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 Post subject: URGENT!!! Relation that is asymmetric, symmetric and
PostPosted: Fri, 21 Oct 2011 15:15:53 UTC 
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Hi guys, i am very new to relations.
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Find a binary relation on Z251 which is not reflexive but is symmetric, antisymmetric and transitive.


My answer would be that it is a empty set.

Say R = {(1,1), (1,2), (2,2), (2,4)}
a R b <=> There exists c belong such that b = c x a
However, this relation would not be asymmetric.

Another answer i have would be that R = Empty set X Z251


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 Post subject: Re: URGENT!!! Relation that is asymmetric, symmetric and
PostPosted: Sat, 22 Oct 2011 04:41:35 UTC 
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I agree that the empty relation satisfies all of those properties.


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 Post subject: Re: URGENT!!! Relation that is asymmetric, symmetric and
PostPosted: Sat, 22 Oct 2011 04:48:04 UTC 
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Well, but what would be a proper answer for this?


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 Post subject: Re: URGENT!!! Relation that is asymmetric, symmetric and
PostPosted: Sat, 22 Oct 2011 05:41:49 UTC 
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aceminer wrote:
Well, but what would be a proper answer for this?


What is not proper about the empty relation?

In fact, you will necessarily have some element that is not related to anything else.

_________________
\begin{aligned}
Spin(1)&=O(1)=\mathbb{Z}/2&\quad&\text{and}\\
Spin(2)&=U(1)=SO(2)&&\text{are obvious}\\
Spin(3)&=Sp(1)=SU(2)&&\text{by }q\mapsto(\mathop{\mathrm{Im}}\mathbb{H}\ni p\mapsto qp\bar{q})\\
Spin(4)&=Sp(1)\times Sp(1)&&\text{by }(q_1,q_2)\mapsto(\mathbb{H}\ni p\mapsto q_1p\bar{q_2})\\
Spin(5)&=Sp(2)&&\text{by }\mathbb{HP}^1\cong S^4_{round}\hookrightarrow\mathbb{R}^5\\
Spin(6)&=SU(4)&&\text{by the irrep }\Lambda_+\mathbb{C}^4
\end{aligned}


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 Post subject: Re: URGENT!!! Relation that is asymmetric, symmetric and
PostPosted: Sat, 22 Oct 2011 06:51:32 UTC 
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Hmm... what i meant would be how should i present this in an answer which is proper. Or would an answer to be the question simply be it is an empty relation?


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 Post subject: Re: URGENT!!! Relation that is asymmetric, symmetric and
PostPosted: Mon, 24 Oct 2011 22:04:08 UTC 
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aceminer wrote:
Hmm... what i meant would be how should i present this in an answer which is proper. Or would an answer to be the question simply be it is an empty relation?


All universal quantifier statements about empty sets are true.

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