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| Format: | Preprint |
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2025
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| Online Access: | https://arxiv.org/abs/2509.00667 |
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| _version_ | 1866909762967306240 |
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| author | Kuramoto, Atsuki |
| author_facet | Kuramoto, Atsuki |
| contents | We introduce triple quadratic residue symbols $[\mathfrak{p}_1, \mathfrak{p}_2, \mathfrak{p}_3]$ for certain finite primes $\mathfrak{p}_i$'s of a real quadratic field $k$ with trivial narrow class group. For this, we determine a presentation of the Galois group of the maximal pro-2 Galois extension over $k$ unramified outside $\mathfrak{p}_1, \mathfrak{p}_2, \mathfrak{p}_3$ and infinite primes, from which we derive mod 2 arithmetic triple Milnor invariants $μ_2(123)$ yielding the triple symbol $[\mathfrak{p}_1, \mathfrak{p}_2, \mathfrak{p}_3] = (-1)^{μ_2(123)}$. Our symbols $[\mathfrak{p}_1, \mathfrak{p}_2, \mathfrak{p}_3]$ describes the decomposition law of $\mathfrak{p}_3$ in a certain dihedral extension $K$ over $k$ of degree 8, determined by $\mathfrak{p}_1, \mathfrak{p}_2$. The field $K$ and our symbols $[\mathfrak{p}_1, \mathfrak{p}_2, \mathfrak{p}_3]$ are generalizations over real quadratic fields of Rédei's dihedral extension of $\mathbb{Q}$ and Rédei's triple symbol of rational primes. We give examples of Rédei type extensions $K$ over real quadratic fields. We also give a cohomological interpretation of our symbols in terms of Massey products. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2509_00667 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | On Triple Quadratic Residue Symbols in Real Quadratic Fields Kuramoto, Atsuki Number Theory 11R32, 57M05 We introduce triple quadratic residue symbols $[\mathfrak{p}_1, \mathfrak{p}_2, \mathfrak{p}_3]$ for certain finite primes $\mathfrak{p}_i$'s of a real quadratic field $k$ with trivial narrow class group. For this, we determine a presentation of the Galois group of the maximal pro-2 Galois extension over $k$ unramified outside $\mathfrak{p}_1, \mathfrak{p}_2, \mathfrak{p}_3$ and infinite primes, from which we derive mod 2 arithmetic triple Milnor invariants $μ_2(123)$ yielding the triple symbol $[\mathfrak{p}_1, \mathfrak{p}_2, \mathfrak{p}_3] = (-1)^{μ_2(123)}$. Our symbols $[\mathfrak{p}_1, \mathfrak{p}_2, \mathfrak{p}_3]$ describes the decomposition law of $\mathfrak{p}_3$ in a certain dihedral extension $K$ over $k$ of degree 8, determined by $\mathfrak{p}_1, \mathfrak{p}_2$. The field $K$ and our symbols $[\mathfrak{p}_1, \mathfrak{p}_2, \mathfrak{p}_3]$ are generalizations over real quadratic fields of Rédei's dihedral extension of $\mathbb{Q}$ and Rédei's triple symbol of rational primes. We give examples of Rédei type extensions $K$ over real quadratic fields. We also give a cohomological interpretation of our symbols in terms of Massey products. |
| title | On Triple Quadratic Residue Symbols in Real Quadratic Fields |
| topic | Number Theory 11R32, 57M05 |
| url | https://arxiv.org/abs/2509.00667 |