Modularity of tadpole Nahm sums in ranks 4 and 5

Fuente: arXiv
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Main Authors: Shi, Changsong, Wang, Liuquan
Format: Preprint
Published: 2025
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author Shi, Changsong
Wang, Liuquan
author_facet Shi, Changsong
Wang, Liuquan
contents Around 2016, Calinescu, Milas and Penn conjectured that the rank $r$ Nahm sum associated with the $r\times r$ tadpole Cartan matrix is modular, and they provided a proof for $r=2$. The $r=3$ case was recently resolved by Milas and Wang. We prove this conjecture for the next cases $r=4,5$. We also prove the modularity of some companion Nahm sums by establishing the corresponding Rogers--Ramanujan type identities. A key new ingredient in our proofs is some rank reduction formulas which allow us to decompose higher rank tadpole Nahm sums to mixed products of some lower rank Nahm-type sums and theta functions.
format Preprint
id arxiv_https___arxiv_org_abs_2504_17737
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Modularity of tadpole Nahm sums in ranks 4 and 5
Shi, Changsong
Wang, Liuquan
Number Theory
Combinatorics
11P84, 33D15, 33D45, 11F03
Around 2016, Calinescu, Milas and Penn conjectured that the rank $r$ Nahm sum associated with the $r\times r$ tadpole Cartan matrix is modular, and they provided a proof for $r=2$. The $r=3$ case was recently resolved by Milas and Wang. We prove this conjecture for the next cases $r=4,5$. We also prove the modularity of some companion Nahm sums by establishing the corresponding Rogers--Ramanujan type identities. A key new ingredient in our proofs is some rank reduction formulas which allow us to decompose higher rank tadpole Nahm sums to mixed products of some lower rank Nahm-type sums and theta functions.
title Modularity of tadpole Nahm sums in ranks 4 and 5
topic Number Theory
Combinatorics
11P84, 33D15, 33D45, 11F03
url https://arxiv.org/abs/2504.17737