[ALPS-users] diagonal correlations

[Robertson Esperanza]

Oh, I forgot to mention that I'm using mps_optim application. How does the
result of MEASURE_AVERAGE differ from MEASURE_LOCAL, if let's say I use "n"
for these parameters? Thanks

On Mon, Feb 6, 2017 at 3:08 PM, Michele Dolfi <dolfim at phys.ethz.ch> wrote:

> Hello,
>
> Could you please be a bit more specific about the application you are
> running?
>
> You are right about the local measurement, but you need MEASURE_LOCAL,
> since you want to value at each site. Since the n_i^2 operator is not yet
> defined in the model library, you need to add it yourself. Basically I
> would do as follow:
> 1. Copy the file models.xml from ALPS_ROOT/lib/xml/models.xml, where
> ALPS_ROOT is the root location of your alps installation.
>
> 2. Add this definition to your local copy, it defines the n^2 operator
> <SITEOPERATOR name=“n_squared" site="x">
>   n(x)*n(x)
> </SITEOPERATOR>
>
> 3. In your input parameters you have now to link to your new model file.
> MODEL_LIBRARY=“path/to/models.xml”
>
> 4. And add your measurement
> MEASURE_LOCAL[Density^2] = “ n_squared"
>
>
> Hope this helps.
>
> Best,
> Michele
>
> --
> ETH Zurich
> Dr. Michele Dolfi
> Institute for Theoretical Physics
> HIT G 32.4
> Wolfgang-Pauli-Str. 27
> 8093 Zurich
> Switzerland
>
> dolfim at phys.ethz.ch
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>
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>
> On 6 Feb 2017, at 07:26, Robertson Esperanza <robbie.esperanza at gmail.com>
> wrote:
>
> Hello,
>
> I only started studying many-body physics, so there might be gaps in my
> knowledge. When using the MEASURE_CORRELATION, why does the measurement
> goes for only site i<j, is it because there will be "blowing up"?
>
> Alternatively, to measure for i=j, i think I could use MEASURE_AVERAGE, of
> let's say (n_i)^2 where n - n_up + n_down. How could I define such
> measurement, where you use an operator successively? Thank you for replying
>
> Robertson Esperanza
>
>
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