Higgs-driven cyclic conformal cosmology (Steinhardt Turok Bars)

[marcus]

I approach this cautiously but with interest. (How often do ideas like this work out?)
http://arxiv.org/pdf/1307.1848v1.pdf
and suggest you jump immediately to page 24 where there is a suggestive graph, Figure 1.

==quote page 24 of Bars Steinhardt Turok 1307.1848==
Fig.(1) is an illustration of our solution for the generic cosmological behavior of the Higgs
field just after the big bang if the Higgs potential has a stable non-trivial minimum, as in Eq.(5), as usually assumed and as required for the Bezrukov-Shaposhnikov Higgs inflation model [12]. This figure describes the generic cosmological evolution of the Higgs field, that must start with fluctuations of Planck size and energy (due to the universal attractor near the singularity [7]), and quickly reduce its amplitude by losing energy to the gravitational field; then after a phase transition, settle down to an almost constant value at the electroweak scale v determined by the dimensionless parameter α in Eq.(3).
==endquote==

 

[marcus]

Here is the caption to Bars Steinhardt Turok Figure 1, and the following text"
==quote 1307.1848 pages 24 and 25==

[CAPTION:] Fig.(1) - After the Big Bang the Higgs field oscillates initially around zero with a large amplitude of the order of the Planck scale. It slowly loses energy to the gravitational field, causing its amplitude to diminish. As it approaches the time or energies of the electroweak scale, it undergoes the phase transition seen in the figure, and then slowly settles to a constant vacuum value v at a stable minimum of the potential.The solution of Fig.(1) changes drastically if the vacuum is metastable after including quantum corrections, which is a possibility suggested by the most recent LHC data for the the Higgs and the top quark masses [29], and assuming no new physics up to the Planck scale. Metastability is incompatible with Higgs inflation and generally causes problems for inflation because the Higgs will typically escape from the metastable phase right after the big bang and roll to a state of negative energy density that can prevent inflation of any sort from occurring.

The exact solutions of the Weyl-invariant theory suggest an alternative cosmology in this case. The generic solution at first behaves as in Fig.(1) after the big bang, all the way through the electroweak phase transition. But after some time (order of the lifetime of the universe) the Higgs oscillations in the electroweak vacuum grow larger and larger, like the mirror image of Fig.(1), taking away energy from the gravitational field and eventually causing a collapse of the universe to a big crunch, while the Higgs does a quantum tunneling to a lower state of the potential. At that stage our exact analysis near the singularity given in [7] takes over to describe interesting new phenomena that occur just after the crunch and before another rebirth of the universe with a big bang. The result is a regularly repeating sequence in which the Higgs field is trapped in its metastable state after a big bang, remains there for a long period of expansion followed by contraction, escapes as the universe approaches the big crunch, passes through to a big bang and becomes trapped again. The evolution can be considered a Higgs-driven cyclic theory of the universe. The details will be presented in a separate paper.
==endquote==

 

[Naty1]

Marcus: BRAVO...
After making [good natured] fun of an early 'cyclic cosmology' thread I posted [based on their book THE ENDLESS UNIVERSE,2007] by Steinhardt and Turok some time ago, I am pleased to see you are 'coming around'...even if 'cautiously'...

But really, now, after all, I am a bit surprised; these guys are now proposing 'antigravity', I believe, to underlie the above paper: From reference paper #7 at the bottom of your "Higgs Driven.." paper:

“Antigravity and the Big Crunch/Big
Bang Transition”
Steinhardt,Turok Bars, Chen

'Antigravity' caught my attention...so I looked at the paper:

In this paper, we present a novel third possibility for the bounce, involving a brief effective antigravity phase between the big crunch and the big bang. The purely
classical, low-energy effective Einstein-scalar description we shall present should be taken only as a first indication of what may be expected when a fundamental theory of
quantum gravity is applied to cosmological singularities. Nevertheless, we shall show that an antigravity phase occurs generically, when we extend geodesically incomplete cosmological solutions to geodesically complete solutions of a Weyl-invariant lift" of the theory:

How we get antigravity without negative mass, if that is really what underlies this, is astonishing.

Separately, I found the following perspective, previous ideas, relative the the cosmological scale factor a[t] in the same paper very interesting: [Page1]

...An alternative idea is that the big bang was a bounce: a transition from contraction to expansion. This idea underlies the cyclic model [3], in which the large-scale structure of the universe is set during an ekpyrotic contraction phase [4, 5], well before the big bang, and then evolves through a big crunch/big bang transition. One possibility for this bounce is a non-singular transition, in which the cosmic scale factor a(t) rebounds at a -finite non-zero value [6]. Einstein general relativity can describe the entire transition, but only at the price of introducing an energy component capable of violating the null energy condition, with the risk of undesirable instabilities. ...
[7{11].

Who would have thought we'd be discussing possible antigravity effects on the scale factor??

 

[Mordred]

interesting paper, I'm currently looking at some of the support papers mentioned on that article. Too early for me to offer any comments ither than interesting proposal. The Higgs inflation model is a good fit to observational data as compared to the slow roll inflation. So at least its got that going for this model.

 

[Naty1]

The Higgs inflation model is a good fit to observational data as compared to the slow roll inflation.

How are they different??

Separately, I'm now wondering why nobody calls dark energy aka the cosmological constant, 'negative gravity'...is there some distinction between 'repulsive gravity' and 'negative gravity'...
is that physics or just language??

 

[Mordred]

The main difference between the 100+ inflationary models lie mainly in the number of degrees of freedom or the number of scalar fields. In the case of Higgs inflation there is a couple of different models, there is the zero scalar higgs inflation model, the single scalar Higgs model and (not positive) the 2 scalar Higgs inflation model.

The slow roll inflation model is a 2 scalar inflation model. May sound primarily mathematical until you look at the mechanism behind the scalar fields. Ie does it use the Higgs Boson, the inflaton, a form of virtual particle production ie false vacuum as an example, A varying form of high to low energy potential of a vacuum such as slow roll and natural inflation, is the field homogenous and isotropic or the opposite? etc.

The slow roll approximation is a popular and well known good fit to observational data as such its used as a comparison for the other models. Some models have been discounted as they deviated too far from the slow roll approximation. examples of those is the hot dark matter Lambda model and 3 to 4 other lambda models. The cold dark matter model used in LCDM is the most accurate to observations of the CDM type models.

Some models have also tried to explain inflation using the gravitino which also involves supersymmetry
http://arxiv.org/abs/hep-ph/0701104

a list of the criteria of the various models is covered on one of the articles that your wife will yell at me again for lol

http://arxiv.org/abs/1303.3787

edit: this manual covers "fields" some of the models Steinhardt refers to is covered in this manual again its lengthy and your wife will scream louder lol
http://arxiv.org/abs/hepth/9912205

 

[Naty1]

The slow roll approximation is a popular and well known good fit to observational data as such its used as a comparison for the other models.

ah, that explains for me the context of your post #4...thanks...

 

[Mordred]

Np I personally and again this is a personal opinion, out of the various inflationary models, I personally feel that the Higgs inflation oriented models do present a probable and highly possible inflationary mechanism. For one its not introducing unusual particles beyond the Goldstone boson. The Higgs we have already confirmed or a high degree of certainty of confirmation. The goldstone however is still questionable. Some higgs inflationary models though I cannot recall which (I think it may be the zero scalar) do not require the goldstone boson. I should also note the the higgs is needed in the false vacuum model by Guth. However the "runaway" inflation presents its own problems. This led to chaotic eternal inflation and bubble universes etc.

The zero scalar Higgs model gradually loses energy in a similar manner as described in the Steinhardt model above.

 

[John86]

New paper

http://arxiv.org/abs/1307.8106
Cyclic Cosmology, Conformal Symmetry and the Metastability of the Higgs
Itzhak Bars, Paul J. Steinhardt, Neil Turok
(Submitted on 30 Jul 2013)
Recent measurements at the LHC suggest that the current Higgs vacuum could be metastable with a modest barrier (height 10^{10-12}{GeV})^{4}) separating it from a ground state with negative vacuum density of order the Planck scale. We note that metastability is problematic for big bang to end one cycle, bounce, and begin the next. In this paper, motivated by the approximate scaling symmetry of the standard model of particle physics and the primordial large-scale structure of the universe, we use our recent formulation of the Weyl-invariant version of the standard model coupled to gravity to track the evolution of the Higgs in a regularly bouncing cosmology. We find a band of solutions in which the Higgs field escapes from the metastable phase during each big crunch, passes through the bang into an expanding phase, and returns to the metastable vacuum, cycle after cycle after cycle. We show that, due to the effect of the Higgs, the infinitely cycling universe is geodesically complete, in contrast to inflation.

 

[Naty1]

From the above cited paper:

pg3...

... a metastable Higgs fits cyclic cosmology to a tee. The current vacuum is required to be metastable (or long-lived unstable), according to the cyclic picture, in order for the current phase of accelerated expansion to end and for a big crunch/big bang transition
to occur that enables a new cycle to begin...

last page...

...In sum, we have shown that the Higgs, if it is metastable, has profound implications for cosmology. For big bang inflationary cosmology, metastability is problematic: it is unexpected, requires highly improbable initial conditions, and predicts a dire future in which the metastable phase ends and the universe collapses in a big crunch. By contrast, metastability dovetails with the cyclic picture for which decay of the current vacuum is a fundamental prediction, required to end the current cycle and begin the next. Remarkably, our Weyl invariant formulation of the standard model has made it possible to construct an action that incorporates all known microphysics and, at the same time, has classical solutions that completely describe cyclic evolution, from bounce to expansion to contraction to bounce again,
with each cycle reproducing similar physics that is like what we observe...

Two comments:
[1] Oh lordy, we all going to die?? [a near quote from a movie I like.]

[2] Any insights on where this model differs from Penrose's ...discussed here?:

https://www.physicsforums.com/showthread.php?t=649836&highlight=weyl+curvature+hypothesis

Be interesting to have some insights on how Penrose's 'Weyl curvature hypothesis' [vanishing Weyl curvature at the big bang 'singularity' evolving to a diverging Weyl curvature at black holes] differs from this 'Weyl invariant formulation'.

 

[Mordred]

I found the paper you posted interesting, its one I want to further study. However could use a bit of advice on. I am unfamiliar with Weyl-invariant action. If someone has good links covering the metrics involved. I would appreciate it.

 

[Mordred]

nvm last post found the info I needed on Weyl-invariant action.

 

[Naty1]

last post found the info I needed on Weyl-invariant action.

Can you post the link or a synopsis?

I tried a few searches and could not find understandable papers...

Thanks

 

[Mordred]

the book I'm studying on it is the "algebra of invarients" by Grace J.H. http://archive.org/details/algebraofinvaria00graciala

I'm also looking over this paper, http://jones.math.unibas.ch/~kraft/Papers/KP-Primer.pdf "CLASSICAL INVARIANT THEORY"

I'm still not familiar enough with it to describe it accurately. This is the reference I plan on studying once I get through the first link.

http://books.google.ca/books?id=zmz...6KOigLEioGoBQ&redir_esc=y#v=onepage&q&f=false

to help understand invarients this link may help correlate

http://en.wikipedia.org/wiki/Invariant_(mathematics )

 

[John86]

http://arxiv.org/abs/1308.3044
Nonperturbative analysis of the evolution of cosmological perturbations through a nonsingular bounce
BingKan Xue, David Garfinkle, Frans Pretorius, Paul J. Steinhardt
(Submitted on 14 Aug 2013)
In bouncing cosmology, the primordial fluctuations are generated in a cosmic contraction phase before the bounce into the current expansion phase. For a nonsingular bounce, curvature and anisotropy grow rapidly during the bouncing phase, raising questions about the reliability of perturbative analysis. In this paper, we study the evolution of adiabatic perturbations in a nonsingular bounce by nonperturbative methods including numerical simulations of the nonsingular bounce and the covariant formalism for calculating nonlinear perturbations. We show that the bounce is disrupted in regions of the universe with significant inhomogeneity and anisotropy over the background energy density, but is achieved in regions that are relatively homogeneous and isotropic. Sufficiently small perturbations, consistent with observational constraints, can pass through the nonsingular bounce with negligible alteration from nonlinearity. We follow scale invariant perturbations generated in a matter-like contraction phase through the bounce. Their amplitude in the expansion phase is determined by the growing mode in the contraction phase, and the scale invariance is well preserved across the bounce.