In quadratic-order degenerate higher-order scalar–tensor (DHOST) theories compatible with gravitational-wave constraints, we derive the most general Lagrangian allowing for tracker solutions characterized by , where is the time derivative of a scalar field ϕ, H is the Hubble expansion rate, and p is a constant. While the tracker is present up to the cubic-order Horndeski Lagrangian , where are constants and X is the kinetic energy of ϕ, the DHOST interaction breaks this structure for . Even in the latter case, however, there exists an approximate tracker solution in the early cosmological epoch with the nearly constant field equation of state . The scaling solution, which corresponds to , is the unique case in which all the terms in the field density and the pressure obey the scaling relation . Extending the analysis to the coupled DHOST theories with the field-dependent coupling between the scalar field and matter, we show that the scaling solution exists for , where and are constants. For the constant Q, i.e., , we derive fixed points of the dynamical system by using the general Lagrangian with scaling solutions. This result can be applied to the model construction of late-time cosmic acceleration preceded by the scaling ϕ-matter-dominated epoch.
{ "_oai": { "updated": "2020-04-18T00:52:10Z", "id": "oai:repo.scoap3.org:45221", "sets": [ "PLB" ] }, "authors": [ { "affiliations": [ { "country": "Portugal", "value": "Instituto de Astrof\u00edsica e Ci\u00eancias do Espa\u00e7o, Faculdade de Ci\u00eancias da Universidade de Lisboa, Lisboa, Portugal" } ], "surname": "Frusciante", "given_names": "Noemi", "full_name": "Frusciante, Noemi" }, { "affiliations": [ { "country": "Japan", "value": "Department of Physics, Faculty of Science, Tokyo University of Science, Tokyo, Japan" } ], "surname": "Kase", "given_names": "Ryotaro", "full_name": "Kase, Ryotaro" }, { "affiliations": [ { "country": "UK", "value": "Institute of Cosmology & Gravitation, University of Portsmouth, Portsmouth, United Kingdom" } ], "surname": "Koyama", "given_names": "Kazuya", "full_name": "Koyama, Kazuya" }, { "affiliations": [ { "country": "Japan", "value": "Department of Physics, Faculty of Science, Tokyo University of Science, Tokyo, Japan" } ], "surname": "Tsujikawa", "email": "shinji@rs.kagu.tus.ac.jp", "full_name": "Tsujikawa, Shinji", "given_names": "Shinji" }, { "affiliations": [ { "country": "Portugal", "value": "Centro de Astrof\u00edsica e Gravita\u00e7\u00e3o \u2013 CENTRA, Departamento de F\u00edsica, Instituto Superior T\u00e9cnico \u2013 IST, Universidade de Lisboa \u2013 UL, Lisboa, Portugal" } ], "surname": "Vernieri", "given_names": "Daniele", "full_name": "Vernieri, Daniele" } ], "titles": [ { "source": "Elsevier", "title": "Tracker and scaling solutions in DHOST theories" } ], "dois": [ { "value": "10.1016/j.physletb.2019.01.009" } ], "publication_info": [ { "page_end": "175", "journal_title": "Physics Letters B", "material": "article", "journal_volume": "790 C", "artid": "34372", "year": 2019, "page_start": "167" } ], "$schema": "http://repo.scoap3.org/schemas/hep.json", "acquisition_source": { "date": "2020-04-18T02:31:32.015791", "source": "Elsevier", "method": "Elsevier", "submission_number": "bcec9160810b11eaad8602163e01809a" }, "page_nr": [ 9 ], "license": [ { "url": "http://creativecommons.org/licenses/by/3.0/", "license": "CC-BY-3.0" } ], "copyright": [ { "holder": "The Author(s)", "statement": "The Author(s)", "year": "2019" } ], "control_number": "45221", "record_creation_date": "2019-01-29T13:31:49.758924", "_files": [ { "checksum": "md5:d0c9b625e3261e09ecbf341a56ec89fd", "filetype": "xml", "bucket": "91daa6a1-4a80-4ada-a7cc-90d846a34d9c", "version_id": "8e83ac07-4353-44d0-b535-8ad2e03f5ecd", "key": "10.1016/j.physletb.2019.01.009.xml", "size": 374849 }, { "checksum": "md5:145ee181642fd5dfe49ec58a03f0ccdc", "filetype": "pdf", "bucket": "91daa6a1-4a80-4ada-a7cc-90d846a34d9c", "version_id": "5b9235c1-0779-4d10-9388-a5fca1564e32", "key": "10.1016/j.physletb.2019.01.009.pdf", "size": 444355 }, { "checksum": "md5:a2f12bf5642c7acb1f8a2d5a356f46e7", "filetype": "pdf/a", "bucket": "91daa6a1-4a80-4ada-a7cc-90d846a34d9c", "version_id": "a3515ceb-fbbd-475c-9992-c86d1290936c", "key": "10.1016/j.physletb.2019.01.009_a.pdf", "size": 751107 } ], "collections": [ { "primary": "Physics Letters B" } ], "abstracts": [ { "source": "Elsevier", "value": "In quadratic-order degenerate higher-order scalar\u2013tensor (DHOST) theories compatible with gravitational-wave constraints, we derive the most general Lagrangian allowing for tracker solutions characterized by <math><mover><mrow><mi>\u03d5</mi></mrow><mrow><mo>\u02d9</mo></mrow></mover><mo>/</mo><msup><mrow><mi>H</mi></mrow><mrow><mi>p</mi></mrow></msup><mo>=</mo><mrow><mi>constant</mi></mrow></math>, where <math><mover><mrow><mi>\u03d5</mi></mrow><mrow><mo>\u02d9</mo></mrow></mover></math> is the time derivative of a scalar field \u03d5, H is the Hubble expansion rate, and p is a constant. While the tracker is present up to the cubic-order Horndeski Lagrangian <math><mi>L</mi><mo>=</mo><msub><mrow><mi>c</mi></mrow><mrow><mn>2</mn></mrow></msub><mi>X</mi><mo>\u2212</mo><msub><mrow><mi>c</mi></mrow><mrow><mn>3</mn></mrow></msub><msup><mrow><mi>X</mi></mrow><mrow><mo>(</mo><mi>p</mi><mo>\u2212</mo><mn>1</mn><mo>)</mo><mo>/</mo><mo>(</mo><mn>2</mn><mi>p</mi><mo>)</mo></mrow></msup><mo>\u25a1</mo><mi>\u03d5</mi></math>, where <math><msub><mrow><mi>c</mi></mrow><mrow><mn>2</mn></mrow></msub><mo>,</mo><msub><mrow><mi>c</mi></mrow><mrow><mn>3</mn></mrow></msub></math> are constants and X is the kinetic energy of \u03d5, the DHOST interaction breaks this structure for <math><mi>p</mi><mo>\u2260</mo><mn>1</mn></math>. Even in the latter case, however, there exists an approximate tracker solution in the early cosmological epoch with the nearly constant field equation of state <math><msub><mrow><mi>w</mi></mrow><mrow><mi>\u03d5</mi></mrow></msub><mo>=</mo><mo>\u2212</mo><mn>1</mn><mo>\u2212</mo><mn>2</mn><mi>p</mi><mover><mrow><mi>H</mi></mrow><mrow><mo>\u02d9</mo></mrow></mover><mo>/</mo><mo>(</mo><mn>3</mn><msup><mrow><mi>H</mi></mrow><mrow><mn>2</mn></mrow></msup><mo>)</mo></math>. The scaling solution, which corresponds to <math><mi>p</mi><mo>=</mo><mn>1</mn></math>, is the unique case in which all the terms in the field density <math><msub><mrow><mi>\u03c1</mi></mrow><mrow><mi>\u03d5</mi></mrow></msub></math> and the pressure <math><msub><mrow><mi>P</mi></mrow><mrow><mi>\u03d5</mi></mrow></msub></math> obey the scaling relation <math><msub><mrow><mi>\u03c1</mi></mrow><mrow><mi>\u03d5</mi></mrow></msub><mo>\u221d</mo><msub><mrow><mi>P</mi></mrow><mrow><mi>\u03d5</mi></mrow></msub><mo>\u221d</mo><msup><mrow><mi>H</mi></mrow><mrow><mn>2</mn></mrow></msup></math>. Extending the analysis to the coupled DHOST theories with the field-dependent coupling <math><mi>Q</mi><mo>(</mo><mi>\u03d5</mi><mo>)</mo></math> between the scalar field and matter, we show that the scaling solution exists for <math><mi>Q</mi><mo>(</mo><mi>\u03d5</mi><mo>)</mo><mo>=</mo><mn>1</mn><mo>/</mo><mo>(</mo><msub><mrow><mi>\u03bc</mi></mrow><mrow><mn>1</mn></mrow></msub><mi>\u03d5</mi><mo>+</mo><msub><mrow><mi>\u03bc</mi></mrow><mrow><mn>2</mn></mrow></msub><mo>)</mo></math>, where <math><msub><mrow><mi>\u03bc</mi></mrow><mrow><mn>1</mn></mrow></msub></math> and <math><msub><mrow><mi>\u03bc</mi></mrow><mrow><mn>2</mn></mrow></msub></math> are constants. For the constant Q, i.e., <math><msub><mrow><mi>\u03bc</mi></mrow><mrow><mn>1</mn></mrow></msub><mo>=</mo><mn>0</mn></math>, we derive fixed points of the dynamical system by using the general Lagrangian with scaling solutions. This result can be applied to the model construction of late-time cosmic acceleration preceded by the scaling \u03d5-matter-dominated epoch." } ], "imprints": [ { "date": "2019-01-17", "publisher": "Elsevier" } ] }