Implementation of this test, however, requires a probe of the structure which is sensitive at these redshifts. However, large scale structure has not yet been definitively observed in the CXB, which makes a clear interpretation difficult.
Perturbation Theory makes it possible to calculate the PDF in the small variance limit .
EPT consists in assuming that the spectral index and the variance are adjustable parameters, and , the nonlinear variance. With this additional degrees of freedom, results from perturbation theory provide a good fit of the PDF's, even in the highly nonlinear regime. The code is designed for large cosmological simulations and incorporates a number of ideas which improve the code's efficiency both in terms of speed of execution and memory use. A simulation containing particles each of dark matter and gas can be run in roughly three days on a 250Mhz DEC Alpha workstation. This Grand Challenge project is using the 512 node Cray T3D in Edinburgh and more recently the Cray T3E at MPI, Garching.