Cosmology of the invisible axion

Abstract

We identify a new cosmological problem for models which solve the strong CP puzzle with an invisible axion, unrelated to the domain wall problem. Because the axion is very weakly coupled, the energy density stored in the oscillations of the classical axion field does not dissipate rapidly; it exceeds the critical density needed to close the universe unless fa <~ 1012 GeV, where fa is the ~lxion decay constant. If this bound is saturated, axions may comprise the dark matter of the universe.Ever since the discovery [ 1 ] of the CP-violating parameter 0 of the strong interactions, the small value of 0 has posed a serious puzzle. Current experimental limits [2] on the electric dipole moment of the neutron require [3] ~< 10 -9. The small value of O is naturally explained in models.with a spontaneously broken Peccei-Quinn symmetry [4], but the resulting axion [5] has not been seen. In a recently proposed variant of the Peccei-Quinn scheme [6,7], the axion mass and its couplings to ordinary matter are inversely proportional to the large vacuum expectation value fa of an [SU(2)

Detecting Solar Axions Using Earth’s Magnetic Field

“…(1). Here we note that some cosmological considerations related to overclosure of the universe suggest a lower bound g aγ > ∼ 10 −15 GeV −1 [6]. For a review of different bounds on axion couplings, see Ref.…”

Dilaton and second-rank tensor fields as supersymmetric compensators

“…This implies that the axion-like field must be very light and extremely weakly coupled. On the other hand, cosmological arguments on the overclosure of the universe also yield an upper bound f < ∼ 10 12 GeV [7]. Of course, these constraints are pertinent, provided the right conditions are implemented in the model for these axion-like particles to address the strong CP problem.…”

String theoretic QCD axion with stabilized saxion and the pattern of supersymmetry breaking

“…As the above result shows, the precise value of v PQ is somewhat model-dependent, but generically around 10 16 GeV. Such a large value of v PQ might cause the cosmological problem that the cosmological axion density produced by initial misalignment overcloses the Universe [42]. Interestingly, for the moduli stabilization scenario under consideration, this cosmological axion problem can be significantly ameliorated by the late decay of saxion [43] which has a right mass to decay right before the big-bang nucleosynthesis (BBN) for the most interesting case that the visible sector superparticle masses are of the order of the weak scale.…”