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.
On Sun, May 31, 2009 at 2:30 PM, comp-phys-alps-users-request@phys.ethz.chwrote:
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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 Content-Type: text/plain; charset=US-ASCII; format=flowed; delsp=yes
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:
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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
Subject: Re: [ALPS-users] Advanced correlation functions To: "comp-phys-alps-users@phys.ethz.ch<mailto:
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"
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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 ________________________________________ From: comp-phys-alps-users-bounces@phys.ethz.ch<mailto:
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] On Behalf Of zhian asadzadeh [zhian.asadzadeh@gmail.com<mailto:
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Sent: Sunday, April 26, 2009 1:54 AM To: Comp-phys-alps-users@phys.ethz.ch<mailto:
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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:
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"
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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:
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[comp-phys-alps-users-bounces@phys.ethz.ch<mailto:
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] On Behalf Of Gang Chen [chggst@physics.ucsb.edu<mailto:
chggst@physics.ucsb.edu
]
Sent: Saturday, April 25, 2009 9:55 AM To: comp-phys-alps-users@phys.ethz.ch<mailto:
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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>>
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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