A1 Refereed original research article in a scientific journal
Particle decay in expanding Friedmann-Robertson-Walker universes
Authors: Juho Lankinen, Iiro Vilja
Publisher: AMER PHYSICAL SOC
Publication year: 2018
Journal: Physical Review D
Journal name in source: PHYSICAL REVIEW D
Journal acronym: PHYS REV D
Article number: ARTN 045010
Volume: 98
Issue: 4
Number of pages: 9
ISSN: 2470-0010
DOI: https://doi.org/10.1103/PhysRevD.98.045010
Abstract
The lack of energy conservation introduces new particle processes in curved spacetime that are forbidden in flat space. Therefore, one has to be very cautious about using the results calculated in Minkowskian space in early Universe applications. This is true for particle decay rates in particular, which need to be calculated using quantum field theory in curved spacetime. Previous studies are usually restricted to using minimal or conformal coupling for the decaying particle, while using a more general coupling would give deeper insight into particle decay. This paper presents the results we obtained for a massive particle decaying in a general power-law universe with arbitrary coupling to gravity. We find that, depending on the value of the gravitational coupling, the effect of gravitation may either strengthen or weaken the decay. The analysis further reveals that, apart from radiation-dominated universe, there are values of the coupling constant for which the decay rate is exactly Minkowskian for all universe types. Because the decay rate may be considerably modified in curved space, these issues need to be considered when doing precise cosmological calculations.
The lack of energy conservation introduces new particle processes in curved spacetime that are forbidden in flat space. Therefore, one has to be very cautious about using the results calculated in Minkowskian space in early Universe applications. This is true for particle decay rates in particular, which need to be calculated using quantum field theory in curved spacetime. Previous studies are usually restricted to using minimal or conformal coupling for the decaying particle, while using a more general coupling would give deeper insight into particle decay. This paper presents the results we obtained for a massive particle decaying in a general power-law universe with arbitrary coupling to gravity. We find that, depending on the value of the gravitational coupling, the effect of gravitation may either strengthen or weaken the decay. The analysis further reveals that, apart from radiation-dominated universe, there are values of the coupling constant for which the decay rate is exactly Minkowskian for all universe types. Because the decay rate may be considerably modified in curved space, these issues need to be considered when doing precise cosmological calculations.
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