# Rotating Black Holes in Higher Order Gravity

## TL;DR

This paper introduces a new method for constructing rotating black hole solutions with stealth scalar hair in higher order gravity theories, revealing novel scalar-dressed black holes with finite scalar fields at horizons.

## Contribution

It develops a technique for finding black hole solutions with stealth hair and presents a new rotating black hole solution with finite scalar fields at horizons in scalar-tensor theories.

## Key findings

- Existence of Einstein metrics with stealth hair under specific geodesic conditions
- Construction of a scalar-dressed rotating black hole with finite scalar field at horizons
- New insights into black hole solutions in higher order gravity theories

## Abstract

We develop a new technique for finding black hole solutions in modified gravity that have "stealth" hair, i.e., hair whose only gravitational effect is to tune the cosmological constant. We consider scalar-tensor theories in which gravitational waves propagate at the speed of light, and show that Einstein metrics can be painted with stealth hair provided there exists a family of geodesics always normal to spacelike surfaces. We also present a novel scalar-dressed rotating black hole that has finite scalar field at both the black hole and cosmological event horizons.