Conventions

Common variable names

This package uses standard variable names throughout for consistency:

• w represents phase-space coordinates (positions and velocities)

• q represents positions only

• p or v represent velocities or momenta

• t represents time arrays

Array shapes

Arrays and Quantity objects in Gala follow consistent shape conventions:

Coordinate arrays: axis=0 is the coordinate dimension. For example, 128 different 3D Cartesian positions have shape (3, 128).

Orbit collections: Arrays have three axes: - axis=0: coordinate dimension - axis=1: time axis - axis=2: different orbits

Energy and momentum

In gala, energy and angular momentum quantities are per unit mass unless otherwise specified. This applies to:

• Potential energy

• Kinetic energy

• Total energy

• Angular momentum

• Linear momentum

• Conjugate momenta