The second session of the New Frontiers in Astronomy and Cosmology conference was friday afternoon.
The plan was to do a leisurely liveblog of the talks.
However, during lunch, there were some interesting developments, which I can hopefully tell you about next week some time, and in the middle of the discussion I was told that I was the session chair for the afternoon and we were starting in two minutes.
And a brilliant session it was too.
But as chair it was a bit hard to take notes and blog it live...
So you get the tape delayed version, editors cut, instead:
We continued after lunch with Big Question II - What was the earliest state of the universe
1) Kostas Skenderis from University of Southampton started with "A holographic theory of the universe"
Starting point is AdS/CFT correspondance, developing a framework for pre-spacetime theories and testing implications.
Easther et al 2011 Constraining holographic inflation with WMAP
Interesting comment made that the preliminary result was that the theories had "unusual properties"...
2) David Spergel from Princeton - "Detecting or Falsifying the Multiverse"
If there are multiverses, in a broadly defined sense, then what subtle observational signatures of this could there be observable within our universe - or conversely are there observable that falsify some class of multiverse conjectures?
Three specific tests:
Negative curvature Ωk Bubble collision signatures in the CMB (from higher energy bubbles that bounced or transitioned to our vacuum)
Vacuum state - are we in the open ocean or a goldfish bowl? Could we detect the boundaries from within
Detailed discussion limited by need for intro and 15 minute format, there were some intriguing possibilities in there, with the Ωk measurements in particular coming soon.
cf Spatial Curvature Falsifies Eternal Inflation - Kleban and Schillo (2012)
We then smoothly transition to
Big Question III - What it the origin of complexity in the universe
3) First up was Marcelo Gleiser from Dartmouth on "Emergent Complexity in the Universe: Origin and Limits"
Premise is Wheeler's "It from Bit", working to come up with a theoretic measure of physical information - ie how do we quantify how complext an actual object is (as opposed to a string of digital data).
Uses solitons to define "configurational entropy" see Entropic Measure for Localized Energy Configurations: Kinks, Bounces, and Bubbles Gleiser and Stamatopolous (2012)
Potentially interesting quantity, may generalize to include gravitational entropy, which has never been well defined.
soliton states with configurational entropy in a simulation of thermal quenching
4) Barry Madore from Carnegie Institution on "Cognitive Astrophysics"
Started off with an interesting take on how to talk physics with your dog (cute doggie).
Important point: "What if the Universe is not speaking our language"?
Nice illustration showing a 3D image intensity map, which to the untrained eye is incomprehensible, but projects to show an easily recognisable image. Very nice metaphor.
Looking for cognitive blind spots, failure to ask what is going on because we are not even aware there is something to be questioned.
Is math actually the appropriate language to talk about the universe.
Downward causality. Ugh.
NB: very interesting topic, and important question with a couple of beautiful illustrative examples.
But, I disagreed with his take on computational completeness and complexity, much more is understood there than I think they appreciate. Downward causality is interesting and clearly deliberately ignored in physics, but also seems a bit overplayed in philosophy.
5) Mark Neyrinck from Johns Hopkins on "Initial Information Folding and Flowing into Complexity"
Very cute application of origami concepts to count folding in phase space and quantify complexity by counting folds and cusps.
Good illustrative understanding from how the void/filament structure forms through the origami analogy and nice perspective on torquing of proto-galaxies
Another possible angle on defining gravitational entropy from mixing during folding (in collisionless approximation)
Links to A Novel Approach to Visualizing Dark Matter Simulations Kaehler, Hahn and Abel (2012) on new way of calculating actual densities from cosmological simulations.
6) Shandarin from University of Kansas on "The Emergence of Complex Structural Patterns: A manifestation of increasing cosmic complexity"
With cold dark matter, in the collisionless limit, the CDM density is on 3D manifold in 6D phase space.
Folding as basic concept. Use tessellation for the quantification.
NB: Interesting test of collisionality if we can show CDM is not on a 3D submanifold
Dinner was in the Franklin Hall, and included the presentation of the first prize awards for the high school and college essayists:
"Speaking of Stars" Z. Li (Charter School of Wilmington - now Swarthmore)
"A Letter to My Dearest Newborn Baby Brother" Y.W.C. Gabrielle (Wellesley)
we then moved to the Franklin Theater for a public lecture by Brian Greene followed by a panel discussion and public questions on the Big Questions.
Interestingly almost all the public questions were on the Multiverse, particularly eternal inflation/bubble collision issues.
So Madore referenced talking about physics to a dog, did he cite Chad Orzel?
> Negative curvature Ω_k 0?
Looks like my comment got eaten. Probably thought the less than sign was the start of an HTML tag.
Negative curvature, an open Universe, is Omega_k greater than zero, IMHO.