144. For lazy, yet curious students
Save This Post as PDFSuppose you are a cosmologist – a postdoc or an assistant professor. A student just knocked your door – he has heard that cosmology (inflation, non-gaussianities, dark energy and dark matter) is a cool subject right now. He is also aware of the fact that you are famous (well, not too much, but that he does to know yet, he-he) young professor. The student wants to be sure that cosmology is indeed the thing worth spending time for. (Well, maybe spending his whole life!)
He asks – “Could you give me an advice – some good introduction in cosmology, I would be able to read and understand what is the subject about”.
Your answer (well, that’s what I would say 
) – “Go take Landau, Lifshitz, volume II in the library”. He will have to learn general relativity anyway, if he is to survive on the battle field, right? He leaves, comes in a week: “It’s very complicated, almost unreadable”. Yes, he is not patient enough to follow the Landau’s path
You reply: “Try the Andrew Liddle’s book…” Same story – he comes back and explains: “This one is too long”.
“Go screw then”, you mumble to yourself, and yet – he is smart, he just calculated the volume of the sphere in N dimensions (you gave him this little problem just to make sure… well, he is Ok). What to do?
Well, here is the answer – give him David Langlois’ recent paper!
It actually has everything that your future student would want to have in order to have a quick glance on the subject and decide – is it really as complicated as Landau and Lifshits thought it should be or not?
David starts with quick introduction into general relativity and cosmology (in particular, discussion of the relevant cosmological parameters is lightning fast), proceeds to puzzles of the standard Pre-Big-Bang cosmology and their resolution by inflation.
All this can be found in (maybe too) many reviews – but where this particular review shines is the introduction into cosmological perturbations for single- and multifield inflationary models. Instead of sending your student to read the Mukhanov’s book (which I would call an equivalent of the Landau-Lifshits for the theory of cosmological perturbations) or Mukhanov-Feldman-Brandenberger’s review and making the little lazy guy unhappy for a month, maybe even not to see him ever again in your office, you just give him the Langlois’ paper! In a couple of days he knows (or he thinks he knows 
) what is curvature perturbation and comoving curvature perturbation, what is 
and why it is interesting, what are adiabatic and entropy perturbations, etc. He had some understanding of inflationary non-gaussianities, curvaton scenario and even the DBI inflation.
He knows that he can deal with all this – seemingly so easy. He is caught, and that is, I would say, the ultimate purpose of any really good introduction level review
Your future student is wrong of course – the subject is not that easy, and even reading Landau-Lifshits II is not sufficient to reach the enlightenment But it just means – he will have many pleasant surprises in the future, which will keep his desire of learning the subject high.
P.S. Sorry for the playfulness, just watched “Love Guru” yesterday.
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