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

Steps on the way to Lightcone cosmological calculator

  1. Aug 5, 2015 #76

    Gaz

    User Avatar

    so the Hubble constant is decreasing?
     
  2. Aug 5, 2015 #77

    Bandersnatch

    User Avatar
    Science Advisor
    Gold Member

    Yes. Look at the table and graph in post #72 above.
    The value of interest is ##H/H_0## and how it changes with time - this is the fractional change, so e.g. a value of 2 means twice the present value of ##H_0##, which is 67-ish km/s/Mpc.
     
  3. Aug 5, 2015 #78

    Gaz

    User Avatar

    thanks it makes sense now =)
     
  4. Aug 5, 2015 #79
    Thanks Jorrie I'll have to update the link to my webpage when the product is finalized. It's unfortunate I can't use this on another forum I've been actively supporting. (More due to the other sites latex structure). Though I do advertise your product on that forum. I found they needed my help far more than here, as their is plenty of expertise on this forum. I've been of greater help on the other forum.

    (If your looking at aspects to add, might I recommend adding density to temperature relations ie the thermodynamic relationships)
     
    Last edited: Aug 5, 2015
  5. Aug 22, 2015 #80

    Jorrie

    User Avatar
    Science Advisor
    Gold Member

    LightCone7s (for "standard"), now appears together with LightCone7z (for "zeit based") in my signature below. Both have the same "LCDM-engine", the only difference being the units being worked in. Billion years (Gy) for "version s" and zeit for "version z". One zeit is simply time divided by 17.3 Gy, a natural timescale of the LCDM model.

    The update from '7' to '7s' is about flexibility in specifying the graph formats, as can be seen under the button "Open Cart Options" (the green area of the LightCone7 (partial) screen shot shown below).

    Chart-Options-Lightcone7.png
     
  6. Jan 25, 2017 #81

    Jorrie

    User Avatar
    Science Advisor
    Gold Member

    Eventually, there is a beta-test version available with some additions on density, density parameters and temperature. It is not the 'Forum official' version yet, but it has other interesting changes. E.g. inputs or now more standard - I have done away with Hubble times as input parameters, because they are not the ones used in the literature. Prime inputs are now the Hubble constant in conventional units, the total density parameter and the radiation-matter equality redshift parameters. The matter density parameter is then still a derived value.

    The range of calculations are also requested as the more conventional redshift (z) in lieu of the simpler, but less well known "S" parameter. Lastly, the output scaling option for "Zeit" has been left out, since it is a potentially non-standard distraction. I hope the updates will enhance the use of the calculator in the educational field.

    The latest beta-test version is available as: LightCone7-2017-01-26.

    Edit: we found an error in Omega-calculations of this version. See the thread https://www.physicsforums.com/threads/evolution-of-the-energy-density-parameters.901681/
    The corrected version is: LightCone 7, Cosmo-Calculator (2017-1).

    Comments/suggestions welcome. I will start a new thread to discuss some of the more subtle aspects of the density parameter calculations.
     
    Last edited: Jan 28, 2017
  7. Jan 25, 2017 #82
    The usage parameters such as ones found in intro level textbooks is probably the most familiar approach and the one that will probably gain the most usage. The parameters you mentioned being the key ones. People are more familiar with redshift than stretch for example. I agree the best approach should be literature based.

    I should have time to help update the user manuals when the testing is done if you'd like my help again on that. I still remember how to edit and text on wikidot
     
    Last edited: Jan 26, 2017
  8. Feb 2, 2017 #83

    Jorrie

    User Avatar
    Science Advisor
    Gold Member

    After some more comments and further testing, it seems like the updated calculator has stabilized on this version: LightCone7-2017-01-30.
    I suggest that we leave it for another week in 'testing mode' and then I will 'release' it into the same url as the previous release, so that no links/sig's need to be updated.
     
  9. Feb 2, 2017 #84
    I've been running various tests as time allows. I haven't found any issues that I can see thus far
     
  10. Feb 3, 2017 #85

    Jorrie

    User Avatar
    Science Advisor
    Gold Member

    Thanks for your effort, Mordred. I have used a specific set of columns as default to highlight the new features, but it may now be time to choose a more general set. It should still be limited so as to not being frightening to newcomers.

    Any suggestions.
     
  11. Feb 9, 2017 #86

    Jorrie

    User Avatar
    Science Advisor
    Gold Member

    I have now changed the link in my Sig below to the latest version that we have tested, with a very basic set of columns as the default, i.e.

    [tex]{\small\begin{array}{|r|r|r|r|r|r|r|r|r|r|r|r|r|r|r|r|} \hline z&T (Gy)&R (Gly)&D_{now} (Gly)&Temp(K) \\ \hline 1.09e+3&3.72e-4&6.27e-4&4.53e+1&2.97e+3\\ \hline 3.39e+2&2.49e-3&3.95e-3&4.42e+1&9.27e+2\\ \hline 1.05e+2&1.53e-2&2.34e-2&4.20e+1&2.89e+2\\ \hline 3.20e+1&9.01e-2&1.36e-1&3.81e+1&9.00e+1\\ \hline 9.29e+0&5.22e-1&7.84e-1&3.09e+1&2.81e+1\\ \hline 2.21e+0&2.98e+0&4.37e+0&1.83e+1&8.74e+0\\ \hline 0.00e+0&1.38e+1&1.44e+1&0.00e+0&2.73e+0\\ \hline -6.88e-1&3.30e+1&1.73e+1&1.12e+1&8.49e-1\\ \hline -8.68e-1&4.79e+1&1.74e+1&1.43e+1&3.59e-1\\ \hline -9.44e-1&6.28e+1&1.74e+1&1.56e+1&1.52e-1\\ \hline -9.76e-1&7.77e+1&1.74e+1&1.61e+1&6.44e-2\\ \hline -9.90e-1&9.27e+1&1.74e+1&1.64e+1&2.73e-2\\ \hline \end{array}}[/tex]

    There are now a total of 18 selectable columns, including the actual density against redshift and also the various density parameters (the Omegas).
    It is very easy to change the default columns in the program, so please let me know if you want to see other columns as default.
    The idea of a small selection is to not overwhelm newcomers with too much data.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted