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Manuscript Title: A computer program for two-particle intrinsic coefficients of fractional parentage
Authors: A. Deveikis
Program title: CESOS
Catalogue identifier: AELT_v1_0
Distribution format: tar.gz
Journal reference: Comput. Phys. Commun. 183(2012)1397
Programming language: Fortran 90.
Computer: Any computer with a FORTRAN90 compiler.
Operating system: Windows XP, Linux.
RAM: The memory demand depends on the number of particles A and the excitation energy of the system Ex. Computation of the A = 6 particle system with the total angular momentum J = 0 and the total isospin T = 1 requires around 4 kB of RAM at Ex = 0, ~ 3 MB at Ex = 3, and ~ 172 MB at Ex = 5.
Keywords: Nuclear shell model, Coefficients of fractional parentage, Antisymmetric A-particle states, Translational invariancy, jt-coupling.
PACS: 03.65.-w, 02.70.-c, 03.65.Fd, 21.60.Cs.
Classification: 17.18.

Nature of problem:
The code CESOS generates a list of two-particle intrinsic coefficients of fractional parentage for several j-shells with isospin.

Solution method:
The method is based on the observation that CESOs may be obtained by diagonalizing the center-of-mass Hamiltonian in the basis set of antisymmetric A-particle oscillator functions with singled out dependence on Jacobi coordinates of two last particles and choosing the subspace of its eigenvectors corresponding to the minimal eigenvalue equal to 3/2.

Restrictions:
One run of the code CESOS generates CESOs for one specified set of (A,Ex, J, T) values only. The restrictions on the (A,Ex, J, T) values are completely determined by the restrictions on the computation of the single-shell CFPs and two-particle multishell CFPs (GCFPs) [1]. The full sets of single-shell CFPs may be calculated up to the j = 9/2 shell (for any particular shell of the configuration); the shell with j ≥ 11/2 cannot get full (it is the implementation constraint). The calculation of GCFPs is limited by A < 86 when Ex = 0 (due to the memory constraints); small numbers of particles allow significantly higher excitations. Any allowed values of J and T may be chosen for the specified values of A and Ex. The complete list of allowed values of J and T for the chosen values of A and Ex may be generated by the GCFP program - CPC Program Library, Catalogue Id. AEBI_v1_0. The actual scale of the CESOs computation problem depends strongly on the magnitude of the A and Ex values. Though there are no limitations on A and Ex values (within the limits of single-shell CFPs and multishell CFPs calculation), however the generation of corresponding list of CESOs is the subject of available computing resources. For example, the computing time of CESOs for A = 6, JT = 10 at Ex = 5 took around 14 hours. The system with A = 11, JT = 1/2 3/2 at Ex = 2 requires around 15 hours. These computations were performed on Pentium 3 GHz PC with 1 GB RAM [2].

Unusual features:
It is possible to test the computed CESOs without saving them to a file. This allows the user to learn their number and approximate computation time and to evaluate the accuracy of calculations.

Additional comments:
The program CESOS uses the code from GCFP program for calculation of the two-particle multishell coefficients of fractional parentage.

Running time:
It depends on the size of the problem. The A = 6 particle system with the JT = 01 took around 31 sec on Pentium 3 GHz PC with 1 GB RAM at Ex = 3 and about 2.6 hours at Ex = 5.

References:
[1] A. Deveikis, A. Juodagalvis, Comp. Phys. Comm. 179 (2008) 607.
[2] A. Deveikis, A. Fedurtsya, Phys. of Part. and Nuc. Lett. 8 (2011) 484.