Thermalization of overpopulated systems in the 2PI formalism

Tsutsui, Shoichiro; Blaizot, Jean‐Paul; Hatta, Yoshitaka

doi:10.1103/physrevd.96.036004

Cited by 11 publications

(9 citation statements)

References 29 publications

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“…Indeed, it was shown using 2PI equations to NLO in a 1/N expansion [39,51,52] that the observed selfsimilar regime at low momenta survives to moderate values λ = 1 [68]. However, it was argued within the 2PI framework that for a large coupling λ = 10, inelastic processes may play an important role at all times in the evolution [72]. The large-N kinetic theory in its present form at NLO, however, lacks such processes.…”

Section: Discussionmentioning

confidence: 99%

Large- N kinetic theory for highly occupied systems

2018

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We consider an effective kinetic description for quantum many-body systems, which is not based on a weak-coupling or diluteness expansion. Instead, it employs an expansion in the number of field components N of the underlying scalar quantum field theory. Extending previous studies, we demonstrate that the large-N kinetic theory at next-to-leading order is able to describe important aspects of highly occupied systems, which are beyond standard perturbative kinetic approaches. We analyze the underlying quasiparticle dynamics by computing the effective scattering matrix elements analytically and solve numerically the large-N kinetic equation for a highly occupied system far from equilibrium. This allows us to compute the universal scaling form of the distribution function at an infrared nonthermal fixed point within a kinetic description, and we compare to existing lattice field theory simulation results.

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Section: Discussionmentioning

confidence: 99%

Large- N kinetic theory for highly occupied systems

2018

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“…The first on-shell number-changing processes, such as 4 → 2 scatterings, appear only at NNLO in the 1=N expansion. Off-shell inelastic processes, such as 3 → 1 processes, exist in the 2PI equations of motion already at NLO [36], where they are found to be important for final thermalization [54]. However, they are not taken into account in the Boltzmann equation.…”

Section: Effective Kinetic Equationmentioning

confidence: 99%

Attractive versus repulsive interactions in the Bose-Einstein condensation dynamics of relativistic field theories

et al. 2017

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We study the impact of attractive self-interactions on the nonequilibrium dynamics of relativistic quantum fields with large occupancies at low momenta. Our primary focus is on Bose-Einstein condensation and nonthermal fixed points in such systems. For a model system, we consider OðNÞ-symmetric scalar field theories. We use classical-statistical real-time simulations as well as a systematic 1=N expansion of the quantum (two-particle-irreducible) effective action to next-to-leading order. When the mean self-interactions are repulsive, condensation occurs as a consequence of a universal inverse particle cascade to the zero-momentum mode with self-similar scaling behavior. For attractive mean selfinteractions, the inverse cascade is absent, and the particle annihilation rate is enhanced compared to the repulsive case, which counteracts the formation of coherent field configurations. For N ≥ 2, the presence of a nonvanishing conserved charge can suppress number-changing processes and lead to the formation of stable localized charge clumps, i.e., Q balls.

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“…The bosons have been taken with a small but finite mass. The situation is similar to the scenario of [21]. The cross sections are not those of perturbative QCD.…”

Section: Discussionmentioning

confidence: 57%

“…The following study [20] suggested a complete hindrance of BEC formation for massless gluons at vanishing momentum. Within the description of a non-equilibrium massive bosonic O(N) theory applying the 2PI formalism of real-time Schwinger-Keldysh quantum field theory it has been recently shown that the formation of a BEC is potentially prevented by particle-number changing processes [21]. However, a concrete kinetic simulation for a possible transient BEC has not been included in these studies.…”

Section: Introductionmentioning

confidence: 99%

Kinetic approach to a relativistic BEC with inelastic processes

et al. 2019

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The phenomenon of Bose-Einstein condensation is investigated in the context of the Color-Glass-Condensate description of the initial state of ultrarelativistic heavy-ion collisions. For the first time, in this paper we study the influence of particle-number changing 2 ↔ 3 processes on the transient formation of a Bose-Einstein Condensate within an isotropic system of scalar bosons by including 2 ↔ 3 interactions of massive bosons with constant and isotropic cross sections, following a Boltzmann equation. The one-particle distribution function is decomposed in a condensate part and a non-zero momentum part of excited modes, leading to coupled integro-differential equations for the time evolution of the condensate and phase-space distribution function, which are then solved numerically. Our simulations converge to the expected equilibrium state, and only for σ 23 /σ 22 1 we find that a Bose-Einstein condensate emerges and decays within a finite lifetime in contrast to the case where only binary scattering processes are taken into account, and the condensate is stable due to particle-number conservation. Our calculations demonstrate that Bose-Einstein Condensates in the very early stage of heavy-ion collisions are highly unlikely, if inelastic collisions are significantly participating in the dynamical gluonic evolution.

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Thermalization of overpopulated systems in the 2PI formalism

Cited by 11 publications

References 29 publications

Large- N kinetic theory for highly occupied systems

Large- N kinetic theory for highly occupied systems

Attractive versus repulsive interactions in the Bose-Einstein condensation dynamics of relativistic field theories

Kinetic approach to a relativistic BEC with inelastic processes

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