Astrophysics, abstract
astro-ph/0410710

From: Selcuk Bayin [view email]
Date: Thu, 28 Oct 2004 17:24:52 GMT   (15kb)

Missing Mass, Dark Energy and the Acceleration of the Universe. Is Acceleration Here to Stay?

In this paper we present an alternative explanation to the acceleration of the universe and the dark energy problems in terms of the Friedmann Thermodynamics. This model has the capability of making definite predictions in-line with the current observations of the universe. According to this model, cosmos was expanding slower at the beginning. During the galaxy formation era (with redshifts [0.54-0.91]), due to a change in the global equation of state it accelerates for a brief period of time. We expect to see this as a discontinuity in the Hubble diagram. Recent data about the galaxies with redshifts 0.5<z<0.9 displays this discontinuity clearly. We expect the deceleration to re-appear as more data with redshifts z>1 is gathered. These galaxies will be among the very first galaxies formed in the universe, thus still showing the kinematics of the pre-galaxy formation era. This point is now clearly evidenced in the recent data by Riess et al. on Type Ia supernovae with redshifts z>1.25 (2004 astro-ph/0402512). In our model, galaxies with redshifts 0<z<0.5 should reflect the kinematics of the universe after the transition is completed. These galaxies are now receding from each other faster. However, for redshifts towards the upper end of this range we still expect to see deceleration. This is in contrast with the predictions of the dark energy models.

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Astrophysics, abstract
astro-ph/0211097

From: Selcuk Bayin <bayin@metu.edu.tr>
Date: Tue, 5 Nov 2002 22:28:29 GMT   (8kb)

Missing Mass and the Acceleration of the Universe. Is Quintessence the only Explanation?

Detailed observations of the temperature fluctuations in the microwave background radiation indicate that we live in an open universe. From the size of these fluctuations it is concluded that the geometry of the universe is quite close to Euclidean. In terms Friedmann models, this implies a mass density within 10% of the critical density required for a flat universe. Observed mass can only account for 30% of this mass density. Recently, an outstanding observation revealed that cosmos is accelerating. This motivated some astronomers to explain the missing 70% as some exotic dark energy called quintessence. In this essay, we present an alternative explanation to these cosmological issues in terms of the Friedmann Thermodynamics. This model has the capability of making definite predictions about the geometry of the universe, the missing mass problem, and the acceleration of the universe in-line with the recent observations. For future observations, we also predict where this model will start differing from the quintessence models.
(This essay received an honorable mention in the Annual Essay Competition of the Gravity Research Foundation for the year 2002-- Ed)

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References and citations for this submission:
SLAC-SPIRES HEP (refers to , cited by, arXiv reformatted)