TY - JOUR

T1 - KSVZ axion model with quasidegenerate minima

T2 - A unified model for dark matter and dark energy

AU - Lloyd-Stubbs, Amy

AU - McDonald, John

PY - 2019/1/15

Y1 - 2019/1/15

N2 - We consider the possibility that dark matter and dark energy can be explained by the minimal Kim-Shifman-Vainshtein-Zakharov axion model. This is possible if the lowest energy minimum of the scalar potential has zero energy density, as can occur in theoretical models of vacuum energy cancellation based on spacetime averaging and in models based on energy parity. Dark energy is then understood as being due to the energy density of the metastable electroweak vacuum relative to a second quasidegenerate minimum. The requirement of quasidegenerate minima is a nontrivial condition which completelydetermines the form of the potential for a given value of the axion decay constant, fa, and the Pecci-Quinn (PQ) scalar self-coupling, λϕ. The existence of the second quasidegenerate minimum imposes a newlower bound on the axion decay constant, fa ≥ 2.39 × 10^{10} λ_{\phi}^{−1/4}GeV. If the PQ symmetry is broken after inflation, then the lower bound on fa implies a lower bound on the amount of axion dark matter,Ω_{a}/Ω_{dm} ≥ (0.28 − 0.46)λ^{−0.291} , where the range is due to the uncertainty in the amount of axion dark matter produced by vacuum realignment, cosmic strings, and domain walls. Therefore, at least 30% of dark mattermust be due to axions if λ_{\phi} ≲ 1. If axions constitute all of the dark matter then the value of fa, and so the form of the scalar potential, is completely fixed for a given value of λϕ, with only a weak dependence on λ_{\phi}.This will allow the inflation and postinflation evolution of the model to be quantitatively studied for a given inflation model and dimensionally natural values of λ_{\phi}.

AB - We consider the possibility that dark matter and dark energy can be explained by the minimal Kim-Shifman-Vainshtein-Zakharov axion model. This is possible if the lowest energy minimum of the scalar potential has zero energy density, as can occur in theoretical models of vacuum energy cancellation based on spacetime averaging and in models based on energy parity. Dark energy is then understood as being due to the energy density of the metastable electroweak vacuum relative to a second quasidegenerate minimum. The requirement of quasidegenerate minima is a nontrivial condition which completelydetermines the form of the potential for a given value of the axion decay constant, fa, and the Pecci-Quinn (PQ) scalar self-coupling, λϕ. The existence of the second quasidegenerate minimum imposes a newlower bound on the axion decay constant, fa ≥ 2.39 × 10^{10} λ_{\phi}^{−1/4}GeV. If the PQ symmetry is broken after inflation, then the lower bound on fa implies a lower bound on the amount of axion dark matter,Ω_{a}/Ω_{dm} ≥ (0.28 − 0.46)λ^{−0.291} , where the range is due to the uncertainty in the amount of axion dark matter produced by vacuum realignment, cosmic strings, and domain walls. Therefore, at least 30% of dark mattermust be due to axions if λ_{\phi} ≲ 1. If axions constitute all of the dark matter then the value of fa, and so the form of the scalar potential, is completely fixed for a given value of λϕ, with only a weak dependence on λ_{\phi}.This will allow the inflation and postinflation evolution of the model to be quantitatively studied for a given inflation model and dimensionally natural values of λ_{\phi}.

KW - COSMOLOGY

U2 - 10.1103/PhysRevD.99.023510

DO - 10.1103/PhysRevD.99.023510

M3 - Journal article

VL - 99

JO - Physical Review D

JF - Physical Review D

SN - 1550-7998

IS - 2

M1 - 023510

ER -