Property of a n-simplex?











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Let $A subseteq mathbb{R}^n$ a open set. Then there exists a subset $B subseteq A$ where $B$ is a $n-$ simplex?.



Is the condition that $A$ is open necessary?










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  • Can you explain more carefully? I don't understand what you're asking at all
    – D_S
    Dec 3 at 4:25










  • I want to know if it is true that: Let $A subseteq mathbb{R}^n$ a open set. Then exist $B$ a $n-$simplex such that $B subseteq A$.
    – Juan Daniel V.F
    Dec 3 at 4:29










  • You can assume that $A$ is an open ball.
    – Lord Shark the Unknown
    Dec 3 at 4:37






  • 1




    The condition that $A$ is open is not necessary. What is necessary (and sufficient), however, is that $A$ contains an open ball (which is implied by $A$ being open). This is the case since every open ball contains an $n$-simplex and every $n$-simplex contains an open ball.
    – munchhausen
    Dec 3 at 4:52










  • There is exactly one counterexample to the claim: The empty set is open but does not contain a simplex. Of course, this might be irrelevant for the context of the question.
    – Ingix
    Dec 3 at 15:58















up vote
0
down vote

favorite












Let $A subseteq mathbb{R}^n$ a open set. Then there exists a subset $B subseteq A$ where $B$ is a $n-$ simplex?.



Is the condition that $A$ is open necessary?










share|cite|improve this question
























  • Can you explain more carefully? I don't understand what you're asking at all
    – D_S
    Dec 3 at 4:25










  • I want to know if it is true that: Let $A subseteq mathbb{R}^n$ a open set. Then exist $B$ a $n-$simplex such that $B subseteq A$.
    – Juan Daniel V.F
    Dec 3 at 4:29










  • You can assume that $A$ is an open ball.
    – Lord Shark the Unknown
    Dec 3 at 4:37






  • 1




    The condition that $A$ is open is not necessary. What is necessary (and sufficient), however, is that $A$ contains an open ball (which is implied by $A$ being open). This is the case since every open ball contains an $n$-simplex and every $n$-simplex contains an open ball.
    – munchhausen
    Dec 3 at 4:52










  • There is exactly one counterexample to the claim: The empty set is open but does not contain a simplex. Of course, this might be irrelevant for the context of the question.
    – Ingix
    Dec 3 at 15:58













up vote
0
down vote

favorite









up vote
0
down vote

favorite











Let $A subseteq mathbb{R}^n$ a open set. Then there exists a subset $B subseteq A$ where $B$ is a $n-$ simplex?.



Is the condition that $A$ is open necessary?










share|cite|improve this question















Let $A subseteq mathbb{R}^n$ a open set. Then there exists a subset $B subseteq A$ where $B$ is a $n-$ simplex?.



Is the condition that $A$ is open necessary?







general-topology convex-analysis simplex






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share|cite|improve this question













share|cite|improve this question




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edited Dec 3 at 4:38









D_S

13.2k51551




13.2k51551










asked Dec 3 at 4:17









Juan Daniel V.F

526




526












  • Can you explain more carefully? I don't understand what you're asking at all
    – D_S
    Dec 3 at 4:25










  • I want to know if it is true that: Let $A subseteq mathbb{R}^n$ a open set. Then exist $B$ a $n-$simplex such that $B subseteq A$.
    – Juan Daniel V.F
    Dec 3 at 4:29










  • You can assume that $A$ is an open ball.
    – Lord Shark the Unknown
    Dec 3 at 4:37






  • 1




    The condition that $A$ is open is not necessary. What is necessary (and sufficient), however, is that $A$ contains an open ball (which is implied by $A$ being open). This is the case since every open ball contains an $n$-simplex and every $n$-simplex contains an open ball.
    – munchhausen
    Dec 3 at 4:52










  • There is exactly one counterexample to the claim: The empty set is open but does not contain a simplex. Of course, this might be irrelevant for the context of the question.
    – Ingix
    Dec 3 at 15:58


















  • Can you explain more carefully? I don't understand what you're asking at all
    – D_S
    Dec 3 at 4:25










  • I want to know if it is true that: Let $A subseteq mathbb{R}^n$ a open set. Then exist $B$ a $n-$simplex such that $B subseteq A$.
    – Juan Daniel V.F
    Dec 3 at 4:29










  • You can assume that $A$ is an open ball.
    – Lord Shark the Unknown
    Dec 3 at 4:37






  • 1




    The condition that $A$ is open is not necessary. What is necessary (and sufficient), however, is that $A$ contains an open ball (which is implied by $A$ being open). This is the case since every open ball contains an $n$-simplex and every $n$-simplex contains an open ball.
    – munchhausen
    Dec 3 at 4:52










  • There is exactly one counterexample to the claim: The empty set is open but does not contain a simplex. Of course, this might be irrelevant for the context of the question.
    – Ingix
    Dec 3 at 15:58
















Can you explain more carefully? I don't understand what you're asking at all
– D_S
Dec 3 at 4:25




Can you explain more carefully? I don't understand what you're asking at all
– D_S
Dec 3 at 4:25












I want to know if it is true that: Let $A subseteq mathbb{R}^n$ a open set. Then exist $B$ a $n-$simplex such that $B subseteq A$.
– Juan Daniel V.F
Dec 3 at 4:29




I want to know if it is true that: Let $A subseteq mathbb{R}^n$ a open set. Then exist $B$ a $n-$simplex such that $B subseteq A$.
– Juan Daniel V.F
Dec 3 at 4:29












You can assume that $A$ is an open ball.
– Lord Shark the Unknown
Dec 3 at 4:37




You can assume that $A$ is an open ball.
– Lord Shark the Unknown
Dec 3 at 4:37




1




1




The condition that $A$ is open is not necessary. What is necessary (and sufficient), however, is that $A$ contains an open ball (which is implied by $A$ being open). This is the case since every open ball contains an $n$-simplex and every $n$-simplex contains an open ball.
– munchhausen
Dec 3 at 4:52




The condition that $A$ is open is not necessary. What is necessary (and sufficient), however, is that $A$ contains an open ball (which is implied by $A$ being open). This is the case since every open ball contains an $n$-simplex and every $n$-simplex contains an open ball.
– munchhausen
Dec 3 at 4:52












There is exactly one counterexample to the claim: The empty set is open but does not contain a simplex. Of course, this might be irrelevant for the context of the question.
– Ingix
Dec 3 at 15:58




There is exactly one counterexample to the claim: The empty set is open but does not contain a simplex. Of course, this might be irrelevant for the context of the question.
– Ingix
Dec 3 at 15:58















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