The frequency response of networks as open systems

Area of Science:

• Systems biology
• Network science
• Control theory

Background:

• Complex systems are often modeled as networks of interacting subsystems.
• These networks interact with their environment via input and output nodes.
• Understanding signal propagation through networks is crucial for system analysis.

Purpose of the Study:

• To quantify how network structure and node selection influence signal amplification or blocking.
• To investigate whether natural and engineered systems differ in their signal propagation characteristics.

Main Methods:

• Utilized the H2-norm to quantify signal amplification in networks.
• Analyzed diverse empirical networks, including biological, technological, and social systems.
• Compared signal propagation properties across different network types.

Main Results:

• Naturally occurring systems (food webs, signaling pathways, gene regulatory circuits) are structured to enhance signal passing.
• Engineered systems (power grids) are designed to suppress signal propagation.
• The H2-norm effectively quantifies the extent of signal amplification regardless of signal type.

Conclusions:

• Network architecture plays a critical role in modulating signal flow.
• Biological and engineered systems exhibit contrasting strategies for signal propagation.
• Findings have implications for designing robust and efficient complex systems.