Mappings

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  1. TheEd's Avatar
    • Exalted and Worshipped Member
    • Posts: 1,213
    Mappings
    If V is a 3-dimensional Lie algebra with basis vectors E,F,G with Lie bracket relations [E,F]=G, [E,G]=0, [F,G]=0 and V' is the Lie algebra consisting of all 3x3 strictly upper triangular matrices with complex entries then would you say the following 2 mappings (isomorphisms) are different? I had to give an example of 2 different isomorphisms between these vector spaces.

    \varphi : V \to V' given by

    \varphi(aE+bF+cG)=\left( \begin{array}{ccc} 0 & a & c\\ 0 & 0 & b\\ 0 & 0 & 0 \end{array} \right)\;,\;\;\;\;\;a,b,c \in \mathbb{C}

    and \bar{\varphi} : V \to V' given by

    \bar{\varphi}(E)=\left( \begin{array}{ccc} 0 & 1 & 0\\ 0 & 0 & 0\\ 0 & 0 & 0 \end{array} \right)

    \bar{\varphi}(F)=\left( \begin{array}{ccc} 0 & 0 & 0\\ 0 & 0 & 1\\ 0 & 0 & 0 \end{array} \right)

    \bar{\varphi}(G)=\left( \begin{array}{ccc} 0 & 0 & 1\\ 0 & 0 & 0\\ 0 & 0 & 0 \end{array} \right)
    Last edited by TheEd; 09-06-2012 at 09:49.
  2. Coursework.info's Avatar
    • Retired TSR Help Bot
    • Location: That galaxy over there
    Mappings
    It's been a while since you posted and nobody's replied yet...maybe you should check out MarkedbyTeachers.com, TSR's sister site. It has the largest library of essays in the UK.

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  3. El Matematico's Avatar
    • Benevolent Member
    • Location: England
    • Posts: 654
    Re: Mappings
    Maybe this post is a little late given that the thread is a week old now, but recall that Lie algebra isomorphisms are also linear transformations, so are determined by their values on the basis elements E,F and G. So it seems your two maps are the same. However, the map you've given is an isomorphism and from this, it doesn't look too difficult to find a second?
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