Retract Rationality and Algebraic Tori
Canadian mathematical bulletin, Tome 63 (2020) no. 1, pp. 173-186
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For any prime number $p$ and field $k$, we characterize the $p$-retract rationality of an algebraic $k$-torus in terms of its character lattice. We show that a $k$-torus is retract rational if and only if it is $p$-retract rational for every prime $p$, and that the Noether problem for retract rationality for a group of multiplicative type $G$ has an affirmative answer for $G$ if and only if the Noether problem for $p$-retract rationality for $G$ has a positive answer for all $p$. For every finite set of primes $S$ we give examples of tori that are $p$-retract rational if and only if $p\notin S$.
Mots-clés :
algebraic tori, retract rationality, Noether problem, invertible lattice
Scavia, Federico. Retract Rationality and Algebraic Tori. Canadian mathematical bulletin, Tome 63 (2020) no. 1, pp. 173-186. doi: 10.4153/S0008439519000079
@article{10_4153_S0008439519000079,
author = {Scavia, Federico},
title = {Retract {Rationality} and {Algebraic} {Tori}},
journal = {Canadian mathematical bulletin},
pages = {173--186},
year = {2020},
volume = {63},
number = {1},
doi = {10.4153/S0008439519000079},
url = {http://geodesic.mathdoc.fr/articles/10.4153/S0008439519000079/}
}
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