Advanced correlation functions - Comp-phys-alps-users

31 May 2009

      Hi All,
I have asked this question earlier, how I can change the code for measuring
advanced correlation functions? I mean I must refer to what file to modify ?
Thanks,
zhian.
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Today's Topics:

Re: current correlation function for fermionic hubbard    model
(Matthias Troyer)
Re: Setting up polaritonic model in ALPS (Matthias Troyer)
Re: Advanced correlation functions (Matthias Troyer)
Re: Advanced correlation functions (Matthias Troyer)
Re: Problems with worms?? (Matthias Troyer)
Re: any news about next  alps release ? (Matthias Troyer)

Message: 1
Date: Sat, 30 May 2009 14:22:22 -0600
From: Matthias Troyer troyer@phys.ethz.ch
Subject: Re: [ALPS-users] current correlation function for fermionic
       hubbard model
To: comp-phys-alps-users@phys.ethz.ch, khalid hassan
       mkhloane@yahoo.com
Message-ID: 6EAA816E-F4FC-498A-ABCF-C2B8A1BB080A@phys.ethz.ch
Content-Type: text/plain; charset=US-ASCII; format=flowed; delsp=yes
On 26 Feb 2009, at 14:25, khalid hassan wrote:
...
Can alps can calculate the current correlation function for the
fermionic hubbard model model for say two site. I have been using
alps to calculate cahrge coorelation function
the charge correlation function is
< n_i n_j > = < c_i^+ c_i  c_i^+ c_i >
This can be done
...
where as the current correlation function is
< j_i j_j > = < c_i^+ c_j  c_k^+ c_l >
We have not implemented bond-bond correlation functions yet, but it
can be done if you are interested.
Matthias

Message: 2
Date: Sat, 30 May 2009 16:49:02 -0600
From: Matthias Troyer troyer@phys.ethz.ch
Subject: Re: [ALPS-users] Setting up polaritonic model in ALPS
To: comp-phys-alps-users@phys.ethz.ch
Message-ID: E831C875-FB09-40A6-9FC9-68CAE96C4CAA@phys.ethz.ch
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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

Message: 3
Date: Sat, 30 May 2009 16:50:51 -0600
From: Matthias Troyer troyer@phys.ethz.ch
Subject: Re: [ALPS-users] Advanced correlation functions
To: comp-phys-alps-users@phys.ethz.ch
Message-ID: CB7794C7-1A03-4A39-BD73-24CF100175D2@phys.ethz.ch
Content-Type: text/plain; charset=US-ASCII; format=flowed; delsp=yes
Just define Sx, which is real:
<SITEOPERATOR name="Sx" site="i">
1/2*(Splus(i)+Sminus(i))
</SITEOPERATOR>
On 28 Apr 2009, at 12:44, Justin David Peel wrote:
...
You're correct. It isn't quite right. It should be divided by i:
<SITEOPERATOR name="Sy" site="x">
1/2*(Splus(x)-Sminus(x))/sqrt(-1)
</SITEOPERATOR>

From: comp-phys-alps-users-bounces@phys.ethz.ch [
comp-phys-alps-users-bounces@phys.ethz.ch
...
] On Behalf Of zhian asadzadeh [zhian.asadzadeh@gmail.com]
Sent: Tuesday, April 28, 2009 5:56 AM
To: comp-phys-alps-users@phys.ethz.ch
Subject: [ALPS-users] Advanced correlation functions
Hi Dear,
Thank you for your guidance, but the mentioned definition for Sy
doesn't work.
And for the first question, how I can change the code for measuring
those  two kind of  correlations? I mean the correlation of first
site with others and middle site with others too.
Thanks,
Zhian.
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Today's Topics:

Re: lapack support in ALPS (Synge Todo)
Re: Advanced correlation functions (Justin David Peel)
Re: Comp-phys-alps-users Digest, Vol 37, Issue 18
(Justin David Peel)

Message: 1
Date: Mon, 27 Apr 2009 19:51:14 +0900
From: Synge Todo <wistaria@comp-phys.orgmailto:wistaria@comp-
phys.org>
Subject: Re: [ALPS-users] lapack support in ALPS
To: comp-phys-alps-users@phys.ethz.ch<mailto:
comp-phys-alps-users@phys.ethz.ch
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Message-ID: <04B17733-4F07-4867-8B22-4343337160BB@comp-phys.org<mailto:
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Dear Fu-Jiun Jiang,
On 2009/04/23, at 23:39, Fu-Jiun Jiang ITP wrote:
...
When install the ALPS with lapack being supported, what command
should be used? In the instruction, it is said
--with-lapack-dir=/path/to/my/lapack/ --with-lapack="-l my_lapack".
Is it true that first one should point to where the lapack library
is.
How about the second one? Thanks.
In many cases, lapack installation will be found automatically without
any options.  If this is not the case, please your
system administrator about the linker options to link your program
against lapack.  For example, if you are linking
liblapack.a and libblas.a in /path/to/my/lapack, then the configure
options should be
--with-lapack-dir=/path/to/my/lapack --with-lapack="-llapack -lblas"
Synge

Message: 2
Date: Mon, 27 Apr 2009 11:35:24 -0600
From: Justin David Peel <justin.peel@utah.edu<mailto:
justin.peel@utah.edu
...
...
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Subject: Re: [ALPS-users] Advanced correlation functions
To: "comp-phys-alps-users@phys.ethz.ch<mailto:
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I'm not sure about only measuring those two correlations (you might
have to change the code for that), but, as to your last question,
you should be able to use Sx:Sx because the Sx operator is defined
in the models.xml file in terms of the raising and lowering
operators. If you want to measure Sy, you would have to add the
following lines to the models.xml file:
<SITEOPERATOR name="Sy" site="x">
1/2*(Splus(x)-Sminus(x))
</SITEOPERATOR>
because it hasn't been defined as far as I can tell.
Good luck,
Justin
________________________________________
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zhian.asadzadeh@gmail.com
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Sent: Sunday, April 26, 2009 1:54 AM
To: Comp-phys-alps-users@phys.ethz.ch<mailto:
Comp-phys-alps-users@phys.ethz.ch
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Subject: [ALPS-users] Advanced correlation functions
Hi All,
I am using DMRG for my problem and I am going to measure diagonal
and offdiagonal correlation functions.
I am interest to obtain the correlation of first site with other
sites and  the middle site with other sites too.
The output of DMRG consist of   all the combinations which are
possible but I just want the two correlations mentioned above
because the output will be very large ( I am studying the
ferrimagnetic chain with 100 sites).
can I do that? how?
And also can I use Sx:Sx for measuring off diagonal correlation
functions?
Thanks,
Zhian.

Message: 3
Date: Mon, 27 Apr 2009 11:42:56 -0600
From: Justin David Peel <justin.peel@utah.edu<mailto:
justin.peel@utah.edu
...
...
...
Subject: Re: [ALPS-users] Comp-phys-alps-users Digest, Vol 37, Issue
      18
To: "comp-phys-alps-users@phys.ethz.ch<mailto:
comp-phys-alps-users@phys.ethz.ch
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  <comp-phys-alps-users@phys.ethz.ch<mailto:

comp-phys-alps-users@phys.ethz.ch
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Someone correct me if I'm wrong, but I believe this isn't very
directly feasible. The ground state vector from the exact ground
state will be in a different basis and have a different length than
the ground state vector from DMRG (it's a truncated basis after all).
________________________________________
From: comp-phys-alps-users-bounces@phys.ethz.ch<mailto:
comp-phys-alps-users-bounces@phys.ethz.ch
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[comp-phys-alps-users-bounces@phys.ethz.ch<mailto:
comp-phys-alps-users-bounces@phys.ethz.ch
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] On Behalf Of Gang Chen [chggst@physics.ucsb.edu<mailto:
chggst@physics.ucsb.edu
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Sent: Saturday, April 25, 2009 9:55 AM
To: comp-phys-alps-users@phys.ethz.ch<mailto:
comp-phys-alps-users@phys.ethz.ch
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Subject: Re: [ALPS-users] Comp-phys-alps-users Digest, Vol 37, Issue
18
Thanks, I want to compute the overlap between the exact ground state
and the state I generated from other method.
best,
Gang
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Today's Topics:

extract the ground state from DMRG or Exact       diagonalization
(Gang Chen)
Re: extract the ground state from DMRG or Exact
diagonalization (Justin David Peel)

Message: 1
Date: Fri, 24 Apr 2009 14:57:02 -0700
From: Gang Chen <chggst@physics.ucsb.edu<mailto:chggst@physics.ucsb.edu
...
<mailto:chggst@physics.ucsb.edumailto:chggst@physics.ucsb.edu>>
Subject: [ALPS-users] extract the ground state from DMRG or Exact
     diagonalization
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Hi All,
If I use DMRG or Exact diagonalization to find the ground state of my
Hamiltonian. How can
I extract the ground state vector (the numerical vector) from my
results?
best,
--
GANG CHEN
Department of Physics
University of California
Santa Barbara, CA 93106
Office: Broida 6216
Phone: 805-893-5260
Fax: 805-893-3378