Trouble For “Dark Energy”?

The 2011 Nobel Prize  in Physics was due to the research which found (since 1998) that far off Type Ia Supernovae appear to be somewhat faint if their Luminosity Distances would be interpreted in terms of the standard (the then) Big Bang Model. And this was thought to be indicating that the far off galaxies are actually farther off; as if space expanded more than what was expected.  Attendant  conclusion  was that  the space must be accelerating so that the embedded galaxies acquire that extra luminosity distance. Thus in 1998, the present version of the Big Bang Model called  “Lambda Cold Dark Matter” was born; here “Lambda” stands for Einstein’s “Cosmological Constant” or equivalently: “Dark Energy”.

This  interpretation that the universe is undergoing an ACCELERATED expansion rather than deceleration is however  based on several tacit assumptions like:

  • Type Ia supernovae are Standard Candles, i.e;. they all have same intrinsic luminosity
  • They explode in a spherically symmetric manner
  • The light coming from them are not attenuated by Lyman-Alpha clouds or inter galactic dusts or by likely atmosphere of planets (still undetected) along the line of sight:

And it is  this supposed ACCELERATED EXPANSION, interpreted in the paradigm of Big-Bang cosmology,  which gave rise to the concept of  “Dark Energy”, an unseen and undetected energy with the mysterious  property that it is associated with NEGATIVE pressure. In contrast, al the other forms of “Energy” we know of, at least, in the context of classical physics, generate POSITIVE pressure.

In turn, it is this fictitious “NEGATIVE” pressure associated with the “DARK ENERGY” which is supposed to be pulling the space apart and forcing it to  accelerate when one would expect that the, after the initial explosion,  cosmic debris would slow down due to their mutual gravitational attraction.

And here is a paper, published in today’s arXiv.org which claims that Type Ia supernovae need not have fixed luminosity. This finding questions the first & the second ASSUMPTIONs behind the idea of exotic “Dark Energy”.

\\
arXiv:1110.5809
Date: Wed, 26 Oct 2011 14:58:53 GMT   (1324kb)

Title: Evidence for Type Ia Supernova Diversity from Ultraviolet Observations with the Hubble Space Telescope

Authors: Xiaofeng Wang et al. (Almost 50 authors)
Categories: astro-ph.HE astro-ph.CO

Comments: 15 pages, 12 figures, submitted to ApJ
\\
We present ultraviolet (UV) spectroscopy and photometry of four Type Ia supernovae (SNe 2004dt, 2004ef, 2005M, and 2005cf) obtained with the UV prismof the Advanced Camera for Surveys on the Hubble Space Telescope. This dataset provides unique spectral time series down to 2000 Angstrom. Significant diversity is seen in the near maximum-light spectra (~ 2000–3500 Angstrom) for this small sample. The corresponding photometric data, together with archival data from Swift Ultraviolet/Optical Telescope observations, provide further evidence of increased dispersion in the UV emission with respect to the optical. The peak luminosities measured in uvw1/F250W are found to correlate with the B-band light-curve shape parameter dm15(B), but with much larger scatter relative to the correlation in the broad-band B band (e.g., ~ 0.4 mag versus ~0.2 mag for those with 0.8 < dm15 < 1.7 mag). SN 2004dt is found as an outlier of this correlation (at > 3 sigma), being brighter than normal SNe~Ia such as SN 2005cf by ~0.9 mag and ~2.0 mag in the uvw1/F250W and uvm2/F220W filters, respectively. We show that different progenitor metallicity or line-expansion velocities alone cannot explain such a large discrepancy. Viewing-angle effects, such as due to an asymmetric explosion, may have a significant influence on the flux emitted in the UV region. Detailed modeling is needed to disentangle and quantify the above effects.

( http://arxiv.org/abs/1110.5809)

————————————————————————————————–
  • SHOULD “Dark Energy” Be ABSENT FROM  PURELY THEORETICAL CONSIDERATIONS TOO?
In 2009, I tried to see whether the total energy of the Big Bang Universe is indeed conserved or not:
“Einstein energy associated with the Friedmann-Robertson-Walker Metric”
A. Mitra, General Relativity and Gravitation, Volume 42, Issue 3, pp.443-469 (2010)
To my surprise, I found that Big – Bang badly violates the revered principle of conservation of energy. Here I also probed where a vacuum universe made of pure “Dark Energy” (Cosmological Constant = Lambda) would honor this cornerstone of physics. But I found that even here energy would not be conserved unless one would have
LAMBDA =0 !
I had done  this and additional studies way back in 2008; and on the basis of them, I had argued in my talk  in the International Symposium on Experimental Gravitation January 5th – 9th 2009, organized by Tata Institute of Fundamental Research, India that there should be no Dark Energy on purely theoretical grounds irrespective of indirect observational interpretations to the contrary:
————————————————————————————————–
  • MORE TROUBLE FOR DARK ENERGY?
  • Arto Annila, Physics Professor at the University of Helsinki has just published a paper  in a recent issue of the Monthly Notices of the Royal Astronomical Society

and which claims  that the supernovae data does not imply that the universe is undergoing an accelerating expansion.

He however claims that light moves following Fermat’s Principle of Least Time and which need not imply Inverse Square Law of Dilution of light intensity:

The principle of least time

As Annila explains, when a ray of light travels from a distant star to an observer’s telescope, it travels along the path that takes the least amount of time. This well-known physics principle is called Fermat’s principle or the principle of least time. Importantly, the quickest path is not always the straight path. Deviations from a straight path occur when light propagates through media of varying energy densities, such as when light bends due to refraction as it travels through a glass prism.

Here is the abstract of his paper:

“The variational principle in its original form á la Maupertuis is used to delineate paths of light through varying energy densities and to associate shifts in frequency and changes in momentum. The gravitational bending and Doppler shift are in this way found as mere manifestations of least-time energy dispersal. In particular, the general principle of least action due to Maupertuis accounts for the brightness of Type 1a supernovae versus redshift without introducing extraneous parameters or invoking conjectures such as dark energy. Likewise, the least-time principle explains the gravitational lensing without the involvement of additional ingredients such as dark matter. Moreover, time delays along curved geodesics relative to straight paths are obtained from the ratio of the local to global energy density. According to the principle of least action the Universe is expanding uniformly due to the irrevocable least-time consumption of diverse forms of bound energy to the lowest form of energy, i.e. the free electromagnetic radiation.”

Surely this would raise many questions. For details see:

http://www.physorg.com/news/2011-10-supernovae-universe-expansion-understood-dark.html

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