Density of rational points on a certain biprojective hypersurface
Volume 219 / 2025
Acta Arithmetica 219 (2025), 1-31
MSC: Primary 11D45; Secondary 11G25, 11G50, 11P55, 14G05
DOI: 10.4064/aa230320-18-6
Published online: 5 May 2025
Abstract
By the circle method, an asymptotic formula is established for the number of rational points of bounded anticanonical height which lie on a certain Zariski-dense subset of the biprojective hypersurface $$\sum _{i=1}^nx_iy_i^2=0$$ in $\mathbb {P}^{n-1}\times \mathbb {P}^{n-1}$, where $n\geq 5$. This confirms the Manin conjecture for this variety. Moreover, we get an upper bound for the number of integer solutions to diagonal quadratic forms, which refines a previous result.