Astronomy and Astrophysics Do We Really See a Cosmological Constant in the Supernovae Data ?

نویسنده

  • M. N. Célérier
چکیده

The magnitude-redshift relation is one of the tools for a direct observational approach to cosmology. The discovery of high redshift Type Ia supernovae (SNIa) and their use as " standard candles " has resurrected interest in this approach. Recently collected data have been used to address the problem of measuring the cosmologi-cal parameters of the universe. Analysed in the framework of homogeneous models, they have yielded, as a primary result, a strictly positive cosmological constant. However, a straight reading of the published measurements, conducted with no a priori idea of which model would best describe our universe at least up to redshifts z ∼ 1, does not exclude the possibility of ruling out the Cosmological Principle-and cosmological constant-hypotheses. It is therefore shown here how the large scale homogeneity of this part of the universe can be tested on our past light cone, using the magnitude-redshift relation, provided sufficiently accurate data from sources at redshifts approaching z = 1 would be available. An example of an inhomoge-neous model with zero cosmological constant reproducing the current observations is given. The presently published SNIa data can thus be interpreted as implying either a strictly positive cosmological constant in a homogeneous universe or large scale inhomogeneity with no constraint on Λ. An increase in the number and measurement accuracy of the candidate " standard candles " at very high redshift is therefore urgently needed, for progress in both fundamental issues of the Cosmological Principle and of the cosmological constant.

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تاریخ انتشار 1999