Exact RG Flow in an Expanding Universe and Screening of the Cosmological Constant

Understand

We obtain the exact renormalization group (RG) flow equation for a self interacting real scalar field in an expanding cosmological background.

• The beta functional for the potential in the local potential approximation is determined in terms of the mode functions defining the vacuum of the theory.
• For a scalar in an inflating universe, which is released in the Bunch-Davies vacuum, the flow equation is analyzed in detail using the optimized cutoff function for the quartically truncated potential.
• In that case, the constant term in the potential, which can in fact be viewed as the cosmological constant, decreases as the IR cutoff is removed, supporting the existence of a quantum mechanical screening mechanism.