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Guru Kalyan Jayasingh
Graduate student at UC San Diego; statistical mechanics & turbulence.
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Posts
publications
Tricritical Directed Percolation Controls the Laminar-Turbulent Transition in Pipes with Body Forces
Published in Physical Review Letters, 2025
Transition to turbulence in shear flows has been established to be a non-equilibrium phase transition. Body forces can make the transition discontinuous. Observed phenomenology can be explained by a new tricritical point near transition, enriching the phase diagram of transitional turbulence.
Recommended citation: Guru K. Jayasingh and Nigel Goldenfeld, Tricritical directed percolation controls the laminar–turbulent transition in pipes with body forces, Phys. Rev. Lett. 135, 104001 (2025). doi:10.1103/PhysRevLett.135.104001 https://doi.org/10.1103/46g3-n7cx
May’s Complexity-Stability Hypothesis in Neural Networks
Published in In Preparation, 2026
May’s 1972 theorem establishes that sufficiently complex random systems are generically unstable, yet evolved ecosystems systematically violate this prediction through structural mechanisms that natural selection has had billions of years to build. This project investigates whether neural networks, as another class of optimized systems, develop analogous stabilizing structure, or remain in the random-matrix regime, and what properties of the optimization process determine the difference.
Universality class of turbulent transitions in stably stratified flows
Published in In Preparation, 2026
In geophysical shear flows, ocean thermoclines, atmospheric boundary layers, stable density stratification suppresses vertical motion and competes with shear-driven turbulence, controlling whether turbulence is sustained or collapses to a laminar state. The laminar-turbulent transition in unstratified shear flow is now understood as a directed percolation (DP) phase transition: the turbulent fraction vanishes continuously at a critical Reynolds number with universal scaling exponents. Whether stratification shifts this critical point, modifies the exponents, or drives the transition into a different universality class entirely is an open question with both fundamental and geophysical significance.
talks
Laminar-turbulent transition in pipes with body forces: continuous, discontinuous or both?
Published:
The laminar-turbulent transition in straight pipes is believed to occur through a continuous non-equilibrium phase transition in the directed percolation universality class. However, in curved pipes or in the presence of body forces it is possible to observe a discontinuous transition and other phenomenology which seem inconsistent with the emerging consensus. Here, we consider the perturbing effects of body forces and incorporate them into a minimal Landau theory of the transition. We calculate the phase diagram as a function of Reynolds number and body force strength, and show that above a threshold strength of the latter, there is a tricritical point which accounts for the observed discontinuity behavior, including spatially heterogeneous states. Our results are consistent with recent experiments in centrifugal pipes and direct numerical simulations of heated flows.
Tricritical Directed Percolation and Transitional Turbulence
Published:
This talk explores how body forces alter the canonical picture of the laminar–turbulent transition in pipe flow. By extending the standard framework of directed percolation to include external forcing, we identify a tricritical regime that interpolates between continuous and discontinuous transitions. The resulting phase diagram reveals how sufficiently strong body forces induce metastability, coexistence, and relaminarization—features observed in curved and centrifugal pipes. The analysis provides a unifying theoretical basis for diverse experimental and numerical observations of forced transitional turbulence.
teaching
At Indian Institute of Technology Bombay
Undergraduate + Graduate courses, In person and Online, 2019
During my time at IIT Bombay, I served as a Teaching Assistant across multiple core and advanced physics courses:
At University of San Diego California
Undergraduate and Graduate courses, UCSD, Dept. of Physics, 2022
At UC San Diego, I have contributed to the Department of Physics’ teaching mission by supporting both graduate and undergraduate courses. A few of the courses include: