SCSC2003 Abstract S7725

Simulating General Relativity

Simulating General Relativity

Submitting Author: Prof. Stanislaw Raczynski

Some examples of the phenomena of general relativity are simulated. This provides a graphical and quite illustrative sight on the main general relativity concepts. The simulations include solutions in 3D (XY +time) and 4D (XYZ+time) spaces. The solutions are more general than those which can be obtained analytically. For example, the approach to the black hole is simulated not only as a radial particle movement, but as an arbitrary trajectory in the 3D space. The distortion of images of far objects seen through a neighborhood of a black hole is simulated using photon trajectories in 4D space. Also the entrance of an arbitrary trajectory into the horizon of the black hole is simulated both with the coordinate time (seen by the static observer) and with the proper time (clock) of the moving body. Time distortion at the neighborhood of the black hole, including the rotating hole (Kerr solution) is shown as a 3D “space-distortion” plot. Interesting simulation experiments are als
o shown for the rotating black hole.

Our approach to this simulation task is object-oriented. The equations of movement and the numerical method are used as usually, but all these elements are encapsulated in the specification of an object, which represents the moving particle. At the run time we create one or more objects and activate them. This way of simulating the movement of one or more particles slows down the simulation, but the loss of speed is not very significant. On the other hand, we have more flexibility while handling the model. As each particle has its own attributes, it can move with its own integration step, and even with its own integration procedure. Each particle can be activated or erased at any time instant, and the particle can generate other ones. For example, a moving body can send light signals (sets of photons), generating the corresponding objects and activating them.

The simulation tool used here is the PASION simulation system. For the PASION (PAScal simulatION) summary consult . The PASION program consists in a series of process declarations. Inside each process the user puts a series of events. Using the terminology of object oriented languages, the PASION processes are object declarations, and events are methods. But PASION ofers something more, namely the clock mechanism. This means that the model time (PASION variable time) is managed by the software and not by the user. The execution of the model events is done according to the event messages, that form the event queue. PASION is a general purpose simulation tool. It supports both discrete event and continuous models.

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