# Holographic Complexity Equals Which Action?

## TL;DR

This paper explores the holographic complexity=action proposal for charged black holes, revealing how electric and magnetic charges influence late-time growth and the effects of surface terms and causal structure, with implications for lower-dimensional theories.

## Contribution

It demonstrates the sensitivity of late-time complexity growth to charge ratios, introduces a surface term to balance electric and magnetic contributions, and connects higher-dimensional results to two-dimensional JT gravity.

## Key findings

- Late-time growth vanishes for purely magnetic black holes.
- Surface terms can equalize electric and magnetic charge effects.
- Causal structure and background choices influence complexity behavior.

## Abstract

We revisit the complexity$=$action proposal for charged black holes. We investigate the complexity for a dyonic black hole, and we find the surprising feature that the late-time growth is sensitive to the ratio between electric and magnetic charges. In particular, the late-time growth rate vanishes when the black hole carries only a magnetic charge. If the dyonic black hole is perturbed by a light shock wave, a similar feature appears for the switchback effect, e.g., it is absent for purely magnetic black holes. We then show how the inclusion of a surface term to the action can put the electric and magnetic charges on an equal footing, or more generally change the value of the late-time growth rate. Next, we investigate how the causal structure influences the late-time growth with and without the surface term for charged black holes in a family of Einstein-Maxwell-Dilaton theories. Finally, we connect the previous discussion to the complexity=action proposal for the two-dimensional Jackiw-Teitelboim theory. Since the two-dimensional theory is obtained by a dimensional reduction from Einstein-Maxwell theory in higher dimensions in a near-extremal and near-horizon limit, the choices of parent action and parent background solution determine the behaviour of holographic complexity in two dimensions.