Hi Dear,

Thank you very much for your consideration. yes my model mixes states with different Sz.
let me know DMRG works with complex vectors or not? and Can I change the basis which DMRG works in it?

Thanks a lot
Mohammad.

On Sun, Mar 1, 2009 at 2:30 PM, <comp-phys-alps-users-request@phys.ethz.ch> wrote:
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Today's Topics:

  1. Operator definition (zhian asadzadeh)
  2. Re: Operator definition (Adrian E. Feiguin)


----------------------------------------------------------------------

Message: 1
Date: Sat, 28 Feb 2009 15:11:34 +0330
From: zhian asadzadeh <zhian.asadzadeh@gmail.com>
Subject: [ALPS-users] Operator definition
To: comp-phys-alps-users@phys.ethz.ch
Message-ID:
       <89e5d6760902280341r7ca16b5fm506e562c4f043c64@mail.gmail.com>
Content-Type: text/plain; charset="iso-8859-1"

Hi  All,

I am using DMRG for my problem,  I need to calculate expectation value of Y
component of Spin operator (Sy) , As a result, I need to define it in the
model.xml file. How I can define it? I tried with
Sy(i)=1/(2*sqrt(-1))*(Splus(i)-Sminus(i)), but I got  incorrect results. I
will be very appreciate if someone could help me?

Thank you very much,
Mohammad.
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Message: 2
Date: Sat, 28 Feb 2009 11:32:00 -0800
From: "Adrian E. Feiguin" <afeiguin@kitp.ucsb.edu>
Subject: Re: [ALPS-users] Operator definition
To: comp-phys-alps-users@phys.ethz.ch
Message-ID: <49A99130.2040704@kitp.ucsb.edu>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

Hi Mohammad,

You are missing the imaginary unit in the definition. In any case, DMRG
at the moment does not work with complex numbers.
You would have to measure Splus and Sminus, and then combine the results.
But all this only makes sense assuming that your Hamiltonian already
mixes states with different Sz. What model are you studying?

Saludos,
<ADRIAN>

zhian asadzadeh wrote:
> Hi  All,
>
> I am using DMRG for my problem,  I need to calculate expectation value
> of Y component of Spin operator (Sy) , As a result, I need to define
> it in the model.xml file. How I can define it? I tried with
> Sy(i)=1/(2*sqrt(-1))*(Splus(i)-Sminus(i)), but I got  incorrect
> results. I will be very appreciate if someone could help me?
>
> Thank you very much,
> Mohammad.
>



End of Comp-phys-alps-users Digest, Vol 36, Issue 1
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