Inflationary paradigm in trouble after Planck2013 ? I doubt it, but

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Discussion Overview

The discussion revolves around the implications of the Planck 2013 data on the inflationary paradigm in cosmology. Participants explore the validity of inflationary models, particularly in light of recent critiques that suggest significant challenges to the paradigm, including issues related to initial conditions, multiverse implications, and the likelihood of certain models.

Discussion Character

  • Debate/contested
  • Exploratory
  • Technical explanation

Main Points Raised

  • Some participants express skepticism about the recent paper by Ijjas, Steinhardt, and Loeb, suggesting that its arguments may be based more on theoretical biases than on solid calculations.
  • Others argue that the paper could be valuable by highlighting severe constraints on certain inflation scenarios, while leaving open the possibility of other models that might evade these constraints.
  • A participant outlines three specific problems identified in the paper: a new type of initial conditions problem, a twist on the multiverse problem, and an inflationary unlikeliness problem, all of which challenge the inflationary paradigm.
  • Concerns are raised about the inflationary paradigm being viewed as a "wishful thinking" solution rather than a robust scientific theory, with references to previous critiques from one of its original proponents.
  • Questions are posed about how to address fundamental cosmological problems, such as the horizon, smoothness, density, and magnetic monopole issues, if the inflationary paradigm is indeed found to be inadequate.

Areas of Agreement / Disagreement

Participants do not reach a consensus; instead, there are multiple competing views regarding the validity and future of the inflationary paradigm, with some expressing doubt and others suggesting that alternative models may still exist.

Contextual Notes

The discussion highlights limitations in the current understanding of inflationary models, particularly regarding the assumptions made about initial conditions and the implications of the Planck 2013 data. There is also a noted dependence on the definitions of terms like "inflationary unlikeliness problem" and "multiverse problem," which may vary among participants.

  • #31
Two CMB b mode polarization experiments are currently underway - EBEX and POLARBEAR.
 
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  • #32
skydivephil said:
From people that I have spoken to that work on PLanck they don't expect to see the B mode because its not designed to detect it. They hope they will get lucky but no one is betting on it.
Yes, this is correct. A rather high tensor amplitude is at the very limit of detectability of the instrument, but the simulations which say that don't take into account realistic systematic errors or the problems of component separation. So a detection of the B modes would be exceptional indeed.

What I was mostly referring to was the E-mode polarization, which Planck should be able to detect at a higher precision than previous experiments. While this is a dirty measurement of the tensor amplitude, it should provide at least some improvement in the constraints.
 
  • #33
Andrei Linde strongly criticizes "Inflationary paradigm in trouble after 2013", in this talk.
 
  • #34
Chronos said:
Two CMB b mode polarization experiments are currently underway - EBEX and POLARBEAR.

Do you know when we can expect from results from these?
 
  • #35
The first science run of EBEX was launched in late December 2012. POLARBEAR became operational in January 2013 and CMB polarization measurements are scheduled to begin in April 2013. No schedule for data release has been announced for either project, AFAIK.
 

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