Self similar collapse and the Raychaudhuri equation Shibendu Gupta Choudhury, Soumya Chakrabarti, Ananda Dasgupta and Narayan Banerjee Eur. Phys. J. C, 79 12 (2019) 1027 Published online: 24 December 2019 DOI: 10.1140/epjc/s10052-019-7559-9