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

Theory vs Phenomenology

  1. Feb 26, 2008 #1


    User Avatar
    Science Advisor

    Theoretical physics, especially high energy physics, is often further divided into "theory" and "phenomenology". Since both refer to theoretical (not experimental) physics, what exactly the difference between them is?

    I would say that
    1. Theory concerns general principles and methods of theoretical physics, while phenomenology concerns their application to a calculation of quantities that in principle can be directly compared with observations.

    On the other hand, my colleague said that
    2. Theory deals with the well founded theoretical results obtained from first principles, while phenomenology deals with not so well founded effective models with a smaller domain of application.

    What do you think?
  2. jcsd
  3. Feb 26, 2008 #2


    User Avatar
    Homework Helper

    obtained from first principles? so are we to believe that string theory or mathematical consistency should be the starting point?

    ppl who believe that QFT (ie. string, branes, etc) should be the start point in building a theory usually post papers at hep-th while those who believe in general relativity to be more fundamental usually post at gr-qc. anyway I digressed.

    hep-ph are less speculative and ideas are usuallly easier to test than those "fundamental theories" in hep-th.
  4. Feb 26, 2008 #3


    User Avatar
    Science Advisor

    Mjsd, your remarks are fine, but do not help to understand the DEFINITIONS of the notions of "theory" and "phenomenology". Can you contribute in that direction?
  5. Feb 26, 2008 #4


    User Avatar

    A working definition, consistent with the papers on the arxiv, is that "theory" as used today, means papers that do not relate to any experiment already completed or to be completed in the foreseeable future.
    "Phenomenology" does relate to .....
    One evidence for these meanings is that even papers about the Higgs, supersymmetry, and other things that might be tested at the LHC are in phenomenology on the arixiv.
    There are those who suggest that "theory" as now construed is not "physics", but I hesitate to define "physics".
  6. Feb 27, 2008 #5
    And why not saying that :
    - (mathematical) theory is related to the theoritical corpus
    - phenomenology is related to practical models based on a theoritical corpus
  7. Mar 2, 2008 #6


    User Avatar
    Science Advisor

    It's a silly distinction - "phenomenology" is, literally translated, "the STUDY of PHENOMENA"! Technically, this would include experimental physics! And I have met many experimental physicists who call themselves "phenomenologists", and they are completely within their rights!

    As far as high-energy physics is concerned (and it's the only place I've ever really seen people make a distinction): "phenomenology" is anything relating to a physical result, such as computing cross sections or lifetimes, mass spectra, etc; and theory is, for lack of a better term, everything else!! I can tell you from personal experience: whether professionals post a paper on "hep-ph" or "hep-th" is ULTRA-subjective!!

    Some people would claim that "theory" is short for "STRING theory" and "phenomenology" is slang for "NOT-STRING theory". But as a "non-string THEORIST" myself, such definitions get my blood boiling! :wink:
  8. Mar 2, 2008 #7


    User Avatar
    Science Advisor

    I think that's crap!
  9. Mar 2, 2008 #8


    User Avatar

    I agree with your definition. Phenomenology, I would say, is concerned with using theoretical models to make direct contact with measurable quantities. Theory is concerned with the rest....the underlying structure of the theories, their self-consistency, general relations, etc. For example I would say that t'Hooft's proof that theoreis with SSB are renormalizable is a theory paper. Papers concerned with using this to predict the production rates of Z and W bosons are phenomenology papers.

    But this is obviously very subjective.

    I would disagree with the second definition. Papers on, say, anomaly cancellations in string theories are theory papers, imho. And I would categorize the use of brane-world models or SUSY to calcualte corrections to cross section calculations as phenomenology papers.

    But I could see how someone might want to put everything related to string theory, brane models, etc as "theory" in the sense that these are all quite speculative. So I kind of see why someone might be tempted to use the second definition but upon closer scrutinity, it does not seem to de a good one, imho.
  10. Mar 2, 2008 #9


    User Avatar
    Science Advisor

    Yea, theres a ton of overlap between th and phenomenology. So much so that the distinction is basically one of name recognition and tradition moreso than anything else.

    Consider the famousr Kobayashi-Maskawa paper. Is it theory or phenomenology? It could be both.
  11. Jul 10, 2010 #10
    check the definitions from a dictionary
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook