A Day at DIAS

Last night I flew back to Ireland for a few days of work here before the Easter Weekend. The schedule of flights from Cardiff to Dublin has changed for the spring, with the afternoon flight much later: at 7.45pm instead of 3.40pm, so I left from Cardiff after work on Monday and had dinner in the airport (an overpriced and barely edible beefburger).

Although there is no teaching in either on Maynooth or Cardiff this week I had to come to Ireland for a few reasons, including giving a seminar today at the Dublin Institute for Advanced Studies (DIAS) this afternoon which provided me with the chance to visit it for the first time.

It being a pleasant morning I walked to DIAS from Connolly Station after taking the train there from Maynooth. It’s about half an hour’s walk.

DIAS is actually spread over several sites. Officially my talk was at the School of Theoretical Physics, but there were some people there from the School of Cosmic Physics, which is located not too far away. There were also a few people from Maynooth there, as there are a number of collaborations going on between the two institutions involving staff and students. There was also a visitor from even further afield, in the form of Cormac O’Rafferty who also visits this blog from time to time.

Anyway I had a nice curry for lunch before the talk, which generated a lot of questions from which I infer that it was either confusing or stimulating (or possibly both). Here are the slides in case anyone feels like taking a look.

For a change I decided to take the train back to Maynooth from Pearse rather than Connolly, but as it was rush hour I found it packed.

Maynooth by contrast is very quiet with most students away for the break. I can also report that the annoying roadworks that have been going outside my Maynooth residence for months have now finished.

Anyway, thanks to my hosts at DIAS for inviting me and I hope my talk was reasonably bearable. Hopefully this will be the first visit of many!


16 Responses to “A Day at DIAS”

  1. Great talk Peter, everybody really enjoyed it! I notice the best talks always have a general introduction before getting to the technical topic of the day, much appreciated. Re DIAS, yes they have a network of Research Associates, which allows physicists from all over the country to use the excellent library etc. In the teaching hols, I spend as much time at DIAS as I do in my own college.

  2. If I remember correctly, you just send a request to one of the Professors, and then it gets approved by the Board. It’s not an elite club, the idea is to strengthen links between physicists in different colleges

  3. By the way, I meant to ask at question time:
    I seem to remember that Schroedinger did some work on cosmology at DIAS in the 1950s, where he applied wave mechanics to the universe as a whole. But I don’r remember if he looked at structure formation….probably not, I guess

  4. ” in the form of Cormac O’Rafferty who also visits this blog from time to time”

    We now know that Cormac is the dark matter. 🙂

  5. Another thing struck me after the talk. It’s well known that Einstein’s suggestion to Lemaitre in the early 1930s to look at the effect of inhomogeneity on expanding models led to the first models of structure formation. I think that constitutes more evidence that AE saw his static model as a blunder in retrospect (not just invalidated by Hubble’s observations). After all, inhomogeneities were inevitable for galaxies to form, therefore it was a mistake not to consider the stability of the model against such effects in 1917…

    • It would be good if there were a more reliable source for this remark than Gamow’s autobiography.

      John Barrow pointed out that Einstein later referred to something else as the biggest blunder of his life (though not in those words), deeming it unlikely in his view that he really believed and/or said that the cosmological constant was his biggest blunder. (This is a footnote in Barrow’s contribution in The Philosophy of Cosmology.)

    • A perfectly homogeneous and isotropic static model is an unstable fixed point. It will remain stable as long as it is not perturbed but if this is a model for the universe, then there is no way to perturb it.

      A model which is approximately homogeneous and isotropic is probably unstable, but I don’t know if there is a general proof of this. (I mean unstable due to the lack of perfect homogeneity, not unstable with respect to slightly increasing or decreasing the density of matter etc.)

    • The Einstein-de Sitter model is also an unstable fixed point. Interestingly, this fact was used as an argument against the Einstein static model, but for the Einstein-de Sitter model and thus for Omega=1 (“it has to be exactly 1 since if not it will evolve away”; check out the references in the paper mentioned in the previous blog entry). One can’t have it both ways.

      • telescoper Says:

        There’s a big difference between perturbing the global density while keeping a homogeneous universe and introducing local density fluctuations…

      • True. But both Einstein and Einstein-de Sitter are unstable to changing the density, even if they remain completely homogeneous and isotropic.

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