Please use this identifier to cite or link to this item:https://hdl.handle.net/20.500.12259/48949
Type of publication: Tezės kituose recenzuojamuose leidiniuose / Theses in other peer-reviewed publications (T1e)
Field of Science: Fizika / Physics (N002)
Author(s): Stepšys, Augustinas;Mickevičius, Saulius;Germanas, Darius;Kalinauskas, Ramutis Kazys
Title: High precision parallel implementation of four-particle harmonic oscillator transformation brackets for nuclear calculations
Is part of: The vital nature sign [elektroninis išteklius] : 9th international scientific conference : abstract book. Kaunas : Vytautas Magnus university, 2015, [no. 9]
Extent: p. 101-101
Date: 2015
Keywords: Nuclear shell model;Parallel techniques;Transformation brackets
Abstract: The microscopic description of nuclear shell model is one of rapidly developing area of modern physics. While solving the Schrödinger's equation, the basis of harmonic oscillator functions has proven to be extremely useful and efficient in describing compact quantum systems, such as nucleons in atomic nuclei and quarks in hadrons. This kind of basis is simple to use, although it has one major disadvantage- it converges quite slow. For this reason the dimensions of matrices becomes very big as the values of quantum numbers, which are describing the elements of matrix. These values are required to find the coefficients for a few particle harmonic oscillator transformation brackets, which are constructed from Clebsh-Gordan, 6j and 9j coefficients. Although the analytical expressions of these coefficients are simple,but big problems arise while doing calculations on the computer. Currently widely used 64 bit (Double) precision is not sufficient for these type of calculations as doing intermediate evaluation of coefficients requires very large factorial values. Therefore calculated coefficients are represented not corectly. Another problem is quite slow calculation, which could be solved by paralleling the computer code and using large computer clusters. This component of multiparticle problem limits its evaluation, so the expansion of limits for algorithms for calculating of harmonic oscillator transformation brackets must be done. Using external parallelization library and mutable precision we created a pack of numerical codes based on the methods of compact expressions of the three and four- particle harmonics oscillator brackets. Program code is written in Fortran 90 programing language. For parallelization of used algorithm MPI parallel communication standard was used. [...]
Internet: https://hdl.handle.net/20.500.12259/48949
Affiliation(s): Fizikos institutas
Fizikos katedra
Gamtos mokslų fakultetas
Vilniaus universitetas
Vytauto Didžiojo universitetas
Appears in Collections:Universiteto mokslo publikacijos / University Research Publications

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