CMB at 50: Princeton early universe panel discussion

[palmer eldtrich]

An interesting discussion at this conference here:
http://physics.princeton.edu/cmb50/videos/20150612_session6_2.mp4
David Spergel said the next project should be to look for something called f and L or is is FNL?
Can someone explain what this is and what its significance is?

What did you guys think of the discussion?
I'm a bit annoyed someone like Alan Guth,Linde or Aguirre wasnt there to defend eternal inflation and no discussion of string gas or non singular bounce cosmologies.

 

[George Jones]

$f_{NL}$ is a measure of non-gaussianity of the CMB anisotropies. See equation (5.2.10) in

http://www.damtp.cam.ac.uk/user/db275/Inflation/Lectures.pdf

 

[marcus]

An interesting discussion at this conference here:
http://physics.princeton.edu/cmb50/videos/20150612_session6_2.mp4
...
What did you guys think of the discussion?
...

Thought it was a great panel discussion: Mukhanov, Steinhardt, Turok, Freese, Penrose---with excellent comments from audience (Witten, David Spergel, Marc Davis...) and Brian Greene moderated very ably as well!
So lively and incisive that even though almost 2 hours I was motivated to watch from beginning to end.
Here's the main menu of the "CMB at 50" conference:
http://physics.princeton.edu/cmb50/program1.shtml
Here are some quotes from the panel:
http://physics.princeton.edu/cmb50/videos/20150612_session6_2.mp4

Neil Turok: “even from the beginning, inflation looked like a kluge to me… I rapidly formed the opinion that these guys were just making it up as they went along… Today inflation is the junk food of theoretical physics… Inflation isn’t radical enough – it’s too much a patchwork. It all rests on rare initial conditions… Akin to solving electron stability with springs… all we have is proof of expansion, not that the driving force is inflation… “because the alternatives are bad you must believe it” isn’t an option that I ascribe to, and one that is prevalent now… inflation is pretty but we should encourage young to think about its problems & be creative (not just do designer inflation)

David Spergel: papers on anthropics don’t teach us anything – which is why it isn’t useful.. sometimes we need to surrender (to anthropics) but that time is not yet now.

Slava Mukhanov: inflation is defined as exponential expansion (physics) + non-necessary metaphysics (Boltzmann brains etc)… we should separate inflation from the landscape… exponential inflation is very useful, the rest [of the metaphysical stuff] is not for scientific discussion… In most papers on initial conditions on inflation, people dig a hole, jump in, and then don’t succeed in getting out… unfortunately now we have three new indistinguishable inflation models a day – who cares?

Paul Steinhardt: inflation is a compelling story, it’s just not clear it is right… I’d appreciate that astronomers presented results as what they are (scale invariant etc) rather than ‘inflationary’… Everyone on this panel thinks multiverse is a disaster.

Roger Penrose: inflation isn’t falsifiable, it’s falsified… BICEP did a wonderful service by bringing all the Inflation-ists out of their shell, and giving them a black eye.

Marc Davis: astronomers don’t care about what you guys are speculating about at all (mulitiverses, pre-big bang, etc).
==endquote==
These excerpts appeared on Peter Woit's blog which also had other links and comments, there was also extensive live Twitter tweeting by people in the audience including David Spergel