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From watching the video and reading one of the papers, I get the sense that the theory being described doesn't work in the usual way. For example, reading the p
by Strilanc 5y ago
From watching the video and reading one of the papers, I get the sense that the theory being described doesn't work in the usual way. For example, reading the paper it talks about "future inputs" determining what happens, which seems impossible if you need to have the entire state specified for each time slice without need to reference other time slices. Instead of having a specific state for time t, and being able to evolve it forward/backward to other times, it is instead applying constraints across spacetime?
In principle, allowing yourself that kind of flexibility could be enough to model quantum mechanics. But I'm not sure why I'd want to do it that way instead of the existing ways. It's not particularly philosophically appealing to me, and objectively speaking it looks like they don't yet have a concrete mathematical model that actually reproduces quantum mechanics. But maybe I'm just ignorant of the latter part's existence.
- SuoDuanDao 5y agoI'm no expert in this field, but aren't the existing assumptions around time being independent at the slice we want to take a major reason why QM and General Relativity can't be reconciled? If so, that would seem like a good reason to look at alternative ideas in this space.
- naasking 5y agoI think that's more or less correct. GR suggests "time" isn't independent, we instead have 4-dimensional "spacetime". The idea that future inputs can influence past configurations can be perfectly sensible in this context. It's like a restricted form of consistent closed timelike curves. There was some development in this direction years ago: The Logic of Quantum Mechanics Derived from Classical General Relativity, https://arxiv.org/abs/quant-ph/9706018 https://arxiv.org/abs/quant-ph/9706018
- myridium 5y agoWhy is GR required? Already in standard QFT (Minkowski metric; flat spacetime; special relativity) the propagator 'violates causality'. Although that phrasing is misleading; it doesn't mean there's any logical inconsistency. 'The future affects the past' you might say. Yes, well, all information about the future is derivable from information about the present. So actually those 'future influences' are determined by the present. In the same way, 'locality' is almost a moot concept, because the analyticity of fields implies that the value of fields at remote locations is determined entirely by the field locally.
- naasking 5y agoMaybe GR isn't required. It seems like the simplest path to understanding how this could work for those who aren't familiar with QM though.
- bollu 5y agoI don't follow the comment about analyticity. I thought fields were real analytic, which meant one needed to use a power series to expand them, which has a potentially infinite amount of information in the Taylor coefficients? So I don't see how the local data "effectively" captures non local information.
- evanb 5y agoI think you may be over-simplifying. We have relativistic quantum-mechanical theories, and we can formulate quantum field theories on curved background spacetimes.
- Koshkin 5y agoBut isn't the spacetime of SR flat?
- 323 5y agoYou might want to read about "block time" or "block universe". In this theory, everything is already pre-computed, like an uncompressed video file. So you can skip to whatever frame you want since there is no state. > It is sometimes referred to as the "block time" or "block universe" theory due to its description of space-time as an unchanging four-dimensional "block", as opposed to the view of the world as a three-dimensional space modulated by the passage of time. https://en.wikipedia.org/wiki/Eternalism_(philosophy_of_time) https://en.wikipedia.org/wiki/Eternalism_(philosophy_of_time...
- zikzak 5y agoPeople who meditate often begin to slowly realize that ideas arise without concious thought. We imagine we are "thinking" but there really is no break in causality where we somehow choose how we want the future to unfold. Our brains are no more exempt from cause and effect than a marble rolling downhill is. It is a mistake to confuse the finger pointing at the moon with the moon itself. We don't preceive everything, our senses are a filter that allows us to navigate but there's no more free will here than a plant turning to follow the sun. Fortunately, we don't experience reality this way. If we did, life would cease to be meaningful.
- thulle 5y ago> there's no more free will here than a plant turning to follow the sun That's a bold claim without presenting anything really backing it up?
- dtjb 5y agoWhile limited, studies using FMRI brain scans can detect "decisions" being made before they're consciously processed. https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0025304 https://journals.plos.org/plosone/article?id=10.1371/journal...