Complexity Growth in Flat Spacetimes
Reza Fareghbal, Pedram Karimi
TL;DR
This work extends the Complexity=Action (CA) proposal to BMSFTs dual to asymptotically flat spacetimes by evaluating the on-shell action on a carefully chosen Wheeler-DeWitt patch. The authors derive the growth rate of complexity $\dot{\mathcal{C}}$ in both $d\ge3$ and $d=2$ cases, showing zero growth at initial times and a late-time behavior that, for $d\ge3$, approaches Lloyd's bound from above, while in $d=2$ it remains constant with a logarithmic deviation. The flat-space results reproduce the corresponding AdS/CFT limits, with the null joint scale $\mathfrak{a}$ playing a key role in the boundary terms. This work clarifies how holographic complexity behaves in ultrarelativistic, flat spacetimes and provides a framework for exploring complexity formation and further flat/BMSFT holography.
Abstract
We use the complexity equals action proposal to calculate the rate of complexity growth for field theories that are the holographic duals of asymptotically flat spacetimes. To this aim, we evaluate the on-shell action of asymptotically flat spacetime on the Wheeler-DeWitt patch. This results in the same expression as can be found by taking the flat-space limit from the corresponding formula related to the asymptotically AdS spacetimes. For the bulk dimensions that are greater than three, the rate of complexity growth at late times approaches from above to Lloyd's bound. However, for the three-dimensional bulks, this rate is a constant and differs from Lloyd's bound by a logarithmic term.
