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I Is the SM of particles physics and Cosmology SM

  1. Sep 2, 2016 #1
    I'm in a deep discussion with a friend. He says that the Standard Model of particle physics is actually known by Standard Model of cosmology and that both are the same and that the SM of particle physics is in the Minkousky geometry.... I disagree about this, I do think that the SM of particle physics is one thing and the SM of cosmology is another, and even if the SM of cosmology includes the SM of particle physics and applies it to concepts like geometry, they are different.
    Who is wrong? Or better, whats is the truth?
     
  2. jcsd
  3. Sep 3, 2016 #2

    Orodruin

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    The Standard Model of cosmology is the ΛCDM model. It is not the same as the SM of particle physics.
     
  4. Sep 3, 2016 #3
    Thanks for the insight Orodruin!
    I have two more questions: Does the SM of particle physics have a geometry? Like Minkousky or Godel? or these things are from cosmology?
    Do you have articles or textbooks about SM and models BSM to recommend?
    Thanks!
     
  5. Sep 3, 2016 #4

    Orodruin

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    The SM of particle physics is a quantum field theory and is usually considered in Minkowski space. This is generally a good enough approximation.
     
  6. Sep 3, 2016 #5
    Thanks a lot for everything!
    Can you or someone give me a help about what disciplines I have to take to be able to understand at least a little of the mathematics in the SM and the models from BSM, like extra dimensions? Linear algebra? Calculus? Which topic of it?
    I'm having a little hard time to understand the theory behind particle physics.
    Thanks again!
     
  7. Sep 4, 2016 #6

    Orodruin

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    In order to understand the SM on a level that is sufficient to actually perform computations you will need:
    • Linear algebra
    • Multivariable calculus
    • Ordinary and partial differential equations
    • Transform and series methods
    • Group theory
    • At least a couple of courses on quantum mechanics
    • Special relativity
    • Quantum field theory
    Note that this is a descriptive list. The points may or may not correspond to actual courses at your university and I might have missed something.
     
  8. Sep 4, 2016 #7
    I don't really understand why cosmologists use the SM of particle physics. Shouldn't they try to express it in a FRW curved spacetime? Can this generalization be done? It's difficult for me to understand why the SM is actually used to speculate about the physical laws of the early Universe.
     
    Last edited: Sep 4, 2016
  9. Sep 4, 2016 #8

    ChrisVer

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    I guess that is not necessary, since (when you use the SM of particle physics in cosmology) the particles interact locally... you don't really see what the interactions between two particles that are separated at cosmo-scales are. Locally everything can be seen pretty flat, as the Earth is flat as long as your communication with your friends (physical) is concerned. It is the same reason why SM of particle physics works on the Earth (which strictly speaking does not have a Minkowski spacetime around it).
    For a scalar field in the very early universe (inflaton) I've seen they use GR.

    Extra dimensions can be learned with topology and geometry (GR).
     
  10. Sep 4, 2016 #9

    mfb

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    They do not, as Orodruin explained in post #2 already.

    For the very early universe, both standard models are combined: space is locally flat to a good approximation, so you can study the particle interactions with the particle physics SM while the scale factor of the universe evolves with the cosmology SM.
     
  11. Sep 4, 2016 #10
    I wasn't thinking about particle interactions. What I had in mind is the vacuum state and how its energy content affects the expansion of the universe.

    The Lagrangian density could, in principle, be written. You just replace the partial derivatives by covariant derivatives. What I don't know if second quatization makes any sense in that case. Probably not.
     
    Last edited: Sep 4, 2016
  12. Sep 5, 2016 #11
    Thanks again! Thanks for the discussion about the use of SM of particle physics in cosmology, really helped me to understand more about the relation about them,

    Thanks so much for the insight!

    Thanks!!!!
     
  13. Sep 5, 2016 #12
    I still don't get it. I don't see how you can calculate how the vacuum energy affects the expansion of the universe based on flat spacetime (a basic assumption of the SM of particle physics).
     
  14. Sep 5, 2016 #13

    mfb

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    This is purely a GR-question, and in GR you can calculate it. The cosmological constant is a free parameter, you don't have to worry about contributions from particle physics.
     
  15. Sep 5, 2016 #14
    OK, but dark energy MUST be something real. Why not the energy density of the vacuum state?
     
  16. Sep 5, 2016 #15

    mfb

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    Physics is not about "real".

    Maybe, but we don't understand the interplay of QFT and GR well enough to make a proper prediction based on that - and it would not really help if we have the cosmological constant as additional contribution. There is no reason why it should be zero.
     
  17. Sep 5, 2016 #16
    When I write "real" I mean "physical".

    That's precisely what I'm asking. Where can I find textbooks/research papers about QFT in curved spacetimes? Is it an idea worth pursuing, or is it a hopeless attempt? (Linking the cosmological constant to the vacuum state energy density).
     
    Last edited: Sep 5, 2016
  18. Sep 5, 2016 #17

    mfb

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    arXiv, inspire, the usual search engines, ...
    QFT in curved spacetimes is interesting, but its applications to our universe are limited to black holes and the very early universe where we have no idea which particles existed at that time.
     
  19. Sep 5, 2016 #18
    We don't understand the universe we live in: we don't know what dark matter is made of and we don't understand what dark energy is either. But there's a huge difference between these two "dark components": we're currrently making experiments trying to find out what dark matter is. However, we seem to be very happy with the description of dark energy that we have: it's just Einstein's cosmological constant. Is that explanation good enough? I don't think so.
     
  20. Sep 5, 2016 #19

    ChrisVer

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    In the context of GR alone, it's more than enough... I would be skeptical if I saw the universe in GR without a cosmological constant... you can "add" it by hand, and not having it there is weird (something looks special)... what was "special" when Einstein dropped it out? that the Universe was not accelerating (to his knowledge).
     
  21. Sep 5, 2016 #20

    Orodruin

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    What gives you this impression? I do not think this is true in general. There are several attempts at giving dark energy some sort of dynamics, but that does not rule out the possibility of currently fitting cosmological data very well with just a cosmological constant.
     
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