Tuesday, December 05, 2006

Independent evidence for dark energy

New paper! We describe observational evidence for dark energy which is independent of the supernova surveys, and therefore not subject to systematic effects from dust, evolution or exotic particle physics (such as photon to axion decay). The figure below shows the likelihood, given best measurements of the age of the universe, the Hubble parameter and the matter fraction, that there was NOT a cosmological epoch with equation of state paramater w < w* (w = pressure / energy density). As you can see, an epoch with a repulsive energy component (w < -1/3) is highly likely. The three curves represent different assumptions about observational errors.


Precision cosmological measurements: independent evidence for dark energy

Authors: Greg Bothun, Stephen D.H. Hsu, Brian Murray
Comments: 4 pages, revtex, 3 figures

We examine whether observations independent of type Ia supernova surveys are sufficient to imply the existence of dark energy. We find that best measurements of the age of the universe $t_0$, the Hubble parameter $H_0$ and the matter fraction $\Omega_m$ strongly favor the existence of a repulsive, acceleration-causing ($w < -1/3$) component of energy if the universe is nearly flat.


Anonymous said...

I'm afraid this also supports the main opponent to DE - namely a quantum gravitational (eg. varying speed of light) cosmology.

DB said...

Brilliant and elegant, as usual!

steve said...

DB: thanks for the compliment!

Kea: Most physicists would probably say that a varying speed of light is less likely than the other possibilities, like dust or axions affecting the SN results.

Anonymous said...

My alternate gravity theory makes the dark energy hypothesis superfluous.

It posits that the gravitational force is mediated by the "radial spreading of infrared luminosity" and not by some yet-to-be specified, inherent and essential property of mass as the traditional, mass-based gravitational theories of Newton and Einstein would have you believe. See photograph above where two of my experiments demonstrate that the spreading of infrared luminosity is attractive contrary to what the introductory textbooks in physics would have you believe.

It just so happens that the timing of the "dimming of the universe" coincides with its "acceleration". If there is less light in the universe, according to my theory, the universe will be less gravitationally bound. Since galaxies rotate around other galaxies and clusters of galaxies rotate around other clusters, the galaxies and clusters will be free fly in a straight line if they become less gravitationally bound. This flying apart in all directions will give the appearance that the expansion rate of the universe is increasing or the universe is accelerating. Form more on this go here or here

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