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Two New Publications at the Open Journal of Astrophysics

Posted in Open Access, The Universe and Stuff with tags , , , , , , on May 29, 2022 by telescoper

Last week was rather busy. Amongst other things I managed to complete the publication process for two more papers in the Open Journal of Astrophysics (one on Tuesday and one on Thursday) although there was a small delay in registering the metadata so I didn’t fully announce them until yesterday. I’ve only just managed to find time today to advertise them here. These two are the sixth and seventh papers in Volume 5 (2022) and the 54th and 55th in all respectively. Both the new papers are in the folder marked Cosmology and Nongalactic Astrophysics.

The first of these two new publications is entitled “The Impact of Quadratic Biases on Cosmic Shear” and is written by Tom Kitching and Anurag Deshpande of the Mullard Space Science Laboratory in Surrey (UK).

Here is a screen grab of the overlay which includes the abstract:

You can click on the image to make it larger should you wish to do so. You can find the arXiv version of this paper directly here.

The second new publication is entitled “Cosmo-Paleontology: Statistics of Fossil Groups in a Gravity-Only Simulation” and is written by Aurora Coissairt, Michael Buehlmann, Eve Kovacs, Xin Liu, Salman Habib and Katrin Heitmann all from the Argonne National Laboratory which is just outside Chicago in the USA.

Here is the overlay of that paper which includes the abstract:

Once again You can click on the image to make it larger should you wish to do so. You can find the arXiv version of the paper here.

We have quite a few more papers in the pipeline so expect to be announcing more quite soon, probably early next month.

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Fuzzy Cosmology at ITP2022

Posted in Biographical, Talks and Reviews, The Universe and Stuff with tags , , , on May 26, 2022 by telescoper

As I usually do when I give a talk (which hasn’t been for a while) I’ve uploaded the slides for the presentation I gave at the Irish Theoretical Physics meeting at DIAS this morning. The title of the talk was Fuzzy Cosmology and the abstract reads:

I discuss some applications of the Schrodinger-Poisson wave-mechanical approach to
cosmological structure formation. The most obvious use of this formalism is to “fuzzy” dark matter,
i.e. dark matter consisting of extremely light particles whose effective de Broglie wavelength is
sufficiently large to be astrophysically relevant, but it can be used to model more general scenarios
and has a number of advantages over standard methods based on Eulerian perturbation theory. I
illustrate the formalism with some calculations for cosmic voids and discuss its application to the
cosmological reconstruction problem(s).

I think it went reasonably well despite there being a hitch at the start because the touchpad on my laptop stopped working. Fortunately I was able to produce an emergency mouse. Anyway, here is a picture of me taken during the talk to prove I was there..

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Gravity Competition!

Posted in The Universe and Stuff with tags , , , on May 26, 2022 by telescoper

There’s a competition running at ITP2022 that involves holding out a copy of the book Gravitation by Misner Thorne & Wheeler in one hand at arm’s length for as long as you can following the instructions below:

The current record is an impressive three minutes! How well can you do?

UPDATE: The winner of the competition was John Brennan, formerly of Maynooth University, with a time of 3 minutes and 29 seconds!

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The Death of the Hubble Parameter

Posted in Biographical, The Universe and Stuff with tags on May 23, 2022 by telescoper

It’s been a very busy day so in lieu of a proper post I thought I’d recycle an old joke with a new picture I took on my way to collect some examination scripts earlier today for marking.

I’m sad to have to use the medium of this blog to report the tragic death of the Hubble parameter. It had been declining for some time and, despite appearing to pick up recently, the end was somewhat inevitable. Condolences to the other parameters, especially Ω (who was in a close relationship with H), on this sad loss.

An older version of this joke, posted 11 years ago, can be found here.

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Job Opportunity in Theoretical Physics at Maynooth!

Posted in Maynooth, The Universe and Stuff on May 21, 2022 by telescoper

Just a very quick reblog of this post because the deadline is tomorrow (22nd May) at 23.30. It’s a for a Lecturer (Assistant Professor) in Theoretical Quantum Physics, interpreted broadly to include quantum computation, quantum information theory, quantum many-body systems, quantum field theory, and applications thereof to condensed matter and high-energy physics, etc.

telescoper's avatarIn the Dark

Just a short post passing on the information that we have a permanent Lectureship (Assistant Professorship) available in the Department of Theoretical Physics at Maynooth University. You can find the details, including a full Job Description and salary, here.

For the purposes of this position we interpret Quantum Physics broadly to include quantum computation, quantum information theory, quantum many-body systems, quantum field theory, and applications thereof to condensed matter and high-energy physics, etc.

This position is the first of several to be advertised across the Departments of Theoretical & Experimental Physics at Maynooth University, in areas including Astronomy and Earth Science, on top of this opportunity at Professorial level in Observational Astrophysics or Cosmology. Watch this space for more details!

The position is available from 1st September 2022 and the deadline for applications is 23.30 on Sunday 22nd May 2022 and you should apply through the Maynooth jobs…

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Science vs Marketing

Posted in Astrohype, Education, Science Politics, The Universe and Stuff with tags , , , on May 20, 2022 by telescoper

I saw a paper some months ago by former Sussex colleague Xavier Calmet and collaborators that attracted quite a lot of press coverage largely based on a press release from the University of Sussex that claimed:

Stephen Hawking’s famous black hole paradox solved after hair-raising discovery

(If you want to learn more about the black hole information paradox you could start here.)

The press release is pure unadulterated hype. The paper in Physical Review Letters is actually rather good in my opinion but it says next to nothing about the black hole information paradox. Unfortunately the Sussex press release was picked up by the BBC’s science editor Pallab Ghosh who turned it into a very garbled article. Unfortunately Ghosh has quite a lot of form when it comes to producing nonsensical takes on science results. See, for example, this piece claiming that recent results from the Dark Energy Survey cast doubt on Einstein’s general theory of relativity when they do nothing of the sort.

Fortunately in the case of the black hole paper David Whitehouse has done a good job at demolishing the “BBC’s black hole baloney” here so I don’t need to repeat the arguments.

What I will mention however is that there is an increasing tendency for university press offices to see themselves entirely as marketing agencies instead of informing and/or educating the public. Press releases about scientific research nowadays rarely make any attempt at accuracy – they are just designed to get the institution concerned into the headlines. In other words, research is just a marketing tool.

This isn’t the only aspect of the marketisation of universities. If an academic tries to organize a public engagement event or do some schools outreach activity, the chances are their institution will hijack it and turn it into a marketing exercise, aimed exclusively at student recruitment. Universities are increasingly unconcerned with education and research and obsessed with income.

Forget the phony controversies about woke politics and free speech manufactured by right-wing press. The real culture war in modern universities is between those who believe in the intrinsic value of higher education and those who see it simply as a means of generating profit by whatever means possible. As in any war, truth is the first casualty.

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New Publication at the Open Journal of Astrophysics

Posted in Open Access, The Universe and Stuff on May 14, 2022 by telescoper

The last couple of days have been very busy but at last I’ve got time to announce a new publication in the Open Journal of Astrophysics! This one is the 5th paper in Volume 5 (2022) and the 53rd in all. It was published on Thursday in fact but I’ve only just found time to mention it here.

The latest publication is entitled “Statistical Uncertainties of the NDW=1 QCD Axion Mass Window from Topological Defects” and is written by Sebastian Hoof & Jana Riess of the Georg-August-Universität Göttingen in Germany and David Marsh of King’s College London.

This paper is in the Cosmology and Nongalactic Astrophysics folder (cross-listed on arXiv from High-Energy Physics).

Here is a screen grab of the overlay which includes the abstract:

 

You can click on the image to make it larger should you wish to do so. You can find the arXiv version of the paper here.

P.S. We have quite a number of papers out there waiting for revised versions to be submitted. I get the feeling that everyone is very busy these days. Hopefully as we emerge from the pandemic things will improve.

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M87: Ring or Artefact?

Posted in The Universe and Stuff with tags , , on May 13, 2022 by telescoper

Following on from yesterday’s post here is an arXiv preprint that I’ve only just seen, though it was submitted on Tuesday 10th May, ahead of yesterday’s announcement about Sagittarius A*. It says inside the manuscript (though not in the arXiv entry) that it was accepted for publication in ApJ on 5th May, though it has not yet appeared there.

The abstract is:

We report our independent image reconstruction of the M 87 from the public data of the Event Horizon Telescope Collaborators (EHTC). Our result is different from the image published by the EHTC. Our analysis shows that (a) the structure at 230 GHz is consistent with those of lower frequency VLBI observations, (b) the jet structure is evident at 230 GHz extending from the core to a few mas, though the intensity rapidly decreases along the axis, and (c) the unresolved core is resolved into bright three features presumably showing an initial jet with a wide opening angle of about 70 deg. The ring-like structures of the EHTC can be created not only from the public data, but also from the simulated data of a point image. Also, the rings are very sensitive to the FOV size. The u-v coverage of EHT lack about 40 micro-asec fringe spacings. Combining with a very narrow FOV, it created the 40 micro-asec ring structure. We conclude that the absence of the jet and the presence of the ring in the EHTC result are both artifacts owing to the narrow FOV setting and the u-v data sampling bias effect of the EHT array. Because the EHTC’s simulations only take into account the reproduction of the input image models, and not those of the input noise models, their optimal parameters can enhance the effects of sampling bias and produce artifacts such as the 40 micro-asec ring structure, rather than reproducing the correct image.

I draw your attention to the sentence “The ring-like structures of the EHTC can be created not only from the public data, but also from the simulated data of a point image”. In other words the authors (Miyoshi, Kato and Makino) are saying that the ring-like structure in the now-iconic image could be an artefact of the image reconstruction process as they can apparently be produced by a point source.

From the manuscript itself:

The EHTC conducted various surveys, but their methods were not objective and biased towards their desires from the very beginning of their analysis. They also failed to perform the basic data checking that VLBI experts always do.

That’s very blunt. The plot thickens!

It’s a lengthy paper and I haven’t gone through it in detail. Comments from experts are welcome through the box below.

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Our own Galactic Black Hole

Posted in The Universe and Stuff with tags , , , , on May 12, 2022 by telescoper

As I mentioned a while ago the Event Horizon Telescope team held a press conference this afternoon and to nobody’s surprise they used it announce an image of the (shadow of the event horizon around the) black hole at the centre of the Milky Way.

Here it is:

You can read the full press release here.

You may recall a great deal of excitement about three years ago concerning the imaging of the “shadow” of the event horizon of the black hole in the centre of the galaxy M87. The question I was asked most frequently back then is that there’s a much closer black hole in the centre of our own Galaxy, the Milky Way, so why wasn’t that imaged first?

It it true is that the black hole in the centre of M87 is ~103 times further away from us than the black hole in the centre of the Milky Way – known to its friends as Sagittarius A* or SgrA* for short – but is also ~103 times more massive, so its Schwarzschild radius is ~103 times larger. In terms of angular resolution, therefore, the observational challenge of imaging the event horizon is similar in the two cases. However, in the the case of the Milky Way’s black hole the timescales involved are much shorter than in M87 and there is a greater level of obscuration along the line of sight. That’s why it took longer to produce the image.

It’s a very difficult observation of course and I’m not sure of the significance of the “lumps” you can see, but the dark region in the centre is what the image is really about and that seems to be exactly the predicted size. The resolution is about 20 microarcseconds. Congratulations to the Event Horizon Telescope team!

If you’re interested in learning more about how this image was made I recommend this short video:

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The Brief Span of Life…

Posted in Art, Literature, The Universe and Stuff with tags , , on May 7, 2022 by telescoper

I found this rather poignant cartoon on Facebook because a friend shared it. Some people have told me they find it depressing. I don’t. I think the finiteness of life is one of the things that makes it bearable.

I don’t know the name of the artist. If anyone does please let me know.

Halley’s Comet last visited us in 1986 when I was 23 and living in Brighton. It will next be visible in 2061, when I shall be 98!

The comet’s orbital period of 75 years or so is brief by astronomical standards, as is the duration of a human life. As Quintus Horatius Flaccus (Horace to you and me) put it in one of his Odes (Book I, Ode 4, line 15):

Vitae summa brevis spem nos vetat incohare longam

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