The ATS theorem, also known as the Aharonov–Bohm theorem, is a fundamental result in quantum mechanics that illustrates the importance of electromagnetic potentials in the behavior of charged particles, even in regions where the electric and magnetic fields are zero.

In approximation theory, several theorems provide fundamental insights into how functions can be approximated by simpler functions, such as polynomials, trigonometric series, or other basis functions. Here are some key theorems and concepts in approximation theory: 1. **Weierstrass Approximation Theorem**: This theorem states that any continuous function defined on a closed interval can be uniformly approximated as closely as desired by a polynomial function.

Analytic number theory is a branch of number theory that uses techniques from mathematical analysis to solve problems about integers and prime numbers. Several important theorems form the foundation of this field. Here are some of the prominent theorems and concepts within analytic number theory: 1. **Prime Number Theorem**: This fundamental theorem describes the asymptotic distribution of prime numbers.

In mathematical analysis and other fields of mathematics, a "lemma" is a preliminary proposition or statement that is proven to aid in the proof of a larger theorem. The term "lemma" comes from the Greek word "lemma," which means "that which is received" or "that which is taken." In effect, results that are designated as lemmas are often foundational results that help establish more complex results.

Fixed-point theorems are fundamental results in mathematics that establish conditions under which a function will have a point that maps to itself. In simpler terms, if you have a function \( f \) defined on a certain space, a fixed point \( x \) satisfies the equation \( f(x) = x \). Fixed-point theorems are widely applicable in various areas such as analysis, topology, and applied mathematics.

Convergence tests are mathematical techniques used to determine whether a series or sequence converges (approaches a finite limit) or diverges (grows indefinitely or does not settle at any finite value). These tests are particularly important in the study of infinite series in calculus and analysis, as they help evaluate the behavior of sums of infinitely many terms.

Niven's theorem is a result in number theory that concerns the rationality of certain integrals. Specifically, it states that if \( a \) is a positive integer, then the integral \[ \int_0^1 x^a (1 - x)^a \, dx \] is a rational number and can be expressed in terms of the binomial coefficient.

The Nielsen–Schreier theorem is a result in group theory that provides a characterization of free groups in terms of their subgroups. The theorem states that every subgroup of a free group is free. More specifically, if \( F \) is a free group, then any subgroup \( H \) of \( F \) is itself a free group, possibly on a different set of generators.

Matlis duality is a concept in commutative algebra that pertains to the study of modules over a Noetherian local ring. It provides a way to relate a module to a dual module that can reflect certain properties of the original module. Specifically, Matlis duality provides an equivalence between the category of finitely generated modules over a Noetherian local ring and the category of certain finitely generated modules over its completion.

The Krull–Akizuki theorem is a result in the field of commutative algebra, specifically concerning the factorization properties of elements in Noetherian rings. It provides a foundation for understanding how the integral closure of an ideal behaves under certain conditions. More specifically, the theorem considers Noetherian rings and the behavior of ideals in them.

The Koecher–Vinberg theorem is a result in the field of arithmetic geometry, specifically concerning the structure of certain types of algebraic varieties. This theorem is particularly relevant in the study of symmetric spaces and the theory of quadratic forms. In broad terms, the Koecher–Vinberg theorem addresses the behavior of closed cones in the context of the theory of quadratic forms, stating conditions under which certain cones can be regarded as "nice" with respect to their arithmetic and geometric properties.

The Hilbert–Burch theorem is a central result in commutative algebra, particularly in the study of finitely generated modules over local rings and the characterization of certain types of ideals in polynomial rings. Named after mathematicians David Hilbert and William Burch, the theorem provides criteria for when a finitely generated R-module has a specific kind of structure.

The Harish-Chandra isomorphism is a fundamental result in the representation theory of Lie groups and Lie algebras, particularly in the context of semisimple Lie groups. It relates the spaces of invariant differential operators on a symmetric space to the space of functions on the Lie algebra of the group. More specifically, consider a semisimple Lie group \( G \) and a maximal compact subgroup \( K \).

Haran's diamond theorem is a result in set theory and the study of topology, specifically dealing with the properties of certain types of topological spaces. The theorem pertains to the concept of "diamonds," which are specific kinds of ordered sets that can encode certain structures in topology. The primary assertion of Haran's diamond theorem characterizes the conditions under which one can embed a specific kind of ordered structure (notably the diamond principle) into a larger structure.

The Crystallographic Restriction Theorem is a concept in the field of crystallography and solid state physics that describes certain symmetries in crystalline materials. It states that the symmetry operations of a crystal, such as rotations, translations, and reflections, impose restrictions on the types of point groups that can be realized in three-dimensional space. More specifically, the theorem states that the only symmetry operations allowed for a crystal lattice in three dimensions must be compatible with the periodicity of the lattice.

The Classification of Finite Simple Groups is a monumental result in the field of group theory, specifically in the area of finite groups. It establishes a comprehensive framework for understanding the structure of finite simple groups, which are the building blocks of all finite groups in a manner akin to how prime numbers function in number theory.

The Chevalley–Warning theorem is a result in algebraic geometry and number theory that concerns the existence of rational points on certain types of algebraic varieties. More specifically, it deals with the solutions of systems of polynomial equations over finite fields.

Bertrand's postulate, also known as Bertrand's conjecture, states that for any integer \( n > 1 \), there exists at least one prime number \( p \) such that \( n < p < 2n \). In other words, there is always at least one prime number between any integer \( n \) and its double \( 2n \). This conjecture was first proposed by the Russian mathematician Joseph Bertrand in 1845.

The Bernstein–Kushnirenko theorem is a result in algebraic geometry and algebraic topology concerning the number of solutions to a system of polynomial equations. More specifically, it provides a bound on the number of common solutions for systems of polynomial equations under certain conditions.