Alleviation of cosmic age problem in interacting dark energy model

We investigate the cosmic age problem associated with the old high-z quasar APM 08279+5255 and the oldest globular cluster M 107, both being difficult to accommodate in ΛCDM model. By evaluating the age of the Universe in a model that has an extremely phantom like form of dark energy (DE), we show that simply introducing the dark energy alone does not remove the problem, and the interaction between dark matter (DM) and DE need to be taken into account. Next, as examples, we consider two interacting DE models. It is found that both these two interacting DE Models can predict a cosmic age much greater than that of ΛCDM model at any redshift, and thus substantially alleviate the cosmic age problem. Therefore, the interaction between DM and DE is the crucial factor required to make the predicted cosmic ages consistent with observations.