Goldberg, Leslie Ann and Jerrum, Mark. (2007) The complexity of ferromagnetic ising with local fields. COMBINATORICS PROBABILITY & COMPUTING, 16 (1). pp. 43-61. ISSN 0963-5483

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Abstract

We consider the complexity of approximating the partition function of the ferromagnetic Ising model with varying interaction energies and local external magnetic fields. Jerrum and Sinclair provided a fully polynomial randomized approximation scheme for the case in which the system is consistent in the sense that the local external fields all favour the same spin. We characterize the complexity of the general problem by showing that it is equivalent in complexity to the problem of approximately counting independent sets in bipartite graphs, thus it is complete in a logically defined subclass of #P previously studied by Dyer, Goldberg, Greenhill and Jerrum. By contrast, we show that the corresponding computational task for the q-state Potts model with local external magnetic fields and q > 2 is complete for all of #P with respect to approximation-preserving reductions.

Item Type:	Journal Article
Subjects:	Q Science > QA Mathematics > QA76 Electronic computers. Computer science. Computer software Q Science > QA Mathematics
Journal or Publication Title:	COMBINATORICS PROBABILITY & COMPUTING
Publisher:	CAMBRIDGE UNIV PRESS
ISSN:	0963-5483
Date:	January 2007
Volume:	16
Number:	1
Number of Pages:	19
Page Range:	pp. 43-61
Identification Number:	10.1017/S096354830600767X
Publication Status:	Published
URI:	http://wrap.warwick.ac.uk/id/eprint/32509

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