Jammed Keplerian gas leads to the formation and disappearance of spiral arms in a coupled map lattice for astronomical objects

TL;DR

This paper models the formation and disappearance of spiral arms in astronomical objects as traffic jams in a coupled map lattice, introducing a new method to evaluate their lifetime based on gas flow rates.

Contribution

It presents a novel traffic jam analogy for spiral arms, introduces the 'light-in and heavy-out' method for their disappearance, and derives an approximate formula for their remaining lifetime.

Findings

The spiral arms behave like traffic jams governed by gas flow.

The 'light-in and heavy-out' method effectively predicts spiral arm disappearance.

The lifetime formula matches simulation results accurately.

Abstract

The formation and disappearance of spiral arms are studied by focusing on jammed Keplerian gas in a coupled map lattice (CML) with a minimal set of procedures for simulating diverse patterns in astronomical objects. The CML shows that a spiral arm is a type of traffic jam, and its motion is governed by both a gas inflow into and outflow from the jam. In particular, we present a new approach to simply and directly evaluating the disappearance of spiral arms, called "light-in and heavy-out". It is based on the gas flow rate difference between the light inflow and heavy outflow leading to the disappearance of traffic jams. Furthermore, we propose an approximate formula for the remaining lifetime of spiral arms, which is immediately derived from the "light-in and heavy-out" approach without calculating their pattern speeds as in conventional differential rotation. The proposed formula is successfully applied to the CML simulations.