Weber, Dennis (2012)
Effective realistic interactions for low momentum Hilbert spaces.
Technische Universität Darmstadt
Ph.D. Thesis, Primary publication
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Item Type: | Ph.D. Thesis | ||||
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Type of entry: | Primary publication | ||||
Title: | Effective realistic interactions for low momentum Hilbert spaces | ||||
Language: | English | ||||
Referees: | Feldmeier, Prof. Dr. Hans ; Roth, Prof. Dr. Robert | ||||
Date: | 2012 | ||||
Place of Publication: | Darmstadt | ||||
Date of oral examination: | 12 November 2012 | ||||
Abstract: | Realistic nucleon-nucleon potentials are an essential ingredient of modern microscopic many-body calculations. These potentials can be represented in two different ways: operator representation or matrix element representation. In operator representation the potential is represented by a set of quantum mechanical operators while in matrix element representation it is defined by the matrix elements in a given basis. Many modern potentials are constructed directly in matrix element representation. While the matrix element representation can be calculated from the operator representation, the determination of the operator representation from the matrix elements is more difficult. Some methods to solve the nuclear many-body problem, such as Fermionic Molecular Dynamics (FMD) or the Green's Function Monte Carlo (GFMC) method, however require explicitly the operator representation of the potential, as they do not work in a fixed many-body basis. It is therefore desirable to derive an operator representation also for the interactions given by matrix elements. In this work a method is presented which allows the derivation of an approximate operator representation starting from the momentum space partial wave matrix elements of the interaction. For that purpose an ansatz for the operator representation is chosen. The parameters in the ansatz are determined by a fit to the partial wave matrix elements. Since a perfect reproduction of the matrix elements in general cannot be achieved with a finite number of operators and the quality of the results depends on the choice of the ansatz, the obtained operator representation is tested in nuclear many-body calculations and the results are compared with those from the initial interaction matrix elements. For the calculation of the nucleon-nucleon scattering phase shifts and the deuteron properties a computer code written within this work is used. For larger nuclei the No Core Shell Model (NCSM) and FMD are applied. The described method to calculate the operator representation is applied to different effective realistic potentials. In a first application the Argonne V18 potential, transformed by means of the Unitary Correlation Operator Method (UCOM), is considered. As second application an operator representation of the Similarity Renormalization Group (SRG) transformed Argonne potential is obtained. Finally an operator representation of the JISP16 interaction, which is specifically designed for the harmonic oscillator basis, is derived by using the same ansatz as for the SRG transformed Argonne potential.Summing up, there is no general set of operators which can be used to describe all the different effective interactions by just adjusting the particular radial functions. However, it is possible to find a suitable operator representation, even for effective operators that are specifically designed for numerical feasibility and are treating each partial wave separately. |
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URN: | urn:nbn:de:tuda-tuprints-32252 | ||||
Classification DDC: | 500 Science and mathematics > 530 Physics | ||||
Divisions: | 05 Department of Physics 05 Department of Physics > Institute of Nuclear Physics |
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Date Deposited: | 20 Dec 2012 17:13 | ||||
Last Modified: | 20 Dec 2012 17:13 | ||||
URI: | https://tuprints.ulb.tu-darmstadt.de/id/eprint/3225 | ||||
PPN: | 386259399 | ||||
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