A-Z

CCI

Center for Complex Interactions

The purpose of CCI is to advance fundamental understanding, prediction, and steering of nonlinear, feedback-driven complex interactions in physical, biological, and engineered systems such as those arising between laser fields and matter, in order to enable the creation and control of emergent structures, states, and dynamics across scales in matter and fields alike.

For this purpose, the CCI brings together researchers from physics, engineering, chemistry, and related disciplines to explore how complex interactions can be harnessed for the development of new materials, fabrication processes, and technologies. CCI aims to serve as a platform for large collaborative research initiatives connecting researchers at Ruhr University Bochum and partner institutions within the University Alliance Ruhr and beyond.

News
  • 13.04.2026: The Rectorate of Ruhr University Bochum has approved the establishment of CCI.

Research Themes

The unifying scientific goal of the Center for Complex Interactions, CCI, is to achieve a deeper understanding of the basic principles of emergence through complex interactions, and to harness complexity to develop predictive, controllable, and ultimately programmable approaches for creating materials and structures through emergent processes.

Across nature, from atomic to macroscopic scales, such emergent organization is ubiquitous, yet its governing principles remain only partially understood. In such processes, driven by nonlinear feedback and evolving far from equilibrium, the cumulative action of many individually simple steps produces outcomes that are qualitatively different from those of any single step.

The specific mechanism is secondary; what matters is the nature of the interaction and its evolution under repeated application. This is an inherently multiscale perspective, applicable from the atomic to macroscopic scales; it enables the creation of materials with adaptive, self-healing, and otherwise inaccessible functionalities. CCI is rooted in this basic-science perspective while pursuing pathways towards practical realization and technological impact.

Fundamental Principles of Emergence

Theoretical approaches to understanding and harnessing complex interactions are multidisciplinary, drawing on concepts and techniques from nonlinear and non-equilibrium statistical physics, control theory, and machine learning.

Understanding the universal mechanisms by which complex interactions give rise to emergent structures, states, and dynamics across scales. This includes the role of nonlinearity, feedback, fluctuations, and non-equilibrium conditions in shaping organized complexity in physical, biological, and engineered systems. By combining approaches from non-equilibrium statistical physics and nonlinear dynamics, we ask questions such as how a nonlinear and strongly stochastic system with access to multiple states selects among them, and why.

Fig.: Theoretical approaches to understanding and harnessing complex interactions are multidisciplinary, drawing on concepts and techniques from nonlinear and non-equilibrium statistical physics, control theory, and machine learning.

Programmable Emergent Materials

Laser pulses repeatedly interact with a material surface. Each pulse nonlinearly induces nanoscale modifications that alter the response of the surface to the subsequent pulses, creating an intrinsic nonlinear feedback that iteratively builds a complex macroscopic pattern, controlled via only a small number of external parameters.

Understanding and harnessing complex interactions to create emergent atomic- to micro-scale structures and functionalities that are not accessible through linear or equilibrium processes. Such outcomes often arise when a process step nonlinearly modifies a material, thereby changing its response to subsequent iterations, so that repeated applications yield qualitatively new outcomes. We further seek to understand how to achieve desired emergent characteristics by controlling a small set of external parameters along non-equilibrium pathways across temporal, spatial, and energy scales.

Fig.: Laser pulses repeatedly interact with a material surface. Each pulse nonlinearly induces nanoscale modifications that alter the response of the surface to the subsequent pulses, creating an intrinsic nonlinear feedback that iteratively builds a complex macroscopic pattern, controlled via only a small number of external parameters. Figure taken from: https://arxiv.org/abs/2503.23474

Predictive Modelling and Steering of Emergence

Phase space representation of how an emergent system is steered from an initial operating state to a new one. First, the system is pushed out of its existing operating point (i.e., the existing point is destabilized), then guided toward a new region in its phase space, and finally allowed to converge to a new state. Here, λ's represent control parameters, and x* denotes the system state.

Developing methods to understand how emergent structures or properties arise spontaneously from system dynamics rather than being externally imposed, and how combinations of properties traditionally considered mutually exclusive can be achieved. We aim to enable predictive steering of such systems between macroscopic states and to identify the order parameters governing transitions between them under uncertainty and stochastic perturbations. We integrate complex systems theory with approaches such as control theory, scientific machine learning, and data-driven modelling.

Fig.: Phase space representation of how an emergent system is steered from an initial operating state to a new one. First, the system is pushed out of its existing operating point (i.e., the existing point is destabilized), then guided toward a new region in its phase space, and finally allowed to converge to a new state. Here, λ's represent control parameters, and x* denotes the system state. Figures taken from: https://arxiv.org/abs/2510.05344

Path-Dependent Production Systems

Photograph of a typical laser-material processing setup, where a high-speed scanner controls the interaction point of the laser on the material.

When nonlinear feedback plays a role, fabrication systems and the structures they create can co-evolve, and final outcomes cannot be reduced to isolated process steps. Instead, each processing step modifies the state of the product in ways that influence subsequent steps, leading to path-dependent outcomes, non-stationary system characteristics, and emergent macroscopic properties arising from locally controlled micro- or mesostructures. Rather than suppressing these effects, our goal is to understand and exploit them to enable controlled emergence in manufacturing, leading to improved performance, reliability, resource efficiency, and first-time-right production.

Fig.: Photograph of a typical laser-material processing setup, where a high-speed scanner controls the interaction point of the laser on the material.

Complex Fields and Laser-Matter Interactions

Using state-of-the-art experimental platforms, we investigate how complex fields and matter interact through nonlinear feedback to produce new structures and functionalities. In particular, ultrafast laser–matter interactions offer unique advantages in this effort: laser fields enable precise spatial and temporal control, can universally induce nonlinear responses in a wide range of materials, and drive systems far from equilibrium. This makes them exceptionally suited for studying and harnessing feedback-driven dynamics. At the same time, complementary approaches, including plasma, electrical, mechanical, and chemical processes, provide additional pathways to access and control complex interactions beyond lasers.

Members

Scientific Members

  • Prof. Dr. F. Ömer Ilday

    Founding director
    Faculty of Electrical Engineering and Information Technology
    Faculty of Physics & Astronomy
    Ruhr University Bochum

The establishment of CCI follows the structural vision associated with the Alexander von Humboldt Professorship award of Prof. F. Ömer Ilday at Ruhr University Bochum.

  • Prof. Dr. Serim Ilday

    Faculty of Electrical Engineering and Information Technology
    Faculty of Physics & Astronomy
    Ruhr University Bochum

About / Structure

CCI is guided by the pursuit of scientific excellence according to the highest international standards. The Center promotes conceptual innovation, interdisciplinary collaboration, and high-risk research directions. Knowledge transfer and technological impact are regarded as natural extensions of its scientific mission.

Founding Phase

CCI is established in a Founding Phase, time-limited to six years, with the explicit objective of creating a robust scientific identity, governance culture, and international visibility. During this phase, priority is given to the development of the Center’s intellectual and organisational structure.

Governance Concept

All governance of CCI is guided by the pursuit of scientific excellence as the overriding criterion, together with the motto of “Built to Change,” with an adaptive governance concept, a deeply rooted international, diverse, and inclusive perspective. Reflecting the latter, the Founding Director and all Co-Directors will serve only a single term, periodically renewing leadership, and each Co-Director is expected to introduce and articulate a new thematic scientific focus during their terms.

Advisory Board

To be announced

Contact

Center for Complex Interactions (CCI)
Ruhr-Universität Bochum
ID Building – Room E1-340
Universitätsstraße 150
44801 Bochum
Germany

Phone: (+49)(0)234 / 32 - 27645

Email: cci(at)ruhr-uni-bochum.de

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