.. _sphx_glr_auto_examples_Solid_State_Physics_plot_Fock.py:


Fock exchange
=============

A simple diagram composed of vertices and lines.




.. image:: /auto_examples/Solid_State_Physics/images/sphx_glr_plot_Fock_001.png
    :align: center





.. code-block:: python


    import matplotlib.pyplot as plt
    from feynman import Diagram

    # If no Axes is given, a new one is initialized.
    diagram = Diagram()

    # Create four vertices.
    v1 = diagram.vertex(xy=(.1,.5), marker='')
    v2 = diagram.vertex(v1.xy, dx=.2)
    v3 = diagram.vertex(v2.xy, dx=.4)
    v4 = diagram.vertex(v3.xy, dx=.2, marker='')

    # Create four lines.
    # By default, 'simple' lines have arrows
    # and others flavours such as 'wiggly' or 'loopy' don't.
    l12 = diagram.line(v1, v2)
    l23 = diagram.line(v2, v3)
    l34 = diagram.line(v3, v4, arrow=True)
    w23 = diagram.line(v2, v3, style='wiggly elliptic')

    # Add labels.
    l12.text("p")
    w23.text("q")
    l23.text("p - q")
    l34.text("p")

    diagram.plot()
    plt.show()

**Total running time of the script:** ( 0 minutes  0.059 seconds)



.. only :: html

 .. container:: sphx-glr-footer


  .. container:: sphx-glr-download

     :download:`Download Python source code: plot_Fock.py <plot_Fock.py>`



  .. container:: sphx-glr-download

     :download:`Download Jupyter notebook: plot_Fock.ipynb <plot_Fock.ipynb>`


.. only:: html

 .. rst-class:: sphx-glr-signature

    `Gallery generated by Sphinx-Gallery <https://sphinx-gallery.readthedocs.io>`_