Entanglement of scales as a possible mechanism for decoherence and thermalization in relativistic heavy ion collisions

Abstract

Despite the fact that a system created in relativistic heavy ion collisions is an isolated quantum system, which cannot increase its entropy in the course of unitary quantum evolution, hydrodynamical analysis of experimental data seems to indicate that the matter formed in the collisions is thermalized very quickly. Based on common consideration of hydrodynamics as an effective theory in the domain of slow-and long-length modes, we discuss the physical mechanisms responsible for the decoherence and emergence of the hydrodynamic behavior in such collisions, and demonstrate how such physical mechanisms work in the case of the scalar field model. We obtain the evolution equation for the Wigner function of a long-wavelength subsystem that describes its decoherence, isotropization, and approach to thermal equilibrium induced by interaction with short-wavelength modes. Our analysis supports the idea that decoherence, quantum-to-classical transition and thermalization in isolated quantum systems are attributed to the experimental context, and are related to a particular procedure of decomposition of the whole quantum system into relevant and irrelevant from an observational viewpoint subsystems.

Femtoscopy scales and particle production in the relativistic heavy ion collisions from Au+Au at 200 AGeV to Xe+Xe at 5.44 ATeV within the integrated hydrokinetic model

“…Once the model is calibrated for description of a particular collision type, based on the experimental charged particle multiplicity dependency on collision centrality and pion p T spectrum slope in the most central events, a wide class of soft observables, including particle yields, particle number ratios, transverse momentum spectra, flow harmonics, femtoscopy scales, can be described simultaneously within iHKM, using the single found setting of model parameters for each experiment set-up (again see Figs. 4,5,6,7,8). The results, obtained in [20,[30][31][32], provide a detailed description of particle production in Au+Au collisions at 10.…”

“…Thus, the thickness of the partonic "pancake" in each case is of the order of 10 −2 fm and 10 −3 fm respectively. not clear (see [1][2][3][4][5][6][7][8][9] for the corresponding discussion), the hypothesis that it takes place, and at some moment the system comes to a state of local thermal and chemical equilibrium, allows one to utilize the relativistic hydrodynamics approximation to describe the system's evolution during the time, while such equilibrium is preserved 2 . The application of hydrodynamical formalism implies utilization of certain equation of state (EoS) for the considered hadron fluid, which cannot be strictly defined at the moment and thus is model dependent.…”

Investigating the QCD dynamical entropy in high-energy hadronic collisions

“…It is well known that produced particle multiplicities in proton-proton and heavy ion collisions are connected with the entropy produced by these reactions [4][5][6][7][8]. In this context, a current hot topic is the relation between decoherence/entanglement and high-energy quantum chromodynamics (QCD) processes [9][10][11][12][13][14][15]. In general, the analyzes are complex since there are interdisciplinary connections of distinct steps of the thermalization process to non-equilibrium dynamics (see for instance the pedagogical review of Ref.…”

Divergences in open quantum systems

“…The observed long-wavelength modes form an open quantum system whose dynamics is governed by a non-Hamiltonian master equation. This situation occurs in inflationary cosmology [2][3][4][5][6][7], QCD jet physics [8], hydrodynamics [9][10][11][12][13][14][15][16][17][18], and in standard implementations of renormalization in holographic field theories [1,19].…”