PreprintCC BY 4.0arXiv
The category of nominal sets is locally monoidal closed
Abstract
The category Nom of nominal sets was proposed by Pitts and Gabbay as a setting for the semantics of abstract syntax with variable bindings. It is well-known that Nom is a topos, also known as the Schanuel topos, and in particular it follows that Nom is locally closed, i.e., every slice category Nom/X is cartesian-closed. In this paper, we show that Nom has a much stronger property: every monoidal (closed) structure on Nom induces a monoidal (closed) structure on all slice categories Nom/X. One monoidal closed structure of particular interest on Nom is the separated product A * B, whose right adjoint A -* B is called the separated function space. In particular, it follows that Nom is locally separatedly closed.
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BibTeX
@misc{bayeh2026category,
title = {{The category of nominal sets is locally monoidal closed}},
author = {Fahimeh Bayeh and Peng Fu and Peter Selinger},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.22551},
eprint = {2609.22551},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.22551},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - The category of nominal sets is locally monoidal closed
AU - Fahimeh Bayeh
AU - Peng Fu
AU - Peter Selinger
PY - 2026
DA - 2026/09/18
PB - arXiv
DO - 10.48550/arxiv.2609.22551
UR - https://arxiv.org/abs/2609.22551
AB - The category Nom of nominal sets was proposed by Pitts and Gabbay as a setting for the semantics of abstract syntax with variable bindings. It is well-known that Nom is a topos, also known as the Schanuel topos, and in particular it follows that Nom is locally closed, i.e., every slice category Nom/X is cartesian-closed. In this paper, we show that Nom has a much stronger property: every monoidal (closed) structure on Nom induces a monoidal (closed) structure on all slice categories Nom/X. One monoidal closed structure of particular interest on Nom is the separated product A * B, whose right adjoint A -* B is called the separated function space. In particular, it follows that Nom is locally separatedly closed.
ER -