The results generally look very good. Most of you have managed to get the correct results. The thing that separates the reports most is the writing. Some have managed to write almost too much and some have not written much at all yet.
It is not easy to explain all the things in all the plots: we are working in Fourier space and with multipoles and what have you, but let me give a few pointers on this.
In general when it comes to explaining the results one way to start is to forget about the specific plots and think of it as writing a story of how structures in CDM, photons and baryons form from early times till today. In telling this story you need to bring in the important events and the physics that goes on. We don’t expect you guys to explain every little detail about the plots, this is not the goal, we want to see that you have understood the basic physics that goes on and to be able to tie important events and concepts to features you see clearly in the plots.
In telling this story one might wants to explain:
What determines how structures grow? Here one might want to talk about growth of perturbations basically being just a fight between forces (+gravity and -pressure) and the expansion rate of the Universe.
What key events do we have that is relevant? Well we have the different eras (R, M, DE) and of course recombination.
What (mainly) sources the gravitational potentials in each eras? Well in R: radiation perturbations. Do radiation cluster (why / why not)? M: matter perturbations. They cluster. DE: matter perturbations. Why do the clustering slow down/stop here?
What interactions between the relevant matter fields are relevant here, i.e. what happens in the primordial plasma before recombination and what happens after?
One good starting point is to use what happens with perturbations in real-space ( https://cmb.wintherscoming.no/theory_observables.php#cmbreal ). Real-space is much easier to understand than Fourier space, but luckily much of it translates over.
If you are writing down a story like this explaining what CDM, photons and baryons do at different times then you will be able to point to the plots showing the effect of what you are telling about so you will end up explaining the plots in the end. Of course, then there are just a few Fourier specific things you need to keep in mind to explain a few other key things about the plots. For example when we consider a mode "k" then this corresponds to fluctuations of a certain scale and comparing this size with that of the horizon gives us two regimes, inside / outside the horizon, for which perturbations act differently which are seen in the plots. Too many of you forgot to even mention this point.
PublishedMay 19, 2024 1:31 AM
- Last modifiedMay 19, 2024 1:31 AM
The results generally look very good. Most of you have managed to get the correct results. The thing that separates the reports most is the writing. Some have managed to write almost too much and some have not written much at all yet.
It is not easy to explain all the things in all the plots: we are working in Fourier space and with multipoles and what have you, but let me give a few pointers on this.
In general when it comes to explaining the results one way to start is to forget about the specific plots and think of it as writing a story of how structures in CDM, photons and baryons form from early times till today. In telling this story you need to bring in the important events and the physics that goes on. We don’t expect you guys to explain every little detail about the plots, this is not the goal, we want to see that you have understood the basic physics that goes on and to be able to tie important events and concepts to features you see clearly in the plots.
In telling this story one might wants to explain:
One good starting point is to use what happens with perturbations in real-space ( https://cmb.wintherscoming.no/theory_observables.php#cmbreal ). Real-space is much easier to understand than Fourier space, but luckily much of it translates over.
If you are writing down a story like this explaining what CDM, photons and baryons do at different times then you will be able to point to the plots showing the effect of what you are telling about so you will end up explaining the plots in the end. Of course, then there are just a few Fourier specific things you need to keep in mind to explain a few other key things about the plots. For example when we consider a mode "k" then this corresponds to fluctuations of a certain scale and comparing this size with that of the horizon gives us two regimes, inside / outside the horizon, for which perturbations act differently which are seen in the plots. Too many of you forgot to even mention this point.