Archive for quad

Cosmology Talks: Eiichiro Komatsu & Yuto Minami on Parity Violation in the Cosmic Microwave Background

Posted in Cardiff, Maynooth, The Universe and Stuff with tags , , , , , , , , on December 2, 2020 by telescoper

It’s time I shared another one of those interesting cosmology talks on the Youtube channel curated by Shaun Hotchkiss. This channel features technical talks rather than popular expositions so it won’t be everyone’s cup of tea but for those seriously interested in cosmology at a research level they should prove interesting.

In this video, Eiichiro Komatsu and Yuto Minami talk about their recent work, first devising a way to extract a parity violating signature in the cosmic microwave background, as manifested by a form of birefringence. If the universe is birefringent then E-mode polarization would change into B-mode as electromagnetic radiation travels through space, so there would be a non-zero correlation between the two measured modes. They  try to measure this correlation using the Planck 2018 data, getting  a 2.4 sigma `hint’ of a result.

A problem with the measurement is that systematic errors, such as imperfectly calibrated detector angles,  could mimic the signal. Yuto and Eiichiro’s  idea was to measure the detector angle by looking at the E-B correlation in the foregrounds, where light hasn’t travelled far enough to be affected by any potential birefringence in the universe. They argue that this allows them to distinguish between the two types of measured E-B correlation. However, this is only the case if there is no intrinsic correlation between the E-mode and B-mode polarization in the foregrounds, which may not be the case, but which they are testing. The method can be applied to any of the plethora of CMB experiments currently underway so there will probably be more results soon that may shed further light on this issue.

Incidentally this reminds me of Cardiff days when work was going on about the same affect using the Quad instrument. I wasn’t involved with Quad but I do remember having interesting chats about the theory behind the measurement or upper limit as it was (which is reported here). Looking at the paper I realize that paper involved researchers from the Department of Experimental Physics at Maynooth University.

P. S. The paper that accompanies this talk can be found here.

Terra Nova

Posted in Art, History, The Universe and Stuff with tags , , , , , , , on February 3, 2012 by telescoper

We’re currently enduring a spell of cold weather here in Cardiff, although I think it might be rather milder here then elsewhere in the UK. My garden thermometer showed a mere -5 C when I looked at it at 7.15 this morning. The other day we had a meeting of half-a-dozen people in one of our large teaching rooms and it was absolutely freezing. I don’t know what was wrong with the heating. Yesterday I actually did a lecture in the same room, but with 80-odd “warm bodies” (or “students” as they are sometimes known) in there, it was bearable.

The cold here of course is nothing compared with that endured by Captain Scott‘s ill-fated expedition to the South Pole, but I mention it here for a number of reasons. First, the centenary of the death of Scott and his companions is coming up next month; the tragedy unfolded in March 1912. There’s actually a very special concert coming up next week, featuring Vaughan Williams’ wonderful music written for the classic film Scott of the Antarctic (which, incidentally, you can actually watch in full on Youtube). I’m definitely going along, and will probably review the performance next week, but quite a number of my colleagues are also going, for reasons which will become obvious..

The concert is special because of the very strong connections between the Scott Expedition and the City of Cardiff. Much of the financial support needed to fund the trek to the South Pole was raised from Cardiff businessmen and Scott’s ship, the Terra Nova, actually set sail from Cardiff (in June 1910) on its journey, first to New Zealand and thence to Antarctica.

Incidentally, an article in this morning’s Western Mail relates to a historic painting of the departure of the Terra Nova which is about to be auctioned:

Cardiff Bay has certainly changed a great deal since 1910, but quite a lot is recognizable, especially the Pierhead Building, which can be seen to the right. The actual docks, the locations of which are revealed by the lines of masts of tall ships, are now mainly filled in. But there is at least one other reminder of this occasion to be found at Cardiff Bay, a large waterfront bar itself called Terra Nova

There’s also a deep connection with the South Pole, and the Antarctic generally, for many members of the Astronomy Instrumentation Group here in the School of Physics & Astronomy at Cardiff University, quite a few of whom have actually been to the South Pole in connection with various experiments, including Quad,  Boomerang and BLAST, because of the unique observing conditions there.