HEP/Astro Seminar, Wednesday 13th January 1999

Implications of Cosmic Repulsion for Gravitational Theory

Philip Mannheim (U. Connecticut)

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Abstract

 With the recent emergence of the fact that $\Omega_{M}(t_0)$ is
 apparently less than one, standard cosmology now faces two particularly
 unpalatable alternatives: either there exists another source of energy to
 precisely bring $\Omega_{tot}(t_0)$ back to one, or else the spatial
 curvature $k$ of the universe is non-zero. In the standard
 Einstein-Friedmann cosmology neither of these options is achievable
 without a fine tuning of the early universe above and beyond that already
 provided by inflation; and, moreover, if inflation is correct, the large
 value inferred for $1-\Omega_{M}(t_0)$ would then entail after
 generations of work, and after an almost 20 year long conviction that
 $\Omega_{M}(t_0)=1$, that the cosmology community apparently does not
 have all that clear an idea as to the primary content of the
 universe. Given the severity of this situation, it is legitimate to
 ask if the problem lies not in unknown astrophysics, but rather in
 the assumed validity of standard gravity itself, with all of the
 problems which cosmology currently faces being readily traceable to
 one single source, namely the Einstein-Friedmann cosmological
 evolution equations themselves. In order to address this question
 we present a general, model independent analysis of the recently
 detected apparent cosmic repulsion, and discuss its potential
 implications for gravitational theory. In particular, we show that a
 non-flat negatively spatially curved universe acts like a
 diverging refractive medium, to thus naturally cause galaxies to
 accelerate away from each other. Additionally, we show that even
 though such a negatively spatially curved universe is not natural
 in standard gravity, it does nonetheless have a natural origin
 within conformal gravity, a fully covariant candidate alternative
 to standard gravity. In conformal cosmology the flatness, horizon,
 universe age, cosmological constant, and cosmic repulsion problems
 are all resolved, and no need is found for dark matter.
 (References: astro-ph/9803135; astro-ph/9804335, Phys Rev D58, 103511,
 1998.)

3:30pm, Smith Lab 4079