M N Barber 1977 J. Phys. A: Math. Gen. 10 1187 doi:10.1088/0305-4470/10/7/016
M N Barber
Show affiliationsThe use of variational approximations in the study and application of renormalization groups is discussed. In particular, a simple approximation is derived which yields an upper bound to the free energy of Ising models on d-dimensional lattices. The optimal transformation, which yields the least upper bound, is determined analytically. The criterion proposed by Kadanoff (1975) to determine the 'best' approximation to the fixed point is found to fail in this case. The reasons for this failure and several of the basic problems posed by variational approximations are discussed.
05.70.Ce Thermodynamic functions and equations of state
82B20 Lattice systems (Ising, dimer, Potts, etc.) and systems on graphs
Issue 7 (July 1977)
M N Barber 1977 J. Phys. A: Math. Gen. 10 1187
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