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Alan H. Guth and David I. Kaiser. Sfakianakis, Evangelos I Massachusetts Institute of Technology. Department of Physics. Massachusetts Institute of Technology. Department of Physics 2014-10-21T16:20:11Z 2014-10-21T16:20:11Z 2014 2014 http://hdl.handle.net/1721.1/91030 892606576 Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2014. This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. Cataloged from student-submitted PDF version of thesis. Includes bibliographical references. In this thesis I study the generation of density perturbations in two classes of inflationary models: hybrid inflation and multifield inflation with non-minimal coupling to gravity. In the case of hybrid inflation, we developed a new method of treating these perturbations that does not rely on a classical trajectory for the fields. A characteristic of the spectrum is the appearance of a spike at small length scales, which could conceivably seed the formation of black holes that can evolve to become the supermassive black holes found at the centers of galaxies. Apart from numerically calculating the resulting spectrum, we derived an expansion in the number of waterfall fields, which makes the calculation easier and more intuitive. In the case of multifield inflation, we studied models where the scalar fields are coupled non-minimally to gravity. We developed a covariant formalism and examined the prediction for non-Gaussianities in these models, arguing that they are absent except in the case of fine-tuned initial conditions. We have also applied our formalism to Higgs inflation and found that multifield effects are too small to be observable. We compared these models to the early data of the Planck satellite mission, finding excellent agreement for the spectral index and tensor to scalar ratio and promising agreement for the existence of iso-curvature modes. by Evangelos I. Sfakianakis. Ph.D. 280 pages eng Massachusetts Institute of Technology M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission. http://dspace.mit.edu/handle/1721.1/7582 Physics. Hybrid and multifield inflation Thesis application/pdf false Publication unknown unknown <Publication xmlns="https://www.openaire.eu/cerif-profile/1.1/" id="a0f5904e-9592-48c6-95aa-8fe7101aa747"> <Type xmlns="https://www.openaire.eu/cerif-profile/vocab/COAR_Publication_Types">http://purl.org/coar/resource_type/c_1843</Type> <Language>eng</Language> <Title>Hybrid and multifield inflation</Title> <PublishedIn> <Publication> </Publication> </PublishedIn> <PublicationDate>2014</PublicationDate> <Authors> <Author> <DisplayName>Sfakianakis, Evangelos I</DisplayName> <Affiliation> <OrgUnit> </OrgUnit> </Affiliation> </Author> </Authors> <Editors> </Editors> <Publishers> <Publisher> <DisplayName>Massachusetts Institute of Technology</DisplayName> <OrgUnit /> </Publisher> </Publishers> <License>http://dspace.mit.edu/handle/1721.1/7582</License> <Keyword>Physics.</Keyword> <Abstract>In this thesis I study the generation of density perturbations in two classes of inflationary models: hybrid inflation and multifield inflation with non-minimal coupling to gravity. In the case of hybrid inflation, we developed a new method of treating these perturbations that does not rely on a classical trajectory for the fields. A characteristic of the spectrum is the appearance of a spike at small length scales, which could conceivably seed the formation of black holes that can evolve to become the supermassive black holes found at the centers of galaxies. Apart from numerically calculating the resulting spectrum, we derived an expansion in the number of waterfall fields, which makes the calculation easier and more intuitive. In the case of multifield inflation, we studied models where the scalar fields are coupled non-minimally to gravity. We developed a covariant formalism and examined the prediction for non-Gaussianities in these models, arguing that they are absent except in the case of fine-tuned initial conditions. We have also applied our formalism to Higgs inflation and found that multifield effects are too small to be observable. We compared these models to the early data of the Planck satellite mission, finding excellent agreement for the spectral index and tensor to scalar ratio and promising agreement for the existence of iso-curvature modes.</Abstract> <Access xmlns="http://purl.org/coar/access_right" > </Access> </Publication>