The spelling of the word "number field" is straightforward. Number is spelled with a "nʌm-bər" /ˈnʌm.bər/ phonetic transcription, pronounced with emphasis on the first syllable and a soft "b" sound. Field is spelled with a "fiːld" /fiːld/ phonetic transcription, with a long "ee" sound in the first syllable and a silent "d". Together, the two words create a compound noun that refers to a subset of a larger mathematical field, such as complex numbers, real numbers or p-adic numbers.
A number field is a fundamental concept in the field of algebraic number theory. It refers to a finite extension of the rational numbers, typically denoted as Q, which is the field of rational numbers. In other words, a number field is an extension field of the rational numbers where additional elements, called algebraic numbers, are adjoined in order to provide a larger set of numbers.
A number field can be thought of as an algebraic structure that encompasses both the rational numbers and the new elements introduced through the extension. These new elements are typically solutions to polynomial equations with rational coefficients. Therefore, a number field contains all the roots of these polynomials, making it a rich and encompassing field.
The elements of a number field possess specific properties such as addition, subtraction, multiplication, and division, allowing for the execution of arithmetic operations within the field. They also possess distinct algebraic properties, such as conjugation and norms, that relate to the structure and behavior of the numbers in the field.
Number fields have numerous significant applications in various branches of mathematics, particularly in algebraic geometry, algebraic topology, and cryptography. They are also crucial in studying Diophantine equations, the distribution of prime numbers, and the structure of number rings. Overall, number fields provide a key framework for exploring and understanding the properties and behavior of numbers beyond the rational realm.
The word "number field" is derived from two components: "number" and "field".
The term "number" originates from the Latin word "numerus", which means "number". It has its roots in Indo-European and is related to the Sanskrit word "namati", meaning "he assigns". Over time, "number" came to refer to the concept of a numerical value or quantity.
The term "field" comes from the Old English word "feld", meaning "open land" or "plain". It shares the same Germanic root as the Dutch word "veld" and the German word "Feld". In mathematics, a "field" describes a set of elements with operations like addition, subtraction, multiplication, and division—similar to the arithmetical operations on numbers.