Dark energy, matter creation and curvature
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Regular Article - Theoretical Physics
Dark energy, matter creation and curvature Víctor H. Cárdenasa Departamento de Física y Astronomía, Facultad de Ciencias, Universidad de Valparaíso, Av. Gran Bretana 1111, Valparaíso, Chile
Received: 3 July 2012 / Revised: 14 August 2012 / Published online: 8 September 2012 © Springer-Verlag / Società Italiana di Fisica 2012
Abstract The most studied way to explain the current accelerated expansion of the universe is to assume the existence of dark energy; a new component that fills the universe, does not form clumps, currently dominates the evolution, and has a negative pressure. In this work I study an alternative model proposed by Lima et al. (Abramo and Lima in Class. Quantum Gravity 13:2953, 1996; Zimdahl in Phys. Rev. D 53:5483, 1996; Zimdahl and Pavón in Mon. Not. R. Astron. Soc. 266:872, 1994), which does not need an exotic equation of state, but assumes instead the existence of gravitational particle creation. Because this model fits the supernova observations as well as the ΛCDM model, I perform in this work a thorough study of this model, considering an explicit spatial curvature. I found that in this scenario we can alleviate the cosmic coincidence problem, basically showing that these two components, dark matter and dark energy, are of the same nature, but they act at different scales. I also shown the inadequacy of some particle creation models, and I study a previously proposed new model that overcomes these difficulties.
1 Introduction Currently the observational evidence coming from supernovae studies [1, 2], cosmic background radiation fluctuations [3], and baryon acoustic oscillations [4], set a strong case for a cosmological (concordance) universe model composed by nearly 70 percent of a mysterious component called dark energy, responsible for the current accelerated expansion, nearly 25 percent of dark matter, which populates the galaxy halos and a small percentage (around 4) is composed by baryonic matter. The nature of these two dark component remains so far obscure [5–7]. In the case of dark matter, we have a set of candidates to be probed with observations and detections in particle accelerators, however, the case of dark energy is more elusive. This component a e-mail:
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not only has to fill the universe at the largest scale homogeneously, and also has the appropriate order of magnitude to be comparable to dark matter, but also has to have a negative pressure equation of state, something that was assumed first to explain inflation in the early universe, inspired by high energy theories of particle physics, but which seems to be awkward to appeal for, at these low energy scales. The alternative way to account for the cosmic acceleration, in the framework of the standard model, is to consider a modification of general relativity at large scales [8, 9]. Some years ago, Prigogine and co-workers [10, 11] presented a very interesting cosmological model where matter creation takes place without spoiling adiabatic expansion. This is possib
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