Chimera States: From Theory and Experiments to Technology and Living Systems

One of the pillars of modern physics is the concept of symmetries. Spontaneously breaking such symmetries typically gives rise to non-trivial phenomena and can explain, for example, why particles have mass. The occurrence of such symmetry-breaking phenomena is not limited to particle physics but occurs across a wide range of physical, chemical and biological systems. Recently discovered examples include chimera states. Chimera states are hybrid states characterized by the coexistence of localized synchronized and unsynchronized dynamics in a given system. Indeed, the name chimera is used here in direct analogy to the hybrid creature in Greek mythology. Such coexisting behavior can even occur in a homogeneous system, thus breaking the underlying symmetry — something that was long thought to be impossible. While over the last 20 years a significant theoretical understanding of this phenomenon has started to emerge, experimental realizations remain scarce and the relevance of the phenomenon in technology and in nature remains to be established – leaving many challenges and fundamental issues to be addressed.

Chimer22 targeted many of these questions. These included but were not restricted to:
1. Do chimera states control biological and/or cognitive functions?
2. Do chimera states play any significant role in natural biochemical mechanisms?
3. In which natural or experimental systems does an effective nonlocal coupling naturally arise?
4. Do chimera states exist all the way down to the quantum scale?
5. What technological advantages do chimera states offer?
6. Which experimental systems are most promising to study chimera states in three dimensions?
7. How can we establish the existence of chimera states in continuum systems experimentally?

Chimer22 invited 23 outstanding experts in this area of research from all over the world, of whom 16 participated in person. To name only a few of the key attendees, who contributed to the big success of Chimer22 by triggering and facilitating discussions and new collaborations, we list:
(a) Rajarshi Roy: Coherence, Chimeras and Passage Time Statistics in Light,
(b) Katharina Krischer: Chimera states, coexistence patterns and multifrequency clusters in systems of nonlinearly coupled amplitude oscillators,
(c) Ying-Cheng Lai: Chaos in Dirac electron optics: Emergence of a relativistic quantum chimera,
(d) Christoph Bruder: Quantum synchronization,
(e) Kanika Bansal: Chimera states in human brain network models,
(f) István Z. Kiss: Weak Chimera States in Modular Electrochemical Oscillator Networks,
(g) Eckehard Schöll: Controlling chimera states in complex networks: interplay of dynamics, network topology, and time delay,
(h) Erik A. Martens: On the Origin of Chimera States in Mechanical Systems.

In particular, young investigators and researcher from related disciplines were given the chance to present their work, which included a successful poster session. Several discussions and new collaborations were facilitated through this. Overall, Chimer22 had 74 registered participants with 44 on-site participants incl. 2 organizers from Germany, Canada, Hungary, Poland, Singapore, the US, Ukraine, Switzerland, Sweden, Japan and India and 30 virtual participants from 16 countries incl. New Zealand, Australia, Cameroon, Korea, Canada, India to name a few.
Out of the 42 talks, 10 were presented virtually and 32 in person.

The key scientific result of Chimer22 is most certainly the various novel collaborations that emerged from the in depth in-person discussions. These collaborations will result in various publications and research grants. Already during the workshop, researchers that had not worked together joint forces to tackle some of the challenges mentioned above. A forthcoming Focus Issue in the journal Chaos will cover the topics of Chimer22 and include papers by leading scientists participating in the workshop.