Roulette Simulation

under construction

There is a range of older documents giving different persectives on the roulette formalism. They may not be up to date.

• Roulette Formalism discussing basic notation and correspondence with code components
• The generic Roulette Formalism
• See also the Lens Models

Calculation of Roulette Amplitudes

The simulator can calculate the roulette amplitudes $\alpha_s^m$ and $\beta_s^m$ for some lens models. It can also take the roulette amplitudes as input, and simulate a distorted image in a neighbourhood.

At present SIS and SIE are supported.

SIS

SIS has the most extensive support.

• The amplitudes.py script calculates algebraic formulæ for the roulette amplitudes and export these to a file (usually sis50.txt) included in the distribution.
• The SIS class reads the file (sis50.txt) and evaluates the formulæ to calculate the amplitudes in a given point (usually corresponding to the centre of the source).
• The datagen.py script can output a new dataset including roulette amplitudes when images are created.
• The roulettegen.py can read the dataset with amplitudes and simulate distorted images using the RouletteRegenerator class.

All of these procedures are reasonably fast and can be tested with little trouble.

SIE

The support for SIE follows the same pattern as SIS, but the symbolic calculation is more time consuming and fewer terms can be supported.

The script sieamplitudes.py generates the algebraic formulæ for SIE. Currently only five terms ($m\le5$) is distributed (sie05.txt).

Point Mass Lens

Point Mass Lenses can be simulated in the roulette model using the PointMassRoulette class. There is no decoupled lens class for pointmass, and therefore the roulette amplitudes cannot be explicitly calculated and exported.