# Download A First Course in Module Theory by Mike E Keating PDF

By Mike E Keating

Long ago 20 years, there was nice growth within the thought of nonlinear partial differential equations. This booklet describes the development, concentrating on attention-grabbing themes in gasoline dynamics, fluid dynamics, elastodynamics and so on. It includes ten articles, each one of which discusses a truly contemporary outcome bought through the writer. a few of these articles evaluate comparable effects earrings and beliefs; Euclidean domain names; modules and submodules; homomorphisms; quotient modules and cyclic modules; direct sums of modules; torsion and the first decomposition; shows; diagonalizing and inverting matrices; becoming beliefs; the decomposition of modules; general varieties for matrices; projective modules; tricks for the routines

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To see this, suppose that / = qg + r and / = q\g + n with deg(r) < deg(g) and deg(ri) < deg(^). Then (q — q\)g = T% — r. But deg(ri — r) cannot be a nonzero multiple of deg(g), so ri — r = 0 and 9 - 9i = 0. 4 The Gaussian integers A Gaussian integer is a complex number of the form a + bi where a, b are ordinary integers. The set of all Gaussian integers is written 1\i]. If c + di is also a Gaussian integer, the sum and product, (a + bi) + (c + di) = (a + c) + (c + d)i and (a + bi) ■ (c + di) = (ac — bd) + {ad + bc)i respectively, are again Gaussian integers.

In one elementary but important special case, a submodule must be given by an eigenvector. 1 Lemma Let F be a field, let A be annxn matrix over F, and let M be the F[X]module obtained from the vector space Fn with X acting as A. Further, suppose that the subspace U of Fn is one-dimensional over F. 11. Example: a triangular matrix action 47 Then U gives an F[X]-submodule of M if and only if U = Fu is an eigenspace of A, where u is an eigenvector for some eigenvalue A of A. Proof Suppose that U does give a submodule, so that U is invariant under A.

Since be = xa for some x e R, c = sac + tbc = (sc + tx)a. 3 Corollary Let R be a Euclidean domain and suppose that a,b € R are coprime. Then RaC\Rb = Rab. 4 Corollary Suppose that p G R is irreducible and that p \ be where b and c are in R. Then either p\b or p\c. Proof Since (p, b) is a divisor of p, either (p, b) = up for some unit u or (p, b) = 1. 2 above. □ We come to the main result on factorization. 5 The Unique Factorization Theorem Suppose that a is a nonzero element of a Euclidean domain R.