CERN Lectures on Cosmology and Particle Physics

By Sean Carroll | October 12, 2011 10:19 am

Here’s a blast from the somewhat-recent past: a set of five lectures I gave at CERN in 2005. It looks like the quality of the recording is pretty good. The first lecture was an overview at a colloquium level; i.e. meant for physicists, but not necessarily with any knowledge of cosmology. The next four are blackboard talks with a greater focus; they try to bring people up to speed on the basic tools you need to think about modern early-universe cosmology.

Obviously I’m not going to watch all five hours of these, so I’ll just have to hope that I’m relatively coherent throughout. (I do remember being a bit jet-lagged.) But I do notice that, while it was only a few years ago, I do appear relatively young and enthusiastic. Ah, the ravages of Time…

Lecture One: Introduction to Cosmology

Lecture Two: Dark Matter

Lecture Three: Dark Energy

Lecture Four: Thermodynamics and the Early Universe

Lecture Five: Inflation and Beyond

  • Sam Gralla

    and… have we learned anything about cosmology and particle physics since then? :)

    Also, in a previous post you eluded to a “classical contribution to dark energy” in addition to the usual (hypothesized) vacuum energy from quantum effects. I’ve never heard this before; what did you have in mind?

  • Thomas

    Sam Gralla: The cosmological constant, maybe?

  • Sam Gralla

    I dunno; people usually pick one or the other. Since we have no idea how to compute the quantum contribution, anyway, it’d seem weird to believe that x % of the true lambda was due to quantum effects and (100 – x) % was due to some new constant in the Lagrangian for the universe.

  • lolz

    Thanks, these will hopefully be really great. I love video lectures because I can pause and rewind whenever I (inevitably) get distracted, want to spend a few moments thinking about a certain point, or work something out. I notice I take about 50% extra time watching a lecture vs attending a class.

    I wish all lectures were recorded, it would be such a useful resource for homework/studying. Going to skip the 1st lecture and go through the rest.

  • Jorge Laris

    Finally I have something interesting to view on Sundays. Thank you very much.

  • David W. Miller

    As much as I loved the look and feel of the old auditorium, the refurbished version is so much nicer. The upshot, though, is that there is no longer a wall of blackboards.

  • Dush

    I just started watching the first one last night and noticed how young you look!

  • Phillip Helbig

    @#3 Steven Weinberg believes that there is the huge particle-physics contribution to the vacuum energy and an almost equally huge but negative classical cosmological constant, so that they almost cancel, thus providing the observed value—unlikely perhaps, but justified on anthropic grounds.

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  • Charlie

    Can someone put a back-of-the-envelope number on the fluctuation that gets us back to inflation? I don’t know if there is any value in this. I just like these kind of numbers. 10^-1000 per m^3 per year ?

  • Joel Rice

    gee -an hour goes by really quick when having fun. Many thanks for posting that video.

  • Sean

    Charlie– the rate of a fluctuation that would take you from our current vacuum “1” to some inflationary state “2” is essentially exp(S2S1), where “exp” means exponential and Si is the entropy of vacuum state i. In fact the entropy of the inflationary state is so much tinier than the entropy of ours that this is basically equal to exp(-S1). The entropy of our current state is approximately S1 = 10120, so the rate is about exp(-10120).

    If you play around a bit you can convince yourself that the units don’t really matter — per Planck volume per Planck time is basically the same as per Hubble volume per Hubble time on these scales.

  • Charlie

    Thanks! That’s a satisfyingly small number. I can see that the difference between a mm and the universe isn’t much to a number like that.

  • Paul Stankus

    Is there room here for friendly competition? Though I’m not nearly at Sean’s level as an expert I delivered a 5-lecture series on intro cosmology for physicists in 2007, which was pretty well received. The video is publicly available, though in an obscure location. Interestingly, completely unknown to me someone picked up one of the segments, edited it down a bit and re-posed it on YouTube. It’s ten minutes long, taken from the section on “Why Brooklyn Is Not Expanding,” pivoting off from a classic bit in an old Woody Allen movie. The reposted segment is here:

    If the public demands it, I can link to the whole series, or maybe even get them up on the ‘Tube. ** End of self-promotional announcement **

  • Shantanu

    Sean , are all CERN lectures on youtube? CERN has a great collection of videos, but its very hard to search for them.

  • Sean

    I don’t know. You might leave a comment on the YouTube page.

  • Jimbo

    Wonderful lex ! I am taking a course in the early universe & these are an immense help. Best of all is that the vids forego factors O(1), concentrating on concepts, but the TASI lex fill in those details. Primo.

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  • Jens

    I can honestly say that 15 minutes into your talks I was lost. You spouted in-the-know jargon like a con-artist!

    Sean, I have an M.S degree in electronics. I love science and everything we are discovering. But I often don’t understand what you say, as much as I want to. Have you ever thought about “dumbing down” your lectures or your posts? At least to the degree that us slobs not versed in the gargon could still be enlightened?

  • FmsRse12

    I have always wondered why we can’t explain galaxy rotation curve as a result of “screening” phenomenon of some sort with some characteristic screening distance……then maybe it’s possible for stars to move at constant speed over large distances from the center of galaxy …..or galaxy wouldn’t hold together if we do this???

  • Phil h

    I think there’s an error on the 5th lecture in terms of the history of science. You claim inflation was created to solve the horizon and flatness problem. Yet in Alan Guth’s book “The Inflationary Universe” he claims that inflation was actually motivated by the monopole problem. It was only afterwards that it was realised that it solves other cosmological problems.

  • Yair

    Wow. The breadth, The Clarity, The Perspective.
    Many thanks for bringing the lectures to our attention.

  • Phil

    I haven’t watched the lectures yet, but I sure hope you mentioned that Catholic priest, Monsignor Georges Henri Joseph Édouard Lemaître, was the first to propose the Big Bang theory origin of the universe, and preceded Hubble in deriving Hubble’s Law in 1927.

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  • Baby Bones

    Thanks Sean. I watched the first lecture and it was very informative for me since it harkened back to an astrophysics class I took in my fourth year of university.

  • James

    Hi Sean, great lectures as ever.

    Can I ask a question about global topology?

    We describe an FRW universe with positive spatial curvature as “closed”, as it has the metric of a three-sphere, but I want to know what this actually means. We derive the three-sphere metric by changing coordinates from r to χ, where χ = Sin(r). Is χ not limited to the interval [0,π/2), since beyond that we are simply reproducing the same r? In which case, is the universe not really one “hemi-threesphere” and not closed in the same way as a full sphere is?

    You state in your book that the “only possible global structure is the complete three-sphere”, but you don’t go into why.

    The book, btw, is excellent (I particularly enjoy the time you spent at the beginning going into diff. geometry etc, although I still don’t quite get the link, other than notational, between differential forms and integral measures, such that we can integrate p-forms as if they were ordinary integrals).

  • Shantanu

    Sean ,what do you think of this paper on Dirac-Milne universe?

  • HK

    @Jensen (20) – Sean recorded a series of lectures called Dark Matter, Dark Energy: The Dark Side of the Universe for the Teaching Company (which is actually how I first learned about him). As the title suggests, the focus is certainly around the dark stuff, but the lectures also cover a lot of the general cosmology topics that he’s referencing and explaining in these CERN videos. I have zero formal training in physics, astrophysics, or cosmology (just a healthy interest and some math background), and was able to follow along quite easily with maybe a little bit of rewinding necessary. The lectures are aimed at a popular audience, so not as many specific ‘industry’ references or examples that were in the CERN lectures, and may be something to look into given your comments…


  • ZLN

    Suppose we do the naive integral for the vacuum energy, but pick a k_max such that I get the 1e-3 eV, what is the value of that k_max?

  • Phillip Helbig

    @27: No, it is not limited to this interval. In fact, one can sometimes travel around such a universe and return to one’s starting position (but only if a) it doesn’t recollapse first and b) it doesn’t expand too quickly). As the old joke goes, if you look hard enough, you can see the back of your head. If you look even harder, you can see Uranus.


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About Sean Carroll

Sean Carroll is a Senior Research Associate in the Department of Physics at the California Institute of Technology. His research interests include theoretical aspects of cosmology, field theory, and gravitation. His most recent book is The Particle at the End of the Universe, about the Large Hadron Collider and the search for the Higgs boson. Here are some of his favorite blog posts, home page, and email: carroll [at] .


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