Question #105618
M3[ Z ]has no nilpotent elements.
1
Expert's answer
2020-03-16T13:55:48-0400

M3[Z]={(a11a12a13a21a22a23a31a32a33),aijZ}M_3[Z]=\{\begin{pmatrix} a_{11} & a_{12}& a_{13} \\ a_{21} & a_{22}& a_{23} \\ a_{31} & a_{32}& a_{33} \\ \end{pmatrix},\\ a_{ij}\in Z\}

Сonsider the basis

E11=(100000000),E12=(010000000),E13=(001000000),E21=(000100000),E22=(000010000),E23=(000001000),E31=(000000100),E32=(000000010),E33=(000000001)E_{11}=\begin{pmatrix} 1 &0&0 \\ 0&0&0\\ 0&0&0 \end{pmatrix}, E_{12}=\begin{pmatrix} 0 &1&0 \\ 0&0&0\\ 0&0&0 \end{pmatrix}, \\ E_{13}=\begin{pmatrix} 0 &0&1 \\ 0&0&0\\ 0&0&0 \end{pmatrix}, E_{21}=\begin{pmatrix} 0&0&0 \\ 1&0&0\\ 0&0&0 \end{pmatrix}, \\ E_{22}=\begin{pmatrix} 0 &0&0 \\ 0&1&0\\ 0&0&0 \end{pmatrix}, E_{23}=\begin{pmatrix} 0 &0&0 \\ 0&0&1\\ 0&0&0 \end{pmatrix}, \\ E_{31}=\begin{pmatrix} 0 &0&0 \\ 0&0&0\\ 1&0&0 \end{pmatrix}, E_{32}=\begin{pmatrix} 0 &0&0 \\ 0&0&0\\ 0&1&0 \end{pmatrix}, \\ E_{33}=\begin{pmatrix} 0 &0&0 \\ 0&0&0\\ 0&0&1 \end{pmatrix}


A=(a11a12a13a21a22a23a31a32a33)=a11E11+a12E12++a13E13+a21E21+a22E22++a23E23+a31E31+a32E32++a33E33A=\begin{pmatrix} a_{11} & a_{12}& a_{13} \\ a_{21} & a_{22}& a_{23} \\ a_{31} & a_{32}& a_{33} \\ \end{pmatrix}=a_{11}E_{11}+a_{12}E_{12}+\\ +a_{13}E_{13}+a_{21}E_{21}+a_{22}E_{22}+\\ +a_{23}E_{23}+a_{31}E_{31}+a_{32}E_{32}+\\ +a_{33}E_{33}


Let's put together a Kelly table and  we denote

O=(000000000)O=\begin{pmatrix} 0 & 0&0 \\ 0 & 0&0\\ 0&0&0 \end{pmatrix}

E11E12E13E21E22E23E31E32E33E11E11E12E13OOOOOOE12OOOE11E12E13OOOE13OOOOOOE11E12E13E21E21E22E23OOOOOOE22OOOE21E22E23OOOE23OOOOOOE21E22E23E31E31E32E33OOOOOOE32OOOE31E32E33OOOE33OOOOOOE31E32E33\begin{matrix} &E_{11} &E_{12}&E_{13}&E_{21}&E_{22}&E_{23}&E_{31}&E_{32}&E_{33}\\ E_{11}& E_{11}&E_{12}&E_{13}&O&O&O&O&O&O\\ E_{12}& O&O&O&E_{11}&E_{12}&E_{13}&O&O&O\\ E_{13}& O&O&O&O&O&O&E_{11}&E_{12}&E_{13}\\ E_{21}& E_{21}&E_{22}&E_{23}&O&O&O&O&O&O\\ E_{22}& O&O&O&E_{21}&E_{22}&E_{23}&O&O&O\\ E_{23}& O&O&O&O&O&O&E_{21}&E_{22}&E_{23}\\ E_{31}& E_{31}&E_{32}&E_{33}&O&O&O&O&O&O\\ E_{32}& O&O&O&E_{31}&E_{32}&E_{33}&O&O&O\\ E_{33}& O&O&O&O&O&O&E_{31}&E_{32}&E_{33} \end{matrix}


Let's show that A20A^2\neq0

A2=(a11E11+a12E12++a13E13+a21E21+a22E22++a23E23+a31E31+a32E32++a33E33)(a11E11+a12E12++a13E13+a21E21+a22E22++a23E23+a31E31+a32E32++a33E33)==a112E11+a11a12E12++a11a13E13+a12a21E11+a12a22E12++a12a23E13+a13a31E11+a13a32E12++a13a33E13+A^2=(a_{11}E_{11}+a_{12}E_{12}+\\ +a_{13}E_{13}+a_{21}E_{21}+a_{22}E_{22}+\\ +a_{23}E_{23}+a_{31}E_{31}+a_{32}E_{32}+\\ +a_{33}E_{33})(a_{11}E_{11}+a_{12}E_{12}+\\ +a_{13}E_{13}+a_{21}E_{21}+a_{22}E_{22}+\\ +a_{23}E_{23}+a_{31}E_{31}+a_{32}E_{32}+\\ +a_{33}E_{33})=\\ =a_{11}^2E_{11}+a_{11}a_{12}E_{12}+\\ +a_{11}a_{13}E_{13}+a_{12}a_{21}E_{11}+a_{12}a_{22}E_{12}+\\ +a_{12}a_{23}E_{13}+a_{13}a_{31}E_{11}+a_{13}a_{32}E_{12}+\\ +a_{13}a_{33}E_{13}+


+a21a11E21+a21a12E22++a21a13E23+a22a21E21+a222E22++a22a23E23+a23a31E21+a23a32E22++a23a33E23++a31a11E31+a31a12E32++a31a13E33+a32a21E31+a32a22E32++a32a23E33+a33a31E31+a33a32E32++a332E33=+a_{21}a_{11}E_{21}+a_{21}a_{12}E_{22}+\\ +a_{21}a_{13}E_{23}+a_{22}a_{21}E_{21}+a_{22}^2E_{22}+\\ +a_{22}a_{23}E_{23}+a_{23}a_{31}E_{21}+a_{23}a_{32}E_{22}+\\ +a_{23}a_{33}E_{23}+\\ +a_{31}a_{11}E_{31}+a_{31}a_{12}E_{32}+\\ +a_{31}a_{13}E_{33}+a_{32}a_{21}E_{31}+a_{32}a_{22}E_{32}+\\ +a_{32}a_{23}E_{33}+a_{33}a_{31}E_{31}+a_{33}a_{32}E_{32}+\\ +a_{33}^2E_{33}=\\


=(a112+a12a21+a13a31)E11++(a11a12+a12a22+a13a32)E12++(a11a13+a12a23+a13a33)E13==(a_{11}^2+a_{12}a_{21}+a_{13}a_{31})E_{11}+\\ +(a_{11}a_{12}+a_{12}a_{22}+a_{13}a_{32})E_{12}+\\ +(a_{11}a_{13}+a_{12}a_{23}+a_{13}a_{33})E_{13}=


+(a21a11+a22a21+a23a31)E21++(a21a12+a222+a23a32)E22++(a21a13+a22a23+a23a33)E23++(a31a11+a32a21+a33a31)E31++(a31a12+a32a22+a33a32)E32++(a31a13+a32a23+a332)E33+(a_{21}a_{11}+a_{22}a_{21}+a_{23}a_{31})E_{21}+\\ +(a_{21}a_{12}+a_{22}^2+a_{23}a_{32})E_{22}+\\ +(a_{21}a_{13}+a_{22}a_{23}+a_{23}a_{33})E_{23}+\\ +(a_{31}a_{11}+a_{32}a_{21}+a_{33}a_{31})E_{31}+\\ +(a_{31}a_{12}+a_{32}a_{22}+a_{33}a_{32})E_{32}+\\ +(a_{31}a_{13}+a_{32}a_{23}+a_{33}^2)E_{33}

If A2=0A^2=0 then

a112+a12a21+a13a31=0a11a12+a12a22+a13a32=0a11a13+a12a23+a13a33=0a21a11+a22a21+a23a31=0a21a12+a222+a23a32=0a21a13+a22a23+a23a33=0a31a11+a32a21+a33a31=0a31a12+a32a22+a33a32=0a31a13+a32a23+a332=0a_{11}^2+a_{12}a_{21}+a_{13}a_{31}=0\\ a_{11}a_{12}+a_{12}a_{22}+a_{13}a_{32}=0\\ a_{11}a_{13}+a_{12}a_{23}+a_{13}a_{33}=0\\ a_{21}a_{11}+a_{22}a_{21}+a_{23}a_{31}=0\\ a_{21}a_{12}+a_{22}^2+a_{23}a_{32}=0\\ a_{21}a_{13}+a_{22}a_{23}+a_{23}a_{33}=0\\ a_{31}a_{11}+a_{32}a_{21}+a_{33}a_{31}=0\\ a_{31}a_{12}+a_{32}a_{22}+a_{33}a_{32}=0\\ a_{31}a_{13}+a_{32}a_{23}+a_{33}^2=0


This system has zero solution only aijZa_{ij}\in Z .

So A20A^2\neq0 .

Then M3[Z]M_3[Z] has no nilpotent elements.


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Comments

Assignment Expert
24.03.20, 14:47

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Shiva
24.03.20, 14:33

Thanks

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