Gauss’s class number one problem for real quadratic fields

Establish the existence of infinitely many real quadratic number fields Q(√d) whose class number equals 1.

Background

The paper contrasts the well-understood case of imaginary quadratic fields—where only nine fields have class number one—with the real quadratic case, where Gauss conjectured infinitely many examples but no proof is known. This classical problem underscores the difficulty of understanding class numbers of real quadratic fields and motivates broader investigations into their divisibility properties.

References

It was conjectured by Gauss that there are infinitely many real quadratic fields with class number one, which is still open.

On the simultaneous $3$-divisibility of class numbers of quadruples of real quadratic fields  (2512.11346 - Banerjee et al., 12 Dec 2025) in Section 1 (Introduction)