Λ-CDM Universe: A Phenomenological Approach With Many Possibilities

Modern cosmological research rests heavily on observational data. Any theoretical model should be corroborated with observation for understanding the viability of that model. Present cosmological picture, emerging out of this theory-observation combination, reveals that, the total energy-density of the Universe is dominated by two dark components, viz., dark matter and dark energy. Observational evidence from various independent sources including SN Ia1,2,3,4,5,6,7,8 suggest that the cosmic expansion is speeding up, i.e. accelerating. This acceleration is supposed to be caused by a yet unknown exotic energy, termed as dark energy. A special feature of dark energy is that it exerts negative pressure which acts as a repulsive force initiating the observed acceleration. Not only that, it is now well-accepted that about two-third of the total energy-density comes in terms of dark energy while the remaining one-third is contributed by matter, both visible and dark9.