Cosmology Challenges: Dark Matter, Dark Energy, Galaxy Formation

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Cosmology is currently grappling with three significant challenges: understanding the nature of dark matter and dark energy, elucidating the timeline and mechanisms of galaxy formation, and reconciling observational discrepancies with the dark matter-driven model of galaxy assembly. Key questions revolve around the dominance of the dark sector in the Universe and the need for improved observational techniques. The formation of galaxies, particularly during the epoch of reionization, requires further investigation into earlier epochs. Observations of ultra-luminous infrared galaxies (ULIRGs) and other phenomena suggest that merging may not be as crucial in defining the Hubble sequence as previously thought. Addressing these challenges is essential for advancing cosmological theories and refining observational methods.
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http://arxiv.org/PS_cache/arxiv/pdf/0712/0712.2865v1.pdf

New Frontiers in Cosmology and Galaxy Formation: Challenges for the Future
Authors: Richard Ellis (Caltech), Joseph Silk (Oxford)
Comments: To appear in "Structure Formation in the Universe", ed. Chabrier, G., Cambridge University Press. High resolution version on this http URL
Subjects: Astrophysics (astro-ph)

(Abridged) Cosmology faces three distinct challenges in the next decade. (1) The dark sector, both dark matter and dark energy, dominates the Universe. Key questions include determining the nature of both. Improved observational probes are crucial. (2) Galaxy formation was initiated at around the epoch of reionization: we need to understand how and when as well as to develop probes of earlier epochs. (3) Our simple dark matter-driven picture of galaxy assembly is seemingly at odds with several observational results, including the presence of ULIRGS at high z, the `downsizing' signature, chemical signatures of alpha-element ratios and suggestions that merging may not be important in defining the Hubble sequence. Understanding the physical implications is a major challenge for theorists and refiniing the observational uncertainties a major goal for observers.

The thing that interests me is the (what is the universe made of) question, and the finding or lack of of what is proposed.
 
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IMO this is 24 carat pure gold mainstream cosmology.
I've the highest respect for Joe Silk and am proud to have met him.
I went and bothered him with a question in his office one time when he was at UCBerkeley.

thanks to your flagging this I added it to the bibliography
lets get the URL for the abstract and also for the high-resolution version
the short abstract is here
http://arxiv.org/abs/0712.2865
the high-resolution version is here on Ellis' Caltech server
http://www.astro.caltech.edu/~rse/chamonix.pdf

An ULIRG is an ultra luminous infrared galaxy
ULIRGs are believed to be places where a lot of star-formation is going on.
 
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https://en.wikipedia.org/wiki/Recombination_(cosmology) Was a matter density right after the decoupling low enough to consider the vacuum as the actual vacuum, and not the medium through which the light propagates with the speed lower than ##({\epsilon_0\mu_0})^{-1/2}##? I'm asking this in context of the calculation of the observable universe radius, where the time integral of the inverse of the scale factor is multiplied by the constant speed of light ##c##.
Why was the Hubble constant assumed to be decreasing and slowing down (decelerating) the expansion rate of the Universe, while at the same time Dark Energy is presumably accelerating the expansion? And to thicken the plot. recent news from NASA indicates that the Hubble constant is now increasing. Can you clarify this enigma? Also., if the Hubble constant eventually decreases, why is there a lower limit to its value?

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