium Media
The electromagnetic emissivity from QCD media away from equilibrium is
studied in the framework of closed time path thermal field theory. For the
dilepton rate a nonequilibrium mesonic medium is considered applying finite
temperature perturbation theory for interactions. The dilepton rate
is derived up to the order . For hard photon production a quark gluon
plasma is assumed and calculations are performed in leading order in the strong
coupling constant. These examples are chosen in order to investigate the role
of possible pinch terms in boson and in fermion propagators, respectively. The
implications of the results for phenomenology are also discussed.Comment: 16 pages LaTeX, 11 figures using epsfig. To be published in the
proceedings of the XXXVII-th Cracow School of Theoretical Physics, Dynamics
of Strong Interactions, Zakopane, June 199
Theoretical Description of Coherent Doublon Creation via Lattice Modulation Spectroscopy
Using a recently developed strong-coupling method, we present a comprehensive
theory for doublon production processes in modulation spectroscopy of a
three-dimensional system of ultracold fermionic atoms in an optical lattice
with a trap. The theoretical predictions compare well to the experimental time
traces of doublon production. For experimentally feasible conditions, we
provide a quantitative prediction for the presence of a nonlinear "two-photon"
excitation at strong modulation amplitudes.Comment: 5 pages, 5 figure
A preliminary checklist of fungi at the Boston Harbor Islands
Between December 2012 and May 2017, we conducted a fungal inventory at the Boston Harbor Islands National Recreation Area (BHI) in Massachusetts. We extensively sampled 4 sites (Grape Island, Peddocks Island, Thompson Island, and World's End peninsula) and occasionally visited 4 others for sampling (Calf Island, Great Brewster Island, Slate Island, and Webb Memorial State Park). We made over 900 collections, of which 313 have been identified. The survey yielded 172 species in 123 genera, 62 families, 24 orders, 11 classes, and 2 phyla. We report 4 species as new, but not formally described, in the genera Orbilia, Resupinatus, and Xylaria. Another collection in the genus Lactarius may be new to science, but further morphological and molecular work is needed to confirm this conclusion. Additionally, Orbilia aprilis is a new report for North America, Proliferodiscus earoleucus represents only the second report for the US, and Chrysosporium sulfureum, a common fungus of some cheeses, was discovered on woodlice (Crustacea: Malacostraca: Isopoda: Oniscidea). We discuss our findings in the light of DNA-based identifications using the ITS ribosomal DNA region, including the advantages and disadvantages of this approach, and stress the need for biodiversity studies in urbanized areas during all seasons
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The olfactory transcriptome and progression of sexual maturation in homing chum salmon Oncorhynchus keta
Reproductive homing migration of salmonids requires accurate interaction between the reception of external olfactory cues for navigation to the spawning grounds and the regulation of sexual maturation processes. This study aimed at providing insights into the hypothesized functional link between olfactory sensing of the spawning ground and final sexual maturation. We have therefore assessed the presence and expression levels of olfactory genes by RNA sequencing (RNAseq) of the olfactory rosettes in homing chum salmon Oncorhynchus keta Walbaum from the coastal sea to 75 km upstream the rivers at the prespawning ground. The progression of sexual maturation along the brain-pituitary-gonadal axis was assessed through determination of plasma steroid levels by time-resolved fluoroimmunoassays (TR-FIA), pituitary gonadotropin subunit expression and salmon gonadotropin-releasing hormone (sgnrh) expression in the brain by quantitative real-time PCR. RNAseq revealed the expression of 75 known and 27 unknown salmonid olfactory genes of which 13 genes were differentially expressed between fish from the pre-spawning area and from the coastal area, suggesting an important role of these genes in homing. A clear progression towards final maturation was characterised by higher plasma 17α,20β-dihydroxy-4-pregnen-3-one (DHP) levels, increased pituitary luteinizing hormone β subunit (lhβ)expression and sgnrh expression in the post brain, and lower plasma testosterone (T) and 17β-estradiol (E2) levels. Olfactomedins and ependymin are candidates among the differentially expressed genes that may connect olfactory reception to the expression of sgnrh to regulate final maturation
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