edoc: No conditions. Results ordered -Date Deposited. 2024-10-12T22:40:03ZEPrintshttps://edoc.unibas.ch/images/uni-logo.jpghttps://edoc.unibas.ch/2017-02-13T13:18:32Z2017-02-13T13:18:32Zhttps://edoc.unibas.ch/id/eprint/51973This item is in the repository with the URL: https://edoc.unibas.ch/id/eprint/519732017-02-13T13:18:32ZParametric resonance after hilltop inflation caused by an inhomogeneous inflaton fieldWe study preheating after hilltop inflation where the inflaton couples to another scalar field, e.g. a right-handed sneutrino, which provides a mechanism for generating the correct initial conditions for inflation and also a decay channel for the inflaton that allows for reheating and non-thermal leptogenesis. In the presence of such a coupling, we find that after the phases of tachyonic preheating and tachyonic oscillations, during which the inflaton field becomes inhomogeneous, there can be a subsequent preheating phase where the fluctuations of the other field get resonantly enhanced, from initial vacuum fluctuations up to amplitudes of the same order (and even larger) as the ones of the inflaton field. This resonant enhancement differs from the usual parametric resonance as the inflaton field is inhomogeneous at the time the enhancement takes place. We study this effect using lattice simulations as well as semi-analytically with a generalized Floquet analysis for inhomogeneous background fields. Stefan AntuschFrancesco CefalaDavid NoldeStefano Orani2016-05-02T09:25:21Z2016-06-30T11:00:10Zhttps://edoc.unibas.ch/id/eprint/39803This item is in the repository with the URL: https://edoc.unibas.ch/id/eprint/398032016-05-02T09:25:21ZHilltop inflation with preinflation from coupling to matter fieldsWe propose a class of models of supersymmetric hilltop inflation (also called "new inflation") where the initial conditions of the inflaton close to the hilltop are generated through "matter field preinflation". This is achieved via a coupling term between the inflaton and matter fields (i.e. Standard Model fields or a right-handed neutrino). The same coupling also opens up a decay channel for the inflaton into Standard Model fields, which allows efficient reheating of the universe. We discuss the multifield dynamics of the inflaton and matter fields during inflation using the delta N formalism and show under which conditions the model effectively reduces to single-field hilltop inflation during the last 60 e-folds. We also study perturbative reheating through the matter-inflaton coupling for a specific example where the matter field is identified with a right-handed (s)neutrino, and demonstrate that in this case the model can generate the observed baryon asymmetry through nonthermal leptogenesis. Stefan AntuschDavid NoldeStefano Orani2016-05-02T09:21:43Z2016-06-30T11:00:10Zhttps://edoc.unibas.ch/id/eprint/39802This item is in the repository with the URL: https://edoc.unibas.ch/id/eprint/398022016-05-02T09:21:43ZBICEP2 implications for single-field slow-roll inflation revisitedIt is generally believed that in single-field slow-roll inflation, a large tensor-to-scalar ratio r>0.1 requires inflaton field values close to or above the Planck scale. Recently, it has been claimed that r>0.15 can be achieved with much smaller inflaton field values Δϕ<MPl/10. We show that in single-field slow-roll inflation, it is impossible to reconcile r>0.1 with such small field values, independently of the form of the potential, and that the recent claim to the contrary is based on an invalid approximation. We conclude that the result of the BICEP2 measurement of r>0.1, if confirmed, truly has the potential to rule out small-field models of single-field slow-roll inflation. Stefan AntuschDavid Nolde2016-05-02T09:07:03Z2016-06-30T11:00:10Zhttps://edoc.unibas.ch/id/eprint/39800This item is in the repository with the URL: https://edoc.unibas.ch/id/eprint/398002016-05-02T09:07:03ZFalse vacuum energy dominated inflation with large $r$ and the importance of $kappa_s$We investigate to which extent and under which circumstances false vacuum energy (V0) dominated slow-roll inflation is compatible with a large tensor-to-scalar ratio r=O(0.1), as indicated by the recent BICEP2 measurement. With V0 we refer to a constant contribution to the inflaton potential, present before a phase transition takes place and absent in the true vacuum of the theory, like e.g. in hybrid inflation. Based on model-independent considerations, we derive an upper bound on the possible amount of V0 domination and highlight the importance of higher-order runnings of the scalar spectral index (beyond αs) in order to realise scenarios of V0 dominated inflation. We study the conditions for V0 domination explicitly with an inflaton potential reconstruction around the inflaton field value 50 e-folds before the end of inflation, taking into account the present observational data. To this end, we provide the up-to-date parameter constraints within ΛCDM + r + αs + κs using the cosmological parameter estimation code Monte Python together with the Boltzmann code CLASS. Stefan AntuschFrancesco CefalaDavid NoldeStefano Orani2016-05-02T08:09:00Z2016-06-30T11:00:10Zhttps://edoc.unibas.ch/id/eprint/39797This item is in the repository with the URL: https://edoc.unibas.ch/id/eprint/397972016-05-02T08:09:00ZHill crossing during preheating after hilltop inflationIn 'hilltop inflation', inflation takes place when the inflaton field slowly rolls from close to a maximum of its potential (i.e. the 'hilltop') towards its minimum. When the inflaton potential is associated with a phase transition, possible topological defects produced during this phase transition, such as domain walls, are efficiently diluted during inflation. It is typically assumed that they also do not reform after inflation, i.e. that the inflaton field stays on its side of the 'hill', finally performing damped oscillations around the minimum of the potential. In this paper we study the linear and the non-linear phases of preheating after hilltop inflation. We find that the fluctuations of the inflaton field during the tachyonic oscillation phase grow strong enough to allow the inflaton field to form regions in position space where it crosses 'over the top of the hill' towards the 'wrong vacuum'. We investigate the formation and behaviour of these overshooting regions using lattice simulations: Rather than durable domain walls, these regions form oscillon-like structures (i.e. localized bubbles that oscillate between the two vacua) which should be included in a careful study of preheating in hilltop inflation. Stefan AntuschDavid NoldeStefano Orani2016-04-28T10:20:47Z2016-06-30T11:00:10Zhttps://edoc.unibas.ch/id/eprint/39795This item is in the repository with the URL: https://edoc.unibas.ch/id/eprint/397952016-04-28T10:20:47ZRealising effective theories of tribrid inflation: Are there effects from messenger fields?Tribrid inflation is a variant of supersymmetric hybrid inflation in which the inflaton is a matter field (which can be charged under gauge symmetries) and inflation ends by a GUT-scale phase transition of a waterfall field. These features make tribrid inflation a promising framework for realising inflation with particularly close connections to particle physics. Superpotentials of tribrid inflation involve effective operators suppressed by some cutoff scale, which is often taken as the Planck scale. However, these operators may also be generated by integrating out messenger superfields with masses below the Planck scale, which is in fact quite common in GUT and/or flavour models. The values of the inflaton field during inflation can then lie above this mass scale, which means that for reliably calculating the model predictions one has to go beyond the effective theory description. We therefore discuss realisations of effective theories of tribrid inflation and specify in which cases effects from the messenger fields are expected, and under which conditions they can safely be neglected. In particular, we point out how to construct realisations where, despite the fact that the inflaton field values are above the messenger mass scale, the predictions for the observables are (to a good approximation) identical to the ones calculated in the effective theory treatment where the messenger mass scale is identified with the (apparent) cutoff scale. Stefan AntuschDavid Nolde