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Questions tagged [equivalence-relations]

Writer Olivia Zamora
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For questions about relations that are reflexive, symmetric, and transitive. These are relations that model a sense of "equality" between elements of a set. Consider also using the (relation) tag.

2,881 questions
0 votes 0 answers 10 views

Showing an equivalence relation of Orbits

I want to show an equivalence relation of Orbits of a flow. Let $ y'=f(y)$ with $y \in\mathbb{R}^n $, f locally Lipschitz, $\phi$ the flow of the ODE. Show that: $y_1\sim y_2 \iff \exists x_2\in I_{... user avatar wolf_31
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0 votes 1 answer 45 views

The quotient space of the equivalence relation $x^2-y = x'^2-y'$

On the euclidean plane $\mathbb{R}^2$ we define an equivalence relation by $(x,y) \sim (x',y')$ iff $x^2 -y = x'^2 - y'$. In other words, I consider the set $$ \mathbb{R}/{\sim} := \{ [(x,y)] \mid (x,... user avatar Reikiri
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0 votes 0 answers 9 views

"Continuous" equivalence relation generated by a continuous weak order.

Let continuous weak order $\succsim\supset\ge$ be a subset of $\mathbb R^2\times\mathbb R^2$. Let $\sim=\succsim\cap\precsim$. A binary relation is an equivalence relation iff it is transitive, ... user avatar dodo
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0 votes 0 answers 24 views

What does the author mean here by the congruence relation generated by -?

I am reading up on Wheel Theory using the notes found at There really doesn't seem to be many online notes for this topic. It starts by motivating ... user avatar Riemann'sPointyNose
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1 vote 0 answers 78 views

Describing quotient set under the equivalence relation $x \sim y$ iff $\sin(x) = \sin(y)$.

I don't have any trouble showing that for any function $f: X \to Y$, the relation $x \sim y$ if and only if $f(x) = f(y)$ is an equivalence relation, all properties of which follow from reflexivity, ... user avatar Cardinality
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1 vote 0 answers 49 views

Proof verification of Set theory problem

Given an infinite set $X$ consider the set of sequences $X^\mathbb{N}$ and the map $s$ that shifts all elements up by $1$ or rather $(a_i)\mapsto (a_{i+1})$. The problem asks to find a map $s_{1/2}$ ... user avatar Math_Images_Only
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3 votes 1 answer 40 views

Improper Equivalence of Integral Quadric Forms is not an Equivalence Relation

An integral quadric form is some instance of $f(x,y)=ax^2+bxy+cy^2$, with $a,b,c$ integers. Let $f(x,y),g(x,y)$ be two integral quadric forms. Then we say that they are improperly equivalent, denoted ... user avatar Luke
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1 vote 1 answer 65 views

Is AC necessary here?

I was trying to prove this statement: Let $f:X\to Y$ a surjective map and $g: X\to Z$ such that $$\forall\,x,y\in X: f(x)=f(y)\implies g(x)=g(y).$$ Then exists a unique map $h:Y\to Z$ such that $g=h\... user avatar bianco
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2 votes 2 answers 41 views

Showing that $x^3 + y = y^3 + x$ is an equivalence relation

I am asked to prove that: $x^3 + y = y^3 + x$ is an equivalence relation. So far I have the following: Reflexive: $m^3 +m = m^3 +m$ Symmetric: $m^3 + n = n^3 + m \rightarrow n^3 + m = m^3 + n$ ... user avatar Peter Petigru
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3 votes 1 answer 63 views

Help finding mistake in proof involving the quotient map.

Consider the plane $\mathbb{R}^2=\mathbb{R}\times\mathbb{R}$ with the product topology which has basis consisting of all open squares of the form $$\tag{1} \left]a,b\right[ \times \left]c,d\right[ \... user avatar Hydrogen
  • 159
0 votes 1 answer 34 views

Proving that the quotient of a set by an equivalent relation is a partition

I need to show that the quotient of a set $S$ with respect to the equivalence relation $\sim$ is a partition of $S$. To show this, we will denote the quotient by $P_\sim.$ Note that $$ P_\sim = \{[a]_\... user avatar Chirag Kar
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3 votes 1 answer 37 views

Characterize open sets of this quotient topology.

Let $X$ the quotient space obtained from $\mathbb{R}\times\{0,1\}$ identifying $(x,0)\sim(x,1)$ if $|x|>1$. Which are the open sets of this quotient topology? First, I've made the next drawing to ... user avatar Fabrizio Gambelín
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2 votes 0 answers 22 views

Objects that change their equivalence class under some transformation

Suppose there is a set of objects on which we can define an equivalence relation. Under some transformations of the space on which the objects are defined, these objects may change their equivalence ... user avatar Damian
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0 votes 2 answers 47 views

When all commutant (centralizer) subgroups are abelian

I have seen the following problem in chapter 9 of Abstract Algebra by Dan Saracino: Let $G$ be a group and for $a,b \in G$ let $a\ R\ b$ mean that $ab=ba$. Must $R$ be an equivalence relation on $G$? ... user avatar khashayar
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0 votes 0 answers 38 views

Intuition behind the definition of matrix similarity/equivalence? [duplicate]

Given two matrices $A$ and $B$, they are similar if: $$B=P^{-1}AP $$ Furthermore, if they are similar they are relative to the same linear transformation (equivalent). However the proof I've checked ... user avatar agaminon
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