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Answers for “素理想的定义是什么?”

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An ideal P of a commutative ring R is prime if it satisfies two properties: first, if the product ab of two elements a and b in R is in P, then at least one of a or b must be in P; second, P is not the entire ring R.

Conditions: R is a commutative ring.; P is an ideal of R.; For all a, b in R, if ab is in P, then a is in P or b is in P.; P is not equal to R.

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A scheme is defined as a topological space together with commutative rings for all of its open sets, which arises from gluing together spectra of commutative rings along their open subsets. Equivalently, a scheme is a ringed space that is locally a spectrum of a commutative ring, or locally isomorphic to an affine space.

Conditions: It involves a topological space.; It involves commutative rings assigned to open sets.; It is constructed by gluing spectra of commutative rings.; It is a ringed space locally isomorphic to an affine space.

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When m is a prime number, mZ is a maximal ideal of Z because any ideal I containing mZ must be of the form kZ (since all ideals of Z are principal). The inclusion mZ ⊆ kZ implies that k divides m.

Conditions: The ambient ring is the ring of integers Z.; m is a prime number.; The ideal under consideration is mZ.

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In commutative algebra, the spectrum of a ring R is the set of all prime ideals of R, and is usually denoted by Spec R. In algebraic geometry, it is simultaneously a topological space equipped with the sheaf of rings O.

Conditions: R is a commutative ring.; The context includes both commutative algebra and algebraic geometry.

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The unit ideal (1) = Z is excluded from being a prime or maximal ideal because both definitions require the ideal to be a proper ideal. A proper ideal must be a strict subset of the ring (I≠RI \ne R).

Conditions: The ambient ring is the ring of integers Z.; The ideal under consideration is the unit ideal (1) = Z.

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6Z is not a prime ideal of Z because 6 is a composite number. The definition of a prime ideal requires that if a product ab lies in the ideal, then at least one factor (a or b) must lie in the ideal.

Conditions: The ambient ring is the ring of integers Z.; The ideal under consideration is 6Z.; 6 is a composite number.

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An affine scheme is a locally ringed space that is isomorphic to the spectrum Spec(R) of a commutative ring R. General schemes are constructed by gluing together open sets of this simple kind, called affine schemes.

Conditions: The object is an affine scheme.; It is a locally ringed space.; It is isomorphic to the spectrum of a commutative ring.

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The zero ideal {0} is a prime ideal of Z because it satisfies the definition of a prime ideal. First, {0} is a proper ideal of Z (since {0} ≠ Z).

Conditions: The ambient ring is the ring of integers Z.; The ideal under consideration is the zero ideal {0}.