Is there such an algebra structure?












0














In a ring, it holds that 1)
$$a×1=a=1×a$$ and 2) $$a×0=0=0×a$$
, so naturally, this 3) also holds
$$0×1=0=1×0$$



Is there such an algebra structure weaker than a ring so that
1) or 2)
does not hold, but 3) still holds?










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  • 5




    Maybe they shouldn’t be called 0 and 1 without specifying their properties.
    – Charlie Frohman
    Nov 24 at 2:18






  • 2




    What does the symbol "$1$" refer to in such a structure if condition (1) doesn't hold?
    – Clive Newstead
    Nov 24 at 2:41
















0














In a ring, it holds that 1)
$$a×1=a=1×a$$ and 2) $$a×0=0=0×a$$
, so naturally, this 3) also holds
$$0×1=0=1×0$$



Is there such an algebra structure weaker than a ring so that
1) or 2)
does not hold, but 3) still holds?










share|cite|improve this question




















  • 5




    Maybe they shouldn’t be called 0 and 1 without specifying their properties.
    – Charlie Frohman
    Nov 24 at 2:18






  • 2




    What does the symbol "$1$" refer to in such a structure if condition (1) doesn't hold?
    – Clive Newstead
    Nov 24 at 2:41














0












0








0


0





In a ring, it holds that 1)
$$a×1=a=1×a$$ and 2) $$a×0=0=0×a$$
, so naturally, this 3) also holds
$$0×1=0=1×0$$



Is there such an algebra structure weaker than a ring so that
1) or 2)
does not hold, but 3) still holds?










share|cite|improve this question















In a ring, it holds that 1)
$$a×1=a=1×a$$ and 2) $$a×0=0=0×a$$
, so naturally, this 3) also holds
$$0×1=0=1×0$$



Is there such an algebra structure weaker than a ring so that
1) or 2)
does not hold, but 3) still holds?







abstract-algebra






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share|cite|improve this question













share|cite|improve this question




share|cite|improve this question








edited Nov 24 at 2:30

























asked Nov 24 at 2:04









athos

82311339




82311339








  • 5




    Maybe they shouldn’t be called 0 and 1 without specifying their properties.
    – Charlie Frohman
    Nov 24 at 2:18






  • 2




    What does the symbol "$1$" refer to in such a structure if condition (1) doesn't hold?
    – Clive Newstead
    Nov 24 at 2:41














  • 5




    Maybe they shouldn’t be called 0 and 1 without specifying their properties.
    – Charlie Frohman
    Nov 24 at 2:18






  • 2




    What does the symbol "$1$" refer to in such a structure if condition (1) doesn't hold?
    – Clive Newstead
    Nov 24 at 2:41








5




5




Maybe they shouldn’t be called 0 and 1 without specifying their properties.
– Charlie Frohman
Nov 24 at 2:18




Maybe they shouldn’t be called 0 and 1 without specifying their properties.
– Charlie Frohman
Nov 24 at 2:18




2




2




What does the symbol "$1$" refer to in such a structure if condition (1) doesn't hold?
– Clive Newstead
Nov 24 at 2:41




What does the symbol "$1$" refer to in such a structure if condition (1) doesn't hold?
– Clive Newstead
Nov 24 at 2:41










1 Answer
1






active

oldest

votes


















0














Sure. It's called a group. Say we have a group made out of four elements, called $0,1,2,3$, where each elements is a mapping of ${0,1,2,3}to{-i,1,i,-1}$ (I did $e^{ipi (n-1)/2}$), and where $times$ is the regular complex multiplication. Then any number multiplied with "$1$" is that number, and any number multiplied with "$0$" means a multiplication by $i$. Then the second equation does not hold, but the third does, since $1$ is the identity element.






share|cite|improve this answer























  • In ring 0 is the identity element of addition while 1 is the one for multiplication
    – athos
    Nov 24 at 3:43










  • And what are those supposed to be in your new structure? If they have the same properties as the ring, then you have a ring, and equation 1 is in the definition of the multiplication, and equation 2 is derived from the properties of the ring. Equation 3 is always true if 1 is true.
    – Andrei
    Nov 24 at 3:47










  • if there’s some structure that has addition and multiplication but maybe not law of distribution?
    – athos
    Nov 24 at 3:58











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1 Answer
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0














Sure. It's called a group. Say we have a group made out of four elements, called $0,1,2,3$, where each elements is a mapping of ${0,1,2,3}to{-i,1,i,-1}$ (I did $e^{ipi (n-1)/2}$), and where $times$ is the regular complex multiplication. Then any number multiplied with "$1$" is that number, and any number multiplied with "$0$" means a multiplication by $i$. Then the second equation does not hold, but the third does, since $1$ is the identity element.






share|cite|improve this answer























  • In ring 0 is the identity element of addition while 1 is the one for multiplication
    – athos
    Nov 24 at 3:43










  • And what are those supposed to be in your new structure? If they have the same properties as the ring, then you have a ring, and equation 1 is in the definition of the multiplication, and equation 2 is derived from the properties of the ring. Equation 3 is always true if 1 is true.
    – Andrei
    Nov 24 at 3:47










  • if there’s some structure that has addition and multiplication but maybe not law of distribution?
    – athos
    Nov 24 at 3:58
















0














Sure. It's called a group. Say we have a group made out of four elements, called $0,1,2,3$, where each elements is a mapping of ${0,1,2,3}to{-i,1,i,-1}$ (I did $e^{ipi (n-1)/2}$), and where $times$ is the regular complex multiplication. Then any number multiplied with "$1$" is that number, and any number multiplied with "$0$" means a multiplication by $i$. Then the second equation does not hold, but the third does, since $1$ is the identity element.






share|cite|improve this answer























  • In ring 0 is the identity element of addition while 1 is the one for multiplication
    – athos
    Nov 24 at 3:43










  • And what are those supposed to be in your new structure? If they have the same properties as the ring, then you have a ring, and equation 1 is in the definition of the multiplication, and equation 2 is derived from the properties of the ring. Equation 3 is always true if 1 is true.
    – Andrei
    Nov 24 at 3:47










  • if there’s some structure that has addition and multiplication but maybe not law of distribution?
    – athos
    Nov 24 at 3:58














0












0








0






Sure. It's called a group. Say we have a group made out of four elements, called $0,1,2,3$, where each elements is a mapping of ${0,1,2,3}to{-i,1,i,-1}$ (I did $e^{ipi (n-1)/2}$), and where $times$ is the regular complex multiplication. Then any number multiplied with "$1$" is that number, and any number multiplied with "$0$" means a multiplication by $i$. Then the second equation does not hold, but the third does, since $1$ is the identity element.






share|cite|improve this answer














Sure. It's called a group. Say we have a group made out of four elements, called $0,1,2,3$, where each elements is a mapping of ${0,1,2,3}to{-i,1,i,-1}$ (I did $e^{ipi (n-1)/2}$), and where $times$ is the regular complex multiplication. Then any number multiplied with "$1$" is that number, and any number multiplied with "$0$" means a multiplication by $i$. Then the second equation does not hold, but the third does, since $1$ is the identity element.







share|cite|improve this answer














share|cite|improve this answer



share|cite|improve this answer








edited Nov 24 at 3:44

























answered Nov 24 at 3:30









Andrei

11k21025




11k21025












  • In ring 0 is the identity element of addition while 1 is the one for multiplication
    – athos
    Nov 24 at 3:43










  • And what are those supposed to be in your new structure? If they have the same properties as the ring, then you have a ring, and equation 1 is in the definition of the multiplication, and equation 2 is derived from the properties of the ring. Equation 3 is always true if 1 is true.
    – Andrei
    Nov 24 at 3:47










  • if there’s some structure that has addition and multiplication but maybe not law of distribution?
    – athos
    Nov 24 at 3:58


















  • In ring 0 is the identity element of addition while 1 is the one for multiplication
    – athos
    Nov 24 at 3:43










  • And what are those supposed to be in your new structure? If they have the same properties as the ring, then you have a ring, and equation 1 is in the definition of the multiplication, and equation 2 is derived from the properties of the ring. Equation 3 is always true if 1 is true.
    – Andrei
    Nov 24 at 3:47










  • if there’s some structure that has addition and multiplication but maybe not law of distribution?
    – athos
    Nov 24 at 3:58
















In ring 0 is the identity element of addition while 1 is the one for multiplication
– athos
Nov 24 at 3:43




In ring 0 is the identity element of addition while 1 is the one for multiplication
– athos
Nov 24 at 3:43












And what are those supposed to be in your new structure? If they have the same properties as the ring, then you have a ring, and equation 1 is in the definition of the multiplication, and equation 2 is derived from the properties of the ring. Equation 3 is always true if 1 is true.
– Andrei
Nov 24 at 3:47




And what are those supposed to be in your new structure? If they have the same properties as the ring, then you have a ring, and equation 1 is in the definition of the multiplication, and equation 2 is derived from the properties of the ring. Equation 3 is always true if 1 is true.
– Andrei
Nov 24 at 3:47












if there’s some structure that has addition and multiplication but maybe not law of distribution?
– athos
Nov 24 at 3:58




if there’s some structure that has addition and multiplication but maybe not law of distribution?
– athos
Nov 24 at 3:58


















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