Cai Easson avoid eternal inflation , use Higgs to seed structure

[marcus]

Cai Easson avoid "eternal inflation", use Higgs to seed structure

Cai and Easson's paper takes off from the seminal paper of Shaposhnikov and Wetterich that is discussed here at BTSM https://www.physicsforums.com/showthread.php?t=560031
Shapo-Wetter predicted 126 GeV Higgs in 2009 on the assumption, among other things, that gravity is safe in the high energy limit, i.e. the couplings run to a fixed point.

The Cai Easson paper is important, I think, and should have its own discussion thread. They demonstrate something which I think many people must have suspected, if they follow the safe gravity literature, namely that you get inflation without needing an inflaton field..

Because as energy scale k grows the dimensionless form of the cosmo constant Λ/k² goes to a finite number which means that the cosmo constant Λ itself becomes infinitely large!

(Since Newton G and cosmic Λ are dimensionful quantities--not numbers--this is a slight abuse of notation but) to put it casually, in safe gravity we have that:
Λ → ∞ and G → 0.

That's certainly suggestive that the running of couplings at high energy density could be enough to cause adequate inflation in the very early universe, without making up a special "inflaton" field.
And Cai Easson paper works that out in some detail, so it is potentially important.

Another extremely nice thing about it is that it uses the quantum fluctuations of the Higgs field to produce the observed incipient structure observed in the blotchy pattern of ancient light (the cosmic background radiation spatial variation power spectrum).

Earlier inflation scenarios had attributed the blotchiness to quantum fluctuations in the imagined "inflaton" field.

Bringing an "inflaton" field into the picture had caused some big head aches. Once you let one in the door it complicates the picture by producing a lot of unnecessary and untestable stuff (that however string theorists can have fun with so you could say its good for something). And the "inflaton" requires considerable fine-tuning so the universe seems rather unlikely to have happened, and so on.

Cai Easson take care of such problems by eliminating the inflaton and running up Lambda.

 

[marcus]

Another reason I'm interested in the Cai Easson paper is that it looks like a good fit with Loop QG. The Loop bounce already has its own brief episode of faster-than-exponential inflation which is termed "superinflation" and occurs naturally in the theory without making up an "inflaton".

But so far this is too brief to provide enough expansion. However the Loop superinflation was derived in models that did not have a positive Λ and did not take account of the fact that Λ could run.

So there is room for some development in this direction, in the Loop approach.

Another reason I like it is that it is based on the Shapo-Wetter vision of how physcs extends Beyond the Standard Model. And this Shapo-Wetter vision is falsifiable.
The LHC might not find Higgs at around 126 GeV, which would blow Shapo-Wetter and Cai Easson as well. It looks to me as if they need to assume the earlier S-W work in a substantial way as their starting point. This is exciting, I think.

Anyway, please have a look at the Cai Easson paper and share your thoughts about it, favorable or not. I'm eager to get some comments on it.

Google "easson higgs inflation" and get http://arxiv.org/abs/1202.1285
Higgs Boson in RG running Inflationary Cosmology
Yi-Fu Cai, Damien A. Easson
(Submitted on 6 Feb 2012)
An intriguing hypothesis is that gravity may be non-perturbatively renormalizable via the notion of asymptotic safety. We show that the Higgs sector of the SM minimally coupled to asymptotically safe gravity can generate the observed near scale-invariant spectrum of the Cosmic Microwave Background through the curvaton mechanism. The resulting primordial power spectrum places an upper bound on the Higgs mass, which for canonical values of the curvaton parameters, is compatible with the recently released Large Hadron Collider data.
5 pages

Please let me know if you see that I'm missing something important here! How I see them going is that to include the effect of the running couplings they do a math transformation which introduces a fictitious scalar field φ (in the new coordinates) which takes the place of a physical inflaton field.
...

 

[marcus]

Damien Easson has put a potentially important idea on the table---one which let's you keep inflation but get rid of the multiverse.
The multiverse is a nuisance that seems to go along with mechanisms people dream up to cause inflation. The problem with most of these imagined mechanisms is "once they get started how do you stop them from happening over and over again?" Like hiccups.

Easson has pointed out a differerent inflation mechanism which at least doesn't lead to the bubble multiverse picture. It might turn out to lead to its own kind of multiverse but that MIGHT be easier to get a handle on, more tractable, and it could be it doesn't lead to a multiverse at all. We have to wait and see how the idea develops. At least there is reason to hope.

There's an odd coincidence. Arizona State University is emerging as an interesting place for physics. Paul Davies and Lawrence Krauss are there as well as Damien Easson (and his associate Yi-Fu Cai.
http://en.wikipedia.org/wiki/Paul_Davies (Bunch-Davies vacuum, Fulling-Davies-Unruh effect, Kelvin medal...)
http://en.wikipedia.org/wiki/Lawrence_M._Krauss