Signatures of directed and spontaneous flocking

Area of Science:

• Physics of complex systems
• Biological physics
• Statistical mechanics

Background:

• Collective motion, or flocking, is a fundamental emergent phenomenon in biological systems, crucial for processes ranging from cellular migration to animal group behavior.
• Understanding the underlying dynamics of collective movement is essential for interpreting biological processes in both natural and experimental settings.

Purpose of the Study:

• To derive novel scaling relations for fluctuations in collective motion under external fields.
• To establish two distinct, complementary criteria for detecting directed collective motion using dynamical and static signatures.
• To provide methods for identifying purposeful movement without direct correlation to environmental cues.

Main Methods:

• Derivation of scaling relations for the fluctuations of the mean direction of motion.
• Analysis of the static density structure factor to capture static density fluctuations.
• Formulation of criteria based on measurable dynamical and static signatures of collective dynamics.

Main Results:

• Successfully derived scaling relations for key fluctuation measures in the presence of a homogeneous external field.
• Developed two criteria: a static criterion effective in large systems and a dynamical criterion requiring long observation times.
• Demonstrated that these criteria can detect directed motion solely from internal collective dynamics.

Conclusions:

• The derived criteria offer a robust way to detect directed collective motion using easily measurable signatures.
• These methods are particularly valuable for analyzing in vivo experimental data where environments are complex and uncontrolled.
• The findings provide powerful tools for confirming or discovering directed collective motion in diverse biological systems.