Brody, D C; Hook, D W and Hughston, L P. 2007. Quantum Phase Transitions Without Thermodynamic Limits. Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, 463(2084), pp. 2021-2030. ISSN 1364-5021 [Article]

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Abstract or Description

A new microcanonical equilibrium state is introduced for quantum systems with finite-dimensional state spaces. Equilibrium is characterized by a uniform distribution on a level surface of the expectation value of the Hamiltonian. The distinguishing feature of the proposed equilibrium state is that the corresponding density of states is a continuous function of the energy, and hence thermodynamic functions are well defined for finite quantum systems. The density of states, however, is not in general an analytic function. It is demonstrated that generic quantum systems therefore exhibit second-order phase transitions at finite temperatures.

Item Type:	Article
Identification Number (DOI):	https://doi.org/10.1098/rspa.2007.1865
Departments, Centres and Research Units:	Computing
Dates:	Date Event 11 May 2007 Accepted 13 June 2007 Published Online 8 August 2007 Published
Item ID:	31410
Date Deposited:	08 Feb 2022 15:40
Last Modified:	08 Feb 2022 23:20
Peer Reviewed:	Yes, this version has been peer-reviewed.
URI:	https://research.gold.ac.uk/id/eprint/31410

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