# Applying down projection operator to Up spin site gives psi with "Sz" = NaN instead of 0.

**URL:** <https://itensor.discourse.group/t/applying-down-projection-operator-to-up-spin-site-gives-psi-with-sz-nan-instead-of-0/1284>\
**Category:** ITensor Julia Questions\
**Tags:** mps, mpo\
**Created:** [November 14, 2023, 4:17am UTC](https://itensor.discourse.group/t/applying-down-projection-operator-to-up-spin-site-gives-psi-with-sz-nan-instead-of-0/1284 "2023-11-14T04:17:34Z")\
**Posts on this page:** 1\
**Showing post:** 2

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**Author:** ![mtfishman](https://yyz2.discourse-cdn.com/free1/user_avatar/itensor.discourse.group/mtfishman/32/11_2.png) [@mtfishman](https://itensor.discourse.group/u/mtfishman)\
**Post date:** [November 14, 2023, 2:45pm UTC](https://itensor.discourse.group/t/applying-down-projection-operator-to-up-spin-site-gives-psi-with-sz-nan-instead-of-0/1284/2 "2023-11-14T14:45:36Z")

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