Proving SL_2(C) Homeomorphic to SU(2)xT & Simple Connectedness

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SUMMARY

The discussion focuses on proving that the special linear group ##SL_2(C)## is homeomorphic to the product of the special unitary group ##SU(2)## and the set ##T## of upper-triangular 2×2-complex matrices with positive real diagonal entries. The mapping defined as ##(u,t) → ut##, where ##u ∈ SU(2)## and ##t ∈ T##, is established as injective. The discussion raises questions about the surjectivity of this mapping and the continuity of both the mapping and its inverse, as well as the behavior of the determinant of ##t## when it is not of the form ##(a,a^{-1})##.

PREREQUISITES
  • Understanding of group theory, particularly the properties of ##SL_2(C)## and ##SU(2)##.
  • Familiarity with QR decomposition in the context of complex matrices.
  • Knowledge of topological concepts such as homeomorphism and continuity.
  • Basic understanding of matrix operations and determinants.
NEXT STEPS
  • Study the properties of homeomorphisms in topology, focusing on examples involving matrix groups.
  • Explore the QR decomposition in detail, specifically its applications in complex linear algebra.
  • Investigate the implications of injective and surjective mappings in group theory.
  • Learn about the determinant function and its significance in the context of upper-triangular matrices.
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Mathematicians, particularly those specializing in algebraic topology, group theory, and linear algebra, as well as students seeking to understand the relationships between different matrix groups and their topological properties.

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Using the QR decomposition (the complex version) I want to prove that ##SL_2(C)## is homeomorphic to the product ##SU(2) × T## where ##T## is the set of upper-triangular 2×2-complex matrices with real positive entries at the diagonal. Deduce that ##SL(2, C)## is simply-connect.

So, I can define a map ##SU(2)×T–>SL(2,C)## given by: ##(u,t) –> ut## where ##u \in SU(2)## and ##t \in T## (from QR decomposition we have that each ##A## in ##GL(2,C)## can be written as ##ut## where ##u \in U(n)## and ##t \in T## (##T## mentioned above)).
We have that the intersection ##SU(2)\cap T=1##.
This map is injective:
if ##u_1t_1=u_2t_2## then this gives
##u_2^{-1}u_1=t_2t_1^{-1} \in SU(2)\cap T## so ##u_1=u_2## and ##t_1=t_2##.
Can I say that this map is surjective by the QR decomposition?
why is this map and its inverse contiuous?

Thanks for help!
 
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