Cotler said there are some configurations of the future that don't correspond to what happened in the past. There isn't anything in the past that would change them.
Giddings encountered a number of paradoxes while studying black holes. He believes that a given state of the universe is only physically possible if it can evolve backwards. He said that the puzzle was a long one. Strominger and Cotler are trying to inspire a new way of thinking about things.
Giddings thinks the approach needs to be further developed. Dittrich came to similar realizations a decade ago while trying to formulate a toy quantum theory with Philipp Hhn. One hope is that such work will eventually lead to a specific rule that governs our universe. The calculation of which specific patterns in the distribution of the matter in the sky are possible and which aren't could be used to test the predictions against observational data. He said you will find this if you look closer. It could be useful.
Isometric and beyond.
Theory and thought experiments show that isometry helps combine the malleability of space-time with quantum theory.
Black holes, intense concentrations of matter that warp space-time into a dead end is one thought experiment. Black holes evaporate over time, wiping out the quantum state of anything that falls in, a seemingly blatant violation of unitarity. Physicists may face a different puzzle if black holes have Hilbert spaces. Strominger thinks there can be a solution that takes this into account.
A detailed quantum theory that explained where everything came from would be another prize. We don't have a universe, but we have a universe. Is that kind of evolution?
Arkani-Hamed doesn't believe that swap in isometry for unitarity goes far enough. One of the leaders of a research program is trying to break free of many fundamental assumptions in quantum theory and general relativity.
He thinks that whatever theory comes next, it will be a completely novel form, just as quantum mechanics was a break from the laws of motion. An example of what a new form might look like is the research program he points to. The volume of a geometric object is known as the amplituhedron. It is much easier to calculate the object's volume than it is to reconstruct the ways a particle collision might play out.
The principle is not used to construct the shape itself. There aren't any assumptions about how particles move. There is a chance for a new perspective on reality, one free from the cherished principles that currently conflict, because of the success of this purely geometric formulation of particle physics. Geometric shapes related to different particles and quantum theories are being explored more and more by researchers.
It is possible that it is a different way to organize unitarity.
The original story was originally published in the journal of the Simons Foundation, an editorially independent publication that covers research developments and trends in mathematics and the physical and life sciences.