..
   Generated automatically by cpp2rst

.. highlight:: c
.. role:: red
.. role:: green
.. role:: param


.. _triqs_ctseg__measure_gt:

triqs_ctseg::measure_gt
=======================

*#include <triqs_ctseg.hpp>*

.. rst-class:: cppsynopsis

      class  :red:`measure_gt`

 Measure for the Green's function in imaginary time
The imaginary-time Green's function is defined as


.. math::
		G^\sigma_{ab}(\tau) = -\langle T_\tau
 c_{a\sigma}(\tau)c_{b\sigma}^\dagger(0) \rangle

..

 and the corresponding improved estimator is given by


.. math::
		F_{ab}^{\sigma}(\tau) = -\int_0^\beta d\tilde{\tau} \sum_{c\sigma'} \langle
 T_\tau n_{c\sigma'}(\tilde{\tau})
 \mathcal{U}^{\sigma\sigma'}_{ac}(\tilde{\tau}-\tau)
 c_{a\sigma}(\tau)c_{b\sigma'}^\dagger(0) \rangle

..

The imaginary-time measurement is most efficient. The performance of the
 algorithm does not scale with the number of points in the grid on which it is
 measured, so this number can and should be chosen large. By Nyquist's theorem,
 the Fourier transform will be correctly reproduce the function in the frequency
 domain on the first :math:`N_\omega\approx N_\tau/4\pi` frequencies.

These measurements are turned on by setting ``measure_gt`` and ``measure_ft``
 to ``true``, respectively. *The number of time points on the grid is specified
 through ``n_tau`` and is the same for both observables.


Public members
--------------

+------------+----------------------------------------+--+
| params     | const triqs_ctseg::qmc_parameters *    |  |
+------------+----------------------------------------+--+
| config     | const triqs_ctseg::configuration *     |  |
+------------+----------------------------------------+--+
| gt         | block_gf<triqs::gfs::imtime> &         |  |
+------------+----------------------------------------+--+
| ft         | block_gf<triqs::gfs::imtime> &         |  |
+------------+----------------------------------------+--+
| fprefactor | std::shared_ptr<precompute_fprefactor> |  |
+------------+----------------------------------------+--+
| beta       | double                                 |  |
+------------+----------------------------------------+--+
| Noverbeta  | double                                 |  |
+------------+----------------------------------------+--+
| Z          | double                                 |  |
+------------+----------------------------------------+--+
| gt_stack   | observable<double>                     |  |
+------------+----------------------------------------+--+
| Z_stack    | observable<double>                     |  |
+------------+----------------------------------------+--+
| counter    | int                                    |  |
+------------+----------------------------------------+--+
| accum      | double                                 |  |
+------------+----------------------------------------+--+


Member functions
----------------

+-------------------------------------------------------------------+--+
| :ref:`(constructor) <triqs_ctseg__measure_gt__constructor>`       |  |
+-------------------------------------------------------------------+--+
| :ref:`accumulate <triqs_ctseg__measure_gt__accumulate>`           |  |
+-------------------------------------------------------------------+--+
| :ref:`collect_results <triqs_ctseg__measure_gt__collect_results>` |  |
+-------------------------------------------------------------------+--+

.. toctree::
    :hidden:

    measure_gt/constructor
    measure_gt/accumulate
    measure_gt/collect_results