GenericPeriodicSpinChain

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GenericPeriodicSpinChain diagonalizes the Heisenberg spin chain with periodic boundary conditions. For example

$PATHTODIAGHAM/build/Spin/src/Programs/GenericOpenSpinChain -s 1 -p 4 --use-lapack

diagonalizes a 4 sites (-p option) spin 1/2 (the -s option should be set two twice the spin per site) with coupling constant J=1 . The code only looks at positive Sz sector and all momentum sectors. The spectrum is stored in a file whose name looks like spin_1_2_periodicchain_n_4.dat with the following content


   #  periodic spin 1/2 chain with 4 sites
   # 2Sz K  E
   0 0 -2
   0 0 1
   0 1 0
   0 2 -1
   0 2 7.4983036091107e-33
   0 3 0
   2 0 1
   2 1 -6.1230317691119e-17
   2 2 -1
   2 3 1.8369095307336e-16
   4 0 1