Symmetry And Group

## Lectures on Lie Groups by D. Milicic

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By D. Milicic

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The contents of this publication were used in classes given via the writer. the 1st was once a one-semester direction for seniors on the collage of British Columbia; it was once transparent that stable undergraduates have been completely able to dealing with undemanding staff conception and its software to uncomplicated quantum chemical difficulties.

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4, ϕ−1 (K) is a Lie subgroup of G and L(ϕ−1 (K)) = {ξ ∈ L(G) | T1 (p ◦ ϕ)(ξ) = 0} = {ξ ∈ L(G) | T1 (ϕ)(ξ) ∈ L(K)}. Let G and H be two Lie groups. Then G × H is a Lie group. 11. Lemma. L(G × H) = L(G) × L(H). Let ∆ be the diagonal in G × G. Then ∆ is a Lie subgroup of G × G. Clearly, the map α : g −→ (g, g) is an isomorphism of G onto ∆. Let H and H be two Lie subgroups of G. Then H × H is a Lie subgroup of G × G. Moreover, α−1 (H × H ) = H ∩ H . 10, we have the following result. 12. Lemma. Let H and H be two Lie subgroups of G.

Let d ∈ D. Then α : g −→ gdg −1 is a continuous map from G into G and the image of α is contained in D. Therefore, the map α : G −→ D is continuous. Since G is connected, and D discrete it must be a constant map. Therefore, gdg −1 = α(g) = α(1) = g for any g ∈ G. It follows that gd = dg for any g ∈ G, and d is in the center of G. 36 2. LIE GROUPS ˜ −→ G is a discrete In particular, the kernel ker p of the covering projection p : G ˜ central subgroup of G. From the above discussion, we conclude that the following result holds.

Therefore the dimension of GL(n, ) is equal to 2n2 . The determinant det : GL(n, ) −→ ∗ is again a Lie group homomorphism. Its kernel is the complex special linear group SL(n, ). As before, we can calculate its differential which is the complex linear form tr : Mn ( ) −→ . Therefore, the tangent space to SL(n, ) at I can be identified with the space of traceless matrices in Mn ( ). It follows that the dimension of SL(n, ) is equal to 2n2 − 2. Let V = p+q and p+q p ϕ(v, w) = i=1 vi w ¯i − vi w ¯i i=p+1 for v, w ∈ V .