Weekly Summer Series

Complex Systems Seminar

in collaboration with Complex Systems Society

When: Each week, Wednesday 3:30 pm

Where: Online

Who can speak: Anyone working on broad areas of nonlinear dynamics and complex systems

Meeting ID: 863 8652 6003, Passcode: 386307

The Speakers

  1. Prof. Lakshmanan (Bharathidasan University)

Title: Collective Dynamical States in Networks of Stuart - Landau Oscillators for Different Couplings and Interactions

Abstract: A large number of nonlinear oscillators exhibiting Hopf bifurcation can be represented approximately by Stuart - Landau oscillators. In this talk I will discuss the possible collective dynamical states in arrays of SL oscillators under different couplings, namely global, nonlocal and local couplings. Considering different types of interactions, including symmetry preserving, symmetry breaking, long range, nonlinear and environmental types, a wide variety of states such as synchronized/desynchronized and swing of synchronized states, chimeras of different types, cluster states, various death states (amplitude/oscillatory and chimera), bifurcation induced tipping to aging, travelling waves, solitary states and so on and their transitions will be briefly discussed. The resultant states are essentially characterised by statistical measures such as strength of incoherence and discontinuity measure. Some open problems will be indicated.

Date and Time: June 23, 2021 at 3:30 PM


2. Dr. Shamik Gupta (Ramakrishna Mission Vivekananda University, Belur Math, WB)

Title: Spontaneous Synchronization in Delay-coupled Nonlinear Dynamical Systems

Abstract:In the context of a paradigmatic nonlinear dynamical system of coupled oscillators with distributed natural frequencies and interacting through a time-delayed mean-field, we derive as a function of the delay exact results for the stability boundary between the incoherent and the synchronized state and the nature in which the latter bifurcates from the former at the critical point. Our results are based on an unstable manifold expansion in the vicinity of the bifurcation, which we apply to both the kinetic equation for the single-oscillator distribution function in the case of a generic frequency distribution and, in the special case of a Lorentzian distribution, to the corresponding reduced dynamics on a special manifold in the space of all possible distribution functions. Besides elucidating the effects of delay on the nature of bifurcation, we show that the reduced dynamics gives an amplitude evolution of unstable modes close to the bifurcation that remarkably coincides with the one derived from the kinetic equation. The manifold thus acts as an attractor in the space of distribution functions. Such an attracting property has parallel in integrable systems as well in certain nonlinear dynamical systems, albeit with a difference: in these cases, the attracting manifold exists in the phase space of the system, while we go beyond this picture in showing the existence of such an attracting manifold in the space of distribution functions. We have demonstrated the validity of such a dynamical scenario in other systems, e.g., in a network of phase-locked loops widely used in electronic circuits, as well as in a system of coupled nonlinear oscillators with both a mean-field and a non-local interaction on a one-dimensional periodic lattice.

Date: 30th June, 2021 at 3:30 pm


3. Prof. Syamal K. Dana (Jadavpur University)

Title: Extreme events in dynamical systems

Abstract: Extreme events are recurrent large events, quite often seen as natural calamities with devastating effects on humans, infrastructures and economy. Common life experiences are earthquake, tsunamis, floods, cyclones and power blackout and share market crashes. A systematic study on the topic becomes a necessity and urgent for the purpose of predicting the time of occurrence of a forthcoming extreme event so that a timely measure can be undertaken ahead of time to mitigate a disaster. A time series analysis of recorded data of rainfall, floods, earthquakes has been continued since long to derive statistical theories on extreme events. A recent trend of research has started in the last 15 years and so to investigate extreme events in nonlinear dynamical systems. Extreme events are seen here as highly irregular large amplitude events while the system remains quiet, most of the time, in a sense that it produces only low amplitude events. I will tell the stories on how extreme events occur in various dynamical systems and their mechanisms of origin as understood from the past studies.

Date: 7th July, 2021 at 3:30 pm


4. Richa Phogat (PhD scholar, IIT Bombay)

Title: Perturbation reverberations in macroscopic network observables

Abstract: Echo is an emerging system behaviour wherein two perturbations applied to a network lead to a change in a macroscopic system observable. A similar but unperturbed change in this system observable following these two perturbations is termed as an echo. We explore the effect of network randomness and degree on this echo behaviour1. Following this, we explore the long term effects of a single perturbation on the same system observable.

Date: July 14, 2021 at 3:30 pm

5. Sayantan Nag Chowdhury (PhD Scholar, ISI Kolkata)

Title: Eco-Evolutionary game theory dynamics

Abstract: The emergence and abundance of cooperation in the context of the Darwinian theory of evolution pose a challenge to date. To overcome this formidable challenge, scientists often resort to Evolutionary Game Theory as a common mathematical framework, and games such as the prisoner’s dilemma and the snowdrift game as metaphors for studying cooperation between unrelated individuals. On the other hand, the concurrence of ecological and evolutionary processes often arises as an integral part of various biological and social systems. Studying a mathematical model that considers both holds promise of insightful discoveries related to the dynamics of cooperation. We upgrade the contemporary multigame by introducing punishment as an additional strategy in addition to the traditional cooperators and defectors. Punishers bear an additional cost from their own resources to try and discourage or prohibit free-riding from selfish defectors. We also incorporate the ecological signature of free space, which has an altruistic-like impact because it allows others to replicate and potentially thrive. I will discuss how this proposed model can offer the individual dominance of cooperators and defectors as well as a plethora of mixed states, where different strategies coexist, followed by maintaining the diversity in a socio-ecological framework. In particular, our model reports the simultaneous presence of different subpopulations through the spontaneous emergence of cyclic dominance, and we determine various stationary points using traditional game-theoretic concepts and stability analysis.

Date: July 21, 2021 at 3:30 pm


6. Dr. Nikita Frolov (Innopolis University, Russia)

Title: Multiplex networks: from emergent dynamics to brain graphs

Abstract: In this talk, I will give an introduction to the concept of multiplex graphs and their relevance in modeling of real networked systems. Along with this introductory part, I will present the recent results on multilayer graphs' dynamics and construction of multiplex brain networks. Our results indicate that multiplex networks demonstrate a variety of dynamical behaviors and facilitate our knowledge on neurodynamics.

Date: July 28, 2021 at 3:30 pm

7. Dr. Ana Teixeira de Melo (Centre for Social Studies, University of Coimbra, Portugal)

Title: How complex is your thinking? Challenging complexity in complexity science

Abstract: The field of Complexity Studies brought about a significant paradigmatic change in Science, contributing to new constructions about the nature of reality and how we know it. Difficult theoretical and methodological challenges have been embraced. Complexity Science(s) has been developing in different domains of knowledge with important implications to how we think, conceptualise and participate in the world, as scientists as well as practitioners and intervenors. But the most difficult challenge of all pertains to the transformation of our modes of thinking which need to not only attend to Complexity features but also embrace and even perform complexity in our coupling with the world, leading to theoretical, methodological and practical novelty in our understanding of the world and capacity to manage change. Edgar Morin has called attention to the implications of a Complexity paradigm in terms of the need to conceptualise the role of the observer in the weaving of Complexity and to change our modes of thinking. Morin distinguished between a ‘restricted’ and a ‘general’ complexity approach where the former fully embraces those implications. In other studies, a distinction was drawn in the literature between studies that refer to complexity thinking or complex systems at the level of the contents of the thinking and those which conceptualise complexity or complex thinking as a process that is commensurate with the processes organising complexity. The key question is: to what extent do complexity scientists truly embrace complexity at the level of their modes of thinking and to what extent is their science truly complex? To what extent is the thinking that organises research in the domains of complexity organisationally congruent with the principles of its target systems and phenomena? This presentation will explore a new theoretical framework attempting to contribute to the operationalisation of complex thinking in different dimensions and properties. It will explore the challenges it raises and its implications for the development of indicators, tools and strategies to promote and to manage the complexity of the thinking in the unfolding of research processes as well as in the design and implementation of interventions targeting ‘real-world’ social and ecological systems.

Date: 4th August, 2021 at 3:30 pm

8. Dr. Pinaki Pal (NIT Durgapur)

Title: Convective patterns and low dimensional modelling

Abstract:Rayleigh-Bénard convection (RBC) of low Prandtl number fluids exhibits a plethora of patterns near the onset of convection. Numerous theoretical as well as experimental works have been performed by the researchers to understand the origin of these patterns, yet the investigation is far from complete. Along with the experimental works and numerical simulations, low dimensional modeling plays an important role in the investigation of these patterns. In the talk I’ll discuss the origin of some of the interesting stationary and time dependent fluid patterns observed near the onset of RBC with the help of some low dimensional models derived from the direct numerical simulations data.

Date: August 11, 2021

9. Vasundhara Rathore (PhD Scholar, IITIndore)

Title: Inhibition induced Explosive synchronization in multilayer networks

Abstract: Inhibitory couplings are crucial for the normal functioning of many real-world complex systems. Inhibition in one layer has been shown to induce explosive synchronization in another positive layer of duplex networks. By extending this framework to multiplex networks, this article shows that inhibition in a single layer can act as a catalyst, leading to explosive synchronization transitions in the rest of the layers feed-forwarded through intermediate layer(s). Considering a layer with inhibitory couplings in multiplex networks of Kuramoto oscillators, we demonstrate that the characteristics of the transition emergent in the other layers can be entirely controlled by the multiplexing and intra-layer coupling strengths of the multiplex networks. The results presented here are important to fathom the synchronization behaviour of coupled dynamical units in multilayer systems possessing inhibitory coupling in one of its layers, representing the importance of multiplexing.

Date: August 18, 2021

10. Dr. Manaoj Aravind (IIT Bombay)

Title: Competitive interplay of Noise and Coupling.

Abstract: While most research efforts have focused on the constructive effect of noise in aiding synchronization of coupled nonlinear systems, we recently explored systems coupled through repulsive interactions that may oppose the effect of noise, and we present the new implications of this competitive interplay of noise and coupling. The test-bed of our study are prototypical repulsively coupled bistable systems, subject to noises with different degrees of cross-correlation. This allows us to explore the nontrivial interaction between repulsive coupling and noise, as well as ascertain the role of noise correlation in the synchronization of such noise driven subsystems. We find that this model exhibits a rich variety of behaviour including complete synchrony, complete anti-synchrony and a unique regime with windows of synchrony interspersed with anti-synchrony. All the observations were ascertained using electronic circuit experiments. In this talk I will present the results and implications of this work in detail.

Date: August 25, 2021

11. Speaker: Dr. Ganesh Bagler (IIIT Delhi)

Title: Computational Gastronomy: A complex systems approach to food and cuisines

Abstract: Cooking forms the core of our cultural identity other than being the basis of nutrition and health. The increasing availability of culinary data and the advent of computational methods for their scrutiny are dramatically changing the artistic outlook towards gastronomy. Starting with a seemingly simple question, ‘Why do we eat what we eat?’ data-driven research conducted in our lab has led to interesting explorations of regional cuisines, recipes, their flavor composition, and health associations. Our investigations have revealed ‘culinary fingerprints’ of regional cuisines across the world. Application of data-driven strategies for investigating the gastronomic data has opened up exciting avenues giving rise to an all-new field of ‘Computational Gastronomy’. This emerging interdisciplinary science asks questions of culinary origin to seek their answers via the compilation of culinary data and their analysis using methods of complex systems, network science, and artificial intelligence. Along with complementary experimental studies, these endeavors have the potential to transform the food landscape by effectively leveraging data-driven food innovations for better health and nutrition.

Date: September 01, 2021

12. Speaker: Dr. Priodyuti Pradhan (Bar-Ilan University)

Title. Understanding Information Localization: Linear to Nonlinear Network Dynamics

Abstract. Networks provide a powerful framework to understand and predict complex real-world systems', modeling them in terms of interacting units. However, such mapping of network structure is merely the first step. To advance, we wish to translate the network map into a predictive framework to track the patterns of information flow between all components. One key factor in this flow is Localization -- the tendency of information to condense in one or few network components vs. the alternative, where information diffuses evenly throughout the network. To predict this, we consider an arbitrary initial pattern of signals spread throughout the networks and seek its eventual long term outcome: will the information diffuse and spread to all the nodes, hence lose coherence, or will it localize in one or several regions, thus converging into a coherent collective signal. We uncover meaningful structural and dynamical patterns in the linear and nonlinear network dynamics. Specifically, we plan to use different dynamical models to understand the information flow patterns.

Date: September 08, 2021


Organizers: dibakar@isical.ac.in, sarika@iiti.ac.in, malayb@iitk.ac.in, shrimali@curaj.ac.in