Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

What is the world made of?

  1. particles

    35.7%
  2. fields

    46.4%
  3. spin networks

    10.7%
  4. strings

    14.3%
  5. string fields

    3.6%
  6. p-branes

    0 vote(s)
    0.0%
  7. matrices

    14.3%
Multiple votes are allowed.
  1. Feb 5, 2007 #1

    Demystifier

    User Avatar
    Science Advisor

    In your opinion, what theorethical objects are the most likely to represent the most fundamental constituents of nature?
     
  2. jcsd
  3. Feb 5, 2007 #2
    I'm missing one alternative: none of the above. Anyway, I voted for fields, but I really think that it is made up of jets, which essentially contain information about both the fields and the observer's position, cf http://www.arxiv.org/abs/hep-th/0701164 . More precisely, the idea is to expand all fields in Taylor series, which encode the fields as Taylor coefficients and the observer's position as the basepoint.
     
  4. Feb 5, 2007 #3

    marcus

    User Avatar
    Science Advisor
    Gold Member
    2015 Award
    Dearly Missed

    I agree. And I would say that "fields" and "spin networks" are essentially the same option, because a spin network is just a way to describe a field without committing to a prior choice of background geometry.

    A spin network is a background independent means to describe a field. Since you don't explicitly mention that general category, one supposes that spin network the one example which stands for the whole class.
     
  5. Feb 5, 2007 #4
    What makes us thing that we have a complete description of the Universe at this point in time? The Universe probably consists of neither, although our best models and theories of the Universe does. There is always room for further explorations. I believe that something similar is said in "Relativity: The Special and General Theory" by Einstein.
     
  6. Feb 6, 2007 #5

    Demystifier

    User Avatar
    Science Advisor

    Maybe I should slightly reformulate the question:
    Which *of known* theorethical objects is most likely to be the most fundamental?
     
  7. Feb 6, 2007 #6

    Demystifier

    User Avatar
    Science Advisor

    This, indeed, is how LQG is usually formulated. Such a formulation assumes that continuous topology is prior to fields, metric, and spin networks.

    However, there are some LQG suggestions that continuous topology does not really exist at the fundamental level. In this case a local field A(x) also does not exist at this level. Consequently, spin networks are more fundamental than fields. (Personally, I do not like such approaches, but they exist.)
     
  8. Feb 6, 2007 #7
    I would like to suggest a write in candidate: bits.
     
  9. Feb 6, 2007 #8

    marcus

    User Avatar
    Science Advisor
    Gold Member
    2015 Award
    Dearly Missed

    That's right! The usual LQG version is that the world is made of fields..

    This was how Rovelli pictured it in his 2004 book Quantum Gravity which I think is still the defining reference.

    With him, it's fields defined on fields. Spin networks are one of several possible devices used to describe fields in a background independent way.

    But you exclude Rovelli's interpretation of LQG---according to you, the spin network option in your poll refers not to usual LQG but I suppose to some more recent work. Do you mean some new papers by Thiemann where he uses the term "algebraic quantum gravity"? That is interesting, but it was just last year and i haven't had enough time to assimilate the new direction. Perhaps the AQG approach really does describe fields, but in a new way, so that it has the same basic ontology.

    I'm afraid the poll was a bit confusing. If you don't allow that spin networks are simply a way (that avoids certain problems) to describe the gravitational field, then I should have selected "fields" in the poll.
     
    Last edited: Feb 6, 2007
  10. Feb 6, 2007 #9
    everything in that list is a different method of modeling systems of causal interactions- thus the Universe is "made" of interactions with Itself-

    edit: and the simplist and most complete way to describe these interactions is with bits
     
    Last edited: Feb 6, 2007
  11. Feb 7, 2007 #10

    Demystifier

    User Avatar
    Science Advisor

    In the not-so-new lectures written by Thiemann (gr-qc/0210094), at page 44 he writes: "One may spaculate that the discrete structure is fundamental and that the analiticity assumptions that we began with should be unimportant, in the final picture everything should be only combinatorical."

    Anyway, at the moment, the "spin network" option has more votes than "strings" for example, so perhaps this option was not so inappropriate.
     
  12. Feb 7, 2007 #11

    Demystifier

    User Avatar
    Science Advisor

    It seems to be more related to the interpretations of QM (see the poll in
    https://www.physicsforums.com/showthread.php?t=146601 )
    than to the question posed in this poll. Are the "bits" are bits on strings, or on particles, or on ...?
     
  13. Feb 7, 2007 #12
    That is pretty much a useless question.
     
  14. Feb 8, 2007 #13

    Chronos

    User Avatar
    Science Advisor
    Gold Member
    2015 Award

    'Fields' is a bit evasive, but the most qualified option. Current theory requires 'fields' to permit the existence of 'particles' in the observed universe. It's a really awkward question, though, IMO. I will take the cowards way out and blame it all on Einstein for creating this mess to begin with.
     
  15. Feb 14, 2007 #14

    vld

    User Avatar

    There is a missing option "spacetime", so I have voted for "fields", which is the closest one (but not identiical).
     
  16. Feb 21, 2007 #15
    Time as a one dimensional object, or if you would time with any duration, is the most fundamental part of our universe. I think of a point not as being a zero dimensional object but as being a single duration of time. I voted for particle, now if you would like to add one more dimension, motion, you could show a field durning this same expanding duration.
     
  17. May 25, 2007 #16

    Demystifier

    User Avatar
    Science Advisor

Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: What is the world made of?
Loading...