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Loop Quantum Gravity and the Concept of the Universe as a Co

  1. Nov 25, 2014 #1
    Disclaimer: I'm just an amateur enthusiast who is a programmer during the day

    I suppose everyone who takes an interest in physics who doesn't have the mathematical tools to further their enquiries end up writing posts like mine, and that at the very least it's nice to see where the ideas reside amongst (or outside of) what is more mathematically sound, or just simply hearing the wisdom of people who know better.</disclaimer>

    I like the idea that the universe is a computational machine, either conceptually or in actuality (I prefer the latter). I also like( or believe) that the universe is indeed deterministic and that there is a granularity of its fundamental units, and the emergent property of it is information. After reading Seth Lloyd's "Computing the Universe", it'd seem he's happy with the conceptual angle (and wouldn't go as far to say it is actually computing "something" more than itself).

    I would very much appreciate if you could humour me on this and see whether there's any potential truth or refutable in my statements.

    - According to Einstein, gravity is not a force but a property of spacetime itself. Could it be that in a computational sense, gravity acts as a barrier to prevent computational complexity exceeding a 'limit' within an area of spacetime? i.e. time is relatively slowed where there is more information, and the number of bit flips required in a more conceptually average time frame would not exceed a limit created by the effect of gravity.

    - I can get my head round wave-particle duality if the fundamental unit is information, and that matter is only emergent when it is interacting with other matter. i.e. matter/information is only observable when it needs to be. The probability wave only needs to collapse when the information is forced to reveal itself at a particular place and time. Could it perhaps be that this preferred form is an 'insurance' that a given locality would not exceed a computational complexity also?

    - Is it possible that matter/information falling into a black hole is equivalent to writing the universe's laws onto its spinning disk? i.e. every unique bit of information is written on there linearly (and I assume written back out but but perhaps encoded differently or the data is effectively wiped (which I understand is considered bad form if the process could not be reversed)).

    My own cobbled-up notion is that the universe can be thought of as a series of computational 'cores' of a similar size or few orders of magnitude larger or smaller than the Planck scale, though I'm slightly confused about Planck scales. My understanding is that it's the most fundamental "unit of action" and perhaps in the computational sense, a unit of action could be considered at two different scales.

    Thanks for reading
     
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  3. Nov 25, 2014 #2

    Doug Huffman

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    Read Leonard Susskind and the Holographic Principle
     
  4. Nov 25, 2014 #3

    atyy

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    The closest notion I can think of is the Bekenstein bound: http://www.scholarpedia.org/article/Bekenstein_bound.

    One derivation of quantum mechanics involving notions of locality and information is Chiribella, D'Ariano and Perinotti's http://arxiv.org/abs/1209.5533. They use a number of assumptions, among which are:
    Principle 4 (Ideal Compression) Information can be compressed in a lossless and maximally efficient fashion.
    Principle 5 (Local tomography) The state of a composite system is determined by the statistics of local measurements on the components.

    I don't think there is any theory like this. The most usual comparison is that the information is conjectured to be stored holographically. Take a look at the Susskind book that Doug Huffman recommended in post #2.
     
  5. Nov 25, 2014 #4

    bhobba

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    Last edited by a moderator: May 7, 2017
  6. Nov 26, 2014 #5
    Thank you for your replies, much appreciated.

    I'd gleaned some of L.Susskind's idea as a lot of his lectures are on YouTube, the idea that the informational content going into a black hole could easy be contained on its surface area. I find him hard to follow without some additional physics knowledge it seems I should have (the equations lining up with one another basically). He goes 'straight into' the physics without a fuss which has made him (and the book you mentioned) harder to follow. Perhaps that's something I can build up to.

    The other references are fascinating and resonate a lot with me. Scott Aaronson's book goes into great detail about computational complexity and I read a large chunk of it last night.

    Thanks to all three of you for your references.
     
  7. Nov 29, 2014 #6
    I found a couple of more references that tie in with my fuzzy notions.

    Edward Fredkin's Finite Nature Hypothesis
    Stephen Wolfram's "A New Kind of of Science"

    I think I'll see what Coursera has to offer to get a more solid foundation of physics and maths to...err... think for myself.
     
  8. Nov 29, 2014 #7

    atyy

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    You should probably stick to Susskind for something solid.
     
    Last edited: Nov 29, 2014
  9. Nov 29, 2014 #8
    I'll bear that in mind, from what I've read these computational analogies are not taken too seriously by the physics community at large.

    Susskind has his whole set of lectures online so I'll get round to them. I do get the impression he teaches his own ideas more than some of the alternatives but I'm attentive all the same.

    Having watches this one about causality... ... I was 'hoping' that his explanation would have involved a black hole causing information loss and subsequently creating causality. Interestingly much of the video revolves around a boolean logic system.
     
  10. Nov 29, 2014 #9

    atyy

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    Yeah, I guess that lecture was extremely speculative. I was thinking something more like what Doug Huffman recommended in post #2, I think he meant https://www.amazon.com/Introduction-Information-String-Theory-Revolution/dp/9812561315, which is speculative also, but much more mainstream. You can also try reading books from his "Theoretical Minimum" series, which are basic non-speculative physics.

    To complement the Susskind book on the holographic universe, here's a short article by Maldacena, who made a very precise conjecture for the holographic principle that can be investigated theoretically. Even if the conjecture were right, it wouldn't describe our universe, but it would be a theory of quantum gravity for some possible universe. http://www.pma.caltech.edu/~physlab/ph10_references/scientificamerican1105-56.pdf
     
    Last edited by a moderator: May 7, 2017
  11. Nov 29, 2014 #10
    Indeed, I understand that video isn't the kind of seminal work he's best known for.

    I previewed the book and much like his online lectures, there's a lot of physics for a mere mortal like myself (having to Google the likes of Rindler space or Fourier transforms), the book is also rich in physics terminology and assumes a fair bit of knowledge. It's something I'll have to work up to. Perhaps if he had a Susskind for Dummies release that would suit me in the current timeframe :)

    On a more philosophical note I'm sceptical of explanations requiring more universes and dimensions, but hopefully with the coming months I can get my head round such a book.

    Thanks again
     
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