MSLED, neutrino oscillations and the cosmological constant

Matias, Joaquim; Burgess, C. P.

doi:10.1088/1126-6708/2005/09/052

Cited by 27 publications

(11 citation statements)

References 112 publications

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“…Although such mixing is not required by the cosmological constant, supersymmetry makes these models more plausible by providing a host of bulk fermions all of whom are required to be light because they are tied by supersymmetry to the massless graviton. Furthermore, the same back-reaction of the branes onto the bulk that helps with the cosmological constant also helps somewhat with the neutrino phenomenology [58]. If such mixing is present neutrino physics should contain potentially interesting evidence for a family of sterile neutrinos.…”

Section: Opportunitiesmentioning

confidence: 98%

The cosmological constant problem: why it’s hard to get dark energy from microphysics

Burgess¹

2015

Post-Planck Cosmology

129

189

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These notes present a brief introduction to 'naturalness' problems in cosmology, and to the Cosmological Constant Problem in particular. The main focus is the 'old' cosmological constant problem, though the more recent variants are also briefly discussed. Several notions of naturalness are defined, including the closely related ideas of technical naturalness and 't Hooft naturalness, and it is shown why these naturally arise when cosmology is embedded within a framework -effective field theories -that efficiently captures what is consistent with what is known about the physics of smaller distances. Some care is taken to clarify conceptual issues, such as the relevance or not of quadratic divergences, about which some confusion has arisen over the years. A set of minimal criteria are formulated against which proposed solutions to the problem can be judged, and a brief overview made of the general limitations of most of the approaches. A somewhat more in-depth discussion is provided of what I view as the most promising approach. These notes are aimed at graduate students with a basic working knowledge of quantum field theory and cosmology, but with no detailed knowledge of particle physics.

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Section: Opportunitiesmentioning

confidence: 98%

The cosmological constant problem: why it’s hard to get dark energy from microphysics

Burgess¹

2015

Post-Planck Cosmology

129

189

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“…• Exotic sterile neutrino physics: Although not absolutely required, the SLED scenario predicts there to be a variety of massless fermions in the extra dimensions, whose mass is protected to be small because they are related by supersymmetry to the graviton or bulk gauge fields. These fermions can mix with Standard Model neutrinos, leading to a potentially rich spectrum of sterile neutrino mixing [64] whose masses are naturally in the sub-eV range due to the large size of the extra dimensions [65,66].…”

Section: Some Observational Implicationsmentioning

confidence: 99%

Technically natural cosmological constant from supersymmetric 6D brane backreaction

Burgess

Nierop

2013

Physics of the Dark Universe

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We provide an explicit example of a higher-dimensional model describing a nonsupersymmetric spectrum of 4D particles of mass M , whose 4D geometryincluding loop effects -has a curvature that is of orderwhere m KK is the extra-dimensional Kaluza-Klein scale and M p is the 4D Planck constant. m KK is stabilized and can in particular satisfy m KK ≪ M . The system consists of a (5+1)-dimensional model with a flux-stabilized supersymmetric bulk coupled to non-supersymmetric matter localized on a (3+1)-dimensional positive-tension brane. We use recent techniques for calculating how extra dimensions respond to changes in brane properties to show (at the classical level) that the extra-dimensional volume adjusts to ensure that the low-energy 4D geometry is exactly flat, independent of the value of the brane tensions. Its mechanism for doing so is the transfer of stabilizing flux between the bulk and the branes. The UV completion of the model can arise at scales much larger than M , allowing the calculation of quantum effects like the zero-point energy of very massive particles in the vacuum. We find that brane-localized loops do not affect the 4D curvature at all, but bulk loops can. These can be estimated on general grounds and we show that supersymmetry dictates that they generate curvatures that are generically of order m 4 KK /M 2 p . For realistic applications this points to a world with two supersymmetric extra dimensions, with supersymmetry in the bulk broken at the sub-eV KK scale -as proposed in hep-th/0304256 -requiring a 6D gravity scale somewhat higher than 10 TeV. Ordinary Standard Model particles are brane-localized and not at all supersymmetric (implying in particular no superpartners or the MSSM). We discuss how the model evades various nogo theorems that would naively exclude it, and briefly outline several striking observational implications for tests of gravity and at the LHC.

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“…Their presence is a required consequence of the supersymmetry of the gravity sector (and resembles the low-energy sector of [120] in this way). Should these mix with Standard Model neutrinos they would provide natural candidates for light sterile neutrinos (along the lines of [121,122]), and could open up new ways to express lepton-number violation at low energies, with possible implications for lepto-and baryogenesis.…”

Section: General Implications and Future Directionsmentioning

confidence: 99%

Yoga Dark Energy: Natural Relaxation and Other Dark Implications of a Supersymmetric Gravity Sector

Burgess,

Dineen,

Quevedo

2021

Preprint

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We construct a class of 4D 'yoga' (naturally relaxed) models for which the vacuum energies of heavy particles do not gravitate. The models contain three ingredients: (i) a relaxation mechanism driven by a scalar field (the 'relaxon'), (ii) a very supersymmetric gravity sector coupled to the Standard Model in which supersymmetry is non-linearly realised, and (iii) an accidental approximate scale invariance expressed through the presence of a low-energy dilaton supermultiplet. All three are common in higher-dimensional and string constructions. Although none suffices on its own, taken together they predict a current Dark Energy density that is of order (M 2 W /M p ) 4 and a gravitino mass of order M 3 W /M 2 p , with M W , M p the weak and Planck scales respectively. The dilaton's vev τ determines the weak scale M W ∼ M p / √ τ and because the relevant part of the scalar potential arises as a function of ln τ it stabilizes τ in a local de Sitter minimum with exponentially large fields obtained using input parameters no larger than O(60), thereby explaining both the size of the electroweak hierarchy and the cosmological constant. Scale invariance implies the dilaton couples to matter like a Brans-Dicke scalar with coupling large enough to be naively ruled out by solar-system tests of gravity. Yet because it comes paired with an axion it escapes fifth-force bounds through the novel screening mechanism described in ArXiV:2110.10352. Cosmological axio-dilaton evolution provides a natural quintessence model for Dark Energy, whose evolution might realize recent proposals to resolve the Hubble tension, and whose axion contributes to Dark Matter. We summarize some of the remaining challenges, comment on implications for inflation and sketch possible UV completions of our approach.

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MSLED, neutrino oscillations and the cosmological constant

Cited by 27 publications

References 112 publications

The cosmological constant problem: why it’s hard to get dark energy from microphysics

The cosmological constant problem: why it’s hard to get dark energy from microphysics

Technically natural cosmological constant from supersymmetric 6D brane backreaction

Yoga Dark Energy: Natural Relaxation and Other Dark Implications of a Supersymmetric Gravity Sector

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