Cosmological complexity in K-essence

Abstract

We calculate the cosmological complexity under the framework of scalar curvature perturbations for a K-essence model with constant potential. In particular, the squeezed quantum states are defined by acting a two-mode squeezed operator which is characterized by squeezing parameters rk and ϕk on vacuum state. The evolution of these squeezing parameters are governed by the Schrödinger equation, in which the Hamiltonian operator is derived from the cosmological perturbative action. With aid of the solutions of rk and ϕk, one can calculate the quantum circuit complexity between unsqueezed vacuum state and squeezed quantum states via the wave-function approach. One advantage of K-essence is that it allows us to explore the effects of varied sound speeds on evolution of cosmological complexity. Besides, this model also provides a way for us to distinguish the different cosmological phases by extracting some basic information, like the scrambling time and Lyapunov exponent etc, from the evolution of cosmological complexity.