Axion couplings in grand unified theories

Agrawal, Prateek; Nee, Michael; Reig, Mario

doi:10.1007/jhep10(2022)141

Cited by 19 publications

(14 citation statements)

References 151 publications

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“…The idea is to remove the mixed QCD axion anomaly (κ s = 0) and direct couplings to quarks (C 0 q = 0). See [66][67][68][69][70][71][72][73][74][75][76][77][78][79][80][81] for variations on axion-matter couplings and their constraints.…”

Section: Jcap03(2024)015mentioning

confidence: 99%

Axio-Chameleons: a novel string-friendly multi-field screening mechanism

Brax,

Burgess,

Quevedo

2024

J. Cosmol. Astropart. Phys.

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Scalar-tensor theories with the shift symmetries required by light scalars are well-explored modifications to GR. For these, two-derivative scalar self-interactions usually dominate at low energies and interestingly compete with the two-derivative metric interactions of GR itself. Although much effort has been invested in single scalars (on grounds of simplicity) these happen to have no two-derivative interactions, requiring such models to explore higher-derivative interactions (that usually would be less important at low-energies). This suggests multiple-scalar sigma models as well-motivated candidates for finding new phenomena in tests of gravity. We identify a new multi-field screening mechanism appropriate for two light scalar fields (an axion and a Brans-Dicke style dilaton) that relies on their mutual two-derivative interactions. We show how very weak axion-matter couplings can introduce axion gradients that can reduce the apparent coupling of the Brans-Dicke scalar to macroscopic matter sources. We further identify a relaxation mechanism that allows this reduction to be amplified to a suppression by the ratio of the axion gradient's length scale to the source's radius (similar in size to the suppression found in Chameleon models). Unlike some screening mechanisms our proposal is technically natural and works deep within the regime of control of the low-energy EFT. It uses only ingredients that commonly appear in the low-energy limit of string vacua and so is likely to have wider applications to models that admit UV completions. We briefly discuss phenomenological implications and challenges for this scenario, which suggests re-examination of decay loss bounds and the value of equivalence-principle tests for different-sized objects.

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Section: Jcap03(2024)015mentioning

confidence: 99%

Axio-Chameleons: a novel string-friendly multi-field screening mechanism

Brax,

Burgess,

Quevedo

2024

J. Cosmol. Astropart. Phys.

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“…Before Pati-Salam symmetry breaking, Spin(4) w × Spin (6) The argument has led to a conundrum. The grand Higgs field 〈T〉, equation ( 46), commutes with ρ 3 and B − L, yet the mass term n n á ñ ¯• T , equation (53), violates conservation of ρ 3 and B − L. This would seem to violate the Noetherian [88] principle relating symmetries to conservation laws. The solution to the conundrum seems to be that 〈T〉 breaks the t-symmetry that links fermions and antifermions, by virtue of 〈T〉 not commuting with the time axis g g º -i t 0 (〈T〉 is nevertheless a Lorentz scalar, because it commutes with the Lorentz bivectors (24)).…”

Section: The Grand Higgs Field Generates a Majorana Mass For The Righ...mentioning

confidence: 99%

“…Yet other possibilities arise if the grand symmetry group is enlarged. For example, axions, which could be the dark matter [49], or not [50], could be accommodated by expanding the group to the product ( ) ( ) Spin 10 U 1 PQ [51][52][53][54] where ( ) U 1 PQ is a Peccei-Quinn symmetry. The present paper follows a different path, which seems to have been overlooked, namely the possibility that the Spin (10) group itself unifies nontrivially with the Lorentz group Spin (3,1) in Spin (11,1).…”

Section: Introductionmentioning

confidence: 99%

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Unification of the four forces in the Spin(11,1) geometric algebra

Hamilton¹

2023

Phys. Scr.

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SO(10), or equivalently its covering group Spin(10), is a well-known promising grand unified group that contains the standard-model group. The spinors of the group Spin(N) of rotations in N spacetime dimensions are indexed by a bitcode with [N/2] bits. Fermions in Spin(10) are described by five bits yzrgb, consisting of two weak bits y and z, and three colour bits r, g, b. If a sixth bit t is added, necessary to accommodate a time dimension, then the enlarged Spin(11,1) algebra contains the standard-model and Dirac algebras as commuting subalgebras, unifying the four forces. The symmetry breaking chain that breaks Spin(11,1) to the standard model appears to be essentially unique, proceeding via the Pati-Salam group. The Higgs sector appears similarly unique, consisting of the dimension~66 adjoint representation of Spin(11,1); in effect, the scalar Higgs sector matches the vector gauge sector. Although the unified algebra is that of Spin(11,1), the persistence of the electroweak Higgs field after grand symmetry breaking suggests that the gauge group before grand symmetry breaking is Spin(10,1), not the full group Spin(11,1). The running of coupling parameters predicts that the standard model should unify to the Pati-Salam group Spin(4)_w times Spin(6)_c at 10^{12} GeV, and thence to Spin(10,1) at 10^{15} GeV. The grand Higgs field breaks t-symmetry, can drive cosmological inflation, and generates a large Majorana mass for the right-handed neutrino by flipping its t-bit. The electroweak Higgs field breaks y-symmetry, and generates masses for fermions by flipping their y-bit.

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“…The aim of this work is to provide benchmark stellar-emission spectra of light particles from main sequence stars over a wide range of stellar masses. We focus, as a start, on what we refer to as the axion, a pseudoscalar a whose Lagrangian includes [15][16][17][18][19]…”

Section: Introductionmentioning

confidence: 99%

Spectra of axions emitted from main sequence stars

Nguyen,

Tanin,

Kamionkowski

2023

J. Cosmol. Astropart. Phys.

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We compute the detailed energy spectra of axions with two-photon coupling produced in stellar cores over a wide range of stellar masses. We focus on main sequence stars and base our calculations on the stellar interior profiles from MESA, for which we provide simple fits in an appendix. The obtained stellar axion spectra, combined with recent models of star formation history and stellar initial mass function, enable us to estimate the properties of the diffuse axion background sourced by all the stars in the universe. The fluxes of this stellar axion background and its decay photons are subdominant to but can in principle be disentangled from those expected from the Sun and the early universe based on their different spectral and spatial profiles.

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Axion couplings in grand unified theories

Cited by 19 publications

References 151 publications

Axio-Chameleons: a novel string-friendly multi-field screening mechanism

Axio-Chameleons: a novel string-friendly multi-field screening mechanism

Unification of the four forces in the Spin(11,1) geometric algebra

Spectra of axions emitted from main sequence stars

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