On 8 Nov 2010, at 18:25, Chong You Quan wrote:

Hi,

I'm using ALPS 1.3.5 on Linux currently. I'm new to ALPS and DMRG and I'd just like to clarify a few questions:
1. For full DMRG application with verbose = 1 using the Heisenberg (spin) model, what is the basis of the RHO's eigenvalues in the output? DMRG truncates the density matrix, so, the basis of the density matrix is that of the spin sites is it? For example, L = 2, then the basis would be |00>, |01>, |10>, |11>.. is it correct? What about the basis of the matrix after truncation? Also, if I would like to get the full wavefunction in the basis of the sites, what should I do?

The DMRG code cannot easily give you the wave function in any meaningful way.

Also if I specify that N is conserved, what is the default value of N? Or does it try all possible N to give the lowest energy state?

Indeed, in that case the conservation is just used to speed up the simulation.

2. I can see that ALPS can be integrated into C++ but I tried googling for examples and documentation to no avail.. Is it in the Trac wiki? If so, must one register for it in order to view the documentation? The d efault documentation seems to specify what the input values represent but don't describe much of the output or how to integrate ALPS into C++.. Am I missing out on some way I can find the documentation for ALPS and how to integrate it in C++?

Do you mean the ALPS libraries? Documentation for them is in the doc subdirectory of the source tree. What of ALPS do you want to use for which purpose?

3. I noticed there were some .dat files after running the DMRG application.. Are those temporary files stored during calculation or are those actual output files? I didn't seem to be able to extract any form of data from those files.. Is it that all the useful output for the DMRG is written to the screen?

The main results are in the xml files that are also written. ALPS 2.0, which will be done soon, will have much more powerful evaluation tools and easier evaluation

4. I'm not sure why but my parameter2xml does not seem to work on any of the example parameter files.. I'm currently just typing out the xml file by hand. Maybe I'm just missing out on something.. Does parameter2xml output to a specific directory or something?

It goes to the local directory and should produce a bunch of XML files. Did you try with the files in the tutorials directory?

5. Almost all of the files on http://www.comp-phys.org/lugano04/Talks.html&nb sp;seem to be broken.. Is it that the links are outdated or something?

Yes, it is outdated - we need to remove the page. There are more recent good lecture notes on the web page of the 2010 Boulder summer school.

Best regards