Black holes have a unique sensitivity to the presence of ultralight matter fields or modifications of the underlying theory of gravity. In the present paper we combine both features by studying an ultralight, dynamical scalar field that is nonminimally coupled to the gravitational Chern-Simons term. In particular, we numerically simulate the evolution of such a scalar field around a rotating black hole in the decoupling approximation and find a new kind of massive scalar hair anchored around the black hole. In the proximity of the black hole, the scalar exhibits the typical dipolar structure of hairy solutions in (massless) dynamical Chern-Simons gravity. At larger distances, the field transitions to an oscillating scalar cloud that is induced by the mass term. Finally, we complement the time-domain results with a spectral analysis of the scalar field characteristic frequencies. 
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                            Chern Simons condensate from misaligned axions
                        
                    
    
            We obtain the nonequilibrium condensate of the Chern Simons density induced by a misaligned homogeneous coherent axion field in linear response. The Chern-Simons dynamical susceptibility is simply related to the axion self-energy, a result that is valid to leading order in the axion coupling but to all orders in the couplings of the gauge fields to other fields within or beyond the standard model except the axion. The induced Chern-Simons density requires renormalization which is achieved by vacuum subtraction. 
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                            - Award ID(s):
- 2111743
- PAR ID:
- 10624939
- Publisher / Repository:
- physical review d
- Date Published:
- Journal Name:
- Physical Review D
- Volume:
- 107
- Issue:
- 8
- ISSN:
- 2470-0010
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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