Early vs late string networks from a minimal QCD Axion
Abstract We propose a new regime of minimal QCD axion dark matter that lies between the pre- and post-inflationary scenarios, such that the Peccei-Quinn (PQ) symmetry is restored only on sufficiently large spatial scales. This leads to a novel cosmological evolution, in which strings and domain wall...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
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SpringerOpen
2024-02-01
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| Series: | Journal of High Energy Physics |
| Subjects: | |
| Online Access: | https://doi.org/10.1007/JHEP02(2024)223 |
| _version_ | 1827214441367732224 |
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| author | Marco Gorghetto Edward Hardy Horia Nicolaescu Alessio Notari Michele Redi |
| author_facet | Marco Gorghetto Edward Hardy Horia Nicolaescu Alessio Notari Michele Redi |
| author_sort | Marco Gorghetto |
| collection | DOAJ |
| description | Abstract We propose a new regime of minimal QCD axion dark matter that lies between the pre- and post-inflationary scenarios, such that the Peccei-Quinn (PQ) symmetry is restored only on sufficiently large spatial scales. This leads to a novel cosmological evolution, in which strings and domain walls re-enter the horizon and annihilate later than in the ordinary post-inflationary regime, possibly even after the QCD crossover. Such dynamics can occur if the PQ symmetry is restored by inflationary fluctuations, i.e. the Hubble parameter during inflation H I is larger than the PQ breaking scale f a , but it is not thermally restored afterwards. Solving the Fokker-Planck equation, we estimate the number of inflationary e-folds required for the PQ symmetry to be, on average, restored. Moreover, we show that, in the large parts of parameter space where the radial mode is displaced from the minimum by de Sitter fluctuations, a string network forms due to the radial mode oscillating over the top of its potential after inflation. In both cases we identify order one ranges in H I /f a and in the quartic coupling λ of the PQ potential that lead to the late-string dynamics. In this regime the cosmological dark matter abundance can be reproduced for axion decay constants as low as the astrophysical constraint 𝒪(108) GeV, corresponding to axion masses up to 10−2 eV, and with miniclusters with masses as large as 𝒪(10)M ⊙. |
| first_indexed | 2024-03-07T15:23:49Z |
| format | Article |
| id | doaj.art-5cd3db048905404991b563469dbde951 |
| institution | Directory Open Access Journal |
| issn | 1029-8479 |
| language | English |
| last_indexed | 2025-03-21T14:31:23Z |
| publishDate | 2024-02-01 |
| publisher | SpringerOpen |
| record_format | Article |
| series | Journal of High Energy Physics |
| spelling | doaj.art-5cd3db048905404991b563469dbde9512024-06-23T11:06:54ZengSpringerOpenJournal of High Energy Physics1029-84792024-02-012024214710.1007/JHEP02(2024)223Early vs late string networks from a minimal QCD AxionMarco Gorghetto0Edward Hardy1Horia Nicolaescu2Alessio Notari3Michele Redi4Deutsches Elektronen-Synchrotron DESYRudolf Peierls Centre for Theoretical Physics, University of OxfordDepartment of Mathematical Sciences, University of LiverpoolDepartament de Física Quàntica i Astrofisíca & Institut de Ciències del Cosmos (ICCUB), Universitat de BarcelonaINFN Sezione di Firenze and Department of Physics and Astronomy, University of FlorenceAbstract We propose a new regime of minimal QCD axion dark matter that lies between the pre- and post-inflationary scenarios, such that the Peccei-Quinn (PQ) symmetry is restored only on sufficiently large spatial scales. This leads to a novel cosmological evolution, in which strings and domain walls re-enter the horizon and annihilate later than in the ordinary post-inflationary regime, possibly even after the QCD crossover. Such dynamics can occur if the PQ symmetry is restored by inflationary fluctuations, i.e. the Hubble parameter during inflation H I is larger than the PQ breaking scale f a , but it is not thermally restored afterwards. Solving the Fokker-Planck equation, we estimate the number of inflationary e-folds required for the PQ symmetry to be, on average, restored. Moreover, we show that, in the large parts of parameter space where the radial mode is displaced from the minimum by de Sitter fluctuations, a string network forms due to the radial mode oscillating over the top of its potential after inflation. In both cases we identify order one ranges in H I /f a and in the quartic coupling λ of the PQ potential that lead to the late-string dynamics. In this regime the cosmological dark matter abundance can be reproduced for axion decay constants as low as the astrophysical constraint 𝒪(108) GeV, corresponding to axion masses up to 10−2 eV, and with miniclusters with masses as large as 𝒪(10)M ⊙.https://doi.org/10.1007/JHEP02(2024)223Axions and ALPsCosmology of Theories BSM |
| spellingShingle | Marco Gorghetto Edward Hardy Horia Nicolaescu Alessio Notari Michele Redi Early vs late string networks from a minimal QCD Axion Journal of High Energy Physics Axions and ALPs Cosmology of Theories BSM |
| title | Early vs late string networks from a minimal QCD Axion |
| title_full | Early vs late string networks from a minimal QCD Axion |
| title_fullStr | Early vs late string networks from a minimal QCD Axion |
| title_full_unstemmed | Early vs late string networks from a minimal QCD Axion |
| title_short | Early vs late string networks from a minimal QCD Axion |
| title_sort | early vs late string networks from a minimal qcd axion |
| topic | Axions and ALPs Cosmology of Theories BSM |
| url | https://doi.org/10.1007/JHEP02(2024)223 |
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