Particle-current fluctuations in a variant of the asymmetric Glauber model

It is conjectured that in cosmological applications the particle current is not modified but finite heat or energy flow. Therefore, comoving Eckart frame is a suitable choice, as it merely ceases the charge and particle diffusion and conserves charges and particles. The cosmic evolution of viscous hadron and parton epochs in casual and non-casual Eckart frame is analyzed. By proposing equations of state deduced from recent lattice QCD simulations including pressure p, energy density ρ, and temperature T, the Friedmann equations are solved. We introduce expressions for the temporal evolution of the Hubble parameter H˙, the cosmic energy density ρ˙, and the share η˙ and the bulk viscous coefficient ζ˙. We also suggest how the bulk viscous pressure Π could be related to H. We conclude that the relativistic theory of fluids, the Eckart frame, and the finite viscous coefficients play essential roles in the cosmic evolution, especially in the hadron and parton epochs.

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Unifying Theory for Casimir Forces: Bulk and Surface Formulations

Universe ◽

10.3390/universe7070225 ◽

2021 ◽

Vol 7 (7) ◽

pp. 225

Author(s):

Giuseppe Bimonte ◽

Thorsten Emig

Keyword(s):

Free Energy ◽

Path Integral ◽

Casimir Force ◽

Hamiltonian Formulation ◽

Current Fluctuations ◽

Practical Application ◽

Casimir Forces ◽

Surface Approach ◽

Maxwell Stress Tensor ◽

Electromagnetic Fluctuation

The principles of the electromagnetic fluctuation-induced phenomena such as Casimir forces are well understood. However, recent experimental advances require universal and efficient methods to compute these forces. While several approaches have been proposed in the literature, their connection is often not entirely clear, and some of them have been introduced as purely numerical techniques. Here we present a unifying approach for the Casimir force and free energy that builds on both the Maxwell stress tensor and path integral quantization. The result is presented in terms of either bulk or surface operators that describe corresponding current fluctuations. Our surface approach yields a novel formula for the Casimir free energy. The path integral is presented both within a Lagrange and Hamiltonian formulation yielding different surface operators and expressions for the free energy that are equivalent. We compare our approaches to previously developed numerical methods and the scattering approach. The practical application of our methods is exemplified by the derivation of the Lifshitz formula.

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Impact of critical current fluctuations on the performance of a coated conductor tape

Superconductor Science and Technology ◽

10.1088/1361-6668/ab4638 ◽

2019 ◽

Vol 32 (12) ◽

pp. 124001 ◽

Cited By ~ 2

Author(s):

Fedor Gömöry ◽

Ján Šouc ◽

Miroslav Adámek ◽

Asef Ghabeli ◽

Mykola Solovyov ◽

...

Keyword(s):

Critical Current ◽

Current Fluctuations ◽

Coated Conductor

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The effects of gas flow on granular currents

Philosophical Transactions of The Royal Society A Mathematical Physical and Engineering Sciences ◽

10.1098/rsta.2007.0021 ◽

2008 ◽

Vol 366 (1873) ◽

pp. 2191-2203 ◽

Cited By ~ 7

Author(s):

M.A Gilbertson ◽

D.E Jessop ◽

A.J Hogg

Keyword(s):

Gas Flow ◽

Gravity Currents ◽

The Future ◽

Particle Current

Currents of particles have been quite successfully modelled using techniques developed for fluid gravity currents. These models require the rheology of the currents to be specified, which is determined by the interaction between particles. For relatively small slow currents, this is determined primarily through friction, which can be controlled and reduced by fluidizing the particles, so that they may become much more mobile. Recent results cannot be predicted using many of the proposed models, and may be defined by the interaction between the particles and the fluid through which they are passing. However, in addition, particles that are only initially fluidized also form currents that are also mobile, but otherwise are different from continuously fluidized currents. The mobility of these currents appears not to be connected to the time taken for them to degas. This suggests that defining the continuous stresses on the particle current may not be sufficient to understand its motion and that a challenge for the future is to understand the structure of these flows and how this affects their motion.

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