Dear Matthias,

Thank you for pointing out that obvious mistake. After reducing the maximum occupancy to 10, there is an error message "Offdiagonal site terms are not implemented in this SSE code" when using dirloop. It is unclear to me when atomic projection operators and bosonic operators are defined accordingly (attached). Please advise and thank you again.

Regards,
Chun-Hsu

> From: troyer@phys.ethz.ch
> To: comp-phys-alps-users@phys.ethz.ch
> Date: Sat, 30 May 2009 16:49:02 -0600
> Subject: Re: [ALPS-users] Setting up polaritonic model in ALPS
>
> On 29 May 2009, at 19:09, Su Chun-Hsu wrote:
> >
> > Dear all,
> > I'm new to using ALPS and not entirely confident with setting up my
> > model,
> > which didn't appear to work at the moment. I'm interested in
> > polaritonic
> > system -- evanescently coupled-cavity system, each cavity containing a
> > two-level atom. I have set up my model in the attached xml, Sminus
> > and Splus
> > are atomic projection operators and b are photon annihilation
> > operator.
> > The total number of excitations (atomic and photonic) is conserved.
> > When I try running it, there is an bad_alloc error. Will anyone
> > be kindly give me some pointers? Much appreciated and thank you very
> > much
> > in advance.
>
> Not knowing exactly what you have in mind I can only say that the
> model looks reasonable. You have to be very careful though as you have
> a large number of local states and already a 2x2 lattice without
> constraints has a Hilbert space of 202^4, which is far too large to be
> solved by exact diagonalization.
>
> With your constraints the Hilbert space is smaller but there is still
> the problem that the ALPS program wants to build the full Hamiltonian
> matrix for two sites. The 2-site Hilbert space in your model is 202^2
> = 40804 states. The matrix for two sites thus 40804 x 40804 = 1 664
> 966 416 elements large, which needs 12.5 GB memory. The allocation of
> this matrix fails and thus there is a bad_alloc exception. Such a
> model is to big to be studied by exact diagonalization. If you reduce
> the maximum occupancy t0 10 or 20 it will work
>
> Matthias
>

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