A What Do Planck 2015 Results Reveal About Power Law Potential Models?

JD_PM
Messages
1,125
Reaction score
156
TL;DR Summary
I am trying to understand why the simple inflationary model with potential ##V(\phi) \propto \phi^2## is disfavored compared to models predicting a smaller tensor-to-scalar ratio.
I am reading Planck 2015 results. In particular, I focused on "Power law potentials" subsection.

The issues I have are

1. I do not understand why the validity of the model can be determined by the value of the ##B## mode.
2. Why the ##B## mode values ##\ln B = −11.6## and ##\ln B = −23.3## for the cubic and quartic potentials , respectively, are regarded as "strongly disfavored" and ##\ln B = −4.7## for the quadratic potential as "moderately disfavored"? What I mean is: what is the threshold value at which we can consider the potential as favored and why?

Thank you! :biggrin:
 
Space news on Phys.org
Different inflationary potential shapes predict different relationships between the tensor perturbations and scalar perturbations. The scalar perturbations contribute primarily to the temperature variations across the sky. The tensor perturbations contribute primarily to the polarization of the observed CMB.

The observed E-mode spectrum is dominated by effects after inflation such as structure formation, so it isn't a very good measure of the tensor perturbations.

The large-scale B-mode spectrum is mostly independent of late-time effects, so it's a nearly direct measurement of the tensor perturbations produced during inflation. So far all we've been able to say is that the magnitude of these perturbations is too small to be detected (yet).

Quadratic potentials for inflation typically predict that we would have detected the tensor perturbations by now. This is shown in Fig. 12 in that paper.
 
https://en.wikipedia.org/wiki/Recombination_(cosmology) Was a matter density right after the decoupling low enough to consider the vacuum as the actual vacuum, and not the medium through which the light propagates with the speed lower than ##({\epsilon_0\mu_0})^{-1/2}##? I'm asking this in context of the calculation of the observable universe radius, where the time integral of the inverse of the scale factor is multiplied by the constant speed of light ##c##.
The formal paper is here. The Rutgers University news has published a story about an image being closely examined at their New Brunswick campus. Here is an excerpt: Computer modeling of the gravitational lens by Keeton and Eid showed that the four visible foreground galaxies causing the gravitational bending couldn’t explain the details of the five-image pattern. Only with the addition of a large, invisible mass, in this case, a dark matter halo, could the model match the observations...
Hi, I’m pretty new to cosmology and I’m trying to get my head around the Big Bang and the potential infinite extent of the universe as a whole. There’s lots of misleading info out there but this forum and a few others have helped me and I just wanted to check I have the right idea. The Big Bang was the creation of space and time. At this instant t=0 space was infinite in size but the scale factor was zero. I’m picturing it (hopefully correctly) like an excel spreadsheet with infinite...
Back
Top