A Polish group containing a Haar null $F_\sigma$subgroup that cannot be enlarged to a Haar null $G_\delta$set
Abstract
Answering a question of Elekes and Vidnyánszky, we construct a Polish metaabelian group $H$ and a subgroup $F\subset H$, which is a Haar null $F_\sigma$set in $H$ that cannot be enlarged to a Haar null $G_\delta$set.
 Publication:

arXiv eprints
 Pub Date:
 April 2016
 arXiv:
 arXiv:1604.00150
 Bibcode:
 2016arXiv160400150B
 Keywords:

 Mathematics  General Topology;
 Mathematics  Group Theory;
 22A10;
 28C10
 EPrint:
 2 pages