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
--
Dominique Delande (Dominique.Delande(a)lkb.upmc.fr)
Laboratoire Kastler-Brossel - Case 74 - Universite P. et M. Curie
4, place Jussieu, F-75252 Paris Cedex 05, FRANCE
Phone : +33 1 44 27 27 97 - Fax : +33 1 44 27 38 45
Acces : Tour 13, Couloir 12-13, 3eme etage - Bureau 316