Tag Archives: Cosmology (general)

I hugely enjoyed this week’s conference ‘Cosomolgy and the Constants of Nature’  at Cambridge University. There were some truly great talks by John Barrow, John Ellis and Thanu Padmanabhan among others, not to mention Joao Magueijo describing his famous ‘variable speed of light’ theory in person. The icing on the cake was that my visit coincided with this week’s announcement of the detection of gravitational waves from the infant universe by the American BICEP2 experiment. If correct, the signal gives very significant experimental support for the theory of cosmic inflation, as well as the phenomenon of gravitational waves predicted by general relativity…..a double whammy if ever there was one.

Yesterday, I was priviliged to attend a seminar on the new results given by George Efstathiou and Anthony Challinor, team leaders on the rival Planck experiment (EU). There’s nothing like hearing a new observation dissected by a rival group and the seminar certainly didn’t disappoint. Both Cambridge physicists concluded that the BICEP 2 result is very robust, at least at face value, with the caveat that the signal needs to be reproduced at more than one frequency. The other caveat is that although the sensitivity of BICEP2 is up to ten times that of Planck,  there is a certain tension between the BICEP2 data and last year’s published data from Planck. I was particularly interested in Professor Efstathiou’s comment that the differing data of the two experiments may be a genuine effect, i.e., may represent some new physics at wide angles (Planck) that doesn’t affect the BICEP2 (small angle) measurements . The next few months should be very interesting indeed for cosmology…(see here for a rigorous discussion of the BICEP2 data by Peter Coles).

I had my own private excitement when I was introduced to Stephen Hawking for the first time. It was a very moving encounter, Professor Hawking remembered my father and his work. Stephen was also very interested in our recent discovery of Einstein’s unpublished attempt at a steady-state model of the cosmos. Indeed, his first remark to me was that steady-state cosmic models were the dominant cosmic paradigm when he started his research career at Cambridge all those years ago. He asked me to send him a copy of Einstein’s paper and I had a stressful evening trying to do so as my college email chose that day to block me for not changing my password often enough – of all days for that to happen!

I can’t quite believe this photo

All in all, it was yet another hugely productive visit to Cambridge University. Every time I come here something dramatic happens but I’m also looking forward to going home, I could do with a rest!

Farewell to Clare college

Update

The American National Pubic Radio ran a piece on our Einstein discovery on today’s Morning Edition. I think it’s quite nice, apart from the usual emphasis on Einstein’s ‘blunders’ (why do journalists always see explorations as blunders?) Still, I’m learning not to be too precious about media stuff…

Today was the last day of the COSMO13 conference, a most enjoyable, if sometimes exhausting conference – so many seminars, not to mention a banquet in Trinity College last night.

The conference finished this morning with lectures on dark energy from Ofer Lahav and Edmund  Copeland, on dark energy and modified gravity by Lam Hui and Claudia de Rahm, and on inflation by Richard Easther. The conference website is here and videos of the presentations will be available here in the next few days.

UPDATE: Videos of the plenary talks and pdfs of talks from the parallel sessions are  now available here.

If I had to summarize the conference in one sentence, I think the take-home message is that recent experimental results in both cosmology (from the PLANCK satellite) and particle physics (from the LHC) are strongly supportive of our basic models, giving strong confidence that our underlying theories are on the right track. The downside is that in each case, the fit is a teeny bit too good for comfort. There is a slightly worrying lack of evidence for physics beyond the standard models so far – a lack of evidence for supersymmetric particles at the LHC (although a low-mass Higgs is in principle good news for SUSY) and a lack of non-Gaussianities and parity violation in the PLANCK measurements of the cosmic microwave background. But the future is bright, especially considering the projected increases in luminosity at the LHC and the possible detection of B-mode polarization in the CMB by PLANCK.

That said, I agree heartily with Ofer Lahav’s comment that it is extraordinary to be living through a paradigm shift in cosmology, namely the discovery of the accelerated expansion (two paradigm shifts if you include inflation). Added to which we are now in an era of precision cosmology. Indeed, measurements of the cosmic microwave background by PLANCK are now reaching such a level of precision that it isn’t always meaningful to talk about agreement or tension with astrophysical measurements – the latter have quite a lot of catching up to according to George Efstathiou!

On a personal note, it’s extraordinary to see Dad’s work on supersymmetry reaching a whole new audience in cosmology, as supersymmetry breaking in the early universe  becomes a major area of research. I can’t tell you how many young researchers eyed my badge in astonishment and then started to quizz me about O’Raifeartaigh models!

Now the conference has finally ended, it’s nice to get back to work on my paper on Einstein’s cosmology in the 1930s – some of the talks here have given me some new ideas. I managed to finish most of the paper here, I’ll always think of it as my Cambridge paper!

I’m at Oxford University this week, at the Cosmology and Quantum Foundations  conference, a symposium that forms part of the recent Establishing the Philosophy of Cosmology project at Cambridge and Oxford.

Physicists don’t always accept the relevance of philosophy in the study of physics, but there is no question that quantum theory has long posed difficult questions of a philosophical nature, not least the interpretation of the quantum wavefunction. In addition, modern cosmology points towards a universe that was once in an extremely small and dense state,  that may or may not have had a finite beginning. As well as the familiar problems of quantum philosophy, this raises a host of other philosophical problems, such as ‘When did the laws of physics become the laws of physics?’ or ‘Were space and time always there or did emerge with the big bang ?’

The conference started at 9.30 this morning with a workshop on cosmic inflation. First up was Andrew Liddle ; after a brief review of the basic postulate of inflation, Andrew explained how the theory soon provided an explanation for the formation of galactical structure (in terms of quantum fluctuations in the early universe inflated to the perturbations observable in the cosmic background radiation). This explanation has since become a major motivation for the theory. Andrew then described new constraints imposed on inflationary models by the data from the Planck satellite.

Andrew’s talk was followed by a seminar by Douglas Spolyar on a new model describing how inflation might have ended (‘supercooled inflation’). I won’t describe it here as part II is due tomorrow. For lunch, we all trooped over to the famous Clarendon lab to hear well-known MIT physicist Max Tegmark give  a rather different sort of talk, ‘The future of life – a cosmic perspective’,  hosted by Oxford’s Future of Humanity Institute. Max’s main thesis was that a cosmological perspective renders existential problems more important, not less. Given that there is a finite chance that mankind is the only conscious life in the universe, if mankind were to die out there would be no-one to observe the universe! It’s a fascinating and provocative argument, and I was pleased to see climate change up there amongst the existentialist risks. However, I wasn’t entirely convinced by Max’s central theme ; apart from the philosophical debate concerning the role of the observer (is he/she really that important?) one wonders are there not more selfish reasons to tackle existential risks (what do I know,  it was an interesting take anyway).

After the Tegmark seminar, it was off to St Anne’s College for the opening of the conference proper. The afternoon session kicked off with a talk by well-known Oxford physicist Simon Saunders on the Many Worlds interpretation of quantum theory. Oxford have a major reputation in this area and I know no better physicist to give an introduction to this topic. It was a fascinating lecture and part II is tomorrow.  After coffee, Max Tegmark gave another excellent talk, this time on ‘The cosmological interpretation of quantum mechanics – unifying the inflationary and quantum multiverses’ (more on this tomorrow).

After dinner with Andrew, I walked around Oxford and took a few photos.There is such fabulous  architecture everywhere you look, no wonder it produces great thinkers. Also, there’s a real thrill in seeing so many locations that are familiar from Inspector Morse , not to mention Lewis.

The Bodlean (I think)

The Bridge of Sighs

The River Thames