Bigger on the Inside: Averted… so far (as referenced in Stop Fittling With That and its Author’s Notes).  The possibility is acknowledged to exist – the field of ontotechnology is working on it even now, in the present of their timeline, under the generic name of “dimensional transcendence”, and it really ought to be possible, since both wormholes and vector control demonstrate that it’s possible to muck about with the topology of space in interesting ways, but no-one’s actually done it yet.