No. In fact, there's no way to search over multi-cores at once in Solr
at all, even before you get to your boosting question. Your different
cores are entirely different Solr indexes, Solr has no built-in way to
combine searches accross multiple Solr instances.
[Well, sort of it can, with
Could you make an additional date field, call it date_boost, that gets
populated in all of the cores EXCEPT the one with the newest articles, and
then boost on this field? Then when you move articles from the 'newest' core
to the rest of the cores you copy over the date to the date_boost field. (I
