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Benchmarking regulator-sourced 2PI and average 1PI flow equations in zero dimensions (2021)
Journal Article
Millington, P., & Saffin, P. M. (2021). Benchmarking regulator-sourced 2PI and average 1PI flow equations in zero dimensions. Journal of Physics A: Mathematical and Theoretical, 54(46), Article 465401. https://doi.org/10.1088/1751-8121/ac2d00

We elucidate the regulator-sourced 2PI and average 1PI approaches for deriving exact flow equations in the case of a zero dimensional quantum field theory, wherein the scale dependence of the usual renormalisation group evolution is replaced by a sim... Read More about Benchmarking regulator-sourced 2PI and average 1PI flow equations in zero dimensions.

Erratum: Alternative flow equation for the functional renormalization group [Phys. Rev. D 100, 101702(R) (2019)] (2021)
Journal Article
Alexander, E., Millington, P., Nursey, J., & Saffin, P. M. (2021). Erratum: Alternative flow equation for the functional renormalization group [Phys. Rev. D 100, 101702(R) (2019)]. Physical Review D, 104(6), Article 069906. https://doi.org/10.1103/physrevd.104.069906

We correct the functional identity reported in our paper for the inverse two-point function, as obtained from the 2PI effective action. The original conclusions are otherwise unaffected. The 2PI effective action is convex with respect to the variable... Read More about Erratum: Alternative flow equation for the functional renormalization group [Phys. Rev. D 100, 101702(R) (2019)].

Gravitational collapse with quantum fields (2021)
Journal Article
Berczi, B., Saffin, P. M., & Zhou, S. (2021). Gravitational collapse with quantum fields. Physical Review D, 104(4), Article L041703. https://doi.org/10.1103/PhysRevD.104.L041703

Gravitational collapse into a black hole has been extensively studied with classical sources. We develop a new formalism to simulate quantum fields forming a black hole. This formalism utilizes well-established techniques used for classical collapse... Read More about Gravitational collapse with quantum fields.

Charge-Swapping Q-balls and Their Lifetimes (2021)
Journal Article
Xie, Q., Saffin, P. M., & Zhou, S. (2021). Charge-Swapping Q-balls and Their Lifetimes. Journal of High Energy Physics, 2021(7), Article 62. https://doi.org/10.1007/jhep07%282021%29062

For scalar theories accommodating spherically symmetric Q-balls, there are also towers of quasi-stable composite Q-balls, called charge swapping Q-balls (CSQs). We investigate the properties, particularly the lifetimes, of these long-lived CSQs in 2+... Read More about Charge-Swapping Q-balls and Their Lifetimes.

Dipole radiation and beyond from axion stars in electromagnetic fields (2021)
Journal Article
Amin, M. A., Long, A. J., Mou, Z., & Saffin, P. M. (2021). Dipole radiation and beyond from axion stars in electromagnetic fields. Journal of High Energy Physics, 2021(6), Article 182. https://doi.org/10.1007/jhep06%282021%29182

We investigate the production of photons from coherently oscillating, spatially localized clumps of axionic fields (oscillons and axion stars) in the presence of external electromagnetic fields. We delineate different qualitative behaviour of the pho... Read More about Dipole radiation and beyond from axion stars in electromagnetic fields.

Deconstructing higher order clockwork gravity (2021)
Journal Article
Avgoustidis, A., Niedermann, F., Padilla, A., & Saffin, P. M. (2021). Deconstructing higher order clockwork gravity. Physical Review D, 103(12), Article 124007. https://doi.org/10.1103/physrevd.103.124007

We consider the higher order clockwork theory of gravitational interactions, whereby a number of gravitons are coupled together with TeV strength, but nevertheless generate a Planck scale coupling to matter without the need for a dilaton. It is shown... Read More about Deconstructing higher order clockwork gravity.

Statistics on Lefschetz thimbles: Bell/Leggett-Garg inequalities and the classical-statistical approximation (2021)
Journal Article
Millington, P., Mou, Z., Saffin, P. M., & Tranberg, A. (2021). Statistics on Lefschetz thimbles: Bell/Leggett-Garg inequalities and the classical-statistical approximation. Journal of High Energy Physics, 2021(3), Article 77. https://doi.org/10.1007/jhep03%282021%29077

Inspired by Lefschetz thimble theory, we treat Quantum Field Theory as a statistical theory with a complex Probability Distribution Function (PDF). Such complex-valued PDFs permit the violation of Bell-type inequalities, which cannot be violated by a... Read More about Statistics on Lefschetz thimbles: Bell/Leggett-Garg inequalities and the classical-statistical approximation.

Simulations of a bubble wall interacting with an electroweak plasma (2021)
Journal Article
Mou, Z., Saffin, P. M., & Tranberg, A. (2021). Simulations of a bubble wall interacting with an electroweak plasma. Journal of High Energy Physics, 2021(2), Article 189. https://doi.org/10.1007/jhep02%282021%29189

We perform large-scale real-time simulations of a bubble wall sweeping through an out-of-equilibrium plasma. The scenario we have in mind is the electroweak phase transition, which may be first order in extensions of the Standard Model, and produce s... Read More about Simulations of a bubble wall interacting with an electroweak plasma.