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Technical Report CMS-TR-20160122

Title Constraints on just enough inflation preceded by a thermal era
Author/s Suratna Das
Indian Institute of Technology, Kanpur 208016, India
Gaurav Goswami
Institute of Engineering and Technology, Ahmedabad University, Navrangpura, Ahmedabad 380009, India
Jayanti Prasad
Inter-University Centre for Astronomy and Astrophysics, Post Bag 4, Ganeshkhind, Pune 411007, India, and
Centre for Modeling and Simulation, University of Pune, Pune 411 007 India
Raghavan Rangarajan
Theoretical Physics Division, Physical Research Laboratory, Navrangpura, Ahmedabad 380009, India
Abstract If the inflationary era is preceded by a radiation-dominated era in which the inflaton too was in thermal equilibrium at some very early time, then the CMB data places an upper bound on the comoving temperature of the (decoupled) inflaton quanta. In addition, if one considers models of “just enough” inflation, where the number of e-foldings of inflation is just enough to solve the horizon and flatness problems, then we get a lower bound on the Hubble parameter during inflation, Hinf, which is in severe conflict with the upper bound from tensor perturbations. Alternatively, imposing the upper bound on Hinf implies that such scenarios are compatible with the data only if the number of relativistic degrees of freedom in the thermal bath in the preinflationary Universe is extremely large (greater than 109 or 1011). We are not aware of scenarios in which this can be satisfied.
Keywords cosmology, inflation, thermal era, CMB
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Citing This Document Suratna Das, Gaurav Goswami, Jayanti Prasad, and Raghavan Rangarajan , Constraints on just enough inflation preceded by a thermal era. Technical Report CMS-TR-20160122 of the Centre for Modeling and Simulation, Savitribai Phule Pune University, Pune 411007, India (2016); available at http://cms.unipune.ernet.in/reports/.
Published Reference, Notes, etc. Phys. Rev. D 93, 023516, 2016
Contact jayanti@iucaa.ernet.in
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