Between rational and integral points

Lead Research Organisation: University of Bristol
Department Name: Mathematics

Abstract

Mathematics is undeniably the universal language of science and nature, whose processes are often governed by equations. This proposal
centres on systems of equations involving polynomials with integer coefficients. The study of rational or integral solutions to Diophantine equations is a subject that is both ancient and difficult, having commanded our attention since the time of the ancient Greeks nearly 2000 years ago. It has had profound interactions with a host of subject areas, ranging from algebraic geometry to complex analysis via mathematical logic and everything in between. At its core this proposal uses analytic methods to tackle a range of long-standing conjectures of about the existence and distribution of solutions to Diophantine equations, working in the context of both rational and integral points, as well as 'Campana-points', which interpolate between the two. In the reverse direction, by studying the distribution of rational and integral points on appropriate systems of Diophantine equations, the PI hopes to shed light on other fundamental areas of research, including the Langlands correspondence and Malle's conjecture about the density of number fields with prescribed Galois group.

Planned Impact

The main beneficiaries of the research will be the academic community. The proposal contains novel and surprising uses of analytic methods to make inroads into very central conjectures in number theory. Once the work is disseminated in conferences and seminars, this is likely to open the door to a flurry of further activity in the field by other researchers in number theory.

One impact of the project is the raised profile of the School of Mathematics at the University of Bristol and an increased activity of the number theory group. This, together with links and exchanges with top international universities will help increase the global standing and prestige of UK science. In turn, this will lead to more applications for undergraduate and PhD places from overseas students (bringing fees), and an increased number of research fellowships funded from outside the UK, such as EU Marie-Curie Fellowships and European research grants. This results in a direct income increase for the relevant mathematics departments and local economies.

This proposal features topics which have been found to captivate the imagination of the general public, with Diophantine equations proving a important bridge to frontline mathematical research. Many number-theoretical results (such as, notably, the proof of Fermat's Last Theorem) have caused great excitement and increased awareness of the general public in mathematical research. Advertising exciting and current mathematical
research in this way will inspire the next generation of mathematicians, the impact of which on future technology and development should not be ignored. As described in the Pathways to Impact document, the reach of the project will be maximised through the PI's close contact with numberphile, in order to make a short Youtube video about an appropriate aspect of the planned research.

Publications

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Bonolis, D Uniform bounds for rational points on hyperelliptic fibrations in Ann. Sc. Norm. Super. Pisa Cl. Sci.

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Browning T (2020) Density of rational points on a quadric bundle in P 3 × P 3 in Duke Mathematical Journal

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Browning T (2021) Arithmetic of higher-dimensional orbifolds and a mixed Waring problem in Mathematische Zeitschrift

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Browning T (2018) Counting rational points on quadric surfaces in Discrete Analysis

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Browning T (2020) Free rational points on smooth hypersurfaces in Commentarii Mathematici Helvetici

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Browning T (2019) Counting rational points on biquadratic hypersurfaces in Advances in Mathematics

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Browning T (2021) The geometric sieve for quadrics in Forum Mathematicum

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Browning T (2022) Equidistribution and freeness on Grassmannians in Algebra & Number Theory

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Browning T (2018) Sieving rational points on varieties in Transactions of the American Mathematical Society

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Browning T (2020) A geometric version of the circle method in Annals of Mathematics

 
Description The study of integer and rational solutions to Diophantine equations is central to modern mathematics. In this proposal several major milestones were achieved.
One of the most significant achievements has been the discovery that analytic number theory over global fields of positive characteristic has a fundamental role to play in the analysis of moduli spaces of rational curves on algebraic varieties over the complex numbers. In joint work with Sawin ("A geometric version of the circle method", Annals of Math.), the Hardy-Littlewood is given a sheaf theoretic interpretation and used to study the compactly supported cohomology of moduli spaces of rational curves on smooth hypersurfaces. This is one of the success stories in the new field of Arithmetic topology.

In joint work with Heath-Brown ("Density of rational points on a quadric bundle in P3xP3", Duke Math. J.), a 20 year old conjecture of Colliot-Thélène is proved concerning the distribution of rational points on a certain quadric bundle. This combines news techniques in the circle method with sophisticated geometry of numbers techniques. The main result is remarkable for being one of the very few examples which actually proves that the thin set version of Manin conjecture is the right point of view in this case.

Finally, in submitted work (https://arxiv.org/abs/2006.02356) that is currently under review at Annals of Mathematics ("The Hasse principle for random Fano hypersurfaces", with Pierre Le Boudec and Will Sawin), a long-standing conjecture of Poonen and Voloch about the Hasse principle holding for random Fano hypersurfaces has almost been completely solved thanks to the work funded through this award. This involved the development of extensive ideas in the geometry of numbers and has inspired follow-up work of the PI on the Hasse principle for random Diophantine equations involving norm forms. The PI has explained this work in a prestigious worldwide online seminar (https://drive.google.com/file/d/1smLzZ2YdDiFAuZy5-qaYhO6bfnEGJhNw/view?usp=sharing).
Exploitation Route We have built a bridge between algebraic geometry and analytic number theory, whereby techniques in harmonic analysis have been found to shed light on long-standing conjectures in the birational geometry of algebraic varieties. This seems to be the beginning of a rich story which is ripe for exploration.
Sectors Education

URL https://arxiv.org/abs/1810.06882