https://doi.org/10.1140/epjc/s10052-025-13850-6
Regular Article - Theoretical Physics
Implications of Raychaudhuri equation and geodesic focusing in interacting two fluid systems
1
Department of Mathematics, Techno India University, 700091, Kolkata, West Bengal, India
2
Department of Mathematics, Brainware University, 700125, Kolkata, West Bengal, India
3
Shinawatra University, Bang Toei, Thailand
4
INTI International University, Nilai, Malaysia
Received:
25
November
2024
Accepted:
19
January
2025
Published online:
30
January
2025
The present work analyses Raychaudhuri equation (RE) in Einstein gravity for two interacting fluids. Focusing theorem, a consequence of RE, is directly related to the singularity theorems of Penrose and Hawking. In the present work, the signature of the Raychaudhuri scalar or convergence scalar has been examined for two types of interaction forms namely, (i) 
(linear) and (ii) 
(non-linear). Finally, the phenomena of focusing of a congruence of geodesics and possible avoidance of singularity have been discussed based on the nature of the two fluids and the interaction term operating between them.
© The Author(s) 2025
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