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Papers by Saswati Roy
Journal of Physics: Conference Series, 2019
Gravitational deflection of light ray is one of the famous predictions of Einstein’s general theo... more Gravitational deflection of light ray is one of the famous predictions of Einstein’s general theory of relativity. The deflection of light ray, as it passes around a gravitational mass, can be calculated by different methods such as null geodesics method and material medium approach. In this paper a comparative study will be done for gravitational deflection of light ray, calculated by different authors using different methods. In this study, different gravitating body such as static, rotating and charged body will be considered which are represented by Schwarzschild metric, Kerr metric, Reissner-Nordström metric and Janis-Newman-Winicour metric.
Zeitschrift für Naturforschung A, 2017
The gravitational deflection of light ray is an important prediction of general theory of relativ... more The gravitational deflection of light ray is an important prediction of general theory of relativity. In this paper we have developed an analytical expression of the deflection of light ray without any weak field approximation due to a charged gravitating body represented by Reissner-Nordström (RN) and Janis-Newman-Winicour (JNW) space-time geometry, using material medium approach. It is concluded that although both the geometries represent the charged, non-rotating, spherically symmetric gravitating body, the effect of charge on the gravitational deflection is just opposite to each other. The gravitational deflection decreases with charge in the RN geometry and increases with charge in the JNW geometry. The calculations obtained here are compared with other methods done by different authors. The formalism is applied to an arbitrarily selected gravitating body, as a test case and compared with the standard Schwarzschild geometry for comparison purposes.
Astrophysics and Space Science, 2015
The deflection of light ray as it passes around a gravitational mass can be calculated by differe... more The deflection of light ray as it passes around a gravitational mass can be calculated by different methods. Such calculations are generally done by using the null geodesics under both strong field and weak field approximation. However, several authors have studied the gravitational deflection of light ray using material medium approach. For a static, non-rotating spherical mass, one can determine the deflection in Schwarzschild field, by expressing the line element in an isotropic form and calculating the refractive index to determine the trajectory of the light ray. In this paper, we draw our attention to the refractive index of light ray in Kerr field using the material medium approach. The frame dragging effects in Kerr field was considered to calculate the velocity of light ray and finally the refractive index in Kerr field geometry was determined. Hence the deflection of light ray in Kerr field was calculated, assuming far field approximation and compared the results with those calculations done earlier using Null geodesics.
Journal of Physics: Conference Series, 2019
Gravitational deflection of light ray is one of the famous predictions of Einstein’s general theo... more Gravitational deflection of light ray is one of the famous predictions of Einstein’s general theory of relativity. The deflection of light ray, as it passes around a gravitational mass, can be calculated by different methods such as null geodesics method and material medium approach. In this paper a comparative study will be done for gravitational deflection of light ray, calculated by different authors using different methods. In this study, different gravitating body such as static, rotating and charged body will be considered which are represented by Schwarzschild metric, Kerr metric, Reissner-Nordström metric and Janis-Newman-Winicour metric.
Zeitschrift für Naturforschung A, 2017
The gravitational deflection of light ray is an important prediction of general theory of relativ... more The gravitational deflection of light ray is an important prediction of general theory of relativity. In this paper we have developed an analytical expression of the deflection of light ray without any weak field approximation due to a charged gravitating body represented by Reissner-Nordström (RN) and Janis-Newman-Winicour (JNW) space-time geometry, using material medium approach. It is concluded that although both the geometries represent the charged, non-rotating, spherically symmetric gravitating body, the effect of charge on the gravitational deflection is just opposite to each other. The gravitational deflection decreases with charge in the RN geometry and increases with charge in the JNW geometry. The calculations obtained here are compared with other methods done by different authors. The formalism is applied to an arbitrarily selected gravitating body, as a test case and compared with the standard Schwarzschild geometry for comparison purposes.
Astrophysics and Space Science, 2015
The deflection of light ray as it passes around a gravitational mass can be calculated by differe... more The deflection of light ray as it passes around a gravitational mass can be calculated by different methods. Such calculations are generally done by using the null geodesics under both strong field and weak field approximation. However, several authors have studied the gravitational deflection of light ray using material medium approach. For a static, non-rotating spherical mass, one can determine the deflection in Schwarzschild field, by expressing the line element in an isotropic form and calculating the refractive index to determine the trajectory of the light ray. In this paper, we draw our attention to the refractive index of light ray in Kerr field using the material medium approach. The frame dragging effects in Kerr field was considered to calculate the velocity of light ray and finally the refractive index in Kerr field geometry was determined. Hence the deflection of light ray in Kerr field was calculated, assuming far field approximation and compared the results with those calculations done earlier using Null geodesics.