Geodesic
Limits of Contraction Groups and the Tits Core
Journal of Lie theory, Tome 24 (2014) no. 4, pp. 957-967

Voir la notice de l'article provenant de la source Heldermann Verlag

The Tits core G+ of a totally disconnected locally compact group G is defined as the abstract subgroup generated by the closures of the contraction groups of all its elements. We show that a dense subgroup is normalised by the Tits core if and only if it contains it. It follows that every dense subnormal subgroup contains the Tits core. In particular, if G is topologically simple, then the Tits core is abstractly simple, and when G+ is non-trivial, it is the smallest dense normal subgroup. The proofs are based on the fact, of independent interest, that the map which associates to an element the closure of its contraction group is continuous.
Classification : 22D05, 20E32
Mots-clés : Totally disconnected locally compact group, simple group, contraction group, Chabauty topology 
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     author = {P.-E. Caprace and C. D. Reid and G. A. Willis },
     title = {Limits of {Contraction} {Groups} and the {Tits} {Core}},
     journal = {Journal of Lie theory},
     pages = {957--967},
     publisher = {mathdoc},
     volume = {24},
     number = {4},
     year = {2014},
     url = {http://geodesic.mathdoc.fr/item/JLT_2014_24_4_JLT_2014_24_4_a2/}
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P.-E. Caprace; C. D. Reid; G. A. Willis . Limits of Contraction Groups and the Tits Core. Journal of Lie theory, Tome 24 (2014) no. 4, pp. 957-967. http://geodesic.mathdoc.fr/item/JLT_2014_24_4_JLT_2014_24_4_a2/