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Tag Archives: rings
Commutative Algebra 5
Morphisms in Algebraic Geometry Next we study the “nice” functions between closed subspaces of . Definition. Suppose and are closed subsets. A morphism is a function which can be expressed as: for some polynomials . We also say f is a regular … Continue reading
Posted in Advanced Algebra
Tagged algebraic geometry, continuity, ideals, morphisms, rings, topology
2 Comments
Commutative Algebra 4
More Concepts in Algebraic Geometry As before, k denotes an algebraically closed field. Recall that we have a bijection between radical ideals of and closed subsets of . The bijection reverses the inclusion so if and only if . Not too … Continue reading
Posted in Advanced Algebra
Tagged algebraic geometry, closed subsets, ideals, irreducible spaces, rings, zariski topology
7 Comments
Commutative Algebra 3
Algebraic Geometry Concepts We have decided to introduce, at this early point, some basics of algebraic geometry in order to motivate the later concepts. In summary, algebraic geometry studies solutions to polynomial equations over a field. First we consider a … Continue reading
Posted in Advanced Algebra
Tagged algebraic geometry, commutative rings, ideals, nullstellensatz, radical ideals, rings, topology, zariski topology
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Commutative Algebra 2
Radical of an Ideal In this installation, we will study more on ideals of a ring A. Definition. If is an ideal, its radical is defined by To fix ideas, again consider the case again. For the ideal (m) where , … Continue reading
Posted in Advanced Algebra
Tagged commutative rings, ideal division, ideals, radical ideals, rings
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Commutative Algebra 1
More About Ideals Recall that we defined three operations on ideals: intersection, sum and product. We can take intersection and sum of any collection of ideals (even infinitely many of them), but we can only define the product of finitely many … Continue reading
Posted in Advanced Algebra
Tagged chinese remainder theorem, coprime ideals, ideals, rings
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Commutative Algebra 0
We’re starting a new series on commutative algebra. This has been in the works for way too long, and eventually we just decided to push ahead with it anyway. Most of the articles will be short, and we’ll try to … Continue reading
Posted in Advanced Algebra
Tagged commutative rings, fields, ideals, integral domains, rings
2 Comments
Semisimple Rings and Modules
After discussing simple modules, the next best thing is to look at semisimple modules, which are just direct sums of simple modules. Here’s a summary of the results we’ll prove: A module is semisimple iff it is a sum of simple … Continue reading
Simple Modules
We briefly talked about modules over a (possibly non-commutative) ring R. An important aspect of modules is that unlike vector spaces, modules are usually not free, i.e. they don’t have a basis. For example, take the Z-module given by Z/2Z. [ Recall: a Z-module is … Continue reading
Posted in Notes
Tagged algebra, associative algebra, division rings, rings, schur's lemma, simple modules
2 Comments
Elementary Module Theory (I)
Modules can be likened to “vector spaces for rings”. To be specific, we shall see later that a vector space is precisely a module over a field (or in some cases, a division ring). This set of notes assumes the … Continue reading
Posted in Notes
Tagged generated submodules, ideals, left ideals, modules, rings, scalar multiplication, simple modules, submodules
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Topology: More on Algebra and Topology
We’ve arrived at the domain where topology meets algebra. Thus we have to proceed carefully to ensure that the topology of our algebraic constructions are well-behaved. Let’s look at topological groups again. Our first task is to show that the … Continue reading
Posted in Notes
Tagged algebra, connected spaces, groups, isomorphism theorems, open maps, orthogonal groups, quotient topology, rings, topology
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Mathematics and Such 