Questions tagged [box-topology]

The box topology is the topology on the cartesian product of sets generated by the cartesian product of open subsets in each component set. Use this tag when your question involves the box topology.

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Equivalence of two metrics on countable product

There is an exercise 9.3#1 from "Topology without tears": Let $(X_i, d_i), i\in \mathbb{N}$, countable infinity of metric spaces, where every metric is bounded: $\forall X_i\forall a, b \in ...
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$x$ and $y$ lie in the same connected subspace of $\mathbb R^\omega$ (in box topology) iff $x-y$ is zero eventually.

$R^ω$ is in the box topology. It is to be shown that $x$ and $y$ lie in the same component of $R^ω$ if and only if the sequence $x−y$ is “eventually zero.” I tried to do it the following way but got ...
Koro's user avatar
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Characterizations of product topology and box topology

Given a collection of topological spaces $X_i$ indexed by the elements $i$ of a set $I$, we consider the set product $P = \prod_{i \in I} X_i$ with projections $p_i : P \to X_i$. There are two methods ...
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Difficulty in showing continuity of a function in different topologies

Suppose that $f: \mathbb R\to \mathbb R^\omega$, where $\omega$ is countably infinite index set, is defined by $f(t)= (t,2t,3t,...)$. The question is to discuss continuity of $f$ in the following ...
Koro's user avatar
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Show that the set of all bounded sequences in $X=\mathbb{R}^\Bbb N$ with the box topology is an open and closed set.

Show that the set of all bounded sequences in $X=\mathbb{R}^\Bbb N$ with the box topology is an open and closed set. I thought of two ways of how to approach this. First one was to note that this set ...
Walker's user avatar
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Can ($X^I$, product topology) and ($X^I$, box topology) be homeomorphic for some nontrivial $X$ and infinite $I$?

Let $X$ be a nontrivial topological space, $I$ be a infinite set, we can endow $X^I$ (the set of all functions $I\to X$) with either the product topology or the box topology. We know that the box ...
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Where does this "proof" that $\Bbb{R}^\omega$ is normal in the box topology go awry?

James Munkres' Topology, 2nd Edition indicates that the space $$\Bbb{R}^\omega := \{ (x_0, x_1, x_2, ...) | x_i \in \Bbb{R}, \forall i < \omega \}$$ equipped with the box topology is completely ...
Rivers McForge's user avatar
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Let $X=\Bbb R^{\Bbb N}$ be equipped with the box topology. Let $A \subset X$ be the set of bounded sequences. Show that $A$ is clopen.

Let $X=\Bbb R^{\Bbb N}$ be equipped with the box topology. Let $A \subset X$ be the set of bounded sequences. Show that $A$ is clopen. To show that $A$ is open I think I don't need to consider $A^c$. ...
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$\prod_{n=1}^{\infty}{\mathbb{R}}$ endowed with the box topology is not first countable.

What I'm trying to prove is that if $X^{+}\subseteq X:=\prod_{n=1}^{\infty}{\mathbb{R}}$ is the set of all positive sequences in $\mathbb{R}$, then no sequence of elements in $X^{+}$ converges to the ...
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Show that a set of sequences is open and closed on box topology

I have the following question on topology: Let $\mathbb R^\mathbb N = \prod_{n=0}^{\infty} \mathbb R$ with the box topology.Show that for all $\bar x = \langle x_n \rangle_n$, the set $ A = \{\bar y ...
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Connectedness in box topology

Let $X_i, \; i\in I$ be connected topological spaces and let $X=\Pi_{i\in I}X_i.$ I am familiar with the theorems that $X$ is a connected space in the product topology but not in the box topology. ...
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Let $[0, 1]^{\mathbb N}$ be equipped with the box topology.

Let $X = [0, 1]^{\mathbb N}$ be equipped with the box topology. Prove or Disprove that $[0, 1]^{\mathbb N}$ is connected. From what I've known $[0, 1]^{\mathbb N}$ is not compact based on this answer. ...
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Countable product of $\mathbb{R}$ is not connected with respect to box topology

From the book Topology, by James Munkres, I am trying to understand that $\mathbb{R}^\omega$ is not connected with respect to box topology. It is written that, We can write $\mathbb{R}^\omega$ as the ...
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Box topology and connectedness property

I've been trying to properly comprehend how the box topology is constructed, which I noticed I don't understand corretly when my professor asked me to show if it's false or true that the box-topology ...
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$X=\prod_{j\in J}X_j$ is Hausdorff(regular) iff each $X_j$ is Hausdorff(regular) on box-topology. Then what about the $T_1$ and product-topology?

The box-topology proof is quite obvious as $\prod{U_j}$ is always open in $X$, where the product-topology may not stand. By the way, if regularity stands, does this mean $T_1$ axiom stands first? Then,...
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Proving $[0,1]^{\omega}$ in box topology is not compact

Here is my attempt at proving this, any ideas if it is completely correct? Let $U^{(0)}=[0,\frac{3}{5}), U^{(1)}=(\frac{2}{5},1]$. Let $x=(x_n)_{n \in \mathbb{N}}$ be an arbitrary sequence of $0's$ ...
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Find a non-constant $f_n : \mathbb{R} \rightarrow \mathbb{R}$ so $f: \mathbb{R} \rightarrow \mathbb{R}^{\omega}$ is continuous.

Find, for every $n \in \omega$, a non-constant function $f_n : \mathbb{R} \rightarrow \mathbb{R}$ so that $f: \mathbb{R} \rightarrow \mathbb{R}^{\omega}$, defined as $f(x) = (f_n(x))_{n \in \omega}$, ...
george45's user avatar
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First countability of $[0,1]^\mathbb{R}$

The proofs I know for the fact that the space $[0,1]^\mathbb{R}$ is not first countable, use the product topology in some step of the demonstration. (Reference) So, I would like to know if this space ...
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Why is the function $f(t)=(t,t,t,t,t,...) $continuous in the product topology but not the box topology?

The function $f:\mathbb R \to \mathbb R^\infty$ given by $f(t)=(t,t,t,t,t\dots)$ is said to be not continuous in the box topology but continuous in the product topology. The example given is $U=(-1,1)\...
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Proving Theorem 19.2 in <Topology> by Munkres

Theorem 19.2 in Munkres Suppose the topology on each space $X_{\alpha}$ is given by a basis $\mathcal{B}_{\alpha}$. The collection of all sets of the form $$\prod_{\alpha \in J} B_{\alpha}$$ where $B_{...
kim's user avatar
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All the product topologies

I wonder what are all the topologies on the product of spaces that satisfy certain properties. For example, let $(X_i,\mathcal{T}_i)_{i\in I}$ be a family of topological spaces and let $X:=\prod_{i\in ...
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Is the weak topology on $\mathbb{R}^{\infty}$ the same as the box topology?

Let $\mathbb{R}^{\infty}=\bigcup\limits_{n=1}^{\infty}\mathbb{R}^{n}$ be the subset of $\mathbb{R}^{\omega}$ consisting of all sequences which are nonzero for only finitely many terms. Give $\mathbb{...
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Showing the infinite product space of $[0, 1]^\omega$ is not compact with respect to the box topology using the notion of open covers

I wish to show that the space $[0,1]^\omega$ in the box topology is not compact using the notion of open covers. The box topology has been a topic where I have struggled in my studies of topology, and ...
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Showing this set is open in the topological space $\mathbb{R}\times\mathbb{R}$

Let $\pi_1 : \mathbb{R}\times \mathbb{R}\to \mathbb{R}$ be the projection on the first coordinate. Let $A$ be the subspace of $\mathbb{R}\times \mathbb{R}$ consisting of all points $(x,y)$ for which ...
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$\mathbb R^{\omega}$ in the box topology not paracompact?

I know that we can't prove that $\mathbb R^{\omega}$ in the box topology is normal, so we can't say for sure that it is paracompact(it is Hausdorff, and every paracompact Hausdorff space is normal). ...
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Show that the $\mathbb{R^N} $ with the box topology is a regular space.

What was I thinking There is a neighborhood W=$\prod_i (-r_i,r_i)$ that does not intersect A . Consider a linear transformation $h_i:x_i \to x_i/r_i$ (linear transformation is a homeomorphism in both ...
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Box topology first countability

I want to show that $\mathbb{R}^2$ with the topology $\tau_\mathcal{B}$ generated by the base $\mathcal{B} = \{U \times V | U \in \tau_1, V \in \tau_2\}$ where $\tau_1$ and $\tau_2$ are topologies for ...
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Is $R^\omega$ in the box topology locally connected or locally path connected?

I have the following lemma: Give $R^\omega$ the box topology. Then $x$ and $y$ lie in the same component of $R^\omega$ if and only if the sequence $x-y$ is "eventually zero". Let $V_n=\{y\in ...
Junk Warrior's user avatar
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Showing a subset is open with respect to a topology

I have asked and read similar questions, but I am still somewhat confused on the notion of "a set being open with respect to some topology". My task is concerning the box topology and the ...
Slippy's user avatar
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Showing a set is open with respect to box vs product topology

I am currently studying topology with Munkres and I am asking for some general proof techniques and clarification rather than just posting my question and wait for a solution. I am given that the real ...
Slippy's user avatar
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Is it possible to show $\mathbb{R}^\omega$ is not metrizable without using the first countable definition and sequence lemma?

I encountered a question about proving that $\mathbb{R}^\omega$, which is the countably infinite product of $\mathbb{R}$ under the product topology, is not metrizable. I have seen many solutions here ...
Edi's user avatar
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What's the interior of $R^{\infty}$ in the $R^{\omega}$ with the box topology and the production topology?

What's the interior of $R^{\infty}$ in the $R^{\omega}$ with the box topology and the production topology? With $R^{\infty}$ being the set of all eventually zero sequences. About the question in Prob. ...
Pump Kin's user avatar
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Box topology and a non-continuous function

I'm having trouble understanding box topologies on infinite spaces. I'm asked to prove that the function f going from ([0,1], standard top.) to ([0,1]^N, box top.) is not continuous. This function ...
Lupetto1927's user avatar
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Net convergence over product and box topology

Let $(x_\alpha)_{\alpha\in \Lambda}$ a net in the topological space $X = \prod_{i\in I}X_i$. Is it true that $x_\alpha \rightarrow x$ iff $p_i(x_\alpha) \rightarrow p_i(x)$ for every $i \in I$ with ...
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Which properties does the box topology conserve?

The Wikipedia article on the Product topology has a wealth of examples of properties conserved by the product topology. The following is a quote from the linked article: " Separation Every product ...
Yehuda Rimon's user avatar
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Is $\mathbb R^J$ normal in the box topology when $J$ is uncountable?

Question: Is $\mathbb R^J$ normal in the box topology when $J$ is uncountable? I know $\mathbb R^J$ is not normal in the product topology, see "Proof" that $\mathbb{R}^J$ is not normal ...
YuiTo Cheng's user avatar
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Nontrivial example of continuous function from $\mathbb R\to\mathbb R^{\omega}$ with box topology on $\mathbb R^{\omega}$

Nontrivial example of a continuous function from $\mathbb R\to \mathbb R^{\omega}$ with box topology on $\mathbb R^{\omega}$ and usual topology on the domain. I can give some trivial example like $...
Curious student's user avatar
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Does the box topology have a universal property?

Given a set of topological spaces $\{X_\alpha\}$, there are two main topologies we can give to the Cartesian product $\Pi_\alpha X_\alpha$: the product topology and the box topology. The product ...
Keshav Srinivasan's user avatar
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Proving $(-1,1)^{\mathbb{N}}$ is not open in the product topology of $\mathbb{R}^{\mathbb{N}}$

Clarification: here $\mathbb{R}^{\mathbb{N}} = \mathbb{R}\times \mathbb{R} \times \cdots$, i.e, countably many copies of $\mathbb{R}$. $(-1,1)^{\mathbb{N}}$ is completely analagous. I don't want a ...
Matheus Andrade's user avatar
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Is $\mathbb{R}^\omega$ endowed with the box topology completely normal (or hereditarily normal)?

Just out of curiosity, I'd like to know more properties of box topology. I found Is $\mathbb{R}^\omega$ a completely normal space, in the box topology? quite interesting, but unfortunately, it hasn't ...
YuiTo Cheng's user avatar
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Is the sequence of real number that are $0$ from some point Sense in the box or product topologies

Let $A=\{(x_n)_{n\in\mathbb{N}}\in\mathbb{R}^\mathbb{N}|\exists M\in\mathbb{N} ,\forall n>M, x_n=0 \}\subset\mathbb{R}^\mathbb{N}$, series of real numbers that are zero from some point forward. ...
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Closures and interiors of real sequences

Let X be the set of all real sequences. For both the box and the product topology, find the closure and the interior of S, where S is the subset of X containing: (a) bounded sequences (b) sequences ...
Gauss the Mauss's user avatar
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Space of Sequences with Finitely Many Nonzero Terms is Paracompact

I just proved the following theorem: If $X$ is a regular space that can be written as a countable union of compact subspaces of $X$, then $X$ is paracompact. I am now working on the following: ...
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Box topology defines a topological vector space?

Is the set of all real summable sequences, endowed with the box topology, a topological vector space? Formally, I am interested in $X=\{(a_1,\ldots):a_n \in \mathbb{R} \ \forall n, \ \sum a_n < \...
MDR's user avatar
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Conditions to make box topology and product topology different

The product of the $A_j$ is the set $\prod_{j\in J} A_j$:=$\{ f: J \rightarrow \bigcup A_j \ | f(j) \in A_j \ for \ each \ j \in J \}$ We usually represent $f$ as $(a_j)=f(j) \in A_j$. For each $k \...
Hikicianka's user avatar
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290 views

Showing the $\ell^2$ topology is different from the Box topology

Let $X$ be the subset of $\Bbb{R}^\omega$ all of sequences $y = (y_i)$ for which $\sum y_i^2 < \infty$. Then $d(x,y) = \left[ \sum_{i=1}^\infty (x_i-y_i)^2 \right]^{1/2}$ defines a metric on $X$, ...
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Connected components of $\mathbb{R^w}$ in box topology [duplicate]

How can I know about all $\mathbb{R^w}$ in box topology? How can I separate $\mathbb{R^w}$ in box topology in to components and path components?in uniform topology I can separate using the path ...
Samiron Parui's user avatar
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Prove that $\mathbb R_l$ $\times$ $\mathbb R_l$ given the box topology has a countable dense subset.

Let $\mathbb R_l$ be $\mathbb R$ given the lower limit topology, i.e. the topology generated by $\{[a, b)\subseteq \mathbb R|a<b\}$. Prove that $\mathbb R_l$$\times$$\mathbb R_l$ given the box ...
FlickerBeat's user avatar
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1 answer
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Continuity on Box Topology

I was reading about box topology and product topology from Munkres's Topology. Their is an example given below: $$\mathbb{R}^{\omega}=\prod_{n\in \mathbb{Z}_+}X_n$$ where $X_n=\mathbb{R}$ for each $n$....
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2 votes
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Projection map for the product, uniform and box topologies

That the canonical projection map (from say $\mathbb{R}^\mathbb{N}$ to $\mathbb{R}$) is continuous for all three topologies is straightforward. But is it also open for the uniform and box topologies? (...
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