Have a look at ‘glute bridges’. They were fundamental for me in treating lower back pain (as directed by a physiotherapist) and my sister, who is a physiotherapist, raved about them too. They seem like they could be a very effective component of a core workout that you can do in ten minutes on a floor in jeans.
I did a lazy search and couldn’t find a decent reference for you sorry but there is loads of stuff on them on non-academic websites.