669 research outputs found
Applicability of the Wigner functional approach to evolution of quantum fields
Evolution of highly excited quantum field is considered in the framework of
Keldysh formalism . It is demonstrated that leading order (LO) term of
semiclassical approximation appears as well-known Classical Statistical
Approximation (CSA). In simple case of spatially homogeneous scalar field
analytical expressions for leading and next-to-leading (NLO) order are
presented. It is shown that the range of applicability of CSA strongly depends
on the properties of the initial state of the systemComment: Based on talk given at the 19th Intenational Seminar QUARKS 201
Sound propagation and Mach cone in anisotropic hydrodynamics
This letter is based on a kinetic theory approach to anisotropic
hydrodynamics. We derive the sound wave equation in anisotropic hydrodynamics
and show that a corresponding wave front is ellipsoidal. The phenomenon of Mach
cone emission in anisotropic hydrodynamics is studied. It is shown that Mach
cone in anisotropic case becomes asymmetric, i. e. in this limit they're two
different angles, left and right with respect to the ultrasonic particle
direction, which are determined by the direction of ultrasonic particle
propagation and the asymmetry coefficient.Comment: 9 pages, 4 figure
Thick GaN film stress-induced self-separation
Cracking of thick GaN films on sapphire substrates during the cooling down
after the growth was studied. The cracking was suppressed by increasing the
film-to-substrate thickness ratio and by using an intermediate carbon buffer
layer, that reduced the binding energy between the GaN film and the substrate.
Wafer-scale self-separation of thick GaN films has been demonstrated.Comment: Published in Proceedings of the 2019 IEEE Conference of Russian Young
Researchers in Electrical and Electronic Engineering (EIConRus
Production of Photons and Dileptons in the Glasma
We study the production of photons and dileptons during the pre-equilibrium
Glasma stage in heavy ion collisions and discuss the implications in light of
the PHENIX data. We find that the measured distributions of such
electromagnetic emissions, while having some features not well understood if
hypothesized to entirely arise from a thermalized Quark-Gluon Plasma, have some
qualitative features that might be described after including effects from a
thermalizing Glasma. The shape and centrality dependence of the transverse
momentum spectra of the so-called "thermal photons" are well described. The
mass and transverse momentum dependence of intermediate mass dileptons also
agree with our estimates. The low transverse momenta from which the excessive
dileptons (in low to intermediate mass region) arise is suggestive of emissions
from a Bose condensate. We also predict the centrality dependence of dilepton
production. Uncertainties in the current approach and improvements in the
future are discussed.Comment: 24 pages, 7 figures, new results and references added in v
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