modern algebra
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What is modern algebra?
Modern algebra is a branch of mathematics that focuses on the general algebraic structure of various sets, such as real numbers, complex numbers, matrices, and vector spaces, rather than the rules and procedures for manipulating their individual elements.
During the 20th century, modern algebra shifted the conceptual hierarchy of classical algebra, with groups, fields, rings, and related concepts becoming the main focus. The primary task of algebra became the elucidation of the properties of each of these structures and of the relationships among them.
Moderne Algebra, a textbook by Dutch mathematician Bartel van der Waerden, presented a new image of the discipline and had a deep effect on almost every branch of mathematics. After the late 1930s, the structural approach in algebra became one of the most dynamic areas of research in mathematics.
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What are some basic objects studied in modern algebra, like groups and rings?
Modern algebra studies the underlying algebraic structure of sets, such as real numbers, complex numbers, matrices, and vector spaces, rather than manipulating individual elements.
Some of the basic objects studied in modern algebra include:
* Groups Groups are systems with a set of elements and a binary operation that satisfy certain axioms, vital for modern algebra with applications in geometry, physics, chemistry and computer science.
* Rings Rings are used extensively in algebraic geometry to study curves in a plane.
* Fields Fields are sets with operations that follow arithmetic rules, such as rational, real, and complex numbers. Fields can be finite or infinite, with finite fields having particular importance for discrete mathematics.5 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
What is a group in modern algebra?
In modern algebra, a group is a system where a set of elements combines with a binary operation, satisfying specific axioms. These axioms ensure the group is closed under the operation, meaning combining any two elements results in another element within the group. The group must also follow the associative law, possess an identity element that leaves other elements unchanged when combined, and ensure each element has an inverse that produces the identity element when combined with the original element. A group is called commutative, or Abelian, if it also satisfies the commutative law.
Group theory's applications extend to physics, chemistry, and computer science and is vital to modern algebra, with its basic structure present in many mathematical phenomena. Groups can represent symmetry and transformations in geometry. Évariste Galois first applied group theory to solve algebraic equations, introducing the concept of a Galois group.
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What is a ring in modern algebra?
In modern algebra, a ring is a set equipped with addition and multiplication operations that adhere to specific rules.
To be a ring, a set must have:
- Addition that is commutative (a + b = b + a) and associative (a + (b + c) = (a + b) + c).
- Multiplication that is associative (a(bc) = (ab)c).
- A zero element that serves as the identity for addition.
- Negatives for all elements, ensuring that adding an element and its negative yields the zero element.
- Distributive laws that connect addition and multiplication: (a(b + c) = ab + ac) and ((a + b)c = ac + bc).
If a ring also satisfies the commutative law of multiplication (ab = ba), it is called a commutative ring. The simplest example of a ring is the set of integers with standard addition and multiplication.
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How do groups and rings differ from each other?
In modern algebra, both groups and rings are systems consisting of sets of elements and operations that satisfy certain axioms.
A group requires a single binary operation that combines two elements to produce another element within the group. This operation must follow the associative law, include an identity element, and ensure each element has an inverse.
A ring, however, has two operations: addition and multiplication. Addition in a ring must be commutative and associative, with an identity element (zero) and negatives for all elements. Multiplication must be associative, and there should be two distributive laws relating addition and multiplication.
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How is modern algebra used in real life or other areas of mathematics?
Modern algebra, which studies the underlying structure of mathematical sets, has deeply influenced various branches of mathematics. Modern algebra shifted the focus from manipulating individual elements to examining the sets themselves.
Élie-Joseph Cartan's work on Lie algebras, which are abstract settings for matrix algebra, demonstrates how modern algebra applies to geometry and physics. Hermann Weyl further expanded this theory to include differential geometry, group theory, and physics applications. Chen Ning Yang and Robert L. Mills successfully applied Lie group theory to explain the strong interaction in particle physics.
Abstract algebra provides the foundation for understanding more complex mathematical structures and their relationships. This approach has led to new theorems and techniques, including the application of computers and probabilistic methods in solving algebraic problems.
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modern algebra, branch of mathematics concerned with the general algebraic structure of various sets (such as real numbers, complex numbers, matrices, and vector spaces), rather than rules and procedures for manipulating their individual elements.
During the second half of the 19th century, various important mathematical advances led to the study of sets in which any two elements can be added or multiplied together to give a third element of the same set. The elements of the sets concerned could be numbers, functions, or some other objects. As the techniques involved were similar, it seemed reasonable to consider the sets, rather than their elements, to be the objects of primary concern. A definitive treatise, Modern Algebra, was written in 1930 by the Dutch mathematician Bartel van der Waerden, and the subject has had a deep effect on almost every branch of mathematics.
Basic algebraic structures
Fields
In itself a set is not very useful, being little more than a well-defined collection of mathematical objects. However, when a set has one or more operations (such as addition and multiplication) defined for its elements, it becomes very useful. If the operations satisfy familiar arithmetic rules (such as associativity, commutativity, and distributivity) the set will have a particularly “rich” algebraic structure. Sets with the richest algebraic structure are known as fields. Familiar examples of fields are the rational numbers (fractions a/b where a and b are positive or negative whole numbers), the real numbers (rational and irrational numbers), and the complex numbers (numbers of the form a + bi where a and b are real numbers and i2 = −1). Each of these is important enough to warrant its own special symbol: ℚ for the rationals, ℝ for the reals, and ℂ for the complex numbers. The term field in its algebraic sense is quite different from its use in other contexts, such as vector fields in mathematics or magnetic fields in physics. Other languages avoid this conflict in terminology; for example, a field in the algebraic sense is called a corps in French and a Körper in German, both words meaning “body.”
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In addition to the fields mentioned above, which all have infinitely many elements, there exist fields having only a finite number of elements (always some power of a prime number), and these are of great importance, particularly for discrete mathematics. In fact, finite fields motivated the early development of abstract algebra. The simplest finite field has only two elements, 0 and 1, where 1 + 1 = 0. This field has applications to coding theory and data communication.
Structural axioms
The basic rules, or axioms, for addition and multiplication are shown in the table, and a set that satisfies all 10 of these rules is called a field. A set satisfying only axioms 1–7 is called a ring, and if it also satisfies axiom 9 it is called a ring with unity. A ring satisfying the commutative law of multiplication (axiom 8) is known as a commutative ring. When axioms 1–9 hold and there are no proper divisors of zero (i.e., whenever ab = 0 either a = 0 or b = 0), a set is called an integral domain. For example, the set of integers {…, −2, −1, 0, 1, 2, …} is a commutative ring with unity, but it is not a field, because axiom 10 fails. When only axiom 8 fails, a set is known as a division ring or skew field.
| Field axioms | |
| axiom 1 | Closure: the combination (hereafter indicated by addition or multiplication) of any two elements in the set produces an element in the set. |
| axiom 2 | Addition is commutative: a + b = b + a for any elements in the set. |
| axiom 3 | Addition is associative: a + (b + c) = (a + b) + c for any elements in the set. |
| axiom 4 | Additive identity: there exists an element 0 such that a + 0 = a for every element in the set. |
| axiom 5 | Additive inverse: for each element a in the set, there exists an element -a such that a + (-a) = 0. |
| axiom 6 | Multiplication is associative: a(bc) = (ab)c for any elements in the set. |
| axiom 7 | Distributive law: a(b + c) = ab + ac and (a + b)c = ac + bc for any elements in the set. |
| axiom 8 | Multiplication is commutative: ab = ba for any elements in the set. |
| axiom 9 | Multiplicative identity: there exists an element 1 such that 1a = a for any element in the set. |
| axiom 10 | Multiplicative inverse: for each element a in the set, there exists an element a-1 such that aa-1 = 1. |
Quaternions and abstraction
The discovery of rings having noncommutative multiplication was an important stimulus in the development of modern algebra. For example, the set of n-by-n matrices is a noncommutative ring, but since there are nonzero matrices without inverses, it is not a division ring. The first example of a noncommutative division ring was the quaternions. These are numbers of the form a + bi + cj + dk, where a, b, c, and d are real numbers and their coefficients 1, i, j, and k are unit vectors that define a four-dimensional space. Quaternions were invented in 1843 by the Irish mathematician William Rowan Hamilton to extend complex numbers from the two-dimensional plane to three dimensions in order to describe physical processes mathematically. Hamilton defined the following rules for quaternion multiplication: i2 = j2 = k2 = −1, ij = k = −ji, jk = i = −kj, and ki = j = −ik. After struggling for some years to discover consistent rules for working with his higher-dimensional complex numbers, inspiration struck while he was strolling in his hometown of Dublin, and he stopped to inscribe these formulas on a nearby bridge. In working with his quaternions, Hamilton laid the foundations for the algebra of matrices and led the way to more abstract notions of numbers and operations.