Number of congruence relations of a 4-element non-cyclic group

81 Views Asked by At

How many congruence relations does a 4-element non-cyclic group have?

Am I right that I have to find the normal subgroups in order to find the congruence relations?

Thanks

1

There are 1 best solutions below

0
On BEST ANSWER

The 4-element non-cyclic group is Klein four-group. An example of this group is the group $\mathcal{P}(S)$ where $S = \{a,b\}$ with the symmetric difference as the binary operation.

There are five congruences on this group by counting the normal subgroups which two of them are trivial normal subgroups. The three non-trivial ones are $\{\varnothing,\{a\}\}$, $\{\varnothing,\{b\}\}$ and $\{\varnothing,\{a,b\}\}$