The DELTA Synchrotron Light Interferometer

Berges, U.

doi:10.1063/1.1757948

Cited by 31 publications

(59 citation statements)

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“…The perturbation series built from the non-homogeneous Feynman rules in Section 5 are free of the pinch singularities previously thought to spoil such perturbative treatments of nonequilibrium field theory, see e.g. [25,[53][54][55]. In our formulation, this absence of pinch singularities is ensured by two factors: (i) the violation of energy conservation at early times and (ii) the statistical distribution functions in free CTP propagators are evaluated at the time of observation.…”

Section: Absence Of Pinch Singularitiesmentioning

confidence: 94%

Perturbative non-equilibrium thermal field theory to all orders in gradient expansion

Millington

Pilaftsis

2013

Physics Letters B

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We present a new perturbative formulation of non-equilibrium thermal field theory, based upon non-homogeneous free propagators and time-dependent vertices. The resulting time-dependent diagrammatic perturbation series are free of pinch singularities without the need for quasi-particle approximation or effective resummation of finite widths. After arriving at a physically meaningful definition of particle number densities, we derive master time evolution equations for statistical distribution functions, which are valid to all orders in perturbation theory and to all orders in a gradient expansion. For a scalar model, we perform a perturbative loopwise truncation of these evolution equations, whilst still capturing fast transient behaviour, which is found to be dominated by energy-violating processes, leading to the non-Markovian evolution of memory effects.

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Section: Absence Of Pinch Singularitiesmentioning

confidence: 94%

Perturbative non-equilibrium thermal field theory to all orders in gradient expansion

Millington

Pilaftsis

2013

Physics Letters B

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“…For example, the equivalence between the classical field theory and the Boltzmann equation [26] would be a good guide for the formal discussions. It is also interesting to discuss, for example, the O(N ) model, where there exist results of dynamical calculations using the two particle irreducible (2PI) effective action [17,18].…”

Section: Summary and Perspectivesmentioning

confidence: 99%

“…Still, classical field obeys classical statistics, then the cutoff momentum should be chosen to be of the order of T or smaller also in these frameworks. While the two-particle irreducible (2PI) effective action approach can treat classical field and particles on the same footing [17][18][19], the numerical cost is large and it is not yet easy to apply to realistic systems under inhomogeneous classical field.…”

Section: Introductionmentioning

confidence: 99%

Replica evolution of classical field in 4+1 dimensional spacetime toward real time dynamics of quantum field

Ohnishi¹,

Matsuda²,

Kunihiro³

et al. 2020

Preprint

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Real-time evolution of replicas of classical field is proposed as an approximate simulator of real-time quantum field dynamics at finite temperatures. We consider N classical field configurations, (φ τ x , π τ x )(τ = 0, 1, • • • N − 1), dubbed as replicas, which interact with each other via the τ -derivative terms and evolve with the classical equation of motion. The partition function of replicas is found to be proportional to that of quantum field in the imaginary time formalism. Since the replica index can be regarded as the imaginary time index, the replica evolution is technically the same as the molecular dynamics part of the hybrid Monte-Carlo sampling. Then the replica configurations should reproduce the correct quantum equilibrium distribution after the long-time evolution. At the same time, evolution of the replica-index average of field variables is described by the classical equation of motion when the fluctuations are small. In order to examine the real-time propagation properties of replicas, we first discuss replica evolution in quantum mechanics. Statistical averages of observables are precisely obtained by the initial condition average of replica evolution, and the time evolution of the unequal-time correlation function, x(t)x(t ) , in a harmonic oscillator is also described well by the replica evolution in the range T /ω > 0.5. Next, we examine the statistical and dynamical properties of the φ 4 theory in the 4+1 dimensional spacetime, which contains three spatial, one replica index or the imaginary time, and one real time. We note that the Rayleigh-Jeans divergence can be removed in replica evolution with N ≥ 2 when the mass counterterm is taken into account. We also find that the thermal mass obtained from the unequaltime correlation function at zero momentum grows as a function of the coupling as in the perturbative estimate in the small coupling region.

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“…2). In this far-from-equilibrium situation, we can use classical-statistical lattice simulations to describe the underlying dynamics [7,8]. Coupling them to the Dirac equation allows us to extract the fermion spectral function nonperturbatively.…”

Section: Introductionmentioning

confidence: 99%

Fermion and gluon spectral functions far from equilibrium

2022

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Motivated by the quark-gluon plasma, we develop a simulation method to obtain the spectral function of (Wilson) fermions non-perturbatively in a non-Abelian gauge theory with large gluon occupation numbers [1]. We apply our method to a non-Abelian plasma close to its non-thermal fixed point, i.e., in a far-from-equilibrium self-similar regime, and find mostly very good agreement with perturbative hard loop (HTL) calculations. For the first time, we extract the full momentum dependence of the damping rate of fermionic collective excitations and compare our results to recent non-perturbative extractions of gluonic spectral functions in two and three spatial dimensions [2, 3].

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The DELTA Synchrotron Light Interferometer

Cited by 31 publications

References 0 publications

Perturbative non-equilibrium thermal field theory to all orders in gradient expansion

Perturbative non-equilibrium thermal field theory to all orders in gradient expansion

Replica evolution of classical field in 4+1 dimensional spacetime toward real time dynamics of quantum field

Fermion and gluon spectral functions far from equilibrium

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