Matrix Product Toolkit | Main / MpDmrgInitResume

This page wasn't able to be restored properly after the spam attacks. It was a bit out of date anyway. For reference, this is the version from 2006:

The trunk version has a new syntax for mp-dmrg-init: Matrix Product Toolkit version HEAD-0.7.3.0 (subversion tree rev 143:146M) (DEBUG) Compiled on Apr 11 2006 at 14:23:49 usage: mp-dmrg-init [options] Allowed options:

  --help                    show this help message
  -H [ --Hamiltonian ] arg  operator to use for the Hamiltonian (wavefunction
                            attribute "Hamiltonian")
  -w [ --wavefunction ] arg initial wavefunction (required)
  -c [ --config ] arg       configuration file (required)
  --orthogonal arg          force the wavefunction to be orthogonal to this
                            state
  -o [ --out ] arg          initial part of filename to use for output files
                            (required)

All of the parameters are now specified by options. Required options are —wavefunction, —config and —out. In addition, you need to specify the Hamiltonian, either via the —Hamiltonian option, or you can set the Hamiltonian attribute of the initial wavefunction (see mp-attr). Example: mp-dmrg-init -H hubbard-20–1−1.lattice:H -c dmrg.conf -w initial.psi -o groundstate There is no lattice parameter anymore, this is now part of the expression defining the Hamiltonian. Eventually, a rather general operator expression will be allowed here, but for the time being the only allowed syntax is “lattice-file/operator”. Typically, operator will be H. You can force the obtained wavefunction to be orthogonal to another wavefunction using the —orthogonal option. (WARNING: this is not yet well tested.) Example: mp-dmrg-init -H hubbard-20–1−1.lattice:H -c dmrg.conf -w initial.psi —orthogonal groundstate.psi -o excitedstate Assuming groundstate.psi was a previously obtained groundstate wavefunction, the DMRG will find the first excited state. This scheme has the advantage over the traditional DMRG method of targetting multiple states in the density matrix, in that there is still only a single state targetted so the full m-dimensional basis is devoted to the excited state. The scaling of the energy to the large m limit can be performed independently for each excited state, which should give an improved estimate for the energy differences.