Left to Their Own Devices, Pricing Algorithms Resort to Collusion

So if they don't communicate with each other, what makes it collusion? How is collusion defined here, and what are the algorithms actually doing?

Surely it takes more than just "not getting into a price war" to call it collusion.

But if the sellers don't communicate about prices, then it's not illegal collusion, right?

Nash equilibrium rediscovered?

Don't tell the folks in compliance that. They won't be happy until margins are negative and no one has a job--including themselves.