Author: Lou PagnuccoLou Pagnucco
Date: Jul 8, 2008 23:15
I have a question on Berry phase for this very simple example:
Define D as the 4X4 diagonal 0-1 matrix
[1000]
[0000]
[0010]
[0000]
Define M as the symmetric 4X4 0-1 matrix
[0001]
[0011]
[0100]
[1100]
Define the parameterized Hamiltonian
H(x,y) = (x^2+y^2)*M + D (x,y real)
The maximum eigenvalue of H(x,y) has only one degeneracy at
(x,y) = (0,0)
Let P(t) be the circular path (sin(t),cos(t)) [0<=t<=2*pi].
The maximum eigenvalue of H on P(t) is always 2 and has an
eigenvector = |1,1,1,1>/2 independent of t.
The Hamiltonian on the path H(sin(t),cos(t)) is constant.
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