Quotients by group actions many important manifolds are constructed as quotients by actions of groups on other manifolds, and this often provides a useful way to understand spaces that may have been constructed by other means. A quotient space is not just a set of equivalence classes, it is a set together with a topology. Consider the quotient vector space xm and the quotient map. Jul 28, 2017 quotient space covers a lot of ground. In all the development above we have created examples of vector spaces primarily as subspaces of other vector spaces.
Linear algebradefinition and examples of vector spaces. Tensor product of vector spaces quotient definition. Whats an intuitive way of looking at quotient spaces. The set of equivalence classes of this equivalence relation is denoted vu and is called the quotient space of v modulo. By is equivalent to modulo, it is meant that for some in, and is another way to say. This is because velocity times time equals displacement. You can have quotient spaces in set theory, group theory, field theory, linear algebra, topology, and others. In quantum mechanics the state of a physical system is a vector in a complex vector space. This is an incredibly useful notion, which we will use from time to time to simplify other tasks.
Quotient spaces in all the development above we have created examples of vector spaces primarily as subspaces of other vector spaces. Muhammad khalid of university of sargodha, sargodha written by atiq ur rehman. Similarly, the quotient space for r 3 by a line through the origin can again be represented as the set of all coparallel lines, or alternatively be represented as the vector space consisting of a plane which only intersects the line at the origin. We will describe a construction of the quotient vector space vu. This rather modest weakening of the axioms is quite far reaching, including. Smith october 14, 2011 abstract an introductory overview of vector spaces, algebras, and linear geometries over an arbitrary commutative. We could also say that the above subset is an a ne subset of v parallel to u through v. In particular, at the end of these notes we use quotient spaces to give a simpler proof than the one given in the book of the fact that operators on nite dimensional complex vector spaces are \uppertriangularizable. We give here three situations in which the quotient space is not only hausdorff, but normal. Notes on quotient spaces santiago canez let v be a vector space over a eld f, and let w be a subspace of v. Quotient spaces and quotient maps university of iowa. Quotient spaces oklahoma state universitystillwater. Another example is the quotient of r n by the subspace spanned by the first m standard basis vectors.
The tensor algebra tv is a formal way of adding products to any vector space v to obtain an algebra. Chapter 3 quotient spaces, direct sums and projections 3. The quotient vector space suppose v is a vector space over k and u. Quotient topological vector spaces quotient topological vector space let x be now a t. Notes on categories, the subspace topology and the product. If w is a subspace of v, then all the vector space axioms are satis. Math 4310 handout quotient vector spaces cornell department.
Quotient spaces are emphasized and used in constructing the exterior and the symmetric algebras of a vector space. First isomorphism proved and applied to an example. Aug 10, 2018 v is the vector space and u is the subspace of v. The quotient space is already endowed with a vector space structure by the construction of the previous section. There is a sense in which we can \divide v by w to get a new vector space.
Examples include the vector space of nbyn matrices, with x, y xy. Michael atiyah based on the previous lectures, we now have the following big picture. A vector space v is a collection of objects with a vector. First, we generalize the lie algebraic structure of general linear algebra gl n, r to this dimensionfree quotient space. What is an intuitive explanation of a quotient space. We define a natural equivalence relation on v by setting v. Of course, the word \divide is in quotation marks because we cant really divide vector spaces in the usual sense of division. Of course, if x was t 0 to begin with, then kqx and x are naturally homeomorphic. With this multiplication operation plus addition coming from its vector space structure, fxi is a. Coordinate system, chart, parameterization let mbe a topological space and u man open set.
So, if you are have studied the basic notions of abstract algebra, the concept of a coset will be familiar to you. Vector spaces handwritten notes msc msc notes these are lecture notes of prof. This quotient space is called the kolmogorov quotient of x, which we will denote kqx. This is a bit of an abstract theorem, so well work with the concrete example above. The point of this example is that physical quantities have units associated with them.
Notes on categories, the subspace topology and the product topology. Examples of building topological spaces with interesting shapes. Quotient spaces v is a vector space and w is a subspace of v. Then v t is the space of displacement vectors in newtonian 3 space. In general, when is a subspace of a vector space, the quotient space is the set of equivalence classes where if. Here i prove three fundamental propositions about cosets of a subspace. So, now we can ask questions about linear independence, span, bases, whatever, in vu. As a vector space, it is spanned by symbols, called simple tensors. Below well provide a construction which starts with a vector space v over a eld f and a subspace sof v, and which furnishes with an entirely new vector space from vswhich is particularly prominent in. In this course you will be expected to learn several things about vector spaces of course. Normality of quotient spaces for a quotient space, the separation axiomseven the ausdorff propertyare difficult to verify. Then modding out by u amounts to zeroing out the components of the basis corresponding to u, i.
No matter what topological space x might be to begin with, the quotient space under this equivalence relation is always t 0. Introductiontovectorspaces,vector algebras,andvectorgeometries richard a. One can, but in general should not, try to visualize the quotient space vw as a subspace of the space v. Mar 06, 2015 we conclude be defining the quotient space vw. If x is a banach space and m is a closed subspace of x, then the quotient xm is again a banach space. We know that planar isometries are examples of groups, and more precisely. Show that w is a subspace of the vector space v of all 3. However, even if you have not studied abstract algebra, the idea of a coset in a vector. Since two cosets of m are either identical or disjoint, the quotient space xm is the set of all the distinct cosets of m.
Observables are linear operators, in fact, hermitian operators acting on this complex vector space. Introduction to vector spaces, vector algebras, and vector geometries. Sometimes the equivalence classes are written as cosets. Namely, any basis of the subspace u may be extended to a basis of the whole space v. Let v be the space of velocity vectors in newtonian 3 space.
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