A controversial rocket scientist in India earned his fourth retraction in October after an investigation at a physics journal found a core part of his work was "inaccurate and paradoxical." Kumar earned his first retraction last year, in Springer Nature’s Scientific Reports; two more followed in March in Wiley’s Global Challenges.

An October 9 notice announcing the retraction of "A closed-form analytical model for predicting 3D boundary layer displacement thickness for the validation of viscous flow solvers" stated: "Following publication, questions were raised regarding the soundness of the analytical model presented in the manuscript. Upon further investigation, the Editors of AIP Advances concluded that the model is flawed. The investigation revealed that the core model is inaccurate and paradoxical because it falsely ignores entropy increases in choked flows and combines two incompatible theories." 

The researcher claims his ideas represent a "paradigm shift" and have applications in a wide range of fields and diseases. He has threatened legal action against editors and publishers for pulling his work, which he asserts could help protect "millions of lives".