Comments on: Duff on Susskind

By: Is our universe natural? | Cosmic Variance

Is our universe natural? | Cosmic Variance — Wed, 28 Jun 2006 03:25:05 +0000

[...] Hey, has anyone heard about this string theory landscape business, and the anthropic principle, and some sort of controversy? Hmm, I guess they have. Perhaps enough that whatever needs to be said has already been thoroughly hashed out. [...]

By: LuboÅ¡ Motl's reference frame

LuboÅ¡ Motl's reference frame — Tue, 14 Feb 2006 13:20:55 +0000

Cosmological constant seesaw preprint

The cosmological constant seesaw mechanism is now described in a preprint.

By: Plato

Plato — Thu, 08 Dec 2005 06:49:18 +0000

Just some thoughts on CSL-1 cosmic string issue and the inception of it from my layman perspective.

CSL-1 cosmic string gravitational lens and 2 more, with many views of the Capodimonte Deep Field OACDF2 with subtle background features, similar to recent Millennium Simulation of evolution of structure in our Universe. Identical stereo pairs are introduced.

By: Not Even Wrong » Blog Archive » The Cosmic Landscape

Not Even Wrong » Blog Archive » The Cosmic Landscape — Thu, 08 Dec 2005 01:06:26 +0000

[...] In coming weeks, it will be interesting to see how the physics community deals with the challenge presented by Susskind’s publicity campaign for changing how theoretical physics is done. So far the initial signs are depressing. Michael Duff’s review in Physics World just more or less respectfully repeats Susskind’s argument, not challenging it in any way. In a review of the Duff review, Clifford Johnson answers the question of whether this sort of thing is still science with “I have not yet made up my own mind whether it sits well with me or not…” He makes a distinction between postdiction and prediction that I don’t quite agree with (if Susskind’s framework accurately postdicted even a few of the known Standard Model parameters, I’d be a believer). He takes the usual stance favored by most sensible string theorists who want to keep working on the theory that they don’t understand the theory well enough yet to know whether they are stuck with the Landscape or not. Finally he thinks there’s a chance that maybe the structure of the Landscape is such that once one anthropically fixed the CC and some other constants, the remaining set of vacua would actually predict something. I don’t see the slightest evidence for this, but it’s the argument many are now using to justify exploring the Landscape and surrounding swampland instead of giving up on string theory and trying to find a better idea. [...]

By: island

island — Wed, 07 Dec 2005 20:09:23 +0000

Anthropic structuring is perpetually inherent is the point, Elliot, I think you’ve missed that LaPlace’s demon is valid in the finite bound closed spherical universe where “god” doesn’t throw dice. We represent a cumulative emergence of something that was determined at the get-go by the constraints that were convolved forward into the matter field by our big bang. The stucturing is perpetually inherent, in other words.

Roughly…

The EWAP, (entropic weak AP), is about environmental enabling:

1) The observed values of all physical and cosmological quantities are not variable, but are fixed by the requirement that there exist sites where carbon-based life will arise and evolve when the universe is old enough for the cumulative gravitational effect to require us to do our thing.

The ESAP is about… why:

There exists one universe that has perpetually inherent stucturing, with the goal of generating and sustaining disspative structures that are capable of enabling a universal scale evolutionary leap ever closer to absolute symmetry.

The EFAP is…

1) Who cares, ours is a blue colar universe, not an academically derived idealization where intelligent information processing is merely an efficiency enabling mechanism.

2) There is a weird implication for some kind of universal self-awareness when the skies light up simultaneously… *que erie music*… I’d hate to read too much into that!

and…

Right-on, Dissident!

… or can we ignore direct observational evidence that the Copernican Cosmological extension is superceded by something that’s more biocentric in nature?…

http://www.flickr.com/photos/rmforall/18135101/in/set-435988/

http://www.flickr.com/photos/rmforall/18135102/in/set-435988/

… and that Einstein was right all along about higher structuring in nature, because the most natural extension of his theory with a cosmological constant is not unstable after all, because matter generation in this model causes the previously described effects which hold the universe flat and stable as it expands?

After all, the creationists might twist it into some kind of supernatural god theory, donchano?

http://www.arxiv.org/abs/astro-ph/0508047/

By: Dissident

Dissident — Wed, 07 Dec 2005 18:01:40 +0000

OK, then I guess the only way this could become really interesting is if the WMAP people came out and said their data is in conflict with current limits – thus explaining the long delay in the official release, I guess.

By: Sean

Sean — Wed, 07 Dec 2005 17:53:07 +0000

Current limits are already better than 10% or so. Anything we discover at this point will count as “nearly” scale-invariant.

By: Dissident

Dissident — Wed, 07 Dec 2005 17:51:50 +0000

Hm, I may have overinterpreted the gossip. I thought Aaron was implying a sizable deviation from 1. Let’s put it this way then: at what level of deviation form 1 would the “new constraint” on inflation become difficult to satisfy? If 5% is OK, what about 10%? 20%? Where does it become troublesome?

By: Sean

Sean — Wed, 07 Dec 2005 17:46:15 +0000

It’s actually the opposite of what Dissident just said, I’m afraid. The generic prediction of inflation models is a nearly scale-invariant spectrum of perturbations. Whatever the precise measurement turns out to be, we already know that it’s nearly scale-invariant; the question is, how close? In fact, if inflation is right, it would be kind of surprising if the spectrum were extremely close to scale-invariant; it’s easier to deviate by 5% or so. So if there is evidence for a deviation from scale invariance, it will fit into the inflationary paradigm very nicely, and would presumably be a stringent new constraint on inflationary models.

By: Dissident

Dissident — Wed, 07 Dec 2005 17:28:59 +0000

#46: A scale-invariant fluctuation spectrum is usually stated to be a prediction of inflation (though the odd Dissident has been known to question that whole line of reasoning, so if true, this would pose a problem for inflation-based scenarios. Maybe time for Luminet et al to get a second hearing on their football universe?