Evaluating Dark Energy Measurement Schemes

Several months ago I came across a video of a talk given by Carroll. I can't remember where it was but I was impressed by his compelling breakdown of the dependency of the "concordance" LCDM model on many poorly understood assumptions.
The talk centered around a theory flow chart that attempted to question every possible part of all the hypotheses on which the model is based. It was a very well written talk, in that he worked his way through the flow chart, adding to it as each question and possibility was addressed.
Now, in the white paper "Insights into Dark Energy: Interplay Between Theory and Observation" this diagram shows up again. I see this on the first page and I think, great a review paper that will go through that talk again except this time with details and references. My mouth waters.
Alas, tis but a shade of my desire. So many things in that flow chart are left completely unexplained. A short compendium:

1) Dust Reddening and\or Photon- axion mixing simulates acceleration

Axions are predicted to change to and from photons in the presence of strong magnetic fields, and this property is used for creating experiments to detect axions... Depending on their mass, axions could plausibly explain the dark matter problem of physical cosmology. --wp

I'd never heard this universe not actually accelerating thing before.

2) Strong Energy Condition violated required for a dark energy.

The strong energy condition stipulates that for every future-pointing timelike vector field , the trace of the tidal tensor measured by the corresponding observers is always non-negative:

--wp

Also, from Carroll's S&G we see that the SEC implies that "gravitation is attractive".

I don't know this is appropriate but I don't WANT the SEC violated. Feel the same way about violations of the Equivalence Principle. EP is one of the most beautiful thought experiment proofs ever! Who would be so cruel as to violate that?

Hey, wheres the HEP?

After reading one of the white papers from the afformentioned report I realize that something even larger than alternative theories is missing from the report. This committee reports to the big three science agencies however it focuses ENTIRELY on astrophysical solutions. The foundations of this branch of physics lie on the boundaries between particle and astro physics. In the case of the cosmological constant solution to Dark Energy the problem is phrased in terms of the famous many magnitude discrepency between standard model theory and astronomical observation. In several cases the theoretical solutions which are difficult or impossible to test/verify astronomically can be tested in the lab or within the solar system. (see the Bean et. al. white paper) The agencies to which the committee reports fund most of these types of experiments too. Why are they written out of the report?

DETF as a career counselor

Another wayside village on the road to the thesis topic is the previously mentioned Dark Energy Task Force report published on June 6 (6/6/06 for you doomsters). This "task force" was created as a combination of two science advisory counsels (like the ones who brought you the food pyramid) to report to the DOE, NASA ,and NSF on what they should do about figuring out Dark Energy. They are reporting mainly to scientists who now wear manager hats so they need a combination of good detective work for the ones who are still or recently were scientists and good beaurocratese for the ones who control the money.

Now, why should time and management be spent on a slight curvature of a nominally straight hubble flow graph? Because whatever makes that curve possible represents a very large departure from either the standard model, the particle physicists golden T-Shirt or the miraculas general relativity solution. A large departure from a well established theory seems to always earn us physicists a gold star, once its understood. Another reason the problem is so "vexing", to use the words of the Quarks to Cosmos top ten problems list, is that in the last thirty years the physics community has seen the creation of an entire new branch on their scale invarient tree. Some of the smartest most competitive minds in the physics world from places like theoretical gravity, so called "high energy" (particle physics), and plain old astronomers are now Cosmologists. This community occupies the central area of the physics Venn Diagram. In many cases these people have other interests and retain titular roles in their former areas but in reality compete mainly in the cosmology arena.

This field became largely popular with the discovery of the CMB and its variations but really exploded with the discovery of the problem of the "missing mass". Thus begins the perfectly exeptable practice of validating one theory (supersymmetry) with the postulates of another, Dark Matter = missing mass. Using one and other as crutches to prove theories otherwise unprovable at that time, theoretical astrophysicists and particle physicists founded a new Commonweal. Recall as well the rising popularity of so-called "multidisciplinary" work. This was an age where large "consortiums" of scientists struggled to add their thin veneer to the towering pile of paradigm built by their fathers and one monthly journal in the nineteenth century had become ten. The habits and traditions built then are bearing fruit today where thousands of papers a year are published electronically or in numerous and divers peer reviewed journals on possible configurations of alternative gravity, quantum fields, strings, branes, and on and on; all to solve this problem of why the hubble flow is curved.

This Task Force is a physicists response to this glut of theory by saying, "Hey wait, we're empiricists, lets measure this!" Of course no one ever really stopped measuring the universe, as evidenced by the "stage II" (now projects) listed in the report, but noone ever really sat down and thought about proving more than yes there is a problem.

What this paper draws out is a practical four part program for figuring out what is causing that curve. Each part is a different way of measuring properties of objects like their brightness, shape or size. Using this information one might be able to back out a "observed or intrinsic distance" and by looking at spectral features, might construe also a redshift z. To do this one needs models, as most astrophysics has been based on models for 60 years, this is exactly the way its always been done. A model is simply a way we think the thing (cluster, supernova, etc) works which provides a way to turn what we measure, (spectral features, light curves, etc) into what we want to know (intrinsic distance, velocity, growth factor etc). We then use another model to turn those distances and velocities into an estimate of the cosmological parameters, like the fraction of energy needed to close the universe and the number used by the DETF the "equation of state" parameter. In each case the model we use includes a number of steps where GR plays an important role. This I consider one of the cruxes of the problem. Those on the task force have taken what appears to be a very consensus building position by choosing the dominant model and "going with it", nominally a very sensible modern science decision, but in this case ignoring the fact that their entire empirical approach relies on a theoretical house of cards.

This is the landscape from a young physicist in the sticks. Lots of big fishes competing to be the first to solve the mystery, pushing for big projects and money but the possibility of something fundamental tugs at the mind.

wheresmysciencesoft? and the DETF

Well so much for free equation hosting. I just wish they had shared their scripts with someone. They were so much better than any equation place on the web. It doesnt really matter. The work I did with it didnt really mean anything anyway.
Newest project. Evaluating the Dark Energy Task Force report for career opportunities. This is interesting in that it is basicly astrophysics written for management types. Lots of repetition and very little science that makes sense beyond the "Figure of Merit" statistics. In places it seems like when they want to mention the basic physics they throw in the "scale factor" equation or something without actually explaining or using it.
But because it was written in this way I was able to see several new concepts without lots of clutter. The things I am wondering about now are:
1) growth factor. This has something to do with density perturbation evolution and compliments the scale factor as an observable. Never heard about this in 2 years of astrophysics.
2) Baryon Acoustic Oscillations. Acoustic waves which get frozen out during the epoch of recombination. My question is, if they are density rings in the CMB and beyond, why dont they show up in topology searches?
3) People dont really think dark energy will be the result of a GR modification. The way they've parameterized the problem in terms of equation of state and used one set of GR equations to model the results make me wonder how we'll be able to tell if it really isnt parameterized by w(a) = wo+(1-a)wa. So much model! Nerve wracking...
4) If one is predisposed to optimism weak lensing holds the most promise weighing in with a figure of merit above 13! This is for a Square Kilometer Array survey of galaxies and 21cm background. (Of course the pessimistic FOM is only 2.1. ) However, weak lensing holds the highest pessimistic possibilities in a space based mission. The cool thing about weak lensing is that its essentially a data mining project. The pictures can be taken for one purpose, say an optical survey of clusters, and then processed to get statistics about the shear of the background galaxies. The measurements of the clusters are important too because they help reduce the source location error.

Theres lots of fun stuff in this report. I like the idea of using data mining to solve problems. When I was an undergrad I wrote a proposal for a class that outlined the creation of a astrophysical data mining center. This would be an institute whos job was to archive astrophysical images and data. The focus would be using new and old data to find planets. Apparently such a thing has since been proposed and funded! To bad Van Romero wasnt a funding agency.


Question: Should I try to write in a more coherent fashion? This would be good for my writing but bad in terms of time usage. Also I am not a huge fan of the little tiny editing window so I would have to find a good plugin for an editor and an editor. Maybe googles beta blogger will solve this problem. Dear diary, I hope I get invited soon! Maybe a google guy will read this and invite me. Gosh I hope they'll add inline latex like mediawiki has. *Fingerscrossed*