Dark Energy and the Fate of the Universe

It is often assumed that in the course of the evolution of the universe, the dark energy either vanishes or becomes a positive constant. However, recently it was shown that in many models based on supergravity, the dark energy eventually becomes negative and the universe collapses within the time comparable to the present age of the universe. We will show that this conclusion is not limited to the models based on supergravity: In many models describing the present stage of acceleration of the universe, the dark energy eventually becomes negative, which triggers the collapse of the universe within the time t = 10^10-10^11 years. The theories of this type have certain distinguishing features that can be tested by cosmological observations.