How reciprocity impacts ordering and phase separation in active nematics?

Area of Science:

• Soft Matter Physics
• Active Matter Systems
• Non-equilibrium Thermodynamics

Background:

• Active nematics exhibit spontaneous symmetry breaking and phase separation.
• Macroscopic properties are often assumed to depend solely on symmetry and conservation laws.
• Microscopic model choice is typically based on convenience rather than fundamental differences.

Purpose of the Study:

• To investigate the impact of microscopic interaction details on the phase behavior of active nematics.
• To determine if different microscopic realizations of apolar active nematics, sharing the same symmetry, lead to distinct ordering transitions.
• To test the prevailing notion that macroscopic properties are independent of microscopic model specifics.

Main Methods:

• Analysis of three distinct microscopic models for apolar active nematics.
• Models share identical symmetry but vary in reciprocal and non-reciprocal interaction implementations.
• Inclusion of a Vicsek-like model for comparative analysis.

Main Results:

• Subtle differences in microscopic interactions dictate whether the ordering transition is continuous or first-order.
• All investigated models demonstrate fluctuation-dominated phase separation.
• Quasi-long-range order is observed in the nematic phase across all models, irrespective of transition type.

Conclusions:

• Microscopic details are crucial in determining the nature of ordering transitions in active nematics.
• The choice of microscopic model, even with shared symmetry, significantly impacts system behavior.
• Active nematic systems consistently exhibit phase separation and quasi-long-range order, highlighting universal features despite microscopic variations.