New light species and the CMB

Brust, Christopher; Kaplan, David E.; Walters, Matthew T.

doi:10.1007/jhep12(2013)058

Cited by 137 publications

(192 citation statements)

References 167 publications

(235 reference statements)

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“…in agreement with [14][15][16][17][18][19][20][21][22]. This implies, in particular, that in order to explain the Planck result of N eff 0.62 when including the direct measurements of H 0 from HST, we need M X /M wimp > 2.5 × 10 5 .…”

Section: Dark Matter Particles As Dark Radiationsupporting

confidence: 75%

“…Recent examples of explicit realizations of the nonthermal, relativistic WIMP scenario for the "dark radiation" include effective theories as well as a supersymmetric construction and many other models [15][16][17][18][19][20][21][22]. Here, we show that such a scenario may also arise with a weakscale WIMP in the context of a non-supersymmetric 3-3-1 model, an electroweak extension of the Standard Model (SM) featuring a gauge group…”

Section: Introductionmentioning

confidence: 83%

“…However, increasing the scale of symmetry breaking up to 10 TeV a viable region opens up that is able to reproduce the measured value N eff ∼ 0.1-0.5 while evading all constraints. If we had used smaller values for g 11 instead, entropy suppression factors would have been significantly larger, ranging from 10 6 all the way up to 10 16 , but such smaller cou- plings are rather disfavored because they induce the WIMP decay.…”

Section: A Wimpy Dark Radiation 3-3-1 Modelmentioning

confidence: 99%

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A 331 WIMPy dark radiation model

et al. 2014

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Recent observations suggest that the number of relativistic degrees of freedom in the early universe might exceed what is predicted in the standard cosmological model. If even a small, percent-level fraction of dark matter particles are produced relativistically, they could mimic the effect of an extra realistic species at matter-radiation equality while obeying BBN, CMB and Structure Formation bounds. We show that this scenario is quite naturally realized with a weakscale dark matter particle and a high-scale "mother" particle within a well-motivated 3-3-1 gauge model, which is particularly interesting for being consistent with electroweak precision measurements, with recent LHC results, and for offering a convincing explanation for the number of generations in the Standard Model.

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Section: Dark Matter Particles As Dark Radiationsupporting

confidence: 75%

Section: Introductionmentioning

confidence: 83%

Section: A Wimpy Dark Radiation 3-3-1 Modelmentioning

confidence: 99%

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A 331 WIMPy dark radiation model

et al. 2014

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“…There are cosmological upper bounds on stable gravitinos (see e.g. [59][60][61][62] and references therein). From CMB measurements one gets m 3/2 ≤ 4.7 eV [60] and from primordial nucleosintesis m 3/2 ≤ 16 eV.…”

Section: Jhep11(2017)066mentioning

confidence: 99%

“…Details on bounds of dark radiation depend sensitively on how and when the particle decoupled and hence need not apply to the light degrees of freedom here considered (see e.g. [61,62]). …”

Section: Jhep11(2017)066mentioning

confidence: 99%

Constraining neutrino masses, the cosmological constant and BSM physics from the weak gravity conjecture

Ibáñez

Lozano²,

Valenzuela

2017

J. High Energ. Phys.

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It is known that there are AdS vacua obtained from compactifying the SM to 2 or 3 dimensions. The existence of such vacua depends on the value of neutrino masses through the Casimir effect. Using the Weak Gravity Conjecture, it has been recently argued by Ooguri and Vafa that such vacua are incompatible with the SM embedding into a consistent theory of quantum gravity. We study the limits obtained for both the cosmological constant Λ 4 and neutrino masses from the absence of such dangerous 3D and 2D SM AdS vacua. One interesting implication is that Λ 4 is bounded to be larger than a scale of order m 4 ν , as observed experimentally. Interestingly, this is the first argument implying a non-vanishing Λ 4 only on the basis of particle physics, with no cosmological input. Conversely, the observed Λ 4 implies strong constraints on neutrino masses in the SM and also for some BSM extensions including extra Weyl or Dirac spinors, gravitinos and axions. The upper bounds obtained for neutrino masses imply (for fixed neutrino Yukawa and Λ 4 ) the existence of upper bounds on the EW scale. In the case of massive Majorana neutrinos with a see-saw mechanism associated to a large scale M 10 10−14 GeV and Y ν 1 10 −3 , one obtains that the EW scale cannot exceed M EW 10 2 − 10 4 GeV. From this point of view, the delicate fine-tuning required to get a small EW scale would be a mirage, since parameters yielding higher EW scales would be in the swampland and would not count as possible consistent theories. This would bring a new perspective into the issue of the EW hierarchy.

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Cosmological Probes of Light Relics

Wallisch

2019

Springer Theses

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One of the primary targets of current and especially future cosmological observations are light thermal relics of the hot big bang. Within the Standard Model of particle physics, an important thermal relic are cosmic neutrinos, while many interesting extensions of the Standard Model predict new light particles which are even more weakly coupled to ordinary matter and therefore hard to detect in terrestrial experiments. On the other hand, these elusive particles may be produced efficiently in the early universe and their gravitational influence could be detectable in cosmological observables. In this thesis, we describe how measurements of the cosmic microwave background (CMB) and the large-scale structure (LSS) of the universe can shed new light on the properties of neutrinos and on the possible existence of other light relics.These cosmological observations are remarkably sensitive to the amount of radiation in the early universe, partly because free-streaming species such as neutrinos imprint a small phase shift in the baryon acoustic oscillations (BAO) which we study in detail in the CMB and LSS power spectra. Building on this analytic understanding, we provide further evidence for the cosmic neutrino background by independently confirming its free-streaming nature in different, currently available datasets. In particular, we propose and establish a new analysis of the BAO spectrum beyond its use as a standard ruler, resulting in the first measurement of this imprint of neutrinos in the clustering of galaxies.Future cosmological surveys, such as the next generation of CMB experiments (CMB-S4), have the potential to measure the energy density of relativistic species at the sub-percent level and will therefore be capable of probing physics beyond the Standard Model. We demonstrate how this improvement in sensitivity can indeed be achieved and present an observational target which would allow the detection of any extra light particle that has ever been in thermal equilibrium.Interestingly, even the absence of a detection would result in new insights by providing constraints on the couplings to the Standard Model. As an example, we show that existing bounds on additional scalar particles, such as axions, may be surpassed by orders of magnitude. For my parents DeclarationThis dissertation is the result of my own work and includes nothing which is the outcome of work done in collaboration except as declared below and specified in the text. Following the tendency of modern research in theoretical physics, most of the material discussed in this dissertation is the result of collaborative research. In particular, Chapters 4 and 6, and Appendices A, C and D are based on work done in collaboration with Daniel Baumann and Daniel Green, published in [1, 2], Chapter 5 and Appendix B are the result of the research done in collaboration with

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New light species and the CMB

Cited by 137 publications

References 167 publications

A 331 WIMPy dark radiation model

A 331 WIMPy dark radiation model

Constraining neutrino masses, the cosmological constant and BSM physics from the weak gravity conjecture

Cosmological Probes of Light Relics

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