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Ideal Quotient


The ideal quotient (a:b), also called a colon ideal, is the ideal in a commutative ring R defined by

 (a:b)={x in R:xb subset= a},

where a and b are ideals. It is an analog of division for ideals.

If b=<g_1,...,g_s>, then x in (a:b) iff xg_i in a for every i=1, ..., s. In particular, quotienting by a principal ideal <q> requires only xq in a (Jensen 2014, p. 67).

For positive integers m and n, the ring of integers gives

 (<m>:<n>)=<m/gcd(m,n)>,

where gcd(m,n) is the greatest common divisor. Thus (<12>:<2>)=<6>, while (<12>:<5>)=<12>. Taking the union of the quotients by successive powers of an ideal gives ideal saturation.


See also

Algebraic Geometry, Algebraic Number Theory, Euler Conductor, Ideal, Ideal Saturation, Principal Ideal

Portions of this entry contributed by Todd Rowland

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References

Jensen, A. N. Lecture Notes: Algebra and Polyhedral Geometry. May 30, 2014. §6.1, pp. 67-68. https://users-math.au.dk/jensen/teaching/2014AlgebraAndPolyhedralGeometry/notes.pdf.

Referenced on Wolfram|Alpha

Ideal Quotient

Cite this as:

Weisstein, Eric W., with contributions by Todd Rowland. "Ideal Quotient." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/IdealQuotient.html

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