Universe¶

class universe

The universe is a top level singleton object, and is automatically initialized when the simulator loads. The universe is a representation of the physical universe that we are simulating, and is the repository for all physical object representations.

All properties and methods on the universe are static, and you never actually instantiate a universe.

Universe has a variety of properties such as boundary conditions, and stores all the physical objects such as particles, bonds, potentials, etc..

static bind(thing, a, b)¶

kinetic_energy¶

A read-only attribute that returns the total kinetic energy of the system

Type:	double

dt¶

Get the main simulation time step.

Type:	double

time¶: Get the current simulation time

temperature¶

Get / set the universe temperature.

The universe can be run with, or without a thermostat. With a thermostat, getting / setting the temperature changes the temperature that the thermostat will try to keep the universe at. When the universe is run without a thermostat, reading the temperature returns the computed universe temp, but attempting to set the temperature yields an error.

boltzmann_constant¶: Get / set the Boltzmann constant, used to convert average kinetic energy to temperature

static particles()¶

List of all the particles in the universe. A particle can be removed from the universe using the standard python del syntax

del universe.particles()[23]

Type:	list

dim¶

Get / set the size of the universe, this is a length 3 list of floats. Currently we can only read the size, but want to enable changing universe size.

Type:	Vector3

static start()¶: Starts the universe time evolution, and advanced the universe forward by timesteps in dt. All methods to build and manipulate universe objects are valid whether the universe time evolution is running or stopped.

static stop()¶: Stops the universe time evolution. This essentially freezes the universe, everything remains the same, except time no longer moves forward.

static step(until=None, dt=None)¶

Performs a single time step dt of the universe if no arguments are given. Optionally runs until until, and can use a different timestep of dt.

Parameters:	until – runs the timestep for this length of time, optional. dt – overrides the existing time step, and uses this value for time stepping, optional.

static grid(shape)¶

Gets a three-dimesional array of particle lists, of all the particles in the system. Each

Parameters:	shape – (length 3 array), list of how many grids we want in the x, y, z directions. Minimum is [1, 1, 1], which will return a array with a single list of all particles.

static virial([origin][, radius][, types])¶

Computes the Virial Tensor for the either the entire simulation domain, or a specific local virial tensor at a location and radius. Optionally can accept a list of particle types to restrict the virial calculation for specify types.

Parameters:	origin – An optional length-3 array for the origin. Defaults to the center of the simulation domain if not given. radius – An optional number specifying the size of the region to compute the virial tensor for. Defaults to the entire simulation domain. types – An optional list of `Particle` types to include in the calculation. Defaults to every particle type.