×

Universal quadratic forms and elements of small norm in real quadratic fields. (English) Zbl 1345.11025

The purpose of this note is to extend previous results of V. Blomer and the author in [Math. Proc. Camb. Philos. Soc. 159, 239–252 (2015; doi:10.1017/S030500411500033X)] to encompass nonclassical quadratic forms (that is, forms with odd cross coefficients), as well as to strengthen some of the statements in that paper and to simplify the proofs. In fact, the arguments in the present paper apply also to the case of nonfree quadratic \(\mathcal O_K\)-lattices, where \(\mathcal O_K\) denotes the ring of integers of a real quadratic field \(K=\mathbb Q(\sqrt{D})\). In this general context, the main result of the paper is the following: For each positive integer \(M\), there are infinitely many real quadratic fields \(K=\mathbb Q(\sqrt{D})\) which do not admit totally positive integral universal \(\mathcal O_K\)-lattices of rank \(M\).

MSC:

11E12 Quadratic forms over global rings and fields
11R11 Quadratic extensions

References:

[1] DOI: 10.1017/S030500411500033X · Zbl 1371.11084 · doi:10.1017/S030500411500033X
[2] DOI: 10.1007/s11139-007-9056-2 · Zbl 1193.11033 · doi:10.1007/s11139-007-9056-2
[3] DOI: 10.1353/ajm.2014.0041 · Zbl 1315.11024 · doi:10.1353/ajm.2014.0041
[4] DOI: 10.4064/aa136-3-3 · Zbl 1234.11040 · doi:10.4064/aa136-3-3
[5] Hardy, An Introduction to the Theory of Numbers (1979) · Zbl 0423.10001
[6] DOI: 10.1090/S0002-9939-1988-0938635-4 · Zbl 0652.10006 · doi:10.1090/S0002-9939-1988-0938635-4
[7] DOI: 10.1007/s000140050133 · Zbl 1120.11301 · doi:10.1007/s000140050133
This reference list is based on information provided by the publisher or from digital mathematics libraries. Its items are heuristically matched to zbMATH identifiers and may contain data conversion errors. In some cases that data have been complemented/enhanced by data from zbMATH Open. This attempts to reflect the references listed in the original paper as accurately as possible without claiming completeness or a perfect matching.