シフト対称性の破れによるアクシオンダークマターに対する束縛効果とその宇宙論的意義

Tohoku University高橋史宜課

Non-thermally trapped inflation by tachyonic dark photon production

We show that a dark Higgs field charged under U(1)$_{\rm H}$ gauge symmetry is trapped at the origin for a long time, if dark photons are produced by an axion condensate via tachyonic preheating. The trapped dark Higgs can drive late-time inflation, producing a large amount of entropy. Unlike thermal inflation, the dark Higgs potential does not have to be very flat, because the effective mass for the dark Higgs is enhanced by large field values of dark photons with extremely low momentum. After inflation, the dark Higgs decays into massive dark photons, which further decay into the SM particles through a kinetic mixing. We show that a large portion of the viable parameter space is within the future experimental searches for the dark photon, because the kinetic mixing is bounded below for successful reheating. We also comment on the Schwinger effect which can hamper the tachyonic production of dark photons, when the mass of dark photon is not the St\"{u}ckelberg mass, but is generated by the Higgs mechanism. Such non-thermal trapped inflation could be applied to other cosmological scenarios such as the early dark energy, known as one of the solutions to the Hubble tension.Comment: 11pages, 7 figures, references adde

Early dark energy by dark Higgs, and axion-induced non-thermal trapping

We propose a new scenario of early dark energy (EDE) with a dark Higgs trapped at the origin. To keep this dark Higgs trapped until around the matter-radiation equality, we use dark photons produced non-thermally by coherent oscillations of axions, which have a much stronger trapping effect than thermal mass. When the trapping ends, the dark Higgs quickly decays into dark photons, which are then red-shifted as radiation. The dark Higgs EDE scenario works well for an ordinary Mexican-hat potential, and the dark Higgs naturally sits at the origin from the beginning, since it is the symmetry-enhanced point. Thus, unlike the axion EDE, there is no need for elaborate potentials or fine-tuning with respect to the initial condition. Interestingly, the axion not only produces dark photons, but also explains dark matter. We find the viable parameter region of the axion decay constant and the axion mass where dark matter and the $H_0$ tension can be simultaneously explained. We also discuss the detectability of the axion in the presence of axion-photon coupling, and show that the axion can be the QCD axion.Comment: 27 pages, 4 figure

Dynamics of Superconformal Axion: Quality and Scalegenesis

We explore a dynamical mechanism to realize the emergence of a global $U(1)_{\rm PQ}$ symmetry and its spontaneous breaking at an intermediate scale for an axion solution to the strong CP problem. Such a dynamics is provided by a new supersymmetric QCD near the middle of conformal window that couples to fields spontaneously breaking the $U(1)_{\rm PQ}$ symmetry. A large anomalous dimension of the $U(1)_{\rm PQ}$ breaking fields leads to the suppression of explicit $U(1)_{\rm PQ}$-violating higher dimensional operators. The $U(1)_{\rm PQ}$ breaking vacuum is generated at a scale hierarchically smaller than the Planck scale by a non-perturbative effect. The $U(1)_{\rm PQ}$ breaking drives the conformal breaking, and all the new quarks become massive. The axion potential is generated by the ordinary color $SU(3)_C$ effect as the $U(1)_{\rm PQ}$ symmetry is only anomalous under the $SU(3)_C$. The saxion direction is stabilized by supersymmetry breaking and cosmologically harmless.Comment: 8 pages, 3 figure

Dissipation of axion energy via the Schwinger and Witten effects

In the presence of an anomalous CP phase in a U(1) gauge theory, a monopole becomes a dyon via the Witten effect. When the anomalous CP phase is promoted to a dynamical field, the axion, the electric charge of the dyon changes according to the coherent motion of the axion oscillation. Once the electric charge exceeds a certain threshold, the Schwinger pair production of charged particles becomes efficient near the surface of the dyon. These non-perturbative effects lead to the back reaction of the axion dynamics by causing the dissipation of the axion oscillation energy and the change of the effective potential due to the Witten effect. Taking these effects into account, we consider the dynamics of the whole system, including the axion, monopole, and charged heavy vector bosons, and discuss to what extent the axion abundance is modified. We also discuss the electric dipole radiation from a bound state of a monopole-anti-monopole pair due to the axion coherent oscillations.Comment: 22 pages, 9 figure