Emily Adlam
speaker
1,263 appearances
3 recordings
1 series
first heard Apr 2025
last heard 20 Jul
Emily Adlam’s voice in public audio — every appearance, attributed to the second.
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recordings per month · last 12 monthsRecordings per month over the last 12 months — 1 in all, peaking in Jul 2026 with 1.
Appearances
Another issue is that quite a lot of, in quantum gravity, for example, the most straightforward way to do a calculation is kind of like fix an external classical space-time boundary and then do quantum gravity sort of inside that boundary.
And so you still seem to need some kind of like Heisenberg cut in much the same ways as you do in sort of standard non-relativistic quantum mechanics.
So there seem to be some conceptual issues and difficulties within quantum gravity surrounding the role of observers.
And since that was sort of already a problem, as I see it in standard quantum mechanics, it seems to me at least plausible there's some link between the problems we're having in quantum gravity and the earlier problems in interpreting quantum mechanics.
I mean, I'm slightly skeptical about making a division between those two problems in a sharp way, precisely because subsystem decompositions themselves are one of the things that start to look quite odd in the point of view of certain kinds of canonical quantization, for example.
So, you know, while I agree that you can look at an individual subsystem and derive useful predictions out of it quantum gravitationally, the
The separation between those two problems itself seems to me to be a kind of approximation and something that we shouldn't rely on conceptually.
Sure.
No, that's fair.
Now, we can use the approximation if our goal is to understand how to make predictions for the quantum gravity of some effectively isolated subsystem.
I think nonetheless, if you're trying to understand, I guess, what quantum gravity is and what it's telling us about space-time and how it links to earlier frameworks and how...
our experience and non-relativistic quantum mechanics merges out of it, I'm slightly sceptical that you can tell that story in a complete and satisfactory way while ignoring these more cosmological issues because they seem quite tightly tied together in the framework of quantum gravity in a way that they maybe are not in earlier physics.
For example, from a relational point of view again, one of the recent directions of investigation in the relational formalism has been looking at the way in which subsystem decompositions depend on a choice of reference frame.
Given a fixed subsystem decomposition, you can for sure do a description of it and describe the physics of just that subsystem sort of relative to the choice of background.
But it seems to me that if you want to tell a complete story about how all that is emerging from what it is underneath, then you are going to have to take into account the fact that the subsystem decomposition itself is not fixed and that the procedure for choosing it is part of the story.
Yeah, that's fair enough.
And I think I agree that we can do a lot of things usefully, but there are also sort of certain questions that seem to be important about the way these things are tied together.
Yeah, as I say, I'm hopeful that there's a minor modification which will succeed and we don't have to make a really large modification.
But if push comes to shove and a large modification is the only thing that will work, then I'm willing to do that.
I'm willing for someone else to do the work.
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