Obituary of John Barrow

Just a quick word to let you know that my obituary of John Barrow (partly based on my blog post here) has now been published in The Observatory Vol. 141 No. 1281 (2021 April) pp. 93-96. The Observatory Magazine isn’t available online so, with the permission of the Editors, I’ve included a link to a PDF of the published version here:

John Barrow Obituary in Observatory by Peter Coles

15 Responses to “Obituary of John Barrow”

  1. There is no online version of the Magazine per se. However, much of it is available online via ADS.

  2. There seems to be a 404 problem with your link to the PDF.

  3. Anton Garrett Says:

    When you say he studied inflation in non-GR scenarios do you mean with a nonzero cosmological cnostant or something more radical (and if so then what, please?)

    • telescoper Says:

      He worked a bit on Brans-Dicke theory, and later, on theories derived from extensions of the Einstein-Hilbert action such as f(R) theory.

      • Anton Garrett Says:

        That’s interesting. Were it not for the square root of the determinant of the metric tensor in the integrand in the action, every f(R) would give the same vacuum field equations – although the interactions with matter would vary with f.

        Anthony Lasenby has been studying quadratic Poincaré gauge theory, in which you have not only an R^2 term but also terms like R^{ijkl}R_{ijkl} and other contractions; and also throws in terms quadratic in the torsion. The hope – not unrealistic – is to find a theory consistent with observation that is renormalisable without need for exotica at the Planck energy. See arXiv:2101.02645

      • telescoper Says:

        Yes, these theories can be cast into a form in which they look like GR plus some effective energy-momentum tensor…

      • telescoper Says:

        John’s motivation for studying e.g. R^2 theories is that you could perhaps think of these as like a series expansion of GR (which is linear in R) with higher-order terms kicking in at high energies.

      • Anton Garrett Says:

        Higher powers than R^2 render the spectrum of the propagator unphysical by Ostrogradsky’s instability.

      • telescoper Says:

        Indeed but the Ostrogradsky “ghosts” can be cancelled if you introduce appropriate cancelling terms; the Palatini formalism does this.

        You might think this is all a bit contrived. I couldn’t possibly comment.

      • Anton Garrett Says:

        But not more contrived than the most popular alternative at the Planck energy…

  4. Anton Garrett Says:

    Did he trace descent from Isaac Barrow, who was also Professor of Geometry at Gresham College and who also held a Cambridge chair (which he resigned in favour of Newton)?

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