Repeated measurements and granular space time

[Heidi]

Hi Pfs,
I would like to know if it would be possible for our known theories to derive
conservation laws if space time was really granular.
I think that entanglement is the only process which would succeed.

 

[weirdoguy]

Our known theories assume continuous spacetime. To derive something in granular spacetime we need models that have it built in. And we don't, at least not developed to the point where we can derive conservation laws.

 

[OlderWannabeNewton]

There was already a thread about this question not too long ago: https://www.physicsforums.com/threads/conservation-of-energy-in-quantum-gravity.1061153/

"Conservation laws" can mean many different things in gravity. The most conservative and well-understood of these, asymptotic boundary conservation laws, would apply just as well in quantum gravity, when you have asymptotic boundaries. Asymptotic boundaries are typically fixed boundary conditions in the gravitational path integral.

If you are asking about quasi-local conservation laws then the situation is more complicated as it is not clear how to specify subregions in quantum gravity. But it would be surprising if some form of conservation laws didn't hold. If you have no asymptotic boundaries and you aren't fixing some bulk subregion in the gravity path integral (which again is poorly understood) then you just have the pure gravitational constraints.

 

[Heidi]

Would it be possible that severall conservation laws could be explained by the fact
that we have processes vhich do not depend on space or time?
Entanglement seems to be not local.
Take the the Foucault's pendulum. It oscillates in a plane that does not depend on
the rotarion of the earth, the position of the sun or other stars. It only depends on
the initial choice , not on far objects.

 

[weirdoguy]

Would it be possible

Everything is possible and nothing is possible if we don't have any concrete model at hand.

Take the the Foucault's pendulum. It oscillates in a plane that does not depend on
the rotarion of the earth

In Earths frame of reference it surely does depend on its rotation.