PROFESSOR T. PADMANABHAN

Observations indicate that our universe can be characterised by three distinct phases of evolution: An early inflationary phase possibly driven by a scalar field, a late-time accelerated phase dominated by dark energy and a transient phase in between, dominated by radiation and matter. The late-time acceleration can be consistently modelled in terms of a cosmological constant (¿¿ provided its value is extremely tiny: ¿LP2 ¿ 10-122 where LP = (Gh/c3)1/2 is the Planck length. A key issue in theoretical physics is to explain the extremely small value of this dimensionless parameter. The speaker will describe how this value can be understood in terms of a new dimensionless parameter (CosMIn) which counts the number of modes inside a Hubble volume that cross the Hubble radius during a specified interval of time. CosMIn has the same (‘conserved’) value during well-defined intervals in the three phases of cosmic evolution, and this fact helps us to determine the numerical value of the cosmological constant. This approach provides a truly unified picture of cosmic evolution relating the early inflationary phase, the late accelerating phase and certain considerations of Planck scale physics. The speaker will also discuss how these ideas are related to a description of cosmic expansion as a quest for holographic equipartition and lead to a novel paradigm to study cosmology. The talk will be at a level understandable to the non-experts and is based on: T. Padmanabhan, Emergent perspective of Gravity and Dark Energy, Res. Astron. Astrophys., 12, 891 (2012) [arXiv:1207.0505] T. Padmanabhan, Hamsa Padmanabhan, Solution to the cosmological constant problem, [arXiv: 1302.3226]