71 research outputs found
Dynamics of Quark-Gluon-Plasma Instabilities in Discretized Hard-Loop Approximation
Non-Abelian plasma instabilities have been proposed as a possible explanation
for fast isotropization of the quark-gluon plasma produced in relativistic
heavy-ion collisions. We study the real-time evolution of these instabilities
in non-Abelian plasmas with a momentum-space anisotropy using a hard-loop
effective theory that is discretized in the velocities of hard particles. We
extend our previous results on the evolution of the most unstable modes, which
are constant in directions transverse to the direction of anisotropy, from
gauge group SU(2) to SU(3). We also present first full 3+1-dimensional
simulation results based on velocity-discretized hard loops. In contrast to the
effectively 1+1-dimensional transversely constant modes we find subexponential
behaviour at late times.Comment: 30 pages, 16 figures. v3 typos fixe
Energy Loss of a Heavy Fermion in an Anisotropic QED Plasma
We compute the leading-order collisional energy loss of a heavy fermion
propagating in a QED plasma with an electron distribution function which is
anisotropic in momentum space. We show that in the presence of such
anisotropies there can be a significant directional dependence of the heavy
fermion energy loss with the effect being quite large for highly-relativistic
velocities. We also repeat the analysis of the isotropic case more carefully
and show that the final result depends on the intermediate scale used to
separate hard and soft contributions to the energy loss. We then show that the
canonical isotropic result is obtained in the weak-coupling limit. For
intermediate-coupling we use the residual scale dependence as a measure of our
theoretical uncertainty. We also discuss complications which could arise due to
the presence of unstable soft photonic modes and demonstrate that the
calculation of the energy loss is safe.Comment: 19 pages, 18 figures. v2 - Correction to normalization of numerical
results; some figures modified as a result; discussion of role of unstable
modes added along with two new figure
Closed-Time Path Integral Formalism and Medium Effects of Non-Equilibrium QCD Matter
We apply the closed-time path integral formalism to study the medium effects
of non-equilibrium gluon matter. We derive the medium modified resummed gluon
propagator to the one loop level in non-equilibrium in the covariant gauge. The
gluon propagator we derive can be used to remove the infrared divergences in
the secondary parton collisions to study thermalization of minijet parton
plasma at RHIC and LHC.Comment: Final version, To appear in Physical Review D, Minor modification,
reference adde
Исследование температурного поля пневматического молотка
Представлены результаты экспериментального исследования изменения температуры поверхности рубильного пневматического молотка М-6 по времени при рубке в различных режимах стальной полосы и плиты, чугунной плиты
Metal enrichment processes
There are many processes that can transport gas from the galaxies to their
environment and enrich the environment in this way with metals. These metal
enrichment processes have a large influence on the evolution of both the
galaxies and their environment. Various processes can contribute to the gas
transfer: ram-pressure stripping, galactic winds, AGN outflows, galaxy-galaxy
interactions and others. We review their observational evidence, corresponding
simulations, their efficiencies, and their time scales as far as they are known
to date. It seems that all processes can contribute to the enrichment. There is
not a single process that always dominates the enrichment, because the
efficiencies of the processes vary strongly with galaxy and environmental
properties.Comment: 18 pages, 8 figures, accepted for publication in Space Science
Reviews, special issue "Clusters of galaxies: beyond the thermal view",
Editor J.S. Kaastra, Chapter 17; work done by an international team at the
International Space Science Institute (ISSI), Bern, organised by J.S.
Kaastra, A.M. Bykov, S. Schindler & J.A.M. Bleeke
The First Magnetic Fields
We review current ideas on the origin of galactic and extragalactic magnetic
fields. We begin by summarizing observations of magnetic fields at cosmological
redshifts and on cosmological scales. These observations translate into
constraints on the strength and scale magnetic fields must have during the
early stages of galaxy formation in order to seed the galactic dynamo. We
examine mechanisms for the generation of magnetic fields that operate prior
during inflation and during subsequent phase transitions such as electroweak
symmetry breaking and the quark-hadron phase transition. The implications of
strong primordial magnetic fields for the reionization epoch as well as the
first generation of stars is discussed in detail. The exotic, early-Universe
mechanisms are contrasted with astrophysical processes that generate fields
after recombination. For example, a Biermann-type battery can operate in a
proto-galaxy during the early stages of structure formation. Moreover, magnetic
fields in either an early generation of stars or active galactic nuclei can be
dispersed into the intergalactic medium.Comment: Accepted for publication in Space Science Reviews. Pdf can be also
downloaded from http://canopus.cnu.ac.kr/ryu/cosmic-mag1.pd
Evolution of the differential transverse momentum correlation function with centrality in Au+Au collisions at GeV
We present first measurements of the evolution of the differential transverse
momentum correlation function, {\it C}, with collision centrality in Au+Au
interactions at GeV. {\it C} exhibits a strong dependence
on collision centrality that is qualitatively similar to that of number
correlations previously reported. We use the observed longitudinal broadening
of the near-side peak of {\it C} with increasing centrality to estimate the
ratio of the shear viscosity to entropy density, , of the matter formed
in central Au+Au interactions. We obtain an upper limit estimate of
that suggests that the produced medium has a small viscosity per unit entropy.Comment: 7 pages, 4 figures, STAR paper published in Phys. Lett.
D* Production in Deep Inelastic Scattering at HERA
This paper presents measurements of D^{*\pm} production in deep inelastic
scattering from collisions between 27.5 GeV positrons and 820 GeV protons. The
data have been taken with the ZEUS detector at HERA. The decay channel
(+ c.c.) has been used in the study. The
cross section for inclusive D^{*\pm} production with
and is 5.3 \pms 1.0 \pms 0.8 nb in the kinematic region
{ GeV and }. Differential cross
sections as functions of p_T(D^{*\pm}), and are
compared with next-to-leading order QCD calculations based on the photon-gluon
fusion production mechanism. After an extrapolation of the cross section to the
full kinematic region in p_T(D^{*\pm}) and (D^{*\pm}), the charm
contribution to the proton structure function is
determined for Bjorken between 2 10 and 5 10.Comment: 17 pages including 4 figure
Observation of Scaling Violations in Scaled Momentum Distributions at HERA
Charged particle production has been measured in deep inelastic scattering
(DIS) events over a large range of and using the ZEUS detector. The
evolution of the scaled momentum, , with in the range 10 to 1280
, has been investigated in the current fragmentation region of the Breit
frame. The results show clear evidence, in a single experiment, for scaling
violations in scaled momenta as a function of .Comment: 21 pages including 4 figures, to be published in Physics Letters B.
Two references adde
Relevance of the diploma section "Civil protection"
На сьогоднішньому етапі реформування вищої освіти навчальна дисципліна «Цивільний захист» вже не є нормативною і виключена з навчальних планів у вищих навчальних закладах, у тому числі технічного профілю. Але соціально-економічна ситуація в країні, нажаль, ускладнюється. Тому зростає необхідність і важливість питань захисту населення в умовах надзвичайних ситуацій.The discipline "Civil Protection" is not normative any more and excluded from the curriculum in higher educational institutions, including the technical profile at the present stage of reforming higher education. However, unfortunately, the socio-economic situation in the country is becoming more complicated. In these conditions, the need and importance of protecting the population in emergency situations is increasing
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