https://doi.org/10.1140/epjc/s10052-025-14459-5
Regular Article - Theoretical Physics
Deflection of light due to Kerr Sen black hole in heterotic string theory using material medium approach
1
Department of Physics, National Institute of Technology, 799046, Agartala, Tripura, India
2
The Institute of Mathematical Sciences, C.I.T. Campus, Taramani, 600113, Chennai, Tamil Nadu, India
3
Department of Physics, Hemvati Nandan Bahuguna Garhwal Central University, 246174, Srinagar Garhwal, Uttarakhand, India
4
Centre for Space Research, North-West University, 2520, Potchefstroom, South Africa
5
Department of Physics, Assam University, 788011, Silchar, Assam, India
Received:
27
April
2025
Accepted:
25
May
2025
Published online:
15
July
2025
The deflection of light in the gravitational field of a massive body can be analyzed through diverse theoretical approaches. The null geodesic approach is commonly employed to calculate light deflection within strong and weak field limits. Alternatively, several studies have explored the gravitational deflection of light using the material medium approach. For a static, non-rotating spherical mass, the deflection in a Schwarzschild field can be determined by expressing the metric in an isotropic form and evaluating the refractive index to trace the light ray’s trajectory. In this study, we extend the above-mentioned approach to the Kerr–Sen black hole spacetime in heterotic string theory, a solution representing a rotating, charged solution in heterotic string theory. The frame-dragging effects inherent to the Kerr–Sen geometry are incorporated to compute the velocity of light rays, enabling the derivation of the refractive index in this field. Considering the far-field approximation, we calculate the deflection of light in the Kerr–Sen spacetime and compare our results with those obtained for the Kerr and Schwarzschild black hole solution in GR.
© The Author(s) 2025
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