Scalarization of Chern-Simons-Kerr black hole solutions and wormholes

Weak gravitational lensing and shadow cast by rotating black holes in axionic Chern–Simons theory

“…In the CS gravitational theory two independent fields are taken into consideration, one is the gravitational field represented by the spacetime metric g µν and other is a scalar field of specific nature. So, in particular, the action for the axionic CS gravitational theory is given by [113]…”

“…s , where M s is the string scale, as η = 2/3 α /48κ, which is of the order O(M P l /M 2 s ). Varying the action (1) with respect to the metric g µν and also with the axion matter field ϕ, the equations of motion can be obtained for the theory as [113],…”

“…The Cotton tensor is obtained by varying the term ϕ R CS with respect to the metric g µν and can be expressed in the following form [113,129]:…”

“…This field being a pseudoscalar, it will impose axial symmetry on any kind of spacetime that we work on. Hence, this nature of the theory provides convenient means to find solutions for rotating compact objects and accordingly, here we consider a metric ansatz for slowly rotating Kerr-type black holes as given by [113]…”

“…One of the interesting modified theories of gravity is the axionic Chern-Simons (CS) modified gravity theory [113]. In this work, we intend to explore the impact of CS gravity on gravitational lensing of a slowly rotating black hole spacetime.…”