An interesting question from “Group Theory: A First Journey,” (page 4, section 2.3).












2














I am currently studying the manuscript Group Theory: A First Journey by Vipul Naik. It is available from the web page. In this manuscript the author proposes the following question:




Suppose the ordering of the elements in the rows and columns is the same. Then what kind of multiplication table would a magma have if it were to be a group? More generally, what are the constraints on the multiplication table corresponding to each of the properties that we can talk of for a binary operation?




(page 4, section 2.3)



No matter from what angle I have thought about this question, I can't seem to grasp what the author wants from his readers.



Anyone?










share|cite|improve this question
























  • For example (as I understand it), if you want your structure to be commutative, your table has to be symmetric, since you want $ab=ba$. If you want every element to be invertible, then you want "1"-s in certain places...
    – Ludolila
    Feb 6 '14 at 14:53












  • Well, the identity and the inverse have nice enough descriptions in this context. For the associativity, it is a bit more tricky, since this involves more than two elements.
    – Tobias Kildetoft
    Feb 6 '14 at 14:55










  • See Latin square.
    – lhf
    Feb 6 '14 at 15:20


















2














I am currently studying the manuscript Group Theory: A First Journey by Vipul Naik. It is available from the web page. In this manuscript the author proposes the following question:




Suppose the ordering of the elements in the rows and columns is the same. Then what kind of multiplication table would a magma have if it were to be a group? More generally, what are the constraints on the multiplication table corresponding to each of the properties that we can talk of for a binary operation?




(page 4, section 2.3)



No matter from what angle I have thought about this question, I can't seem to grasp what the author wants from his readers.



Anyone?










share|cite|improve this question
























  • For example (as I understand it), if you want your structure to be commutative, your table has to be symmetric, since you want $ab=ba$. If you want every element to be invertible, then you want "1"-s in certain places...
    – Ludolila
    Feb 6 '14 at 14:53












  • Well, the identity and the inverse have nice enough descriptions in this context. For the associativity, it is a bit more tricky, since this involves more than two elements.
    – Tobias Kildetoft
    Feb 6 '14 at 14:55










  • See Latin square.
    – lhf
    Feb 6 '14 at 15:20
















2












2








2







I am currently studying the manuscript Group Theory: A First Journey by Vipul Naik. It is available from the web page. In this manuscript the author proposes the following question:




Suppose the ordering of the elements in the rows and columns is the same. Then what kind of multiplication table would a magma have if it were to be a group? More generally, what are the constraints on the multiplication table corresponding to each of the properties that we can talk of for a binary operation?




(page 4, section 2.3)



No matter from what angle I have thought about this question, I can't seem to grasp what the author wants from his readers.



Anyone?










share|cite|improve this question















I am currently studying the manuscript Group Theory: A First Journey by Vipul Naik. It is available from the web page. In this manuscript the author proposes the following question:




Suppose the ordering of the elements in the rows and columns is the same. Then what kind of multiplication table would a magma have if it were to be a group? More generally, what are the constraints on the multiplication table corresponding to each of the properties that we can talk of for a binary operation?




(page 4, section 2.3)



No matter from what angle I have thought about this question, I can't seem to grasp what the author wants from his readers.



Anyone?







group-theory binary-operations magma






share|cite|improve this question















share|cite|improve this question













share|cite|improve this question




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edited Nov 28 at 22:51









Shaun

8,344113578




8,344113578










asked Feb 6 '14 at 14:50









Valera Rozuvan

304111




304111












  • For example (as I understand it), if you want your structure to be commutative, your table has to be symmetric, since you want $ab=ba$. If you want every element to be invertible, then you want "1"-s in certain places...
    – Ludolila
    Feb 6 '14 at 14:53












  • Well, the identity and the inverse have nice enough descriptions in this context. For the associativity, it is a bit more tricky, since this involves more than two elements.
    – Tobias Kildetoft
    Feb 6 '14 at 14:55










  • See Latin square.
    – lhf
    Feb 6 '14 at 15:20




















  • For example (as I understand it), if you want your structure to be commutative, your table has to be symmetric, since you want $ab=ba$. If you want every element to be invertible, then you want "1"-s in certain places...
    – Ludolila
    Feb 6 '14 at 14:53












  • Well, the identity and the inverse have nice enough descriptions in this context. For the associativity, it is a bit more tricky, since this involves more than two elements.
    – Tobias Kildetoft
    Feb 6 '14 at 14:55










  • See Latin square.
    – lhf
    Feb 6 '14 at 15:20


















For example (as I understand it), if you want your structure to be commutative, your table has to be symmetric, since you want $ab=ba$. If you want every element to be invertible, then you want "1"-s in certain places...
– Ludolila
Feb 6 '14 at 14:53






For example (as I understand it), if you want your structure to be commutative, your table has to be symmetric, since you want $ab=ba$. If you want every element to be invertible, then you want "1"-s in certain places...
– Ludolila
Feb 6 '14 at 14:53














Well, the identity and the inverse have nice enough descriptions in this context. For the associativity, it is a bit more tricky, since this involves more than two elements.
– Tobias Kildetoft
Feb 6 '14 at 14:55




Well, the identity and the inverse have nice enough descriptions in this context. For the associativity, it is a bit more tricky, since this involves more than two elements.
– Tobias Kildetoft
Feb 6 '14 at 14:55












See Latin square.
– lhf
Feb 6 '14 at 15:20






See Latin square.
– lhf
Feb 6 '14 at 15:20












1 Answer
1






active

oldest

votes


















2














Consider the existence of unique inverses. What does this do to the rows and columns of the multiplication table? For example, what if $astar b = c$ but then $astar d = c$ too?



You'll also need an identity element, and in particular this must be a two-sided identity, meaning $estar x = x star e = x$. Without loss of generality we can take $e$ to be the first element by rows and columns. How should the first row and the first column be related?



As far as associativity goes, I'm not sure there's a particularly good way of describing this in terms of the group multiplication table. It just has to work. (If you can think of a good way, please let me know!)






share|cite|improve this answer

















  • 1




    About testing associativity, see math.stackexchange.com/questions/511682/….
    – lhf
    Feb 7 '14 at 9:59











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1 Answer
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1 Answer
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active

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2














Consider the existence of unique inverses. What does this do to the rows and columns of the multiplication table? For example, what if $astar b = c$ but then $astar d = c$ too?



You'll also need an identity element, and in particular this must be a two-sided identity, meaning $estar x = x star e = x$. Without loss of generality we can take $e$ to be the first element by rows and columns. How should the first row and the first column be related?



As far as associativity goes, I'm not sure there's a particularly good way of describing this in terms of the group multiplication table. It just has to work. (If you can think of a good way, please let me know!)






share|cite|improve this answer

















  • 1




    About testing associativity, see math.stackexchange.com/questions/511682/….
    – lhf
    Feb 7 '14 at 9:59
















2














Consider the existence of unique inverses. What does this do to the rows and columns of the multiplication table? For example, what if $astar b = c$ but then $astar d = c$ too?



You'll also need an identity element, and in particular this must be a two-sided identity, meaning $estar x = x star e = x$. Without loss of generality we can take $e$ to be the first element by rows and columns. How should the first row and the first column be related?



As far as associativity goes, I'm not sure there's a particularly good way of describing this in terms of the group multiplication table. It just has to work. (If you can think of a good way, please let me know!)






share|cite|improve this answer

















  • 1




    About testing associativity, see math.stackexchange.com/questions/511682/….
    – lhf
    Feb 7 '14 at 9:59














2












2








2






Consider the existence of unique inverses. What does this do to the rows and columns of the multiplication table? For example, what if $astar b = c$ but then $astar d = c$ too?



You'll also need an identity element, and in particular this must be a two-sided identity, meaning $estar x = x star e = x$. Without loss of generality we can take $e$ to be the first element by rows and columns. How should the first row and the first column be related?



As far as associativity goes, I'm not sure there's a particularly good way of describing this in terms of the group multiplication table. It just has to work. (If you can think of a good way, please let me know!)






share|cite|improve this answer












Consider the existence of unique inverses. What does this do to the rows and columns of the multiplication table? For example, what if $astar b = c$ but then $astar d = c$ too?



You'll also need an identity element, and in particular this must be a two-sided identity, meaning $estar x = x star e = x$. Without loss of generality we can take $e$ to be the first element by rows and columns. How should the first row and the first column be related?



As far as associativity goes, I'm not sure there's a particularly good way of describing this in terms of the group multiplication table. It just has to work. (If you can think of a good way, please let me know!)







share|cite|improve this answer












share|cite|improve this answer



share|cite|improve this answer










answered Feb 6 '14 at 17:06









Alexander Gruber

20k25102171




20k25102171








  • 1




    About testing associativity, see math.stackexchange.com/questions/511682/….
    – lhf
    Feb 7 '14 at 9:59














  • 1




    About testing associativity, see math.stackexchange.com/questions/511682/….
    – lhf
    Feb 7 '14 at 9:59








1




1




About testing associativity, see math.stackexchange.com/questions/511682/….
– lhf
Feb 7 '14 at 9:59




About testing associativity, see math.stackexchange.com/questions/511682/….
– lhf
Feb 7 '14 at 9:59


















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