Constraints on the cosmic equation of state: Age conflict versus phantom energy

Age-redshift relations in an accelerated universe

¹ Instituto de Astrofísica de Canarias, 38200 La Laguna, Tenerife, Spain e-mail: jcn@ll.iac.es
² Departamento de Astrofísica, Facultad de Física, Universidad de la Laguna, 38071 La Laguna, Tenerife, Spain

Received: 24 November 2003
Accepted: 24 March 2004

Abstract

The currently available values and confidence limits for , H₀ and globular cluster ages still indicate that the dark energy that dominates the Universe could also be a form of quintessence or phantom energy. In fact, current cosmological values favor phantom energy. To increase the likelihood of a cosmological constant as dark energy instead of phantom energy, the possibilities seem to lie in reducing globular cluster ages, the Hubble constant, or both, and possibly advancing the epoch of globular cluster formation. For a set of possible dark energy equations of state that includes the cosmological constant, quintessence or phantom energy, age-redshift analytical expressions for null curvature universes that include ordinary matter are derived together with the corresponding ages for these universes. “Cosmic coincidences” are found for the currently accepted values of when evaluating the age of the Universe with a cosmological constant or a phantom energy as dark energies.