Dark energy radiation

Berghaus, Kim V.; Graham, Peter W.; Kaplan, David E.; Rajendran, Surjeet

doi:10.1103/physrevd.104.083520

Cited by 36 publications

(35 citation statements)

References 49 publications

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“…The strong friction needed to generate the right level of primordial density perturbations requires a thermal bath of dark radiation coupled to the dark energy. Assuming even weak mixing with the standard model, such a dark radiation could be probed directly in a variety of ways [22].…”

Section: Discussionmentioning

confidence: 99%

“…Some of these sectors may have multiple vacua and possibly transitioned between them as the universe was heated before the bounce and cooled after the bounce 2 . Such a vacuum switching adds a φ-independent contribution to the CC which would show up in the EFT under consideration as a constant shift ∆V in the potential V of φ V = −g 3 φ −→ V = −g 3 φ + ∆V (22) This shift must be positive in order to explain the observed CC value today.…”

Section: E Bouncing and Expanding To The Present Epochmentioning

confidence: 99%

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Thermal Perturbations from Cosmological Constant Relaxation

Ji,

Kaplan,

Rajendran

et al. 2021

Preprint

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We probe the cosmological consequences of a recently proposed class of solutions to the cosmological constant problem. In these models, the universe undergoes a long period of inflation followed by a contraction and a bounce that sets the stage for the hot big bang era. A requirement of any successful early universe model is that it must reproduce the observed scale-invariant density perturbations at CMB scales. While these class of models involve a long period of inflation, the inflationary Hubble scale during their observationally relevant stages is at or below the current Hubble scale, rendering the de Sitter fluctuations too weak to seed the CMB anisotropies. We show that sufficiently strong perturbations can still be sourced thermally if the relaxion field serving as the inflaton interacts with a thermal bath, which can be generated and maintained by the same interaction. We present a simple model where the relaxion field is derivatively (i.e. technically naturally) coupled to a non-abelian gauge sector, which gets excited tachyonically and subsequently thermalizes due to its nonlinear self-interactions. This model explains both the smallness of the cosmological constant and the amplitude of CMB anisotropies.

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Section: Discussionmentioning

confidence: 99%

Section: E Bouncing and Expanding To The Present Epochmentioning

confidence: 99%

Thermal Perturbations from Cosmological Constant Relaxation

Ji,

Kaplan,

Rajendran

et al. 2021

Preprint

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“…Next, we couple this mediator to the dark matter and study the effects of the interaction between the neutrino and the dark matter. In principle, one could also couple the mediator to radiation emanating from the kinetic energy of dark energy [9], but these effects should be similar to those of the self-interacting neutrino effects considered here.…”

Section: Introductionmentioning

confidence: 94%

“…Given that a Majorana mass for the right-handed neutrino softly breaks lepton number, it could reasonably be at or below the scale of neutrino masses, ∼ 0.1 eV. As a standard model singlet, such a right handed neutrino is of significant phenomenological interest since it can be a portal into a variety of dark sectors including those associated with the physics of dark matter or dark energy [4][5][6][7][8][9][10][11][12][13][14][15][16]. The dark matter can exist at any scale while the physics directly associated with dark energy would be light, at scales comparable to the scale of neutrinos.…”

Section: Introductionmentioning

confidence: 99%

Neutrino interactions in the late universe

Green

Kaplan

Rajendran

2021

J. High Energ. Phys.

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The cosmic neutrino background is both a dramatic prediction of the hot Big Bang and a compelling target for current and future observations. The impact of relativistic neutrinos in the early universe has been observed at high significance in a number of cosmological probes. In addition, the non-zero mass of neutrinos alters the growth of structure at late times, and this signature is a target for a number of upcoming surveys. These measurements are sensitive to the physics of the neutrino and could be used to probe physics beyond the standard model in the neutrino sector. We explore an intriguing possibility where light right-handed neutrinos are coupled to all, or a fraction of, the dark matter through a mediator. In a wide range of parameter space, this interaction only becomes important at late times and is uniquely probed by late-time cosmological observables. Due to this coupling, the dark matter and neutrinos behave as a single fluid with a non-trivial sound speed, leading to a suppression of power on small scales. In current and near-term cosmological surveys, this signature is equivalent to an increase in the sum of the neutrino masses. Given current limits, we show that at most 0.5% of the dark matter could be coupled to neutrinos in this way.

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“…Υ(T ) is the temperature-dependent dissipation term that accounts for the frictional effect of sphaleron transitions between gauge vacua. This has been computed in the generic case of a gauge sector (with trace normalization T R and dimension d R of the representation) and an associated light fermion to be [33]:…”

Section: Inflation In a Thermal Bathmentioning

confidence: 99%

Warming up cold inflation

DeRocco,

Graham,

Kalia

2021

Preprint

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The axion is a well-motivated candidate for the inflaton, as the radiative corrections that spoil many single-field models are avoided by virtue of its shift symmetry. However, axions generically couple to gauge sectors. As the axion slow-rolls during inflation, this coupling can cause the production of a non-diluting thermal bath, a situation known as "warm inflation." This thermal bath can dramatically alter inflationary dynamics and observable predictions. In this paper, we demonstrate that a thermal bath can form for a wide variety of initial conditions, including starting from zero initial temperature in the universe. Furthermore, we find that axion inflation becomes warm over a large range of couplings, and explicitly map the parameter space for two axion inflation potentials. We show that in large regions of parameter space, axion inflation models once assumed to be safely "cold" are in fact warm, and must be reevaluated in this context.

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Dark energy radiation

Cited by 36 publications

References 49 publications

Thermal Perturbations from Cosmological Constant Relaxation

Thermal Perturbations from Cosmological Constant Relaxation

Neutrino interactions in the late universe

Warming up cold inflation

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