Dark matter?

The Core Question: about rotation curves and emergent properties in galaxies

We derive the expected rotation curve of galaxies from Keplerian mechanics, as measured in our solar system: one dominant central mass (the Sun: 99.86%) and eight relatively small objects (planets: 0.14%).

A galaxy, however, is fundamentally different: billions of equivalent masses in a distributed network, without clear hierarchy. With such an extreme scale change—from a 1+8 system to a system with billions×billions of interactions—I wonder:

Is it possible that emergent properties arise that cannot be predicted by simple extrapolation of Keplerian mechanics?

My Reasoning:

With a gradual velocity gradient (from v₁ at the center to v₂ at the edge) and billions of stars, the velocity difference between neighboring stars is negligibly small. This suggests the system behaves as a coherent, self-correcting "fluid" with properties including:

1.  Cohesion: Stars maintain a coherent mass through mutual gravity
2.  Self-correction: The 360° nature of gravity automatically compensates local perturbations through surrounding stars
3.  Statistical stability: Billions of stars provide inherent network stability
4.  Collective behavior: The system may exhibit properties unpredictable from individual components

So the question is: 

-   Are galaxies modeled in N-body simulations as emergent, self-correcting systems with collective behavior?
-   Or are they calculated as collections of individual Keplerian trajectories?
-   Could non-linear effects or emergent phenomena—like those in fluid dynamics (turbulence, resonances)—contribute to the flat rotation curve at galactic scales?