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dc.contributor.authorPeterson, Courtney M.
dc.contributor.authorTegmark, Max Erik
dc.date.accessioned2011-12-02T16:36:11Z
dc.date.available2011-12-02T16:36:11Z
dc.date.issued2011-07
dc.date.submitted2010-12
dc.identifier.issn0556-2813
dc.identifier.urihttp://hdl.handle.net/1721.1/67346
dc.description.abstractWe derive semianalytic formulas for the local bispectrum and trispectrum from general two-field inflation and provide a simple geometric recipe for building observationally allowed models with large non-Gaussianity. We use the δN formalism to express the bispectrum in terms of spectral observables and the transfer functions, which encode the superhorizon evolution of modes. Similarly, we calculate the trispectrum and show that the trispectrum parameter τNL can be expressed entirely in terms of spectral observables, which provides a new consistency relation for two-field inflation. To generate observably large non-Gaussianity during inflation, we show that the sourcing of curvature modes by isocurvature modes must be extremely sensitive to a change in the initial conditions orthogonal to the inflaton trajectory and that the amount of sourcing must be nonzero. Under some minimal assumptions, we argue that the first condition is satisfied only when neighboring trajectories in the two-dimensional field space diverge during inflation. Geometrically, this means that the inflaton must roll along a ridge in the potential V for some time during inflation and that its trajectory must turn somewhat in field space. Therefore, it follows that under our assumptions, two-field scenarios with attractor solutions necessarily produce small non-Gaussianity. This explains why it has been so difficult to achieve large non-Gaussianity in two-field inflation and why it has only been achieved in a small fraction of models where the potential and/or the initial conditions are fine-tuned. Some of our conclusions generalize at least qualitatively to multifield inflation and to scenarios where the interplay between curvature and isocurvature modes can be represented by the transfer function formalism.en_US
dc.description.sponsorshipNational Science Foundation (U.S.) (grant AST-0708534)en_US
dc.description.sponsorshipNational Science Foundation (U.S.) (grant AST-0908848)en_US
dc.description.sponsorshipDavid & Lucile Packard Foundationen_US
dc.language.isoen_US
dc.publisherAmerican Physical Societyen_US
dc.relation.isversionofhttp://dx.doi.org/10.1103/PhysRevD.84.023520en_US
dc.rightsArticle is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use.en_US
dc.sourceAPSen_US
dc.titleNon-Gaussianity in two-field inflationen_US
dc.typeArticleen_US
dc.identifier.citationPeterson, Courtney, and Max Tegmark. “Non-Gaussianity in Two-field Inflation.” Physical Review D 84.2 (2011) © 2011 American Physical Societyen_US
dc.contributor.departmentMassachusetts Institute of Technology. Department of Physicsen_US
dc.contributor.departmentMIT Kavli Institute for Astrophysics and Space Researchen_US
dc.contributor.approverTegmark, Max Erik
dc.contributor.mitauthorTegmark, Max Erik
dc.relation.journalPhysical Review Den_US
dc.eprint.versionFinal published versionen_US
dc.type.urihttp://purl.org/eprint/type/JournalArticleen_US
eprint.statushttp://purl.org/eprint/status/PeerRevieweden_US
dspace.orderedauthorsPeterson, Courtney; Tegmark, Maxen
dc.identifier.orcidhttps://orcid.org/0000-0001-7670-7190
mit.licensePUBLISHER_POLICYen_US
mit.metadata.statusComplete


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