# Imposing a discontinuity at interface using DG method

**URL:** <https://fenicsproject.discourse.group/t/imposing-a-discontinuity-at-interface-using-dg-method/11780>\
**Category:** dolfinx\
**Created:** [July 19, 2023, 7:40pm UTC](https://fenicsproject.discourse.group/t/imposing-a-discontinuity-at-interface-using-dg-method/11780 "2023-07-19T19:40:17Z")\
**Posts on this page:** 1\
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**Author:** ![leshinka](https://yyz2.discourse-cdn.com/free1/user_avatar/fenicsproject.discourse.group/leshinka/32/5789_2.png) [@leshinka](https://fenicsproject.discourse.group/u/leshinka)\
**Post date:** [October 29, 2023, 9:18pm UTC](https://fenicsproject.discourse.group/t/imposing-a-discontinuity-at-interface-using-dg-method/11780/18 "2023-10-29T21:18:07Z")

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I have  
\nabla u \cdot \hat{n}(+) = \alpha (u\_{+} - u\_{-})  
and because the flux is continuous, then I also have  
\nabla u \cdot \hat{n}(-) = \alpha (u\_{-} - u\_{+})

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