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arXiv:1208.4721 · International Journal of Modern Physics C

HAMILTON OPERATORS, DISCRETE SYMMETRIES, BRUTE FORCE AND SYMBOLICC++

WILLI-HANS STEEB, YORICK HARDY

Published Nov 4, 2012• 0 citations
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Abstract

To find the discrete symmetries of a Hamilton operator Ĥ is of central importance in quantum theory. Here, we describe and implement a brute force method to determine the discrete symmetries given by permutation matrices for Hamilton operators acting in a finite-dimensional Hilbert space. Spin and Fermi systems are considered as examples. A computer algebra implementation in SymbolicC++ is provided.

DOI
10.1142/s0129183112500957

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To find the discrete symmetries of a Hamilton operator Ĥ is of central importance in quantum theory. Here, we describe and implement a brute force method to determine the discrete symmetries given by permutation matrices for Hamilton operators acting in a finite-dimensional Hilbert space. Spin and Fermi systems are considered as examples. A computer algebra implementation in SymbolicC++ is provided.
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Iterative methods that operate with the full Hamiltonian matrix in the untrimmed Hilbert space of a finite system continue to be important tools for the study of one- and two-dimensional quantum spin models, in particular in the presence of frustration. To reach sensible system sizes such numerical calculations heavily depend on the use of symmetries. We describe a divide-and-conquer strategy for implementing translation symmetries of finite spin clusters, which efficiently uses and extends the "sublattice coding" of H. Q. Lin [Phys. Rev. B 42, 6561 (1990)]. With our method, the Hamiltonian matrix can be generated on-the-fly in each matrix vector multiplication, and problem dimensions beyond 10^{11} become accessible.