Nonequilibrium photons as a signature of quark-hadron phase transition

Lee, Da-Shin; Ng, Kin-Wang

doi:10.1016/s0370-2693(99)00092-1

Cited by 2 publications

(5 citation statements)

References 17 publications

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“…This method for studying nonequilibrium phenomena has been developed by Schwinger and Keldysh [15]. In recent years, it has been applied in particle physics and cosmology by one of us [16,17].…”

Section: Influence Functional and Langevin Equationmentioning

confidence: 99%

Nonequilibrium dynamics of moving mirrors in quantum fields: Influence functional and the Langevin equation

Lee

2005

Phys. Rev. D

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We employ the Schwinger-Keldysh formalism to study the nonequilibrium dynamics of the mirror with perfect reflection moving in a quantum field. In the case where the mirror undergoes the small displacement, the coarse-grained effective action is obtained by integrating out the quantum field with the method of influence functional. The semiclassical Langevin equation is derived, and is found to involve two levels of backreaction effects on the dynamics of mirrors: radiation reaction induced by the motion of the mirror and backreaction dissipation arising from fluctuations in quantum field via a fluctuation-dissipation relation. Although the corresponding theorem of fluctuation and dissipation for the case with the small mirror's displacement is of model independence, the study from the first principles derivation shows that the theorem is also independent of the regulators introduced to deal with short-distance divergences from the quantum field. Thus, when the method of regularization is introduced to compute the dissipation and fluctuation effects, this theorem must be fulfilled as the results are obtained by taking the short-distance limit in the end of calculations. The backreaction effects from vacuum fluctuations on moving mirrors are found to be hardly detected while those effects from thermal fluctuations may be detectable.Zero-point fluctuations due to the imposition of the boundary conditions can lead to an impact on macroscopic physics. One of the most celebrated examples is the attractive Casimir force between two parallel conducting plates [1]. However, the dynamics of fluctuations subject to the moving boundary may also be detectable, sometimes referred to as the dynamical Casimir effects [2,3,4,5,6,7,8,9]. Consider a perfectly reflecting mirror moving in quantum fields. The boundary conditions on quantum fields corresponding to perfect reflection result in the interaction of the mirror with the fields. The motion of the mirror, which leads to the moving boundary, can create quantum radiation that in turn damps out the motion of the mirror as a result of the motion-induced radiation reaction force. In fact, as required by Lorentz invariance of quantum fields, this radiation reaction force vanishes for a motion with uniform velocity. In a motion of uniform acceleration, the mirror suffers from the same fluctuations as if it was at rest in a thermal bath due to the Unruh effects [10], also leading to the zero dissipative radiation reaction force. Fulling and Davies have computed this force for a moving mirror in a massless scalar field in the 1+1 dimensional spacetime. It turns out that the induced dissipative force is proportional to the third time derivative of the mirror's position [7]. In 3+1 dimensional spacetime, the problem has been studied by Ford and Vilenkin in terms of a first order approximation of the mirror's displacement. The corresponding dissipative force then is given by the fifth time derivative of the position in the non-relativistic limit [8]. However, as we know, all quantum field...

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Section: Influence Functional and Langevin Equationmentioning

confidence: 99%

Nonequilibrium dynamics of moving mirrors in quantum fields: Influence functional and the Langevin equation

Lee

2005

Phys. Rev. D

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“…where we define the dimensionless field, θ(η) = ϕ(η)/(a(η)f a ). Within the Hartree approximation, the photon production processes do not involve photons in the intermediate states [11,13]. To avoid the gauge ambiguities, we will work in the coulomb gauge and concentrate only on physical transverse gauge field, A T ( x, η) [11,13].…”

Section: Equations Of Motionmentioning

confidence: 99%

“…Within the Hartree approximation, the photon production processes do not involve photons in the intermediate states [11,13]. To avoid the gauge ambiguities, we will work in the coulomb gauge and concentrate only on physical transverse gauge field, A T ( x, η) [11,13]. Then, the Heisenberg field equation for A T ( x, η) can be read off from the quadratic part of the Lagrangian in the form…”

Section: Equations Of Motionmentioning

confidence: 99%

“…Recently, the authors of Ref. [8] were motivated by the recent understanding of the important role of the spinodal instability and parametric resonance that provide the nonlinear and nonperturbative mechanisms in the quantum particle production driven by the large amplitude oscillations of the coherent field [9][10][11][12][13]. They re-examined the issue of the dissipation of the axion field resulting from the production of its quantum fluctuations.…”

Section: Introductionmentioning

confidence: 99%

“…In this paper, we will re-examine the damping dynamics of the axion arising from photon production in an expanding universe in the context of the non-equilibrium quantum field theory. The goal of this study is to present a detailed and systematical study of the above-mentioned problem using a fully non-equilibrium formalism [9][10][11][12][13]. We will derive the coupled nonperturbative equation for the axion field and the mode equations for the photon field in a flat Robertson-Walker spacetime within the nonperturbative Hartree approximation that is implemented to consistently take the back reaction effects into account.…”

Section: Introductionmentioning

confidence: 99%

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Photon production of axionic cold dark matter

Lee

2000

Phys. Rev. D

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Using the nonequilibrium quantum field theory, photon production from the coherently oscillating axion field in a flat Robertson-Walker cosmology is reexamined. First neglecting the Debye screening of the baryon plasma to photons, we find that the axions will dissipate into photons via spinodal instability in addition to parametric resonance. As a result of the pseudoscalar nature of the axion-photon coupling, we observe a circular polarization asymmetry in the photons produced. However, these effects are suppressed to an insignificant level in the expanding universe. We then briefly discuss a systematic way of including the plasma effect which can further suppress the photon production. We note that the formalism of the problem can be applied to any pseudoscalar field coupled to a photon in a thermal background in a general curved spacetime.PACS number͑s͒: 14.80. Mz, 95.35.ϩd, 98.80.Cq

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Nonequilibrium photons as a signature of quark-hadron phase transition

Cited by 2 publications

References 17 publications

Nonequilibrium dynamics of moving mirrors in quantum fields: Influence functional and the Langevin equation

Nonequilibrium dynamics of moving mirrors in quantum fields: Influence functional and the Langevin equation

Photon production of axionic cold dark matter

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