A composite solution to the EDGES anomaly

Mathur, Anubhav; Rajendran, Surjeet; Ramani, Harikrishnan

doi:10.48550/arxiv.2102.11284

Cited by 3 publications

(3 citation statements)

References 30 publications

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“…Since we, nonetheless, recover ρ b /ρ γ = ρ b /ρ γ , this difference does not affect any CMB observables, but can play an important role in hidden sector BBN. While hidden BBN does not affect visible sector CMB observables, it may have interesting observational consequences that warrant further study [32][33][34][35][36].…”

Section: Discussionmentioning

confidence: 95%

Towards a Realistic Model of Dark Atoms to Resolve the Hubble Tension

Blinov,

Krnjaic,

2021

Preprint

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It has recently been shown that a subdominant hidden sector of atomic dark matter in the early universe can resolve the Hubble tension while maintaining good agreement with most precision cosmological observables. However, such a solution requires a hidden sector whose energy density ratios are the same as in our sector and whose recombination also takes place at redshift z ≈ 1100, which presents an apparent fine tuning. We introduce a realistic model of this scenario that dynamically enforces these coincidences without fine tuning. In our setup, the hidden sector contains an identical copy of Standard Model (SM) fields, but has a smaller Higgs vacuum expectation value (VEV) and a lower temperature. The baryon asymmetries and reheat temperatures in both sectors arise from the decays of an Affleck-Dine scalar field, whose branching ratios automatically ensure that the reheat temperature in each sector is proportional to the corresponding Higgs VEV. The same setup also naturally ensures that the Hydrogen binding energy in each sector is proportional to the corresponding VEV, so the ratios of binding energy to temperature are approximately equal in the two sectors. Furthermore, our scenario predicts a correlation between the SM/hidden temperature ratio and the atomic dark matter abundance and automatically yields values for these quantities that resolve the Hubble tension.

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Section: Discussionmentioning

confidence: 95%

Towards a Realistic Model of Dark Atoms to Resolve the Hubble Tension

Blinov,

Krnjaic,

2021

Preprint

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“…MCP models have recently been explored in detail as potential explanations of the anomalously small spin temperature of the hydrogen atoms measured by the EDGES experiment [22,[24][25][26][27]. This anomaly can be resolved if the baryons were cooled by scattering with DM particles.…”

Section: Millicharged Particle Modelmentioning

confidence: 99%

Dark radiation constraints on portal interactions with hidden sectors

Adshead¹,

Ralegankar²,

Shelton³

2022

Preprint

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We update dark radiation constraints on millicharged particle (MCP) and gauged baryon-number-minus-lepton-number (B − L) extensions of the Standard Model (SM). In these models, a massive SM gauge singlet mediator couples the SM plasma to additional SMsinglet light degrees of freedom. In the early Universe, these new light particles are populated via the interaction of the SM with the MCP, or the new B − L gauge boson, and act as dark radiation. The presence of dark radiation in the early Universe is tightly constrained by current and upcoming cosmic microwave background (CMB) measurements. We update bounds on MCPs from current measurements of N eff and show that future CMB experiments will be able to rule out or discover the extended MCP model invoked to explain the EDGES anomaly. Our analysis of the gauged B − L model goes beyond previous studies by including quantum-statistical and out-of-equilibrium effects. Further, we account for the finite lifetime of the B − L gauge boson, which boosts the subsequent right-handed neutrino energy density. We also develop a number of approximations and techniques for simplifying and solving the relevant Boltzmann equations. We use our approximations to develop a lower bound on the radiation density in a generic hidden sector with a light relic that is insensitive to the details of the hidden sector, provided the mediator interacts more strongly with the hidden sector than with the SM.

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“…This anomalously large depth has received considerable attention in the literature. Many studies explain the depth either by postulating excess cooling of cosmic hydrogen due to novel physical mechanisms (Barkana 2018;Muñoz & Loeb 2018;Berlin et al 2018;Houston et al 2018;Li et al 2021;Mathur et al 2021), or by bringing into play a part of the excess radio background observed at relevant frequencies (Feng & Holder 2018;Pospelov et al 2018;Moroi et al 2018;Sierra & Fong 2018;Fraser et al 2018;Ewall-Wice et al 2018;Jana et al 2018;Chianese et al 2019;Lawson & Zhitnitsky 2019;Choi et al 2020;. Some studies invoke even more exotic scenarios, such as a modified Hubble parameter at cosmic dawn (Hill & Baxter 2018;Costa et al 2018;Wang & Zhao 2018;Xiao et al 2019), new coupling terms in the spin temperature (Widmark 2019;Lambiase & Mohanty 2020;Dhuria et al 2021), or special classes of dark energy and dark matter models (Mukhopadhyay et al 2021).…”

Section: Introductionmentioning

confidence: 99%

Implications of the cosmological 21-cm absorption profile for high-redshift star formation and deep JWST surveys

Mittal,

Kulkarni

2022

Preprint

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Apart from its anomalously large depth, the cosmological 21-cm absorption signal measured by the EDGES collaboration also has a shape that is distinctly different from theoretical predictions. This peculiar shape requires the establishment of a cosmic Ly 𝛼 background within 25 Myr at redshift 𝑧 ∼ 20 and a cosmic X-ray background within 50 Myr at redshift 𝑧 ∼ 15. Models with non-traditional components such as super-adiabatic baryonic cooling or an excess radio background explain the depth of the observed profile, but still conspicuously fail to explain its shape. In this paper, we quantify the requirements imposed by the EDGES measurement on sources of Ly 𝛼 and X-ray photons at cosmic dawn. In extreme cases, the Ly 𝛼 and X-ray emissivities require to be enhanced by up to an order of magnitude relative to traditional models. Furthermore, this enhancement needs to be active only for a short duration. We find that under conventional assumptions for the cosmic star formation density, standard stellar populations are incapable of meeting these conditions. Only highly unusual models of massive metal-free stars seem to provide a possible mechanism. Conversely, if the sources of Ly 𝛼 and X-ray photons are compelled to have standard properties, the EDGES measurement puts strong demands on the cosmic star formation rate density. This provides interesting falsifiable predictions for high-redshift galaxy surveys enabled by JWST. We derive predictions for galaxy UV luminosity functions and number densities, and show that a deep JWST survey with a limiting UV magnitude of 𝑚 UV,lim = 32 would potentially be able to rule out the predictions enforced by the EDGES measurement.

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A composite solution to the EDGES anomaly

Cited by 3 publications

References 30 publications

Towards a Realistic Model of Dark Atoms to Resolve the Hubble Tension

Towards a Realistic Model of Dark Atoms to Resolve the Hubble Tension

Dark radiation constraints on portal interactions with hidden sectors

Implications of the cosmological 21-cm absorption profile for high-redshift star formation and deep JWST surveys

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