Quantifying the potential and flux landscapes for nonequilibrium multiverse, a new scenario for time arrow

Wang, Hong; Li, Xinyu; Wang, Jin

doi:10.1007/jhep02(2021)105

Cited by 8 publications

(8 citation statements)

References 32 publications

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“…Substituting the equations ( 49) and ( 50) into (52), one can obtain 53) is consistent with the results in [34,35]. Again, in (53), we neglected all the terms including  a. All of these terms are small compared with…”

Section: Classical Hamiltonian Of the Total Systemsupporting

confidence: 78%

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Quantum geometrical current and coherence of the open gravitation system: loop quantum gravity coupled with a thermal scalar field

Wang

2023

Phys. Scr.

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Open quantum systems interacting with the environments often show interesting behaviors, such as decoherence, non-unitary evolution, dissipation, etc. It is interesting but still challenging to study the open quantum gravitation system interacting with the environments. In this work, we develop a general parameterized theoretical framework for the open quantum gravitation system. We studied a specific model where a real scalar field plays the role of the environment and the spacetime is assumed to be homogeneous and isotropic. We quantize the spacetime through the loop quantum gravity. We show that if the scalar field is in the thermal equilibrium state, the spacetime geometry will reach the equilibrium state after the transient relaxation. For the non-steady state, the quantum geometry current emerges. We point out that the quantum geometry current and the coherence can together drive the evolution of the spacetime geometry. This provides us a new view on the evolution of the spacetime geometry. Our results show that the coherence of the spacetime monotonically decreases as the temperature of the bath decreases. It helps the understanding of how a classical cold universe can emerge from an initial hot quantum universe.

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Section: Classical Hamiltonian Of the Total Systemsupporting

confidence: 78%

“…Since both F mn and F nm represent the same current between the state |m〉 and |n〉. For convenience, we ignore the one which is smaller than zero to reach the following definition [53,54]…”

Section: Quantum Geometrical Current and Coherencementioning

confidence: 99%

Quantum geometrical current and coherence of the open gravitation system: loop quantum gravity coupled with a thermal scalar field

Wang

2023

Phys. Scr.

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“…There have been many attempts to resolve the problem of time [4,5,7,62,63]. To date, no one has been able to generally overcome these difficulties completely [4].…”

Section: Problem Of Time In Quantum Gravity and Quantum Cosmologymentioning

confidence: 99%

“…In conventional path integral quantum mechanics (for isolated systems), any path in the phase space has the same amplitude. Equations ( 61) and (63) show that in quantum gravity, the amplitudes of different paths in phase space may differ. This is distinct from the usual unitary quantum mechanics.…”

Section: Heat Radiation Dominated Evolution Of the Quantum Universementioning

confidence: 99%

Quantum cosmology of the flat universe via closed real-time path integral

Wang

2022

Eur. Phys. J. C

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Quantum cosmology is crucial to understand the evolution of the early universe. Despite significant progress, challenges still remain. For example, the role of time in quantum cosmology is unclear. Furthermore, the influence of the environment on the evolution of the quantum universe is challenging. In this work, we studied the evolution of the quantum universe non-perturbatively using the closed real-time path integral. The environments coupled to the quantum universe being considered are the radiation, the non-relativistic matter, or the dark matter. We evaluated the influence functional of the massless scalar field coupled with the flat FRW universe. We studied the evolution of the quantum universe by setting the initial state of spacetime as a Gaussian wave packet. In different scenarios, we show that the classical trajectory of the universe is consistent with the quantum evolution of the wave packet. The coherence, the absolute quantum fluctuation and the Gibbs entropy all monotonically increase with time, yet the relative quantum fluctuation decreases with time. We show that for a given size of the radiation dominated universe, the lower temperature corresponds to a more quantum universe. We find that the minimal coupling of the free massless scalar field with the flat FRW spacetime generally gives rise to the memory characterized via non-Markovian correlations. Finally, we show that under higher radiation temperatures, a small universe has a higher chance of a transition to a bigger universe.

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“…There have been many attempts trying to resolve the time issue [4,5,7,64,65]. But up to now, no one has been able to generally overcome these difficulties completely [4].…”

Section: The Time Issue In Quantum Gravity and Quantum Cosmologymentioning

confidence: 99%

Quantum cosmology of the flat universe via closed real-time path integral

Wang¹,

Wang²

2021

Preprint

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Understanding the evolution of the universe through the quantum cosmology approach is still not fully realized yet. Introducing the Brown-Kuchař dust field as the time variable, we studied the evolution of the quantum universe nonperturbatively by the closed real time path integral. We evaluated the influence functional of the massless scalar field coupled with the flat FRW universe. By setting the initial state of the spacetime as a Gaussian wave packet, we studied the evolution of the quantum universe. In the proper time coordinate, if the evolution of the universe is driven by the thermal radiation or the non-relativistic particles, we show a quantum spacetime can decohere to a classical spacetime. As the temperature of the thermal radiation decreases, the small quantum universe grows up to a larger classical universe. We show that whatever the form of the matter is, the classical trajectory of the universe is always consistent with the quantum evolution of the wave packet. We find that in different scenarios, the variation of the coherence is always consistent with the variation of the Gibbs entropy. We also studied the transition of the flat FRW universe starting from certain initial state of the spacetime. We illustrate that the transition probability is closely related to the Vilenkin's tunneling from nothing scenario. We show that the quantum universe can grow only when the initial state of the spacetime is distributed. We also show that under the larger cosmological constant or the higher radiation temperature a small universe has a higher chance of the transition to a bigger universe. Finally, we point out that in the proper time coordinate, the minimal coupling of the free massless field with the flat FRW spacetime can generally give rise to the memory characterized by non-Markovian correlations.

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Quantifying the potential and flux landscapes for nonequilibrium multiverse, a new scenario for time arrow

Cited by 8 publications

References 32 publications

Quantum geometrical current and coherence of the open gravitation system: loop quantum gravity coupled with a thermal scalar field

Quantum geometrical current and coherence of the open gravitation system: loop quantum gravity coupled with a thermal scalar field

Quantum cosmology of the flat universe via closed real-time path integral

Quantum cosmology of the flat universe via closed real-time path integral

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