New Semiclassical Picture of Vacuum Decay

Braden, Jonathan; Johnson, Matthew C.; Peiris, Hiranya V.; Pontzen, Andrew; Weinfurtner, Silke

doi:10.1103/physrevlett.123.031601

Cited by 66 publications

(96 citation statements)

References 40 publications

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“…Indeed, there is a cold atom analog of vacuum decay in field theory from experimental [5,6], theoretical [7], and simulational [8,9] perspectives. This inspires the request for vacuum decay in field theory via classically allowed channel, which is recently realized in lattice simulation [10] and formulated in real-time formalism [11].…”

Section: Introductionmentioning

confidence: 95%

“…The semiclassical picture of vacuum decay introduced above could be traced back to the stochastic approach to vacuum decay in [12,13], where the initial conditions for the subsequent classical evolution could be drawn from realizations of random Gaussian fields that inherit the same statistics as the quantum fluctuations [10]. The simplest realizations for such initial conditions of semiclassical vacuum decay is the flyover vacuum decay [14,15], where field velocity occasionally develops * schwang@cosmos.phy.tufts.edu a Gaussian profile large enough to classically overcome the barrier directly from a homogeneous field at false vacuum.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Occurrence of semiclassical vacuum decay

Wang

2019

Phys. Rev. D

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Recently, a novel phenomenon is observed for vacuum decay to proceed via classically allowed dynamical evolution from initial configurations of false vacuum fluctuations. With the help of some occasionally developed large fluctuations in time derivative of a homogeneous scalar field that is initially sitting at the false vacuum, the flyover vacuum decay is proposed if the initial Gaussian profile of field velocity contains a spatial region where the field velocity is large enough to flyover the potential barrier. In this paper, we point out that, even if the initial profile of field velocity is nowhere to be large enough to classically overcome the barrier, the semiclassical vacuum decay could still be possible if the initial profile of field velocity extends over large enough region.

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Section: Introductionmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

Occurrence of semiclassical vacuum decay

Wang

2019

Phys. Rev. D

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“…A possible experimental setup was discussed in [39,40]. It was further studied in [26,27], where it was shown to exhibit a parametric instability in a region of parameter space.…”

Section: Two-component Atomic Condensatementioning

confidence: 99%

“…One promising suggestion is that the metric, rather than the time coordinate, should be made complex [20,23]. More recently, attempts have been made at developing a formalism using only real time coordinates in analogy with what can be done in non-relativistic Quantum Mechanics [24,25] or with numerical techniques used in cold atom like the Truncated Wigner Approximation [26,27]. It was also proposed that instantons may be generalized using Picard-Lefschetz thimbles [28][29][30][31] or other functional techniques [32,33].…”

Section: Introductionmentioning

confidence: 99%

Parametrized path approach to vacuum decay

Michel

2020

Phys. Rev. D

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We develop a new real-time approach to vacuum decay based on a reduction to a finite number of degrees of freedom. The dynamics is followed by solving a generalized Schrödinger equation. We first apply this method to a real scalar field in Minkowski space and compare the decay rate with that obtained by the instanton approach. The main difference is in the early-time dynamics, where the decay is faster due to the tail of the wave function. We then apply it to a cold atom model recently proposed to simulate vacuum decay experimentally. This approach will be extended to include gravity in a future work. * florent.c.michel@durham.ac.uk 1 If 0 is a typical potential scale, one may choose 0 ∼ 0 ∼ 0 ∕( ℏ) −1∕( +1) , where is the celerity of light. 2 after excluding the zero modes associated with translation invariance, which are taken into account by the first factor arXiv:1911.12765v1 [quant-ph]

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“…In practise, this means that φ cl satisfies the classical equations of motion, where the initial data, φ cl 0 and φ cl 1 , is drawn from the Gaussian distribution (2.9). This approximation has been used in many calculations, including early-Universe simulations (for instance [3,4,41,42]), bubble nucleation [40,43,44] and thermalization [8,9,37]. It is clear from these expressions that the exponent I is purely imaginary, and so the exponential term in (2.6) is purely a phase, leading to a highly oscillatory integral.…”

Section: The Closed-time Path Integralmentioning

confidence: 99%

Quantum tunnelling, real-time dynamics and Picard-Lefschetz thimbles

Mou

Saffin

Tranberg

2019

J. High Energ. Phys.

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We follow up the work, where in light of the Picard-Lefschetz thimble approach, we split up the real-time path integral into two parts: the initial density matrix part which can be represented via an ensemble of initial conditions, and the dynamic part of the path integral which corresponds to the integration over field variables at all later times. This turns the path integral into a two-stage problem where, for each initial condition, there exits one and only one critical point and hence a single thimble in the complex space, whose existence and uniqueness are guaranteed by the characteristics of the initial value problem. In this paper, we test the method for a fully quantum mechanical phenomenon, quantum tunnelling in quantum mechanics. We compare the method to solving the Schrödinger equation numerically, and to the classical-statistical approximation, which emerges naturally in a well-defined limit. We find that the Picard-Lefschetz result matches the expectation from quantum mechanics and that, for this application, the classical-statistical approximation does not.-1 -There are a number of ways to try and sidestep this problem. One is to solve for the time evolution of the fields, or correlators of the fields, through some effective, systematically truncated, evolution equations. Good examples include the classical statistical approximation, where an ensemble mimicking the quantum initial density matrix are evolved using straightforward classical equations of motion. In cases where the occupation numbers are large, and the system is far from thermal equilibrium, this is a powerful and easily implementable approximation (see for instance [3][4][5][6][7]). Truncated Schwinger-Dyson equations for two-or higher-point correlators have been used to good effects for the approach to equilibrium, as well as in cosmological applications involving scalar and fermion fields (see [8][9][10][11]). Stochastic equations have also proven a valuable tool for concrete cases, that allow for a mapping of the full dynamics to such a description in a systematic way (see for instance [12,13]).In some cases, however, one must return to the direct computation of the path integral (1.2), but standard Monte-Carlo techniques, routinely and effectively applied to euclidean systems in QCD, fall short. A number of ways to try and resolve this sign problem have been proposed. Stochastic quantization is particularly promising, providing a Langevin type equation to sample the field space [14-16]. For a real-time path integral, the procedure leads to complex Langevin equations, driving the field φ away from the real axis sampling the entire complex plane. This effective doubling of the degrees of freedom helps to significantly improve convergence and one may show that under sensible assumptions, the correct physical result is achieved .Another remedy for the sign problem is to again complexify the real integration variables φ, but rather than doubling the dimensionality of field space R n → C n , we constrain the field variables to live on a...

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New Semiclassical Picture of Vacuum Decay

Cited by 66 publications

References 40 publications

Occurrence of semiclassical vacuum decay

Occurrence of semiclassical vacuum decay

Parametrized path approach to vacuum decay

Quantum tunnelling, real-time dynamics and Picard-Lefschetz thimbles

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