Element structure of special linear group:SL(2,3)

This article gives specific information, namely, element structure, about a particular group, namely: special linear group:SL(2,3).
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This article gives detailed information about the element structure of special linear group:SL(2,3).

See also element structure of special linear group of degree two over a finite field.

Conjugacy and automorphism class structure

Conjugacy classes

Note that since we are over field:F3, $-1=2$, so all the $-1$s below can be rewritten as $2$s.

Conjugacy class representative	Conjugacy class size	List of all elements of conjugacy class	Order of elements in conjugacy class
$\left(\begin{array}{cc}1& 0\\ 0& 1\\ \end{array}\right)$	1	$\left(\begin{array}{cc}1& 0\\ 0& 1\\ \end{array}\right)$	1
$\left(\begin{array}{cc}-1& 0\\ 0& -1\\ \end{array}\right)$	1	$\left(\begin{array}{cc}-1& 0\\ 0& -1\\ \end{array}\right)$	2
$\left(\begin{array}{cc}1& 1\\ 0& 1\\ \end{array}\right)$	4	[SHOW MORE] $\left(\begin{array}{cc}1& 1\\ 0& 1\\ \end{array}\right)$, $\left(\begin{array}{cc}-1& 1\\ -1& 0\\ \end{array}\right)$, $\left(\begin{array}{cc}1& 0\\ -1& 1\\ \end{array}\right)$, $\left(\begin{array}{cc}0& 1\\ -1& -1\\ \end{array}\right)$	3
$\left(\begin{array}{cc}1& -1\\ 0& 1\\ \end{array}\right)$	4	[SHOW MORE] $\left(\begin{array}{cc}1& -1\\ 0& 1\\ \end{array}\right)$, $\left(\begin{array}{cc}-1& -1\\ 1& 0\\ \end{array}\right)$, $\left(\begin{array}{cc}1& 0\\ 1& 1\\ \end{array}\right)$, $\left(\begin{array}{cc}0& -1\\ 1& -1\\ \end{array}\right)$	3
$\left(\begin{array}{cc}-1& 1\\ 0& -1\\ \end{array}\right)$	4	[SHOW MORE] $\left(\begin{array}{cc}-1& 1\\ 0& -1\\ \end{array}\right)$, $\left(\begin{array}{cc}1& 1\\ -1& 0\\ \end{array}\right)$, $\left(\begin{array}{cc}-1& 0\\ -1& -1\\ \end{array}\right)$, $\left(\begin{array}{cc}0& 1\\ -1& 1\\ \end{array}\right)$	6
$\left(\begin{array}{cc}-1& -1\\ 0& -1\\ \end{array}\right)$	4	[SHOW MORE] $\left(\begin{array}{cc}-1& -1\\ 0& -1\\ \end{array}\right)$, $\left(\begin{array}{cc}1& -1\\ 1& 0\\ \end{array}\right)$, $\left(\begin{array}{cc}-1& 0\\ 1& -1\\ \end{array}\right)$, $\left(\begin{array}{cc}0& -1\\ 1& 1\\ \end{array}\right)$	6
$\left(\begin{array}{cc}0& -1\\ 1& 0\\ \end{array}\right)$	6	[SHOW MORE] $\left(\begin{array}{cc}0& -1\\ 1& 0\\ \end{array}\right)$, $\left(\begin{array}{cc}0& 1\\ -1& 0\\ \end{array}\right)$, $\left(\begin{array}{cc}1& 1\\ 1& -1\\ \end{array}\right)$, $\left(\begin{array}{cc}-1& 1\\ 1& 1\\ \end{array}\right)$, $\left(\begin{array}{cc}1& -1\\ -1& -1\\ \end{array}\right)$, $\left(\begin{array}{cc}-1& -1\\ -1& 1\\ \end{array}\right)$	4

Automorphism classes

Below are the orbits under the action of the automorphism group, i.e., the automorphism classes of elements of the group.

List of representatives for each conjugacy class in the automorphism class	Number of conjugacy classes in the automorphism class	Size of each conjugacy class	Automorphism class size	Order of elements in conjugacy class
$\left(\begin{array}{cc}1& 0\\ 0& 1\\ \end{array}\right)$	1	1	1	1
$\left(\begin{array}{cc}-1& 0\\ 0& -1\\ \end{array}\right)$	1	1	1	2
$\left(\begin{array}{cc}1& 1\\ 0& 1\\ \end{array}\right)$, $\left(\begin{array}{cc}1& -1\\ 0& 1\\ \end{array}\right)$	2	4	8	3
$\left(\begin{array}{cc}-1& 1\\ 0& -1\\ \end{array}\right)$, $\left(\begin{array}{cc}-1& -1\\ 0& -1\\ \end{array}\right)$	2	4	8	6
$\left(\begin{array}{cc}0& -1\\ 1& 0\\ \end{array}\right)$	1	6	6	4

Interpretation as special linear group of degree two

Further information: element structure of special linear group of degree two over a finite field

Nature of conjugacy class	Eigenvalue pairs of all conjugacy classes	Characteristic polynomials of all conjugacy classes	Minimal polynomials of all conjugacy classes	Size of conjugacy class (generic odd $q$)	Size of conjugacy class ($q=3$)	Number of such conjugacy classes (generic odd $q$)	Number of such conjugacy classes ($q=3$)	Total number of elements (generic odd $q$)	Total number of elements ($q=3$)	Representative matrices (one per conjugacy class)
Scalar	$\{1,1\}$ or $\{-1,-1\}$	$x^2-2x+1$ or $x^2+2x+1$	$x-1$ or $x+1$	1	1	2	2	2	2	$\left(\begin{array}{cc}1& 0\\ 0& 1\\ \end{array}\right)$ and $\left(\begin{array}{cc}-1& 0\\ 0& -1\\ \end{array}\right)$
Not diagonal, Jordan block of size two	$\{1,1\}$ or $\{-1,-1\}$	$x^2-2x+1$ or $x^2+2x+1$	$x^2-2x+1$ or $x^2+2x+1$	$(q^2-1)/2$	4	4	4	$2(q^2-1)$	16	[SHOW MORE] $\left(\begin{array}{cc}1& 1\\ 0& 1\\ \end{array}\right)$, $\left(\begin{array}{cc}1& -1\\ 0& 1\\ \end{array}\right)$, $\left(\begin{array}{cc}-1& 1\\ 0& -1\\ \end{array}\right)$, $\left(\begin{array}{cc}-1& -1\\ 0& -1\\ \end{array}\right)$
Diagonalizable over field:F9, not over field:F3. Must necessarily have no repeated eigenvalues.	pair of square roots of $-1$ in field:F9	$x^2+1$	$x^2+1$	$q(q-1)$	6	$(q-1)/2$	1	$q(q-1{)}^2/2$	6	$\left(\begin{array}{cc}0& -1\\ 1& 0\\ \end{array}\right)$
Diagonalizable over field:F3 with distinct diagonal entries	--	--	--	$q(q+1)$	12	$(q-3)/2$	0	$q(q+1)(q-3)/2$	0	--
Total	NA	NA	NA	NA	NA	$q+4$	7	$q^3-q$	24	NA

Interpretation as double cover of alternating group

Further information: element structure of double cover of alternating group

$SL(2,3)$ is isomorphic to $2\cdot A_n,n=4$. Recall that we have the following rules to determine splitting and orders. The rules listed below are only for partitions that already correspond to even permutations, i.e., partitions that have an even number of even parts:

Hypothesis: does the partition have at least one even part?	Hypothesis: does the partition have a repeated part? (the repeated part may be even or odd)	Conclusion: does the conjugacy class split from $S_n$ to $A_n$ in 2?	Conclusion: does the fiber in $2\cdot A_n$ over a conjugacy class in $A_n$ split in 2?	Total number of conjugacy classes in $2\cdot A_n$ corresponding to this partition (4 if Yes to both preceding columns, 2 if Yes to one and No to other, 1 if No to both)	Number of these conjugacy classes where order of element = lcm of parts	Number of these conjugacy classes where order of element = twice the lcm of parts
No	No	Yes	Yes	4	2	2
No	Yes	No	Yes	2	1	1
Yes	No	No	Yes	2	0	2
Yes	Yes	No	No	1	0	1

Partition	Partition in grouped form	Does the partition have at least one even part?	Does the partition have a repeated part?	Conclusion: does the conjugacy class split from $S_n$ to $A_n$ in 2?	Conclusion: does the fiber in $2\cdot A_n$ over a conjugacy class in $A_n$ split in 2?	Total number of conjugacy classes in $2\cdot A_n$ corresponding to this partition (4 if Yes to both preceding columns, 2 if Yes to one and No to other, 1 if No to both)	Size of each conjugacy class	Size formula (we take the size formula in $S_n$, multiply by 2, and divide by the number (1,2, or 4) two columns preceding	Total number of elements (= twice the size of the $S_n$-conjugacy class)	Element orders	Formula for element orders
1 + 1 + 1 + 1	1 (4 times)	No	Yes	No	Yes	2	1	$\frac{2}{2}\frac{4!}{(1{)}^4(4!)}$	2	1 (1 class), 2 (1 class)	$\mathrm{l}\mathrm{c}\mathrm{m}\{1\}$ (1 class) $2\mathrm{l}\mathrm{c}\mathrm{m}\{1\}$ (1 class)
2 + 2	2 (2 times)	Yes	Yes	No	No	1	6	$\frac{2}{1}\frac{4!}{(2{)}^2(2!)}$	6	4	$2\mathrm{l}\mathrm{c}\mathrm{m}\{2\}$ (1 class)
3 + 1	3 (1 time), 1 (1 time)	No	No	Yes	Yes	4	4	$\frac{2}{4}\frac{4!}{(3)(1)}$	16	3 (2 classes) 6 (2 classes)	$\mathrm{l}\mathrm{c}\mathrm{m}\{3,1\}$ (2 classes) $2\mathrm{l}\mathrm{c}\mathrm{m}\{3,1\}$ (2 classes)
Total	--	--	--	--	--	7	--	--	24	--	--