Inhomogeneous cosmology research plans

• Notes from Monday 16 Sep and Friday 20 Sep discussions...

• something lke an alphabet, literature guide, for new people to the field - whitepaper
  • 2011 CQG focus papers (CQG = Classical & Quantum Gravity)
  • publication (ArXiv + formal publication) of the "alphabet", introduction to inhomogeneous cosmology helps in community growth
  • European Commission, NCN, ANR, ... open access initiative 2020 - CC-BY licence
• Do we want a highly pedagogical guide to inhomogeneous cosmology (doctoral/master student level)?
  • Plebanski & Krasinski; some of the Ellis, Maartens, MacCallum;
• whitepaper extra science questions
  • what is the physics behind the various codes (ET, gevolution, ...) available?
    • initial condition hypersurfaces, what mathematical/physical framework? framework = set of libraries and functions
    • Sage can be slow for calculating Riemann tensor and other symbolic calculus so on because of python layers?
    • developing the C (or equivalent) level codes/libraries should be a high priority
  • what assumptions are made by the codes? which ones are motivated by numerical reasons and unphysical? * which numerical effects mix up various physical effects? * interpretation problem of numerical simulations?
  • foliation-dependence of scalar averaging? is it physical?
  • multi-fluids - can Roberto's methods be applied?
    • for computational purposes multifluid can be modelled as a "horrible" single fluid (requires assumptions of interactions between fluids)?
    • how do the equations-of-state (highly abused term; it's thermodynamical, based on macroscopical statistics of particles, in cosmology we're not really justified in using this terminology?) relate to one another?
  • LCDM "tensions" could (should?) be a priority for us
    • postdictions - useful challenge for inhomogeneous cosmology
    • update Buchert Roukema Ostrowski Kleinert - prioritise LCDM view on "most important tensions"
      • H_0 tension; lack of power l < 20 in CMB; CMB anomalies (cold spot)? Lyman alpha foest BAO estimates; power at high vs low length (or mass) scales
  • crossovers with quantum physics? maybe via black hole calculations?
    • search for crossovers, can we learn from other fields? geometric (geometry+topology) n+1 spacetimes, particle descriptions

• Julius, Thomas, Leo, Jan, Pierre, Colin, Martin, Roberto, Hayley, Justyna, Andrzej K, Michele