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issp-center-dev / mVMC

A numerical solver package for a wide range of quantum lattice models based on many-variable Variational Monte Carlo method
http://www.pasums.issp.u-tokyo.ac.jp/mvmc/en/
GNU General Public License v3.0
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4-point correlation functions? #17

Closed nikita-astronaut closed 3 years ago

nikita-astronaut commented 3 years ago

Dear mVMC developers,

in a recent paper https://arxiv.org/pdf/2005.14142.pdf mVMC was used to compute dimer-dimer correlations order, which is a 4-point spin and 8-point fermion correlation function.

However, in current public version of mVMC this functionality is absent (at least not mentioned in Documentation).

Is it possible that 4-point correlations are already available? If not, perhaps you could push this commit (even though probably not very well tested) and briefly explain how to use it?

Thanks a lot!

Best wishes, Nikita

tmisawa commented 3 years ago

Dear Nikita,

We implemented the function that can calculate N-body Green functions (GreenFuncN in locgrn.c or GreenFuncN_real in locgrn_real.c) for Sz=0 systems. By using the function, you can calculate the N-body Green functions. However, to do so, it is necessary to modify the source codes (eg. implementing a proper input/output format).

Best, Takahiro Misawa

nikita-astronaut commented 3 years ago

Dear Takahiro,

thanks for reaching me out.

Cal I please ask you to elaborate a little bit, like which files/functions I will need to modify in order to output the N-point green function? For instance, above the definition of N-point GF, you have 2-point GF GreenFunc2_real which is only used in the computation of Hamiltonian. So I can not understand how it is used for calculations observables (where is it called to compute observables) ?

Thanks a lot!

Best wishes, Nikita

nikita-astronaut commented 3 years ago

I think I got it.