# The Cosmological parameter: constant or dynamical

journal contribution

posted on 2022-01-05, 11:20 authored by Aroonkumar Beesham, Rakesh Kumar TiwariAfter providing a brief history of the cosmological constant, some early
cosmological models are discussed. The most popular current cosmological model is the ΛCDM
model, but there are several problems associated with this model, e.g., the cosmological constant
problem and fine tuning. The idea of a dynamical cosmological parameter (Λ) is then introduced,
which appears to fit observations better, and which can solve many problems associated with
a constant Λ. The relationship between a variable Λ and bulk viscosity is then elucidated. It
is then shown that some versions of f(R, T) theory can be regarded as equivalent to general
relativity with a variable Λ. Some Chaplygin gas cosmological models can also be re-cast as
variable Λ models.