.. DO NOT EDIT.
.. THIS FILE WAS AUTOMATICALLY GENERATED BY SPHINX-GALLERY.
.. TO MAKE CHANGES, EDIT THE SOURCE PYTHON FILE:
.. "examples_gallery/fields/plot_nematic_field.py"
.. LINE NUMBERS ARE GIVEN BELOW.

.. only:: html

    .. note::
        :class: sphx-glr-download-link-note

        :ref:`Go to the end <sphx_glr_download_examples_gallery_fields_plot_nematic_field.py>`
        to download the full example code.

.. rst-class:: sphx-glr-example-title

.. _sphx_glr_examples_gallery_fields_plot_nematic_field.py:


Plotting a nematic field
========================

This example shows how to visualize a nematic tensor field
:math:`\boldsymbol Q = S(\boldsymbol n \otimes \boldsymbol n - \mathbb{1}/2)`.
The field shown here contains a :math:`+\frac12` defect at the origin, where the
director :math:`\boldsymbol n` rotates by :math:`\pi` around the defect and the nematic
order :math:`S` vanishes.

.. GENERATED FROM PYTHON SOURCE LINES 11-22



.. image-sg:: /examples_gallery/fields/images/sphx_glr_plot_nematic_field_001.png
   :alt: Nematic field with a $+1/2$ defect
   :srcset: /examples_gallery/fields/images/sphx_glr_plot_nematic_field_001.png
   :class: sphx-glr-single-img





.. code-block:: Python


    from pde import CartesianGrid, Tensor2Field

    grid = CartesianGrid([[-2, 2], [-2, 2]], 24)

    order = "tanh(2 * sqrt(x**2 + y**2))"  # nematic order vanishing at the defect
    q_xx = f"0.5 * {order} * x / sqrt(x**2 + y**2)"
    q_xy = f"0.5 * {order} * y / sqrt(x**2 + y**2)"
    field = Tensor2Field.from_expression(grid, [[q_xx, q_xy], [q_xy, f"-({q_xx})"]])

    field.plot(kind="nematic", title="Nematic field with a $+1/2$ defect")


.. rst-class:: sphx-glr-timing

   **Total running time of the script:** (0 minutes 0.321 seconds)


.. _sphx_glr_download_examples_gallery_fields_plot_nematic_field.py:

.. only:: html

  .. container:: sphx-glr-footer sphx-glr-footer-example

    .. container:: sphx-glr-download sphx-glr-download-jupyter

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

    .. container:: sphx-glr-download sphx-glr-download-python

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

    .. container:: sphx-glr-download sphx-glr-download-zip

      :download:`Download zipped: plot_nematic_field.zip <plot_nematic_field.zip>`