Misc,
Solution to the cosmological constant problem
(Feb 13, 2013)
Abstract
The current, accelerated, phase of expansion of our universe can be modeled
in terms of a cosmological constant. A key issue in theoretical physics is to
explain the extremely small value of the dimensionless parameter Łambda L\_P^2
\~ 3.4 x 10^-122, where L\_P is the Planck length. We show that this value can
be understood in terms of a new dimensionless parameter N, which counts the
number of modes inside a Hubble volume crossing the Hubble radius, from the end
of inflation until the beginning of the accelerating phase. Theoretical
considerations suggest that N = 4\pi. On the other hand, N is related to ln
(Łambda L\_P^2) and two other parameters which will be determined by high
energy particle physics: (a) the ratio between the number densities of photons
and matter and (b) the energy scale of inflation. For realistic values of
(n\_/ n\_m) \~ 4.3 x 10^10 and E\_inf \~ 10^15 GeV, our postulate N
=4leads to the observed value of the cosmological constant. This provides a
unified picture of cosmic evolution relating the early inflationary phase to
the late accelerating phase.
