Site Map
Contacts
Follow us on Facebook Follow us on Twitter YouTube channel
Centro de Astrofísica da Universidade do Porto

Constraining cosmologies with fundamental constants - I. Quintessence and K-essence

R. I. Thompson, C. J. A. P. Martins, P. E. Vielzeuf

Abstract
Many cosmological models invoke rolling scalar fields to account for the observed acceleration of the expansion of the universe. These theories generally include a potential V(ɸ) which is a function of the scalar field ɸ. Although V(ɸ) can be represented by a very diverse set of functions, recent work has shown the under some conditions, such as the slow roll conditions, the equation of state parameter w is either independent of the form of V(ɸ) or is part of family of solutions with only a few parameters. In realistic models of this type the scalar field couples to other sectors of the model leading to possibly observable changes in the fundamental constants such as the fine structure constant a and the proton to electron mass ratio µ. Although the current situation on a possible variance of a is complicated there are firm limitations on the variance of µ in the early universe. This paper explores the limits this puts on the validity of various cosmologies that invoke rolling scalar fields. We find that the limit on the variation of µ puts significant constraints on the product of a cosmological parameter w +1 times a new physics parameter ζ2µ, the coupling constant between µ and the rolling scalar field. Even when the cosmologies are restricted to very slow roll conditions either the value of ζµ must be at the lower end of or less than its expected values or the value of w + 1 must be restricted to values vanishingly close to 0. This implies that either the rolling scalar field is very weakly coupled with the electromagnetic field, small ζµ, very weakly coupled with gravity, (w + 1) ≈ 0 or both. These results stress that adherence to the measured invariance in µ is a very significant test of the validity of any proposed cosmology and any new physics it requires. The limits on the variation of µ also produces a significant tension with the reported changes in the value of α.

Keywords
cosmological parameters – dark energy – early Universe

Monthly Notices of the Royal Astronomical Society
Volume 428, Page 2232
January 2013

>> ADS>> DOI

Institute of Astrophysics and Space Sciences

Institute of Astrophysics and Space Sciences (IA) is a new but long anticipated research infrastructure with a national dimension. It embodies a bold but feasible vision for the development of Astronomy, Astrophysics and Space Sciences in Portugal, taking full advantage and fully realizing the potential created by the national membership of the European Space Agency (ESA) and the European Southern Observatory (ESO). IA resulted from the merging the two most prominent research units in the field in Portugal: the Centre for Astrophysics of the University of Porto (CAUP) and the Center for Astronomy and Astrophysics of the University of Lisbon (CAAUL). It currently hosts more than two-thirds of all active researchers working in Space Sciences in Portugal, and is responsible for an even greater fraction of the national productivity in international ISI journals in the area of Space Sciences. This is the scientific area with the highest relative impact factor (1.65 times above the international average) and the field with the highest average number of citations per article for Portugal.

Proceed on CAUP's website|Go to IA website