What you know you can't explain, but you feel it. You've felt it your entire life, that there's something wrong with the world. You don't know what it is, but it's there, like a splinter in your mind, driving you mad.
What you know you can't explain, but you feel it. You've felt it your entire life, that there's something wrong with the world. You don't know what it is, but it's there, like a splinter in your mind, driving you mad.
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SpinChainFirstly, we make a lattice for a spin 1/2 chain, 20 sites. The default Hamiltonian will be the isotropic Heisenberg model spinchain-u1 -L 20 -S 0.5 -o lattice Now we make a random initial state with quantum number {$S^z=0$}, called 'psi' mp-random -l lattice -q 0 -o psi Run the DMRG program for the Heisenberg model, being the operator 'H' in the lattice. Here we are using m=50 states kept and the default is a single-site algorithm with a density matrix mixing term. mp-dmrg -w psi -H lattice:H -m 50 Repeat this command as needed until it is converged. The Hamiltonian operator can be more complicated. For example, for a bilinear-biquadratic {$S=1$} chain with {$S=1/2$} edge states at coupling {$\theta=0.3$}, and a reduced coupling strength 0.7J at the edges, use a lattice spinchain-u1 -L 20 -S 1 --SpinEdge=0.5 -o lattice with the Hamiltonian as lattice:"cos(0.3*pi)*(H1Bulk + 0.7*H1Edge) + sin(0.3*pi)*(H2Bulk + 0.7*H2Edge)" This same procedure can be done with {$SU(2)$} symmetry, by constructing the lattice with spinchain-su2 L 20 -S 0.5 -o lattice instead. |