Dear all,
Since at least r7593 (end of July 2015), it is possible to study with MPS inhomogeneous systems, for example an 1D inhomogeneous Bose-Hubbard model with an harmonic trap by using 'inhomogeneous chain lattice' for the lattice and the following definition for the Hamiltonian
<HAMILTONIAN name="harm boson Hubbard"> <PARAMETER name="mu" default="0"/> <PARAMETER name="t" default="1"/> <PARAMETER name="V" default="0"/> <PARAMETER name="t'" default="0"/> <PARAMETER name="V'" default="0"/> <PARAMETER name="U" default="0"/> <PARAMETER name="t0" default="t"/> <PARAMETER name="t1" default="t'"/> <PARAMETER name="V0" default="V"/> <PARAMETER name="V1" default="V'"/> <PARAMETER name="K" default="0"/> <BASIS ref="boson"/> <SITETERM site="i"> <PARAMETER name="mu#" default="mu"/> <PARAMETER name="U#" default="U"/> <PARAMETER name="K#" default="K"/> -mu#*n(i)+U#*n(i)*(n(i)-1)/2+K#*n(i)*(x-0.5*(L-1))^2 </SITETERM> <BONDTERM source="i" target="j"> <PARAMETER name="t#" default="0"/> <PARAMETER name="V#" default="0"/> -t#*(bdag(i)*b(j)+bdag(j)*b(i)) + V#*n(i)*n(j) </BONDTERM> </HAMILTONIAN>
I would like to use an inhomogeneous BONDTERM. I tried things like -(t#+tharm#*(i+j-L)^2)*(bdag(i)*b(j)+bdag(j)*b(i)) or -(t#+tharm#*(x-0.5*(L-1))^2)*(bdag(i)*b(j)+bdag(j)*b(i)) in the definition of the Hamiltonian, but they all produce error messages indicating that mps_optim cannot evaluate such a Hamiltonian.
I thus have two questions: * Is inhomogeneous BONDTERM possible with MPS, and how to proceed? * MORE IMPORTANTLY: How can I figure out whether it is possible or not? I find nothing in the documentation, nothing in the Wiki. Is the only solution to look in the guts of the code, or to ask on the mailing list?
Thanks a lot in advance for your help.
Dominique