Algebraic numbers

Definition

Algebraic numbers are complex numbers that are roots of non-zero polynomial equations with integer coefficients. They include rational numbers, irrational numbers like the square root of 2, and even some complex numbers like the cube root of -1. Their significance lies in the study of Diophantine approximation and transcendence theory, which explore how these numbers can be approximated by rational numbers and their relationship to transcendental numbers.

5 Must Know Facts For Your Next Test

1. Every rational number is an algebraic number because it can be expressed as a root of a linear polynomial like $ax + b = 0$.
2. Irrational algebraic numbers, such as $\\sqrt{2}$, are solutions to polynomial equations like $x^2 - 2 = 0$.
3. The set of algebraic numbers is countable, whereas the set of real numbers is uncountable, making algebraic numbers a smaller subset.
4. Transcendental numbers, like $e$ and $\\pi$, cannot be expressed as roots of any polynomial with integer coefficients and highlight the distinction between algebraic and non-algebraic numbers.
5. Diophantine approximation deals with how closely algebraic numbers can be approximated by rational numbers, revealing deep connections between number theory and algebra.

Review Questions

• How do algebraic numbers relate to Diophantine equations, and what role do they play in finding integer solutions?
  • Algebraic numbers often arise as solutions to Diophantine equations, which seek integer solutions for polynomial expressions. For instance, an equation like $x^2 + y^2 = z^2$ can yield algebraic solutions when expressed in terms of integer coordinates. By understanding the nature of algebraic numbers, we can analyze which forms of these equations yield solvable cases and find specific integer solutions through various number theoretic techniques.
• Discuss the importance of distinguishing between algebraic and transcendental numbers in the context of Diophantine approximation.
  • Distinguishing between algebraic and transcendental numbers is crucial in Diophantine approximation because algebraic numbers can be approximated by rational numbers with varying degrees of accuracy. In contrast, transcendental numbers defy such approximation by rational sequences. This distinction informs how mathematicians study the limits and bounds related to approximating real values through rational means, leading to deeper insights in number theory.
• Evaluate how the properties of algebraic numbers impact their use in transcendence theory and the implications for understanding irrationalities.
  • The properties of algebraic numbers significantly influence their role in transcendence theory by demonstrating how certain irrationalities can arise from roots of polynomials with integer coefficients. This interplay reveals that while some irrational values are expressible in a polynomial sense, others are not—thus leading to transcendental classifications. Understanding these distinctions helps mathematicians grasp the fundamental nature of different number types and their behaviors within mathematical constructs, especially when proving results about specific constants like $e$ or $\\pi$.

Related terms

Diophantine equations: Polynomial equations where the solutions are required to be integers.

Transcendental numbers: Numbers that are not algebraic, meaning they cannot be roots of any non-zero polynomial equation with integer coefficients.

Approximation theory: A branch of mathematics focused on how functions can be approximated with simpler functions, including the approximation of real numbers by rational numbers.