Some Facts
Every homomorphic image of a finitely generated module is finitely generated. In general, submodules of finitely generated modules need not be finitely generated. As an example, consider the ring R = Z of all polynomials in countably many variables. R itself is a finitely generated R-module (with {1} as generating set). Consider the submodule K consisting of all those polynomials with zero constant term. Since every polynomial contains only finitely many terms whose coefficients are non-zero, the R-module K is not finitely generated.
In general, a module is said to be Noetherian if every submodule is finitely generated. A finitely generated module over a Noetherian ring is a Noetherian module (and indeed this property characterizes Noetherian rings): A module over a Noetherian ring is finitely generated if and only if it is a Noetherian module. This resembles, but is not exactly Hilbert's basis theorem, which states that the polynomial ring R over a Noetherian ring R is Noetherian. Both facts imply that a finitely generated algebra over a Noetherian ring is again a Noetherian ring.
More generally, an algebra (e.g., ring) that is a finitely-generated module is a finitely-generated algebra. Conversely, if a finitely generated algebra is integral (over the coefficient ring), then it is finitely generated module. (See integral element for more.)
Let be an exact sequence of modules. Then M is finitely generated if are finitely generated. There are some partial converses to this. If M is finitely generated and M'' is finitely presented (which is stronger than finitely generated; see below), then is finitely-generated. Also, is Noetherian (resp. Artinian) if and only if are Noetherian (resp. Artinian).
Let B be a ring and A its subring such that B is a faithfully flat right A-module. Then a left A-module F is finitely generated (resp. finitely presented) if and only if the B-module is finitely generated (resp. finitely presented).
Read more about this topic: Finitely-generated Module
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“I’m not afraid of facts, I welcome facts but a congeries of facts is not equivalent to an idea. This is the essential fallacy of the so-called “scientific” mind. People who mistake facts for ideas are incomplete thinkers; they are gossips.”
—Cynthia Ozick (b. 1928)
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