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[{"key": "dc.contributor.advisor", "value": "Maalampi, Jukka", "language": null, "element": "contributor", "qualifier": "advisor", "schema": "dc"}, {"key": "dc.contributor.author", "value": "Leskinen, Juuso", "language": null, "element": "contributor", "qualifier": "author", "schema": "dc"}, {"key": "dc.date.accessioned", "value": "2016-05-04T12:22:08Z", "language": null, "element": "date", "qualifier": "accessioned", "schema": "dc"}, {"key": "dc.date.available", "value": "2016-05-04T12:22:08Z", "language": null, "element": "date", "qualifier": "available", "schema": "dc"}, {"key": "dc.date.issued", "value": "2016", "language": null, "element": "date", "qualifier": "issued", "schema": "dc"}, {"key": "dc.identifier.other", "value": "oai:jykdok.linneanet.fi:1532837", "language": null, "element": "identifier", "qualifier": "other", "schema": "dc"}, {"key": "dc.identifier.uri", "value": "https://jyx.jyu.fi/handle/123456789/49643", "language": null, "element": "identifier", "qualifier": "uri", "schema": "dc"}, {"key": "dc.description.abstract", "value": "T\u00e4ss\u00e4 pro gradu -tutkielmassa tarkastellaan hiukkasfysiikan standardimallin U(1)_PQ-laajennukseen kuuluvan uuden skalaarikent\u00e4n, aksionin, roolia kosmologiassa. Aluksi esittelemme valittuja paloja kosmologian standardimallista, joita tarvitsemme tarkasteltaessa aksionikent\u00e4n evoluutiota varhaisessa maailmankaikkeudessa. Teemme my\u00f6s katsauksen varhaisen maailmankaikkeuden faasitransitioihin ja niiden mukanaan tuomiin topologisiin defekteihin. \n\nK\u00e4ymme my\u00f6s l\u00e4pi ns. U(1)_A-ongelman ja t\u00e4t\u00e4 seuranneen vahvan CP-ongelman perusteet. J\u00e4lkimm\u00e4isen ongelman yhten\u00e4 eleganteimmista ratkaisuista pidet\u00e4\u00e4n ns. Peccei-Quinn -laajennusta ja aksionikentt\u00e4\u00e4. T\u00e4m\u00e4n minimaalisen laajennuksen globaali kiraalinen U(1)_PQ-symmetria voidaan liitt\u00e4\u00e4 hiukkasfysiikan standardimalliin usealla eri tavalla, joten kiinnit\u00e4mme huomiota kirjallisuudessa ehdotettuihin erilaisiin aksionimalleihin. Tarkastelemme my\u00f6s yleisesti aksionien hiukkasfenomenologiaa, teemme yleisen katsauksen kirjallisuuteen ja listaamme eri astrofysikaalisista havainnoista saatavia rajoitteita malliparametreille. Esittelemme my\u00f6s lyhyesti aksionien l\u00f6yt\u00e4miseksi kehitettyj\u00e4 havaintomenetelmi\u00e4 ja koej\u00e4rjestelmi\u00e4.\n\nTutkielman p\u00e4\u00e4painona on tarkastella aksionien roolia pime\u00e4n aineen hiukkasena. Aksionit voivat muodostaa kosmologian standardimallin vaatiman kylm\u00e4n pime\u00e4n aineen populaation joko ns. nolla-liikem\u00e4\u00e4r\u00e4 -moodiratkaisujen koherentilla oskillaatiolla, tai U(1)_PQ-symmetrian spontaanista symmetriarikosta syntyvien topologisten defektien, kuten s\u00e4ikeiden ja sein\u00e4mien hajoamisella aksioneiksi. Laskemme n\u00e4iden mekanismien tuottaman aksionien energiatiheyden, ja keskustelemme aksionituoton yksityskohdista, kuten aksionikent\u00e4n tuottamista isokurvatuurifluktuaatioista inflaation aikana. Lopuksi teemme my\u00f6s katsauksen kirjallisuudessa ehdotetun aksionien muodostaman Bose-Einstein kondensaatin keskeisiin v\u00e4itt\u00e4miin.", "language": "fi", "element": "description", "qualifier": "abstract", "schema": "dc"}, {"key": "dc.description.abstract", "value": "In this master's thesis we study the cosmological consequences of the new scalar field, the axion, that appears in the U(1)_PQ extension of the standard model of particle physics. We start by presenting some essential fragments of the standard model of Big Bang cosmology, that are needed when we describe the evolution of the axion field in the early Universe. We also review the basics of phase transitions in the early Universe, and go through the creation and evolution of the topological defects that emerge from these symmetry-breaking transitions.\n\nWe also study the so-called U(1)_A problem of the QCD, and the resolution that yields the strong CP problem that are closely related to the axion physics. The minimal Peccei-Quinn extension and the axions are usually taken to be the most elegant solution to this latter problem. The global and chiral U(1)_PQ required by this extension can be implemented into the theory in multiple ways, and therefore we study the different axion models proposed in the literature. We also go through certain phenomenological aspects of axions, and review the model-parameter constraints coming from astrophysical observations. A discussion of the different direct detection methods and experiments is also given.\n\nThe focal point of this thesis is to study the role of axions as a candidate for dark matter. Through the coherent oscillation of the so-called zero-momentum modes of the axion field and the decay of axionic topological defects (cosmic strings, domain walls) the Universe can contain a significant axionic cold dark matter population, that is an essential part of the cosmological concordance model (Lambda-CDM). Following the earlier work presented in the literature, we compute the contribution of the axion dark matter to the overall energy density, and also discuss the finer details of these mechanisms, such as the possible isocurvature fluctuations that the axion field can produce during inflation. We also give a brief review on the proposed idea of the axion Bose-Einstein condensate.", "language": "en", "element": "description", "qualifier": "abstract", "schema": "dc"}, {"key": "dc.description.provenance", "value": "Submitted using Plone Publishing form by Juuso Leskinen (juoslesk) on 2016-05-04 12:22:07.462254. Form: Pro gradu -lomake (https://kirjasto.jyu.fi/julkaisut/julkaisulomakkeet/pro-gradu-lomake). JyX data: [jyx_publishing-allowed (fi) =True]", "language": "en", "element": "description", "qualifier": "provenance", "schema": "dc"}, {"key": "dc.description.provenance", "value": "Submitted by jyx lomake-julkaisija (jyx-julkaisija.group@korppi.jyu.fi) on 2016-05-04T12:22:08Z\nNo. of bitstreams: 2\nURN:NBN:fi:jyu-201605042429.pdf: 1455811 bytes, checksum: 061dd9c579f5427425223f5307477bf2 (MD5)\nlicense.html: 4772 bytes, checksum: 909d19c8c620ef8cb5d8bb4d69b1c405 (MD5)", "language": "en", "element": "description", "qualifier": "provenance", "schema": "dc"}, {"key": "dc.description.provenance", "value": "Made available in DSpace on 2016-05-04T12:22:08Z (GMT). No. of bitstreams: 2\nURN:NBN:fi:jyu-201605042429.pdf: 1455811 bytes, checksum: 061dd9c579f5427425223f5307477bf2 (MD5)\nlicense.html: 4772 bytes, checksum: 909d19c8c620ef8cb5d8bb4d69b1c405 (MD5)\n Previous issue date: 2016", "language": "en", "element": "description", "qualifier": "provenance", "schema": "dc"}, {"key": "dc.format.extent", "value": "1 verkkoaineisto (99 sivua)", "language": null, "element": "format", "qualifier": "extent", "schema": "dc"}, {"key": "dc.format.mimetype", "value": "application/pdf", "language": null, "element": "format", "qualifier": "mimetype", "schema": "dc"}, {"key": "dc.language.iso", "value": "eng", "language": null, "element": "language", "qualifier": "iso", "schema": "dc"}, {"key": "dc.rights", "value": "In Copyright", "language": "en", "element": "rights", "qualifier": null, "schema": "dc"}, {"key": "dc.subject.other", "value": "aksioni", "language": null, "element": "subject", "qualifier": "other", "schema": "dc"}, {"key": "dc.title", "value": "Axion cosmology", "language": null, "element": "title", "qualifier": null, "schema": "dc"}, {"key": "dc.type", "value": "master thesis", "language": null, "element": "type", "qualifier": null, "schema": "dc"}, {"key": "dc.identifier.urn", "value": "URN:NBN:fi:jyu-201605042429", "language": null, "element": "identifier", "qualifier": "urn", "schema": "dc"}, {"key": "dc.type.ontasot", "value": "Pro gradu -tutkielma", "language": "fi", "element": "type", "qualifier": "ontasot", "schema": "dc"}, {"key": "dc.type.ontasot", "value": "Master\u2019s thesis", "language": "en", "element": "type", "qualifier": "ontasot", "schema": "dc"}, {"key": "dc.contributor.faculty", "value": "Matemaattis-luonnontieteellinen tiedekunta", "language": "fi", "element": "contributor", "qualifier": "faculty", "schema": "dc"}, {"key": "dc.contributor.faculty", "value": "Faculty of Sciences", "language": "en", "element": "contributor", "qualifier": "faculty", "schema": "dc"}, {"key": "dc.contributor.department", "value": "Fysiikan laitos", "language": "fi", "element": "contributor", "qualifier": "department", "schema": "dc"}, {"key": "dc.contributor.department", "value": "Department of Physics", "language": "en", "element": "contributor", "qualifier": "department", "schema": "dc"}, {"key": "dc.contributor.organization", "value": "University of Jyv\u00e4skyl\u00e4", "language": "en", "element": "contributor", "qualifier": "organization", "schema": "dc"}, {"key": "dc.contributor.organization", "value": "Jyv\u00e4skyl\u00e4n yliopisto", "language": "fi", "element": "contributor", "qualifier": "organization", "schema": "dc"}, {"key": "dc.subject.discipline", "value": "Elektroniikka", "language": "fi", "element": "subject", "qualifier": "discipline", "schema": "dc"}, {"key": "dc.subject.discipline", "value": "Electronics", "language": "en", "element": "subject", "qualifier": "discipline", "schema": "dc"}, {"key": "dc.date.updated", "value": "2016-05-04T12:22:08Z", "language": null, "element": "date", "qualifier": "updated", "schema": "dc"}, {"key": "yvv.contractresearch.funding", "value": "0", "language": null, "element": "contractresearch", "qualifier": "funding", "schema": "yvv"}, {"key": "dc.type.coar", "value": "http://purl.org/coar/resource_type/c_bdcc", "language": null, "element": "type", "qualifier": "coar", "schema": "dc"}, {"key": "dc.rights.accesslevel", "value": "openAccess", "language": "fi", "element": "rights", "qualifier": "accesslevel", "schema": "dc"}, {"key": "dc.type.publication", "value": "masterThesis", "language": null, "element": "type", "qualifier": "publication", "schema": "dc"}, {"key": "dc.subject.oppiainekoodi", "value": "4022", "language": null, "element": "subject", "qualifier": "oppiainekoodi", "schema": "dc"}, {"key": "dc.subject.yso", "value": "kosmologia", "language": null, "element": "subject", "qualifier": "yso", "schema": "dc"}, {"key": "dc.subject.yso", "value": "hiukkasfysiikka", "language": null, "element": "subject", "qualifier": "yso", "schema": "dc"}, {"key": "dc.subject.yso", "value": "pime\u00e4 aine", "language": null, "element": "subject", "qualifier": "yso", "schema": "dc"}, {"key": "dc.format.content", "value": "fulltext", "language": null, "element": "format", "qualifier": "content", "schema": "dc"}, {"key": "dc.rights.url", "value": "https://rightsstatements.org/page/InC/1.0/", "language": null, "element": "rights", "qualifier": "url", "schema": "dc"}, {"key": "dc.type.okm", "value": "G2", "language": null, "element": "type", "qualifier": "okm", "schema": "dc"}]
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