Analysis of techni-dilaton as a dark matter candidate

Abstract

The almost conformal dynamics of walking technicolor (TC) implies the existence of the approximate scale invariance, which breaks down spontaneously by the condensation of anti-techni and techni-fermions. According to the Goldstone theorem, a spinless, parity-even particle, called technidilaton (TD), then emerges at low energy. If TC exhibits an extreme walking, TD mass, MTD, is parametrically much smaller than that of techni-fermions (∼ 1 TeV), while its decay constant is comparable to the cutoff scale of walking TC. We analyze the light, decoupled TD as a dark matter candidate and study cosmological productions of TD, both thermal and non-thermal, in the early Universe. The thermal population is governed dominantly by single TD production processes involving vertices breaking the scale symmetry, while the non-thermal population is by the vacuum misalignment and is accumulated via harmonic and coherent oscillations of misaligned classical TD fields. The non-thermal population turns out to be dominant and large enough to explain the abundance of presently observed dark matter, while the thermal population is highly suppressed due to the large TD decay constant. Several cosmological and astrophysical limits on the light, decoupled TD are examined to find that the mass MTD is constrained to be in a range, 0.01eV < ∼ MTD < ∼ 500 eV. From the combined constraints on cosmological productions and astrophysical observations, we find that the light, decoupled TD can be a good dark matter candidate with the mass around a few hundreds of eV for typical models of (extreme) walking TC. We finally mention possible designated experiments to detect the TD dark matter.

Dilatonic black holes in gravity’s rainbow with a nonlinear source: the effects of thermal fluctuations

“…In Ref. [57], it was shown that dilaton field can be an appropriate candidate for dark matter. In addition, in order to have deep picture regarding the nature of dark energy, a new scalar field can be added to the field content of original theory [58,59].…”

Very light dilaton and naturally light Higgs boson

“…, where s(T ) is the entropy density at temperature T , we find the dilaton dark matter contributes to energy of our present universe as [29,30] Ω σ h 2 ∼ 0.5 δσ…”

“…According to the current standard big-bang cosmology, cold dark matter with a cosmological constant, so-called the ΛCDM fits the current observations such as the cosmic microwave background (CMB) best [32,33]. A very light dilaton has been shown to be one of the best candidates for the cold dark matter [29,30].…”

“…As long as the scale symmetry is broken very close to the (quasi) infrared fixed point of the UV theory, there will be a large separation of two scales f ∼ Λ SB and M , the dynamical (or infrared) scale of the (quasi) scale-invariant UV theory. We then have |E vac | ∼ M 4 f 4 and the dilaton can be very light [29,30]. Since the UV completion of the Higgs sector is assumed to be (quasi) scale-invariant, one can impose the scale invariance at the cutoff scale on the standard model in the sense of Bardeen's naturalness [14].…”

“…Very light dilaton as dark matter has been studied in [29,30] in the context of walking technicolor. The light dilaton in our model might be detected in similar experiments such as a microwave cavity experiment under strong magnetic fields.…”