@@ -1,155 +1,155 @@ -\documentstyle{article} -\parindent0cm -%\textwidth 15.5cm\textheight 22.0cm\columnwidth\textwidth -%\hoffset-1.5cm\voffset-1.5cm -\begin{document} -%\parskip 10pt plus 1pt \parindent 0pt -\title{The {LIE} Package} -\author{Carsten and Franziska Sch\"obel\\ -The Leipzig University, Computer Science Dept.\\ -Augustusplatz 10/11, O-7010 Leipzig, Germany\\ -Email: cschoeb@aix550.informatik.uni-leipzig.de} -\date{22 January 1993} -\maketitle -{\bf LIE} is a package of functions for the classification of real n-dimensional -Lie algebras. It consists of two modules: {\bf liendmc1} and {\bf lie1234}. -\\[0.3cm]{\large\bf liendmc1}\\[0.1cm] -With the help of the functions in this module real n-dimensional Lie algebras -$L$ with a derived algebra $L^{(1)}$ of dimension 1 can be classified. $L$ has -to be defined by its structure constants $c_{ij}^k$ in the basis -$\{X_1,\ldots,X_n\}$ with $[X_i,X_j]=c_{ij}^k X_k$. The user must define an -ARRAY LIENSTRUCIN($n,n,n$) with n being the dimension of the Lie algebra $L$. -The structure constants LIENSTRUCIN($i,j,k$):=$c_{ij}^k$ for $i). -\end{verbatim} -{\tt } corresponds to the dimension $n$. The procedure simplifies -the structure of $L$ performing real linear transformations. The returned -value is a list of the form -\begin{verbatim} - (i) {LIE_ALGEBRA(2),COMMUTATIVE(n-2)} or - (ii) {HEISENBERG(k),COMMUTATIVE(n-k)} -\end{verbatim} -with $3\leq k\leq n$, $k$ odd.\\ -The concepts correspond to the following theorem ({\tt LIE\_ALGEBRA(2)} -$\rightarrow L_2$, {\tt HEISENBERG(k)} $\rightarrow H_k$ and -{\tt COMMUTATIVE(n-k)} $\rightarrow C_{n-k}$):\\[0.2cm] -{\bf Theorem.} Every real $n$-dimensional Lie algebra $L$ with a 1-dimensional -derived algebra can be decomposed into one of the following forms:\\[0.1cm] -\hspace*{0.3cm} (i) $C(L)\cap L^{(1)}=\{0\}\, :\; L_2\oplus C_{n-2}$ -or\\[0.05cm] -\hspace*{0.3cm} (ii) $C(L)\cap L^{(1)}=L^{(1)}\, :\; H_k\oplus C_{n-k}\quad -(k=2r-1,\, r\geq 2)$, with\newpage -\hspace*{0.3cm} 1. $C(L)=C_j\oplus (L^{(1)}\cap C(L))$ -and dim$\,C_j=j$ ,\\[0.05cm] -\hspace*{0.3cm} 2. $L_2$ is generated by -$Y_1,Y_2$ with $[Y_1,Y_2]=Y_1$ ,\\[0.05cm] -\hspace*{0.3cm} 3. $H_k$ is generated by $\{Y_1,\ldots,Y_k\}$ with\\ -\hspace*{0.7cm} $[Y_2,Y_3]=\cdots =[Y_{k-1},Y_k]=Y_1$.\\[0.2cm] -(cf. \cite{cssmp92})\\[0.2cm] -The returned list is also stored as LIE\_LIST. The matrix LIENTRANS gives the -transformation from the given basis $\{X_1,\ldots ,X_n\}$ into the standard -basis $\{Y_1,\ldots ,Y_n\}$: $Y_j=($LIENTRANS$)_j^k X_k$.\\[0.1cm] -A more detailed output can be obtained by turning on the switch TR\_LIE: -\begin{verbatim} - ON TR_LIE; -\end{verbatim} -before the procedure LIENDIMCOM1 is called.\\[0.1cm] -The returned list could be an input for a data bank in which mathematical -relevant properties of the obtained Lie algebras are stored.\\[0.3cm] -{\large\bf lie1234}\\[0.1cm] -This part of the package classifies real low-dimensional Lie algebras $L$ -of the dimension -$n:=$dim$\,L=1,2,3,4$. $L$ is also given by its structure constants $c_{ij}^k$ -in the basis $\{X_1,\ldots,X_n\}$ with $[X_i,X_j]=c_{ij}^k X_k$. An ARRAY -LIESTRIN($n,n,n$) has to be defined and LIESTRIN($i,j,k$):=$c_{ij}^k$ for -$i). -\end{verbatim} -{\tt } should be the dimension of the Lie algebra $L$. The procedure -stepwise simplifies the commutator relations of $L$ using properties of -invariance like the dimension of the centre, of the derived algebra, -unimodularity etc. The returned value has the form: -\begin{verbatim} - {LIEALG(n),COMTAB(m)}, -\end{verbatim} -where $m$ corresponds to the number of the standard form (basis: -$\{Y_1,\ldots,Y_n\}$) in an enumeration scheme. The corresponding enumeration -schemes are listed below (cf. \cite{ntz-preprint27/92},\cite{mmpreprint1979}). -In case that the standard form in the enumeration scheme depends on one (or two) -parameter(s) $p_1$ (and $p_2$) the list is expanded to: -\begin{verbatim} - {LIEALG(n),COMTAB(m),p1,p2}. -\end{verbatim} -This returned value is also stored as LIE\_CLASS. The linear transformation from -the basis $\{X_1,\ldots,X_n\}$ into the basis of the standard form -$\{Y_1,\ldots,Y_n\}$ is given by the matrix LIEMAT: -$Y_j=($LIEMAT$)_j^k X_k$.\newpage -By turning on the switch TR\_LIE: -\begin{verbatim} - ON TR_LIE; -\end{verbatim} -before the procedure LIECLASS is called the output contains not only the -list LIE\_CLASS but also the non-vanishing commutator relations in the -standard form.\\[0.1cm] -By the value $m$ and the parameters further examinations of the Lie algebra -are possible, especially if in a data bank mathematical relevant properties -of the enumerated standard forms are stored.\\[0.3cm] -{\large\bf Enumeration schemes for lie1234}\\[0.2cm] -\hspace*{0.3cm}\begin{tabular}{l|l}returned list LIE\_CLASS& -the corresponding commutator relations\\[0.1cm]\hline -{LIEALG(1),COMTAB(0)}&commutative case\\[0.1cm]\hline -{LIEALG(2),COMTAB(0)}&commutative case\\[0.1cm] -{LIEALG(2),COMTAB(1)}&$[Y_1,Y_2]=Y_2$\\[0.1cm]\hline -{LIEALG(3),COMTAB(0)}&commutative case\\[0.1cm] -{LIEALG(3),COMTAB(1)}&$[Y_1,Y_2]=Y_3$\\[0.1cm] -{LIEALG(3),COMTAB(2)}&$[Y_1,Y_3]=Y_3$\\[0.1cm] -{LIEALG(3),COMTAB(3)}&$[Y_1,Y_3]=Y_1,[Y_2,Y_3]=Y_2$\\[0.1cm] -{LIEALG(3),COMTAB(4)}&$[Y_1,Y_3]=Y_2,[Y_2,Y_3]=Y_1$\\[0.1cm] -{LIEALG(3),COMTAB(5)}&$[Y_1,Y_3]=-Y_2,[Y_2,Y_3]=Y_1$\\[0.1cm] -{LIEALG(3),COMTAB(6)}&$[Y_1,Y_3]=-Y_1+p_1 Y_2,[Y_2,Y_3]=Y_1,p_1\neq 0$\\[0.1cm] -{LIEALG(3),COMTAB(7)}&$[Y_1,Y_2]=Y_3,[Y_1,Y_3]=-Y_2,[Y_2,Y_3]=Y_1$\\[0.1cm] -{LIEALG(3),COMTAB(8)}&$[Y_1,Y_2]=Y_3,[Y_1,Y_3]=Y_2,[Y_2,Y_3]=Y_1$\\[0.1cm]\hline -{LIEALG(4),COMTAB(0)}&commutative case\\[0.1cm] -{LIEALG(4),COMTAB(1)}&$[Y_1,Y_4]=Y_1$\\[0.1cm] -{LIEALG(4),COMTAB(2)}&$[Y_2,Y_4]=Y_1$\\[0,1cm] -{LIEALG(4),COMTAB(3)}&$[Y_1,Y_3]=Y_1,[Y_2,Y_4]=Y_2$\\[0.1cm] -{LIEALG(4),COMTAB(4)}&$[Y_1,Y_3]=-Y_2,[Y_2,Y_4]=Y_2,$\\ - &$[Y_1,Y_4]=[Y_2,Y_3]=Y_1$\\[0.1cm] -{LIEALG(4),COMTAB(5)}&$[Y_2,Y_4]=Y_2,[Y_1,Y_4]=[Y_2,Y_3]=Y_1$\\[0.1cm] -{LIEALG(4),COMTAB(6)}&$[Y_2,Y_4]=Y_1,[Y_3,Y_4]=Y_2$\\[0.1cm] -{LIEALG(4),COMTAB(7)}&$[Y_2,Y_4]=Y_2,[Y_3,Y_4]=Y_1$\\[0.1cm] -{LIEALG(4),COMTAB(8)}&$[Y_1,Y_4]=-Y_2,[Y_2,Y_4]=Y_1$\\[0.1cm] -{LIEALG(4),COMTAB(9)}&$[Y_1,Y_4]=-Y_1+p_1 Y_2,[Y_2,Y_4]=Y_1,p_1\neq 0$\\[0.1cm] -{LIEALG(4),COMTAB(10)}&$[Y_1,Y_4]=Y_1,[Y_2,Y_4]=Y_2$\\[0.1cm] -{LIEALG(4),COMTAB(11)}&$[Y_1,Y_4]=Y_2,[Y_2,Y_4]=Y_1$ -\end{tabular}\\ -\hspace*{0.3cm}\begin{tabular}{l|l}returned list LIE\_CLASS& -the corresponding commutator relations\\[0.1cm]\hline -{LIEALG(4),COMTAB(12)}&$[Y_1,Y_4]=Y_1+Y_2,[Y_2,Y_4]=Y_2+Y_3,$\\ - &$[Y_3,Y_4]=Y_3$\\[0.1cm] -{LIEALG(4),COMTAB(13)}&$[Y_1,Y_4]=Y_1,[Y_2,Y_4]=p_1 Y_2,[Y_3,Y_4]=p_2 Y_3,$\\ - &$p_1,p_2\neq 0$\\[0.1cm] -{LIEALG(4),COMTAB(14)}&$[Y_1,Y_4]=p_1 Y_1+Y_2,[Y_2,Y_4]=-Y_1+p_1 Y_2,$\\ - &$[Y_3,Y_4]=p_2 Y_3,p_2\neq 0$\\[0.1cm] -{LIEALG(4),COMTAB(15)}&$[Y_1,Y_4]=p_1 Y_1+Y_2,[Y_2,Y_4]=p_1 Y_2,$\\ - &$[Y_3,Y_4]=Y_3,p_1\neq 0$\\[0.1cm] -{LIEALG(4),COMTAB(16)}&$[Y_1,Y_4]=2 Y_1,[Y_2,Y_3]=Y_1,$\\ - &$[Y_2,Y_4]=(1+p_1) Y_2,[Y_3,Y_4]=(1-p_1) Y_3,$\\ - &$p_1\geq 0$\\[0.1cm] -{LIEALG(4),COMTAB(17)}&$[Y_1,Y_4]=2 Y_1,[Y_2,Y_3]=Y_1,$\\ - &$[Y_2,Y_4]=Y_2-p_1 Y_3,[Y_3,Y_4]=p_1 Y_2+Y_3,$\\ - &$p_1\neq 0$\\[0.1cm] -{LIEALG(4),COMTAB(18)}&$[Y_1,Y_4]=2 Y_1,[Y_2,Y_3]=Y_1,$\\ - &$[Y_2,Y_4]=Y_2+Y_3,[Y_3,Y_4]=Y_3$\\[0.1cm] -{LIEALG(4),COMTAB(19)}&$[Y_2,Y_3]=Y_1,[Y_2,Y_4]=Y_3,[Y_3,Y_4]=Y_2$\\[0.1cm] -{LIEALG(4),COMTAB(20)}&$[Y_2,Y_3]=Y_1,[Y_2,Y_4]=-Y_3,[Y_3,Y_4]=Y_2$\\[0.1cm] -{LIEALG(4),COMTAB(21)}&$[Y_1,Y_2]=Y_3,[Y_1,Y_3]=-Y_2,[Y_2,Y_3]=Y_1$\\[0.1cm] -{LIEALG(4),COMTAB(22)}&$[Y_1,Y_2]=Y_3,[Y_1,Y_3]=Y_2,[Y_2,Y_3]=Y_1$ -\end{tabular} -\bibliography{lie} -\bibliographystyle{plain} -\end{document} +\documentstyle{article} +\parindent0cm +%\textwidth 15.5cm\textheight 22.0cm\columnwidth\textwidth +%\hoffset-1.5cm\voffset-1.5cm +\begin{document} +%\parskip 10pt plus 1pt \parindent 0pt +\title{The {LIE} Package} +\author{Carsten and Franziska Sch\"obel\\ +The Leipzig University, Computer Science Dept.\\ +Augustusplatz 10/11, O-7010 Leipzig, Germany\\ +Email: cschoeb@aix550.informatik.uni-leipzig.de} +\date{22 January 1993} +\maketitle +{\bf LIE} is a package of functions for the classification of real n-dimensional +Lie algebras. It consists of two modules: {\bf liendmc1} and {\bf lie1234}. +\\[0.3cm]{\large\bf liendmc1}\\[0.1cm] +With the help of the functions in this module real n-dimensional Lie algebras +$L$ with a derived algebra $L^{(1)}$ of dimension 1 can be classified. $L$ has +to be defined by its structure constants $c_{ij}^k$ in the basis +$\{X_1,\ldots,X_n\}$ with $[X_i,X_j]=c_{ij}^k X_k$. The user must define an +ARRAY LIENSTRUCIN($n,n,n$) with n being the dimension of the Lie algebra $L$. +The structure constants LIENSTRUCIN($i,j,k$):=$c_{ij}^k$ for $i). +\end{verbatim} +{\tt } corresponds to the dimension $n$. The procedure simplifies +the structure of $L$ performing real linear transformations. The returned +value is a list of the form +\begin{verbatim} + (i) {LIE_ALGEBRA(2),COMMUTATIVE(n-2)} or + (ii) {HEISENBERG(k),COMMUTATIVE(n-k)} +\end{verbatim} +with $3\leq k\leq n$, $k$ odd.\\ +The concepts correspond to the following theorem ({\tt LIE\_ALGEBRA(2)} +$\rightarrow L_2$, {\tt HEISENBERG(k)} $\rightarrow H_k$ and +{\tt COMMUTATIVE(n-k)} $\rightarrow C_{n-k}$):\\[0.2cm] +{\bf Theorem.} Every real $n$-dimensional Lie algebra $L$ with a 1-dimensional +derived algebra can be decomposed into one of the following forms:\\[0.1cm] +\hspace*{0.3cm} (i) $C(L)\cap L^{(1)}=\{0\}\, :\; L_2\oplus C_{n-2}$ +or\\[0.05cm] +\hspace*{0.3cm} (ii) $C(L)\cap L^{(1)}=L^{(1)}\, :\; H_k\oplus C_{n-k}\quad +(k=2r-1,\, r\geq 2)$, with\newpage +\hspace*{0.3cm} 1. $C(L)=C_j\oplus (L^{(1)}\cap C(L))$ +and dim$\,C_j=j$ ,\\[0.05cm] +\hspace*{0.3cm} 2. $L_2$ is generated by +$Y_1,Y_2$ with $[Y_1,Y_2]=Y_1$ ,\\[0.05cm] +\hspace*{0.3cm} 3. $H_k$ is generated by $\{Y_1,\ldots,Y_k\}$ with\\ +\hspace*{0.7cm} $[Y_2,Y_3]=\cdots =[Y_{k-1},Y_k]=Y_1$.\\[0.2cm] +(cf. \cite{cssmp92})\\[0.2cm] +The returned list is also stored as LIE\_LIST. The matrix LIENTRANS gives the +transformation from the given basis $\{X_1,\ldots ,X_n\}$ into the standard +basis $\{Y_1,\ldots ,Y_n\}$: $Y_j=($LIENTRANS$)_j^k X_k$.\\[0.1cm] +A more detailed output can be obtained by turning on the switch TR\_LIE: +\begin{verbatim} + ON TR_LIE; +\end{verbatim} +before the procedure LIENDIMCOM1 is called.\\[0.1cm] +The returned list could be an input for a data bank in which mathematical +relevant properties of the obtained Lie algebras are stored.\\[0.3cm] +{\large\bf lie1234}\\[0.1cm] +This part of the package classifies real low-dimensional Lie algebras $L$ +of the dimension +$n:=$dim$\,L=1,2,3,4$. $L$ is also given by its structure constants $c_{ij}^k$ +in the basis $\{X_1,\ldots,X_n\}$ with $[X_i,X_j]=c_{ij}^k X_k$. An ARRAY +LIESTRIN($n,n,n$) has to be defined and LIESTRIN($i,j,k$):=$c_{ij}^k$ for +$i). +\end{verbatim} +{\tt } should be the dimension of the Lie algebra $L$. The procedure +stepwise simplifies the commutator relations of $L$ using properties of +invariance like the dimension of the centre, of the derived algebra, +unimodularity etc. The returned value has the form: +\begin{verbatim} + {LIEALG(n),COMTAB(m)}, +\end{verbatim} +where $m$ corresponds to the number of the standard form (basis: +$\{Y_1,\ldots,Y_n\}$) in an enumeration scheme. The corresponding enumeration +schemes are listed below (cf. \cite{ntz-preprint27/92},\cite{mmpreprint1979}). +In case that the standard form in the enumeration scheme depends on one (or two) +parameter(s) $p_1$ (and $p_2$) the list is expanded to: +\begin{verbatim} + {LIEALG(n),COMTAB(m),p1,p2}. +\end{verbatim} +This returned value is also stored as LIE\_CLASS. The linear transformation from +the basis $\{X_1,\ldots,X_n\}$ into the basis of the standard form +$\{Y_1,\ldots,Y_n\}$ is given by the matrix LIEMAT: +$Y_j=($LIEMAT$)_j^k X_k$.\newpage +By turning on the switch TR\_LIE: +\begin{verbatim} + ON TR_LIE; +\end{verbatim} +before the procedure LIECLASS is called the output contains not only the +list LIE\_CLASS but also the non-vanishing commutator relations in the +standard form.\\[0.1cm] +By the value $m$ and the parameters further examinations of the Lie algebra +are possible, especially if in a data bank mathematical relevant properties +of the enumerated standard forms are stored.\\[0.3cm] +{\large\bf Enumeration schemes for lie1234}\\[0.2cm] +\hspace*{0.3cm}\begin{tabular}{l|l}returned list LIE\_CLASS& +the corresponding commutator relations\\[0.1cm]\hline +{LIEALG(1),COMTAB(0)}&commutative case\\[0.1cm]\hline +{LIEALG(2),COMTAB(0)}&commutative case\\[0.1cm] +{LIEALG(2),COMTAB(1)}&$[Y_1,Y_2]=Y_2$\\[0.1cm]\hline +{LIEALG(3),COMTAB(0)}&commutative case\\[0.1cm] +{LIEALG(3),COMTAB(1)}&$[Y_1,Y_2]=Y_3$\\[0.1cm] +{LIEALG(3),COMTAB(2)}&$[Y_1,Y_3]=Y_3$\\[0.1cm] +{LIEALG(3),COMTAB(3)}&$[Y_1,Y_3]=Y_1,[Y_2,Y_3]=Y_2$\\[0.1cm] +{LIEALG(3),COMTAB(4)}&$[Y_1,Y_3]=Y_2,[Y_2,Y_3]=Y_1$\\[0.1cm] +{LIEALG(3),COMTAB(5)}&$[Y_1,Y_3]=-Y_2,[Y_2,Y_3]=Y_1$\\[0.1cm] +{LIEALG(3),COMTAB(6)}&$[Y_1,Y_3]=-Y_1+p_1 Y_2,[Y_2,Y_3]=Y_1,p_1\neq 0$\\[0.1cm] +{LIEALG(3),COMTAB(7)}&$[Y_1,Y_2]=Y_3,[Y_1,Y_3]=-Y_2,[Y_2,Y_3]=Y_1$\\[0.1cm] +{LIEALG(3),COMTAB(8)}&$[Y_1,Y_2]=Y_3,[Y_1,Y_3]=Y_2,[Y_2,Y_3]=Y_1$\\[0.1cm]\hline +{LIEALG(4),COMTAB(0)}&commutative case\\[0.1cm] +{LIEALG(4),COMTAB(1)}&$[Y_1,Y_4]=Y_1$\\[0.1cm] +{LIEALG(4),COMTAB(2)}&$[Y_2,Y_4]=Y_1$\\[0,1cm] +{LIEALG(4),COMTAB(3)}&$[Y_1,Y_3]=Y_1,[Y_2,Y_4]=Y_2$\\[0.1cm] +{LIEALG(4),COMTAB(4)}&$[Y_1,Y_3]=-Y_2,[Y_2,Y_4]=Y_2,$\\ + &$[Y_1,Y_4]=[Y_2,Y_3]=Y_1$\\[0.1cm] +{LIEALG(4),COMTAB(5)}&$[Y_2,Y_4]=Y_2,[Y_1,Y_4]=[Y_2,Y_3]=Y_1$\\[0.1cm] +{LIEALG(4),COMTAB(6)}&$[Y_2,Y_4]=Y_1,[Y_3,Y_4]=Y_2$\\[0.1cm] +{LIEALG(4),COMTAB(7)}&$[Y_2,Y_4]=Y_2,[Y_3,Y_4]=Y_1$\\[0.1cm] +{LIEALG(4),COMTAB(8)}&$[Y_1,Y_4]=-Y_2,[Y_2,Y_4]=Y_1$\\[0.1cm] +{LIEALG(4),COMTAB(9)}&$[Y_1,Y_4]=-Y_1+p_1 Y_2,[Y_2,Y_4]=Y_1,p_1\neq 0$\\[0.1cm] +{LIEALG(4),COMTAB(10)}&$[Y_1,Y_4]=Y_1,[Y_2,Y_4]=Y_2$\\[0.1cm] +{LIEALG(4),COMTAB(11)}&$[Y_1,Y_4]=Y_2,[Y_2,Y_4]=Y_1$ +\end{tabular}\\ +\hspace*{0.3cm}\begin{tabular}{l|l}returned list LIE\_CLASS& +the corresponding commutator relations\\[0.1cm]\hline +{LIEALG(4),COMTAB(12)}&$[Y_1,Y_4]=Y_1+Y_2,[Y_2,Y_4]=Y_2+Y_3,$\\ + &$[Y_3,Y_4]=Y_3$\\[0.1cm] +{LIEALG(4),COMTAB(13)}&$[Y_1,Y_4]=Y_1,[Y_2,Y_4]=p_1 Y_2,[Y_3,Y_4]=p_2 Y_3,$\\ + &$p_1,p_2\neq 0$\\[0.1cm] +{LIEALG(4),COMTAB(14)}&$[Y_1,Y_4]=p_1 Y_1+Y_2,[Y_2,Y_4]=-Y_1+p_1 Y_2,$\\ + &$[Y_3,Y_4]=p_2 Y_3,p_2\neq 0$\\[0.1cm] +{LIEALG(4),COMTAB(15)}&$[Y_1,Y_4]=p_1 Y_1+Y_2,[Y_2,Y_4]=p_1 Y_2,$\\ + &$[Y_3,Y_4]=Y_3,p_1\neq 0$\\[0.1cm] +{LIEALG(4),COMTAB(16)}&$[Y_1,Y_4]=2 Y_1,[Y_2,Y_3]=Y_1,$\\ + &$[Y_2,Y_4]=(1+p_1) Y_2,[Y_3,Y_4]=(1-p_1) Y_3,$\\ + &$p_1\geq 0$\\[0.1cm] +{LIEALG(4),COMTAB(17)}&$[Y_1,Y_4]=2 Y_1,[Y_2,Y_3]=Y_1,$\\ + &$[Y_2,Y_4]=Y_2-p_1 Y_3,[Y_3,Y_4]=p_1 Y_2+Y_3,$\\ + &$p_1\neq 0$\\[0.1cm] +{LIEALG(4),COMTAB(18)}&$[Y_1,Y_4]=2 Y_1,[Y_2,Y_3]=Y_1,$\\ + &$[Y_2,Y_4]=Y_2+Y_3,[Y_3,Y_4]=Y_3$\\[0.1cm] +{LIEALG(4),COMTAB(19)}&$[Y_2,Y_3]=Y_1,[Y_2,Y_4]=Y_3,[Y_3,Y_4]=Y_2$\\[0.1cm] +{LIEALG(4),COMTAB(20)}&$[Y_2,Y_3]=Y_1,[Y_2,Y_4]=-Y_3,[Y_3,Y_4]=Y_2$\\[0.1cm] +{LIEALG(4),COMTAB(21)}&$[Y_1,Y_2]=Y_3,[Y_1,Y_3]=-Y_2,[Y_2,Y_3]=Y_1$\\[0.1cm] +{LIEALG(4),COMTAB(22)}&$[Y_1,Y_2]=Y_3,[Y_1,Y_3]=Y_2,[Y_2,Y_3]=Y_1$ +\end{tabular} +\bibliography{lie} +\bibliographystyle{plain} +\end{document}