Recurrence condensation during critical transitions in complex systems.

Critical transitions in complex systems pose challenges for the healthy functioning of natural and engineered systems, sometimes with catastrophic outcomes. These critical points, where small changes cause large regime shifts, are difficult to detect-especially in noisy, high-dimensional settings. We investigate such a transition from chaotic to periodic oscillations via intermittency in a turbulent fluid mechanical system by using recurrence analysis.

Early warnings are too late when parameters change rapidly.

Tipping (or sudden transition) from a desirable state to an undesirable one can result in catastrophic changes, affecting natural environments, human societies and economies. Early warning signals (EWSs) are developed to forewarn such an impending tipping. However, when control parameters are varied fast, we observe that EWSs detect an impending tipping past bifurcation points; this questions the applicability of EWSs in preventing tipping.

Nonmonotonic emergence of order from chaos in turbulent thermoacoustic fluid systems.

Self-sustained order can emerge in complex systems due to internal feedback between coupled subsystems. Here, we present our discovery of a nonmonotonic emergence of order amidst chaos in a turbulent thermoacoustic fluid system. Fluctuations play a vital role in determining the dynamical state and transitions in a system.

On the nature of nonequilibrium phase transition in a complex system.

The transition from a chaotic to a periodic oscillatory state can be smooth or abrupt in real-world complex systems. We study smooth and abrupt transitions in a turbulent reactive flow system. The turbulent reactive flow system consists of the flame, the acoustic field, and the hydrodynamic field interacting nonlinearly.

The circular movement of synchronous extreme precipitation preceding Kerala floods in 2018 and 2019.

In 2018 and 2019, Kerala, the southernmost state in India, experienced extreme precipitation, leading to appallingly devastating floods that damaged life and property. Kerala is vulnerable to flooding due to its topography, geographical location, and meteorology. Several phenomena have been attributed to these extreme precipitations; however, no single explanation suffices to explain such complex climate phenomena.