Relaxion: A landscape without anthropics

Nelson, Ann; Prescod-Weinstein, Chanda

doi:10.1103/PhysRevD.96.113007

Title: Relaxion: A landscape without anthropics

Abstract

The relaxion mechanism provides a potentially elegant solution to the hierarchy problem without resorting to anthropic or other fine-tuning arguments. This mechanism introduces an axion-like field, dubbed the relaxion, whose expectation value determines the electroweak hierarchy as well as the QCD strong $C P$ -violating $\bar{θ}$ parameter. During an inflationary period, the Higgs mass squared is selected to be negative and hierarchically small in a theory which is consistent with ’t Hooft’s technical naturalness criteria. However, in the original model proposed by Graham, Kaplan, and Rajendran, the relaxion does not solve the strong $C P$ problem, and in fact contributes to it, as the coupling of the relaxion to the Higgs field and the introduction of a linear potential for the relaxion produces large strong $C P$ violation. Herein we resolve this tension by considering inflation with a Hubble scale which is above the QCD scale but below the weak scale, and estimating the Hubble temperature dependence of the axion mass. The relaxion potential is thus very different during inflation than it is today. We find that provided the inflationary Hubble scale is between the weak scale and about 3 GeV, the relaxion resolves the hierarchy, strong $C P$ , and dark matter problems in a way that is technically natural.

Authors:

Nelson, Ann ^[1]; Prescod-Weinstein, Chanda ^[1]

Univ. of Washington, Seattle, WA (United States). Dept. of Physics

Publication Date:: Wed Dec 20 00:00:00 EST 2017

Research Org.:: Univ. of Washington, Seattle, WA (United States)

Sponsoring Org.:: USDOE Office of Science (SC), High Energy Physics (HEP); National Science Foundation (NSF)

OSTI Identifier:: 1595818

Alternate Identifier(s):: OSTI ID: 1414328

Report Number(s):: arXiv:1708.00010v2
Journal ID: ISSN 2470-0010; PRVDAQ; TRN: US2101497

Grant/Contract Number:: SC0011637; PHY-1066293

Resource Type:: Accepted Manuscript

Journal Name:: Physical Review D

Additional Journal Information:: Journal Volume: 96; Journal Issue: 11; Journal ID: ISSN 2470-0010

Publisher:: American Physical Society (APS)

Country of Publication:: United States

Language:: English

Subject:: 72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS

Citation Formats


                    Nelson, Ann, and Prescod-Weinstein, Chanda. Relaxion: A landscape without anthropics.  United States: N. p., 2017. 
Web.  doi:10.1103/PhysRevD.96.113007.

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                    Nelson, Ann, & Prescod-Weinstein, Chanda. Relaxion: A landscape without anthropics.  United States.  https://doi.org/10.1103/PhysRevD.96.113007

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                    Nelson, Ann, and Prescod-Weinstein, Chanda. Wed .  
"Relaxion: A landscape without anthropics".  United States.  https://doi.org/10.1103/PhysRevD.96.113007.  https://www.osti.gov/servlets/purl/1595818.

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@article{osti_1595818,

  title        = {Relaxion: A landscape without anthropics},

  author       = {Nelson, Ann and Prescod-Weinstein, Chanda},

  abstractNote = {The relaxion mechanism provides a potentially elegant solution to the hierarchy problem without resorting to anthropic or other fine-tuning arguments. This mechanism introduces an axion-like field, dubbed the relaxion, whose expectation value determines the electroweak hierarchy as well as the QCD strong CP-violating θ¯ parameter. During an inflationary period, the Higgs mass squared is selected to be negative and hierarchically small in a theory which is consistent with ’t Hooft’s technical naturalness criteria. However, in the original model proposed by Graham, Kaplan, and Rajendran, the relaxion does not solve the strong CP problem, and in fact contributes to it, as the coupling of the relaxion to the Higgs field and the introduction of a linear potential for the relaxion produces large strong CP violation. Herein we resolve this tension by considering inflation with a Hubble scale which is above the QCD scale but below the weak scale, and estimating the Hubble temperature dependence of the axion mass. The relaxion potential is thus very different during inflation than it is today. We find that provided the inflationary Hubble scale is between the weak scale and about 3 GeV, the relaxion resolves the hierarchy, strong CP, and dark matter problems in a way that is technically natural.},

  doi          = {10.1103/PhysRevD.96.113007},

  journal      = {Physical Review D},

  number       = 11,

  volume       = 96,

  place        = {United States},

  year         = {Wed Dec 20 00:00:00 EST 2017},

  month        = {Wed Dec 20 00:00:00 EST 2017}

}

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Journal Article:

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https://doi.org/10.1103/PhysRevD.96.113007

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