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2answers
52 views

How is this an example of a Universal Property?

I'm totally lost on this problem, which is from a set of notes by Tom Leinster on Category Theory: Let $\phi: G \to H$ be a homomorphism of groups. Associated with $\phi$ are the diagrams $ker(\phi) ...
2
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0answers
35 views

Show that $H *_{G} (G/N) \cong H/N'$ where $f(N)=N' \subset H$.

I was doing some group theory and this exercise came up. Let $f: G \to H$ be a group morphism and $N$ a normal subgroup of $G$. Denote $\pi: G \to G/N$ and let $N'$ be the normal closure of $f(N)$. ...
2
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1answer
50 views

“Canonical” symmetrization/skew-symmetrization/alternation of multilinear functions

Is there some precise sense in which the "alternation" functor $A$ that maps a multilinear function $f\colon M^d\to N$ to the alternating multilinear function $A(f)\colon M^d\to N$ defined by $$ ...
11
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2answers
133 views

Is there a concept of a “free Hilbert space on a set”?

I am looking for a "good" definition of a Hilbert space with a distinct orthonormal basis (in the Hilbert space sense) such that each basis element corresponds to an element of a given set $X$. Before ...
0
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1answer
43 views

Continuity of sum/product using characteristic property

I'm self studying Lee's Introduction to Topological Manifolds, and I'm familiarising myself to the characteristic/universal property view of topology. One of the exercises in chapter 3 goes as ...
1
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1answer
41 views

Lifts of embeddings of Lie algebras to their universal enveloping algebras

Let $k$ be an algebraically closed field, and let $(\mathfrak{h},[\;,\;])$ be a finite dimensional abelian Lie algebra $k$. Let $(\mathfrak{g},[\;,\;])$ be a finite dimensional Lie algebra over $k$ ...
5
votes
2answers
90 views

Is there a logical interpretation for equalizer and co-equalizer?

I know the logical equivalent to several universal constructions. For example product $\times$ is $\land$ and co-product $+$ is $\lor$. The associated arrows are projection and inclusion. The ...
3
votes
1answer
53 views

About the Stone-Čech universal property

There's something I am missing here and I don't know what it is. I understand that the Stone-Čech compactification of $X$ satisfies the property that for every continuous map $f: X \rightarrow K$ ...
0
votes
1answer
51 views

Tensor Algebra = Universal Property of FORGETFUL FUNCTOR?

Hi there in wiki the tensor algebra is defined w.r.t. the adjoint of the forgetful functor rather than the forgetful functor itself - why so? Besides, does the existence of such algebras for every ...
0
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1answer
41 views

Existence of Initial Object implies Existence of Terminal Object? [closed]

Consider an initial object always exists in a category. Reversing all arrows now. Does this guarantee the existence of terminal objects in that category?
0
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1answer
47 views

Characteristic Property = Universal Property?

Problem They seem to be the same -almost! But are they really or is it just unlucky accident that they look so similar however describe totally different notions? Example I was trying to set the ...
0
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0answers
11 views

Universal property of tensor products of real Hilbert spaces

I have the following exercise where I could need some hints: Let H1, H2 be real Hilbert spaces. Prove that there is a weak Hilbert-Schmidt mapping $$ p: H_1 \times H_2 \rightarrow H_1 \otimes H_2 ...
5
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0answers
61 views

Universal Property for Tangent Space

As far as I know there are basically three different approaches to the tangent space -all of them coming with advantages and disadvantages: Though the oldest one precisely represents the derivative ...
0
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0answers
17 views

Subset/subgroups/etc as Equalizers using Pushouts

I am trying to show that in a given category $\mathcal{C}$ which has pushouts, we can show that any morphism $f:X\rightarrow Y$ is an equalizer of some pair of morphisms. My solution to this is by ...
1
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3answers
45 views

Would this proof be considered true.Proving a property of a operation

Ok so the operation [x] is defined to be equal to the integer such that it is $\leq x$ From this definition it holds that : $$ [x] \leq x $$ I need to prove that $$ [x+n] = [x] + n $$ My proof ...
2
votes
1answer
46 views

$F$ entire with $\lim_{k \rightarrow \infty} F(z + N_{k}) = h(z)$ for every $h$ entire

Prove that there exists an entire function with the following "universal" property: given any entire function $h$, there is an increasing sequence $\{ N_{k}\}_{k=1}^{\infty}$ of positive integers ...
2
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0answers
25 views

Disjoint Union Topology universal property as instance of final topology's universal property [duplicate]

I'm studying the final topology on a set $X$ induced by a family $\{f_\alpha:X_\alpha\rightarrow X\mid \alpha\in A\}$ and know of its universal property, namely that given a function $g:X\rightarrow ...
0
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2answers
90 views

Universal Property of Localization

Let $R$ be a commutative ring with $1\not =0$, and let $D\ni 1$ be a multiplicative subset of $R$. Consider the universal characterization of $D^{-1}R$: There is a morphism $\pi\colon R\to D^{-1}R$ ...
10
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2answers
137 views

How to get used to commutative diagrams? (the case of products).

I've returned to Aluffi's book (after getting the basics of groups from Herstein's) and I hit the same brick wall that made me put it aside. My general problem is this: I can't seem to get used to ...
0
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0answers
55 views

Universal property of free spaces

In class we had developed the notion of a free space in preparation for our study of tensor product. There is one statement in my notes about the universal property of free spaces that has been ...
1
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1answer
53 views

Extending the universal property of tensor product

Suppose that we defined a tensor product of vector spaces $U$ and $V$ as a quotient of a vector space with basis $V \times W$ by the vector space spanned by $-(u_1+u_2,v)+(u_1,v)+(u_2,v), ...
2
votes
1answer
58 views

How to use universal constructions to create this category/object?

Given an a category $\mathcal{C}$ what is the most concise way to construct the smallest one object category $\mathcal{D}$ such that there exists a faithful functor from $\mathcal{C} \to \mathcal{D}$? ...
2
votes
1answer
98 views

Why does the fiber coproduct in $\mathbf{Set}$ actually satisfy the universal property?

Suppose you have two morphisms $f\colon A\to B$ and $g\colon A\to C$. Then the fiber coproduct of $B$ and $C$ over $A$ exists and is the disjoint union $B\coprod C$ where we identify $fx$ and $gx$ for ...
1
vote
2answers
76 views

Binary number theory

I want to know if there exists some book about "Binary number theory", I'm interesting in this because there many problems of ICPC about this topic. Thanks in advance
2
votes
1answer
52 views

Distinguishing characteristic and spurious properties

When working in set theory with definitions of somehow primitive notions like ordered pairs (Kuratowski) or ordinal numbers (von Neumann) one is supposed to use only the characteristic properties of ...
1
vote
1answer
29 views

Universal property of sum of ideals

If $A$ is a commutative algebra over the field $K$, and $I,J$ are ideals of $A$ (in particular, they are also algebras over $K$), is it possible to characterize the ideal they generate together $I + J ...
3
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3answers
110 views

Can an object be universal with respect to several properties?

Does anyone know an example of an object $A$ in some category $\mathcal C$ such that $A$ satisfies at the same time more than one universal property? Of course, when I say that $A$ is universal with ...
15
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1answer
176 views

Universal property of de Rham differential.

Suppose $A$ is a commutative algebra over a field $k$. It is well known that there is a module that generalizes the notion of differential $1$-forms. It is denoted $\Omega^1_{k}(A)$ and is called the ...
7
votes
1answer
104 views

Universal properties of “interesting” families of graphs

Can cycles – and/or other "interesting" families of graphs like paths, trees, hypercubes, etc. – be characterized by a universal property in the category of graphs? I admit that there is ...
1
vote
1answer
224 views

Direct (Inductive) limit of (locally convex) TVEs and universal property

This is not really a question, I'd just like to discuss a little about universal properties (more specifically, the direct limit) in TVEs. I'm trying to work with universal properties in Topological ...
1
vote
1answer
229 views

Anti-derivation of an exterior algebra

Let $K$ be a commutative ring. $M$ is a free $K$-module of rank $m$. $E(M)$ is the exterior algebra defined by $M$. $\iota$ is a $K$-homomorphism from $M$ to $E(M)$ such that $\iota(x)=-x$. Since ...
0
votes
1answer
175 views

Quotient function [closed]

Let $f : X \to Y$ be a quotient map, and $g : X \to Z$ a continuous function such that $g(x_1) = g(x_2)$ whenever $f(x_1) = f(x_2)$. Show that there exists a unique continuous function $h : Y \to Z$ ...
3
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0answers
48 views

A mathematical object that can be characterised by axioms as well as by universal constructions

This question (more specifically one of the comments) prompted me to ask this question: Can someone give me an example of a mathematical object that one can characterize both via axioms and universal ...
6
votes
1answer
203 views

Axioms vs. Universal Constructions/Properties

What (exactly) is the difference between defining a mathematical object by it's axioms and by a universal construction ? Please take my 3 opinions into consideration, as they also contain more ...
6
votes
2answers
289 views

Why is category theory not just another theory? [closed]

Consider category theory as one theory among many others: with a simple signature and some simple axioms. Compare it with - e.g. - group theory as another theory with a simple signature and some ...