Ian G. Moss

This paper aims to gather together some of the basic ideas behind the theory of false vacuum decay in quantum Ising models, focusing on the application of spin chains as analogue systems to false vacuum decay in elementary particle theory. Elementary results on quantum Ising models are rewritten to more closely resemble the original literature on false vacuum decay. A highly speculative conjecture for the false vacuum decay rate in a two dimensional quantum Ising model is also put forward.

We present a theory of false vacuum decay induced by spherical nucleation seeds. The type of seed considered has a boundary characterized by surface energy terms. The theory applies to false vacuum decay at zero and finite temperatures. Seeded nucleation may be important for enabling future false vacuum decay experiments on analog systems using Bose Einstein condensates (BEC). We show that our theory of seeded nucleation at finite temperature applied to a potassium BEC in two spatial dimensions agrees with numerical, real-time, simulations. Published by the American Physical Society 2024

Cold-atom analog experiments are a promising new tool for studying relativistic vacuum decay, enabling one to empirically probe early-Universe theories in the laboratory. However, existing proposals place stringent requirements on the atomic scattering lengths that are challenging to realize experimentally. Here we eliminate these restrictions and show that any stable mixture between two states of a bosonic isotope can be used as a faithful relativistic analog. This greatly expands the landscape of suitable experiments, and will expedite efforts to study vacuum decay with cold atoms.

Metastability stems from the finite lifetime of a state when a lower-energy configuration is available but only by tunnelling through an energy barrier. It is observed in many natural situations, including in chemical processes and in electron field ionization. In classical many-body systems, metastability naturally emerges in the presence of a first-order phase transition. A prototypical example is a supercooled vapour. The extension to quantum field theory and quantum many-body systems has attracted significant interest in the context of statistical physics, protein folding and cosmology, for which thermal and quantum fluctuations are expected to trigger the transition from the metastable state (false vacuum) to the ground state (true vacuum) through the probabilistic nucleation of spatially localized bubbles. However, the long-standing theoretical progress in estimating the relaxation rate of the metastable field through bubble nucleation has not been validated experimentally. Here we experimentally observe bubble nucleation in isolated and coherently coupled atomic superfluids, and we support our observations with numerical simulations. The agreement between our observations and an analytic formula based on instanton theory confirms our physical understanding of the decay process and promotes coherently coupled atomic superfluids as an ideal platform to investigate out-of-equilibrium quantum field phenomena.

The theory of false vacuum decay in a thermal system may have a crossover from predominantly thermal transitions to quantum transitions as the temperature is decreased. New numerical methods and results are presented here that can be used to model thermal and vacuum bubble nucleation in this regime for cosmology and for laboratory analog of early universe phase transitions.

Cold atomic gases offer the prospect of simulating the physics of the very early Universe in the laboratory. In the condensate phase, the gas is described by a field theory with key features of high energy particle theory. This paper describes a three level system which undergoes a first order phase transition through the nucleation of bubbles. The theoretical investigation shows bubbles nucleating in two dimensions at non-zero temperature. There is good agreement between the bubble nucleation rates calculated from a stochastic projected Gross–Pitaevskii equation and from a non-perturbative instanton method. When an optical box trap is included in the simulations, the bubbles nucleate preferentially near the walls of the trap.

This note analyses on the long wavelength dynamics of a two horizon analogue black hole system in one spatial dimension. By introducing an effective scalar-dilaton model we show that closed form expressions can be obtained for the time-dependent Hawking flux and the energy density of the Hawking radiation. We show that, in the absence superluminal modes, there is a vacuum instability. This instability is recognisable to relativists as the analogue to the destabilisation of the Cauchy horizon of a black hole due to vacuum polarization.

Particle production from the vacuum is a remarkable aspect of particle physics. Prime examples are the Schwinger process of particle production in strong electric fields and the Hawking process of particle production from black holes. These processes can be viewed as quantum tunnelling of particles from the vacuum. The tunnelling approach, and the closely related instanton or complex path approaches, are reviewed here with emphasis on paths in the complex coordinate plane. The method is applied to particle production from a black hole in a magnetic field, where ultra-high energy charged particles are produced.

The theory of false vacuum decay in a thermal system may have a cross-over from predominantly thermal transitions to quantum transitions as the temperature is decreased. New numerical methods and results are presented here that can be used to model thermal and vacuum bubble nucleation in this regime for cosmology and for laboratory analogues of early universe phase transitions.

Cold atomic gases offer the prospect of simulating the physics of the very early universe in the laboratory. In the condensate phase, the gas is described by a field theory with key features of high energy particle theory. This paper describes a three level system which undergoes a first order phase transition through the nucleation of bubbles. The theoretical investigation shows bubbles nucleating in two dimensions at non-zero temperature. There is good agreement between the bubble nucleation rates calculated from a Stochastic Projected Gross-Pitaevskii equation and from a non-perturbative instanton method. When an optical box trap is included in the simulations, the bubbles nucleate preferentially near the walls of the trap.