Padmanabhan, T.2012-03-022012-03-022005-04-10http://hdl.handle.net/11007/86Recent cosmological observations suggest that nearly seventy per cent of the energy density in the universe is unclustered and has negative pressure. Several conceptual issues related to the modelling of this component ('dark energy’), which is driving an accelerated expansion of the universe, are reviewed with special emphasis on the cosmological constant as the possible choice for the dark energy.enDark EnergyCosmological cosmological constantEnergy densityArticle