**AAS 198th Meeting, June 2001**

*Session 6. The Early Universe*

Display, Monday, June 4, 2001, 9:20am-6:30pm, Exhibit Hall
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## [6.06] Cosmological Spacetimes with Galactic Sheets and Voids: Breakdown of Friedmann Models

*E. P. Tryon (Hunter College and Graduate Center of The City University of New York)*

A new set of cosmological spacetimes with galactic sheets
and voids is being developed. Einstein's field equations are
solved (in four dimensions) by an iterative procedure that
converges rapidly for relevant values of input parameters. A
few of the simplest solutions have already been obtained.
They display a remarkable feature: space is virtually flat
over cosmological distances for arbitrary values of Omega
(with the cosmological constant regarded as vacuum energy
contributing to Omega). Virtual flatness is readily seen to
be a feature of all spacetimes in the set, which comprises a
considerable variety of sheets and voids.

This work demonstrates that linkage between geometry and
Omega is not a robust prediction of general relativity, but
only a special feature of Friedmann models (apparently
arising from their simplifying assumption of perfect
homogeneity). Cosmological interpretations of data that have
assumed the traditional Friedmann relation between geometry
and Omega therefore require modification. Most obviously,
standard inflation's prediction of flatness does not imply a
critical density of mass-energy.

Acceleration (or deceleration) of the cosmic expansion is
virtually the same as in Friedmann models for the simple
solutions obtained thus far, but might conceivably be
different for more complex structures and kinematics now
under study.

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