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Manuscript Title: A Fortran code for solving the Kadanoff-Baym equations for a homogeneous fermion system.
Authors: H.S. Kohler, N.H. Kwong, H.A. Yousif
Program title: kb
Catalogue identifier: ADKQ_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 123(1999)123
Programming language: Fortran.
Computer: CRAY C90.
Operating system: UNICOS, IRIX 6.4.
RAM: 60M words
Word size: 64
Keywords: Statistical physics, Thermodynamics, Quantum transport, Nonequilibrium green, Functions, Kadanoff-Baym equations, Momentum relaxation, Semiconductor transport, Nuclear reactions.
Classification: 23.

Nature of problem:
The output of this program describes the thermalisation by internal collisions in a nonrelativistic infinite fermion system. It is most useful when applied to situations where the time scales of relaxation, individual collisions and quantum coherence are overlapping: some examples are nuclear heavy ion collisions and femtosecondscale carrier kinetics in excited semiconductors.

Solution method:
The equations are solved on a momentum grid, marching along both axes in the two-time plane. The bulk of the processing time is spent in the time-stepping and evaluating the collision integrals. The time-stepping is done by a two-pass iteration, while the collision integrals are computed by Fast Fourier Transform.

Unusual features:
The program uses the three dimensional Fast Fourier Transform routine CFFT3D of the SGI library or the subroutine CCFFT3D of the Cray library.

Running time:
The running time depends mainly on the parameter ntimes. Table 1 shows the running times on the Cray C90 of the Pittsburgh Supercomputing Center and on the SGI of the University of Arizona Center of Computing and Information Technology. The Cray C90 has 16 processors with a peak aggregate speed of 16 Gflops, and a main memory of 512 Mwords or 4 Gbytes. The calculations of Table 1 were made for the nuclear case and for the following parameters: ntl=61, nq=4620, nvec=48 and mod_store=3 (cylindrical symmetry). Serial processing on one processor was used.