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In mathematics, **Diophantine geometry** is the study of Diophantine equations by means of powerful methods in algebraic geometry. By the 20th century it became clear for some mathematicians that methods of algebraic geometry are ideal tools to study these equations.^{ [1] }

Four theorems in Diophantine geometry which are of fundamental importance include these ones:^{ [2] }

Serge Lang published a book *Diophantine Geometry* in the area, in 1962, and by this book he coined the term "Diophantine Geometry".^{ [1] } The traditional arrangement of material on Diophantine equations was by degree and number of variables, as in Mordell's *Diophantine Equations* (1969). Mordell's book starts with a remark on homogeneous equations *f* = 0 over the rational field, attributed to C. F. Gauss, that non-zero solutions in integers (even primitive lattice points) exist if non-zero rational solutions do, and notes a caveat of L. E. Dickson, which is about parametric solutions.^{ [3] } The Hilbert–Hurwitz result from 1890 reducing the Diophantine geometry of curves of genus 0 to degrees 1 and 2 (conic sections) occurs in Chapter 17, as does Mordell's conjecture. Siegel's theorem on integral points occurs in Chapter 28. Mordell's theorem on the finite generation of the group of rational points on an elliptic curve is in Chapter 16, and integer points on the Mordell curve in Chapter 26.

In a hostile review of Lang's book, Mordell wrote:

In recent times, powerful new geometric ideas and methods have been developed by means of which important new arithmetical theorems and related results have been found and proved and some of these are not easily proved otherwise. Further, there has been a tendency to clothe the old results, their extensions, and proofs in the new geometrical language. Sometimes, however, the full implications of results are best described in a geometrical setting. Lang has these aspects very much in mind in this book, and seems to miss no opportunity for geometric presentation. This accounts for his title "Diophantine Geometry."

^{ [4] }

He notes that the content of the book is largely versions of the Mordell–Weil theorem, Thue–Siegel–Roth theorem, Siegel's theorem, with a treatment of Hilbert's irreducibility theorem and applications (in the style of Siegel). Leaving aside issues of generality, and a completely different style, the major mathematical difference between the two books is that Lang used abelian varieties and offered a proof of Siegel's theorem, while Mordell noted that the proof "is of a very advanced character" (p. 263).

Despite a bad press initially, Lang's conception has been sufficiently widely accepted for a 2006 tribute to call the book "visionary".^{ [5] } A larger field sometimes called arithmetic of abelian varieties now includes Diophantine geometry along with class field theory, complex multiplication, local zeta-functions and L-functions.^{ [6] } Paul Vojta wrote:

- While others at the time shared this viewpoint (e.g., Weil, Tate, Serre), it is easy to forget that others did not, as Mordell's review of
*Diophantine Geometry*attests.^{ [7] }

A single equation defines a hypersurface, and simultaneous Diophantine equations give rise to a general algebraic variety *V* over *K*; the typical question is about the nature of the set *V*(*K*) of points on *V* with co-ordinates in *K*, and by means of height functions quantitative questions about the "size" of these solutions may be posed, as well as the qualitative issues of whether any points exist, and if so whether there are an infinite number. Given the geometric approach, the consideration of homogeneous equations and homogeneous co-ordinates is fundamental, for the same reasons that projective geometry is the dominant approach in algebraic geometry. Rational number solutions therefore are the primary consideration; but integral solutions (i.e. lattice points) can be treated in the same way as an affine variety may be considered inside a projective variety that has extra points at infinity.

The general approach of Diophantine geometry is illustrated by Faltings's theorem (a conjecture of L. J. Mordell) stating that an algebraic curve *C* of genus *g* > 1 over the rational numbers has only finitely many rational points. The first result of this kind may have been the theorem of Hilbert and Hurwitz dealing with the case *g* = 0. The theory consists both of theorems and many conjectures and open questions.

- 1 2 Hindry & Silverman 2000, p. vii, Preface.
- ↑ Hindry & Silverman 2000, p. viii, Preface.
- ↑ Mordell 1969, p. 1.
- ↑ "Mordell : Review: Serge Lang, Diophantine geometry". Projecteuclid.org. 2007-07-04. Retrieved 2015-10-07.
- ↑ Marc Hindry. "
*La géométrie diophantienne, selon Serge Lang*" (PDF). Gazette des mathématiciens. Retrieved 2015-10-07. - ↑ "Algebraic varieties, arithmetic of",
*Encyclopedia of Mathematics*, EMS Press, 2001 [1994] - ↑ Jay Jorgenson; Steven G. Krantz. "The Mathematical Contributions of Serge Lang" (PDF). Ams.org. Retrieved 2015-10-07.

**Algebraic geometry** is a branch of mathematics, classically studying zeros of multivariate polynomials. Modern algebraic geometry is based on the use of abstract algebraic techniques, mainly from commutative algebra, for solving geometrical problems about these sets of zeros.

In mathematics, a **Diophantine equation** is a polynomial equation, usually involving two or more unknowns, such that the only solutions of interest are the integer ones. A **linear Diophantine equation** equates to a constant the sum of two or more monomials, each of degree one. An **exponential Diophantine equation** is one in which unknowns can appear in exponents.

In arithmetic geometry, the **Mordell conjecture** is the conjecture made by Louis Mordell that a curve of genus greater than 1 over the field **Q** of rational numbers has only finitely many rational points. In 1983 it was proved by Gerd Faltings, and is now known as **Faltings's theorem**. The conjecture was later generalized by replacing **Q** by any number field.

In mathematics, the **arithmetic of abelian varieties** is the study of the number theory of an abelian variety, or a family of abelian varieties. It goes back to the studies of Pierre de Fermat on what are now recognized as elliptic curves; and has become a very substantial area of arithmetic geometry both in terms of results and conjectures. Most of these can be posed for an abelian variety *A* over a number field *K*; or more generally.

In mathematics, **Roth's theorem** is a fundamental result in diophantine approximation to algebraic numbers. It is of a qualitative type, stating that algebraic numbers cannot have many rational number approximations that are 'very good'. Over half a century, the meaning of *very good* here was refined by a number of mathematicians, starting with Joseph Liouville in 1844 and continuing with work of Axel Thue (1909), Carl Ludwig Siegel (1921), Freeman Dyson (1947), and Klaus Roth (1955).

In mathematics, **arithmetic geometry** is roughly the application of techniques from algebraic geometry to problems in number theory. Arithmetic geometry is centered around Diophantine geometry, the study of rational points of algebraic varieties.

In number theory and algebraic geometry, a **rational point** of an algebraic variety is a point whose coordinates belong to a given field. If the field is not mentioned, the field of rational numbers is generally understood. If the field is the field of real numbers, a rational point is more commonly called a real point.

This is a glossary of **arithmetic and diophantine geometry** in mathematics, areas growing out of the traditional study of Diophantine equations to encompass large parts of number theory and algebraic geometry. Much of the theory is in the form of proposed conjectures, which can be related at various levels of generality.

A **height function** is a function that quantifies the complexity of mathematical objects. In Diophantine geometry, height functions quantify the size of solutions to Diophantine equations and are typically functions from a set of points on algebraic varieties to the real numbers.

In arithmetic geometry, the **Bombieri–Lang conjecture** is an unsolved problem conjectured by Enrico Bombieri and Serge Lang about the Zariski density of the set of rational points of an algebraic variety of general type.

In mathematics, a **thin set in the sense of Serre**, named after Jean-Pierre Serre, is a certain kind of subset constructed in algebraic geometry over a given field *K*, by allowed operations that are in a definite sense 'unlikely'. The two fundamental ones are: solving a polynomial equation that may or may not be the case; solving within *K* a polynomial that does not always factorise. One is also allowed to take finite unions.

In mathematics, **Siegel's theorem on integral points** states that for a smooth algebraic curve *C* of genus *g* defined over a number field *K*, presented in affine space in a given coordinate system, there are only finitely many points on *C* with coordinates in the ring of integers *O* of *K*, provided *g* > 0.

In number theory, the **Néron–Tate height** is a quadratic form on the Mordell–Weil group of rational points of an abelian variety defined over a global field. It is named after André Néron and John Tate.

In mathematics, **Arakelov theory** is an approach to Diophantine geometry, named for Suren Arakelov. It is used to study Diophantine equations in higher dimensions.

**Arithmetic dynamics** is a field that amalgamates two areas of mathematics, dynamical systems and number theory. Classically, discrete dynamics refers to the study of the iteration of self-maps of the complex plane or real line. Arithmetic dynamics is the study of the number-theoretic properties of integer, rational, p-adic, and/or algebraic points under repeated application of a polynomial or rational function. A fundamental goal is to describe arithmetic properties in terms of underlying geometric structures.

In mathematics, in the field of algebraic number theory, an ** S-unit** generalises the idea of unit of the ring of integers of the field. Many of the results which hold for units are also valid for

In mathematics, the **Mordell–Weil theorem** states that for an abelian variety over a number field , the group of *K*-rational points of is a finitely-generated abelian group, called the **Mordell–Weil group**. The case with an elliptic curve and the rational number field **Q** is **Mordell's theorem**, answering a question apparently posed by Henri Poincaré around 1901; it was proved by Louis Mordell in 1922. It is a foundational theorem of Diophantine geometry and the arithmetic of abelian varieties.

In arithmetic geometry, the **Tate–Shafarevich group**Ш(*A*/*K*) of an abelian variety *A* (or more generally a group scheme) defined over a number field *K* consists of the elements of the Weil–Châtelet group WC(*A*/*K*) = H^{1}(*G*_{K}, *A*) that become trivial in all of the completions of *K* (i.e. the *p*-adic fields obtained from *K*, as well as its real and complex completions). Thus, in terms of Galois cohomology, it can be written as

**Aleksei Nikolaevich Parshin**, sometimes romanized as **Alexey Nikolaevich Paršin**, is a Russian mathematician, specializing in arithmetic geometry.

- Baker, Alan; Wüstholz, Gisbert (2007).
*Logarithmic Forms and Diophantine Geometry*. New Mathematical Monographs.**9**. Cambridge University Press. ISBN 978-0-521-88268-2. Zbl 1145.11004. - Bombieri, Enrico; Gubler, Walter (2006).
*Heights in Diophantine Geometry*. New Mathematical Monographs.**4**. Cambridge University Press. ISBN 978-0-521-71229-3. Zbl 1115.11034. - Hindry, Marc; Silverman, Joseph H. (2000).
*Diophantine Geometry: An Introduction*. Graduate Texts in Mathematics.**201**. ISBN 0-387-98981-1. Zbl 0948.11023. - Lang, Serge (1997).
*Survey of Diophantine Geometry*. Springer-Verlag. ISBN 3-540-61223-8. Zbl 0869.11051. - Mordell, Louis J. (1969).
*Diophantine Equations*. Academic Press. ISBN 978-0125062503. - "Diophantine geometry",
*Encyclopedia of Mathematics*, EMS Press, 2001 [1994]

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