The BBC Proms having started on Sunday (20th July), I decided to listen to some of the concerts via BBC Sounds. One can’t get BBC Radio 3 on the radio here in the Republic, at least not this far from the border.
I was disappointed, then, to see that BBC Sounds is no longer available to listeners outside the UK. Apparently The BBC is making BBC Sounds exclusively available to UK license fee payers, meaning users outside the UK, including those in Ireland, will no longer be able to access the full service. This change came into effect yesterday (21st July).
So here I am, as I write this, on 22nd July, listening to this evening’s Promenade concert via BBC Sounds. No, I’m not doing anything illegal or unlawful. Neither did I last night, when I listened to Mahler’s Symphony No. 7. It’s just that the change has been implemented in a very peculiar and confusing way.
To start with, this is what I see a see on my screen right now:
I don’t think you get the top message if you listen in the UK, but then you might be listening on the radio anyway.
At the top it says use the BBC.com or the BBC App. For one thing I can’t find any sign of the “BBC App” on PlayStore on anywhere else. For another, BBC.com offers only Radio 4, BBC World Service and a random selection of podcasts. So neither of those options are any good for listening to Radio 3.
If you click to “Find out how to listen to other BBC stations” you get this page which “explains”:
Earlier this year, we launched a new audio service outside the UK on BBC.com and the BBC app. This includes access to BBC Radio 4 and BBC World Service English, thousands of hours of podcasts (including Global News Podcast, World of Secrets and Infinite Monkey Cage) – as well as some of the best of the BBC’s journalism and storytelling including news and history programming.
As part of the announcement, we said we planned to close BBC Sounds to audiences living outside the UK later this year, making it available exclusively to people in the UK. Anyone who lives in the UK will still be able to use the BBC Sounds app when they go on holiday abroad. We can now confirm that BBC Sounds closed for listeners based outside the UK on 21 July 2025.
Leaving aside the mystery of the “BBC app”, this suggests that BBC Sounds is closed to listeners outside the UK. Except it isn’t.
The article goes on to explain:
Please use the links below for live listening access to the BBC’s other radio stations from across the UK, including BBC Radio 1, Radio 2 and Radio 3, 6Music, 1Xtra and Asian Network, Radio 4Xtra and 5Live, all the BBC’s stations from the UK nations and every local radio station in England.
In other words, it takes you back to BBC Sounds, which is where I am listening now! As far as I understand it, one can still listen to the live internet stream of BBC Radio on BBC Sounds, so it’s not closed to listeners outside the UK after all. What is closed (to us foreigners) is the back catalogue of past recordings. I only ever listen to live broadcasts, however, so after all that it’s business as usual for me.
I was (pleasantly) surprised to learn a few weeks ago that I shall be teaching particle physics again next academic year. That means that I’ll have to update to the notes to reflect the latest news from CERN. Researchers from the LHCb collaboration have published evidence for CP violation in baryons. The paper is published in Naturehere.
For those of you not up with the lingo, CP is an operator that combines C (charge-conjugation, i.e. matter versus anti-matter) and P (parity, i.e. inversion of coordinates). Parity has been known since the 1950s to be violated in weak interactions, so the weak nuclear force distinguishes between states of odd and even parity. CP violation was first demonstrated in the 1960s CP in the decays of neutral kaons resulted in the Nobel Prize in 1980 for its discoverers Cronin and Fitch. CP violation has subsequeuntly been seen in many other meson decays.
But the mesons (consisting of a quark and an antiquark) are only half of the family of particles made from quarks; the others are the baryons which are made of three quarks (c.f. James Joyce’s “Three quarks for Muster Mark” in Finnegans Wake). Antibaryons consist of three antiquarks, but such are not mentioned in Finnegans Wake.
The baryons concerned in the LHCb experiment contain an up quark, a down quark and a beauty quark and were produced in proton–proton collisions at the Large Hadron Collider in 2011–2018. These baryons and antibaryons can decay via multiple channels. In one, a baryon decays to a proton, a positive K-meson and a pair of pions – or, conversely, an antibaryon decays to an antiproton, a negative K-meson and a pair of pions. CP violation should create an asymmetry between these processes, and the researchers found evidence of this asymmetry in the numbers of particles detected at different energies from all the collisions.
A problem with calculating the magnitude of this effect for baryons is that there is a contribution from the strong force – see the curly line indicating a gluon in the lower panel on the left above – and that is much harder to compute than a pure weak force (represented by the wavy lines indicating W– bosons. Yo will see that the tree and loop diagrams involve quark mixing, a process that allows quarks of different generations to couple via weak interactions; there is a buW vertex in the top panel and a tsW vertex in the bottom one. Given the uncertainties, it seems the results are consistent with the level of CP violation predicted in the Standard Model of particle physics.
The big question surrounding this result is whether it can account for the fact that our Universe – or at least our part of it -contains a preponderance of baryons over anti-baryons, so somehow the interactions going on during the Big Bang must have shown a preference for the former over the latter. This problem of baryogenesis is not explained in the Standard Model and, since these results are consistent with the Standard Model, the answer to that question is “no”…
It’s Saturday morning again, so it’s time again for an update of papers published at the Open Journal of Astrophysics. Since the last update we have published six new papers, which brings the number in Volume 8 (2025) up to 98, and the total so far published by OJAp up to 333. I expect we’ll pass the century for this year sometime next week.
The papers published this week, with their overlays, are as follows. You can click on the images of the overlays to make them larger should you wish to do so.
The first paper to report is “Reconstructing Galaxy Cluster Mass Maps using Score-based Generative Modeling” by Alan Hsu (Harvard), Matthew Ho (CMU), Joyce Lin (U. Wisconsin-Madison), Carleen Markey (CMU), Michelle Ntampaka (STScI), Hy Trac (CMU) & Barnabás Póczos (CMU), all based in the USA. This paper was published on 14th July 2025 in the folder Cosmology and NonGalactic Astrophysics. It presents a diffusion-based generativbe AI model for reconstructing density profiles for galaxy clusters from observational data.
The overlay is here:
The officially-accepted version can be found on arXiv here.
You can find the officially accepted version of this paper on arXiv here.
The fourth paper this week is “Why Machine Learning Models Systematically Underestimate Extreme Values” by Yuan-Sen Ting (Ohio State University). This one was published on July 16th in the folder marked Instrumentation and Methods for Astrophysics. This paper presents a theoretical framework for understanding and addressing a bias that suppresses the dynamic range of variables in applications of machine learning to astronomical data analysis. Here is the overlay:
You can find the officially accepted version of this paper on arXiv here.
The penultimate article for this week is “Bridging Machine Learning and Cosmological Simulations: Using Neural Operators to emulate Chemical Evolution” by Pelle van de Bor, John Brennan & John A. Regan (Maynooth University) and Jonathan Mackey (Dublin Institute for Advanced Studies), all based in Ireland. This paper uses machine learning, in the form of neural operators, to emulate the Grackle method of solving non-equilibrium chemistry equations in cosmological hydrodynamic simulations and was published on 16th July also in the folder Instrumentation and Methods for Astrophysics. The overlay is here:
The final, accepted version of the paper is on arXiv here.
The last article published this week is “Astronomical Cardiology: A Search For Heartbeat Stars Using Gaia and TESS” by Jowen Callahan, D. M. Rowan, C. S. Kochanek and K. Z. Stanek (all of Ohio State University, USA). This paper presents a study of a sample of 112 new spectroscopic binaries called hearbeat stars (because their light curves resemble electrocardiagrams). It was published on 16th July 2025 in the folder marked Solar and Stellar Astrophysics. The overlay is here:
You can find the officially-accepted version on arXiv here.
And that’s all the papers for this week. I’ll do another update next Saturday.
The Government of Ireland has just announced details of a scheme called Global Talent Ireland. Full details of the scheme can be found here but, in a nutshell, the scheme aims to attract exceptional mid-career and established researchers from across the globe to Ireland. Researchers funded through this programme are required to transfer their research activities from their current location to any Eligible Research Body in Ireland. Given its commitment to equality, diversity and inclusion, Research Ireland welcomes applications from women and those from historically underserved communities.
The programme budget includes the resources to build a research team (e.g., staff, consumables and travel) to carry out high-impact, world-class research, and additional start-up costs to support the researcher’s move to Ireland. These positions are available for any area of research supported by Research Ireland.
The programme comprises two streams: Rising Stars and Research Leaders. High level details are outlined in the table below:
The timescale for this is very short (as the window lies in the vacations for people likely to be recruited). In the case of Maynooth, which I assume is an Eligible Research Body, there is a first-stage internal process for Expressions of Interest to be completed by 29th July (i.e. less than two weeks away). There is then a selection for submissions to be forwarded to the Government by August 28th 2025.
As the timescale is so short I would ask anyone interested in taking up such a position in the Department of Physics at Maynooth University to contact me as soon as possible, as both the Head of Department and Dean of the Faculty of Science and Engineering are away at the moment. Ireland’s recent decision to join CERN as well as membership of the European Southern Observatory and the European Space Agency might be good strategic grounds for an application.
Those interested in other areas of research would be advised to contact the relevant Departments as soon as possible. The selection process is bound to be very competitive, but you can’t win the prize if you don’t buy a ticket!
Stock viscosity image: Photo by Fernando Serrano on Pexels.com
I thought I’d mention here a paper now on arXiv that I co-wrote with my PhD student Aoibhinn Gallagher. Here is the abstract:
The Schrödinger-Poisson formalism has found a number of applications in cosmology, particularly in describing the growth by gravitational instability of large-scale structure in a universe dominated by ultra-light scalar particles. Here we investigate the extent to which the behaviour of this and the more general case of a Schrödinger-Newton system, can be described in terms of classical fluid concepts such as viscosity and pressure. We also explore whether such systems can be described by a pseudo-Reynolds number as for classical viscous fluids. The conclusion we reach is that this is indeed possible, but with important restrictions to ensure physical consistency.
arXiv:2507.08583
It is based on work that his in her now-completed PhD thesis, along with another paper mentioned here. I have been interested for many years in the Schrödinger-Newton system (or, more specifically, the Schrödinger-Poisson system in the case where self-gravitational forces are involved). In its simplest form this involves a wave-mechanical representation, in the form of an effective Schrödinger equation, of potential flow described classically by an Euler equation. More recently we got interested in the extent to which such an approach could be used to model viscous fluids represented by a Navier-Stokes equation rather than an Euler equation. That was largely because the effective Planck constant that arises in this representation has the same dimensions as kinematic viscosity (but there’s more to it than that).
In the paper we explored a limited aspect of this, by looking at situations where there is no vorticity (so still a potential flow) but there is viscosity. There aren’t many examples of fluid flow in which there is viscosity but no vorticity, and most of those that do exist are about one-dimensional flow along channels or pipes with boundary conditions that don’t really apply to astrophysics, but one example we did look at in detail was the dissipiation of longitudinal waves in such a fluid.
One upshot of this work is that one can indeed describe some aspects of quantum-mechnical fluids such as ultra-light scalar matter in terms of classical fluid properties, such as viscosity, but you have to be careful. For more information, read the paper!
There was some sad news for cosmologists last week in that the Government of the United States of America – specifically the National Science Foundation (NSF) and the Department of Energy (DOE) – has cancelled the next generation of ground-based cosmic microwave background experiments, called CMB-S4. This would have been the fourth generation This would have consisted of several dedicated telescopes equipped with highly sensitive superconducting cameras.
The plan was that these telescopes would spend about seven years listening to the microwave sky at two locations already recognized for their suitability: the South Pole, which was to host several telescopes of varying sizes to observe across a wide range of microwave frequencies; and the Atacama Plateau in Chile, a high-desert site which would have hosted two large telescopes that can also observe several different frequencies. The South Pole telescopes were to conduct an ultra-deep survey of 3% of the sky, while the Atacama telescopes would conduct a complementary ultra-wide and deep survey of 70% of the sky. Together, the two sites promised to provide a dramatic leap forward in our understanding of the fundamental nature of space and time and the evolution of the Universe.
Longstanding readers of this blog will remember that in 2014 the BICEP2 experiment at the South Pole was claimed to have detected the B-mode polarization signal that would be a diagnostic of primordial gravitational waves generated during a burst of cosmic inflation. That result was later shown to be dominated by Galactic dust emission which could not be identified from its spectral properties, as BICEP2 operated at only one frequency. With an order of magnitude more detectors than previous ground-based CMB experiments, wider frequency coverage, and better control of systematic errors, CMB-S4 would have reduced the limits on earlier observations by a factor of five, enabling either the direct detection of primordial gravitational waves or ruling out large classes of inflationary models and dramatically impacting current thought on cosmic inflation.
For more technical information about CMB-S4 see the 2021 White Paper here.
Despite its very strong science case, and the fact that it was ranked as second-highest priority in the 2020 Decadal Survey, it seems that CMB-S4 is no more. Sad.
It’s Saturday morning again, so it’s time again for an update of papers published at the Open Journal of Astrophysics. Since the last update we have published seven new papers, which brings the number in Volume 8 (2025) up to 92, and the total so far published by OJAp up to 327.
This was a slightly strange week, starting with the fact that there were no new arXiv announcements on Monday 7th July because of the 4th July holiday in the USA on Friday so no papers were published that day. We were not able to publish any papers on Wednesday 9th July either because Crossref was offline for 24 hours that day while its data was migrated into the cloud. Our publishing process requires a live connection with Crossref to deposit metadata upon publication so we can’t publish while that service is down. Fortunately the update seems to have gone well and normal services resumed the following day. That partially accounts for the fact that four of this week’s papers were published on 10th July.
Anyway, The papers published this week, with their overlays, are as follows. You can click on the images of the overlays to make them larger should you wish to do so.
The officially-accepted version can be found on arXiv here.
The second paper is “Low redshift post-starburst galaxies host abundant HI reservoirs” by Sara Ellison (U. Victoria, Canada) and 10 others based in China, UK, Spain, USA and Canada. This one was also published oon Tuesday 8th July but in the folder Astrophysics of Galaxies. This paper uses 21cm observations of a sample of post-starburst galaxies, to show that they contain large reservoirs of neutral hydrogen. Here is the overlay:
You can find the final version of the manuscript on arXiv here.
You can find the officially-accepted version of the paper on arXiv here.
The penultimate paper for this week, and the last of the batch published on 10th July, is “Systematically Measuring Ultra-Diffuse Galaxies. VIII. Misfits, Miscasts, and Miscreants” by Dennis Zaritsky, Richard Donnerstein, and Donghyeon J. Khim (Steward Observatory, U. Arizona, USA). This paper presents a morphological study of weird and wonderful galaxies as part of an effort to Systematically Measure Ultra-Diffuse Galaxies (the SMUDGes survey). It is in the folder marked Astrophysics of Galaxies. The overlay is here:
You can find the officially-accepted version of the paper on arXiv here.
The last article published this week is “Differential virial analysis: a new technique to determine the dynamical state of molecular clouds” by Mark R. Krumholz (ANU, Australia), Charles J. Lada (Harvard, USA) & Jan Forbrich (U. Herts, UK). This paper presents simple analytic models of supported and collapsing molecular clouds, tested using full 3D simulations and applied to observed clouds in Andromeda. It is in the folder marked Astrophysics of Galaxies and was published yesterday, i.e on Friday 11th July 2025. Here is the overlay
You can find the officially-accepted version on arXiv here.
And that’s all the papers for this week. I will, however, take this opportunity to mention that a while ago I was interviewed about the Open Journal of Astrophysics by Colin Stuart on behalf of the Foundational Questions Institute; the write-up of the interview can be found here.
At the Social Dinner at the EAS in Cork I got talking to a young postgraduate student while we were both in the queue for burgers. We chatted about the trials and tribulations of doing a PhD and about the general perception that it is a very hard slog. What I said was that, although at times it was definitely tough going, I had the best time of my life doing my PhD – well, DPhil actually – and I know many others who feel the same. I think you need work hard, but also enjoy it.
Me having received my Doctorate in 1989.
The main point is that a postgraduate research degree is very different from a programme of undergraduate study. For one thing, as a research student you are expected to work on your own a great deal of the time. That’s because nobody else will be doing precisely the same project so, although other students will help you out with some things, you’re not trying to solve the same problems as your peers as is the case with an undergraduate. Your supervisor will help you of course and make suggestions (of varying degrees of helpfulness), but a PhD is still a challenge that you have to meet on your own.
(Incidentally, I don’t think it is good supervisory practice to look over a research student’s shoulder all the time. It’s part of the purpose of a PhD that the student learns to go it alone. There is a balance of course, but my own supervisor was rather “hands off” and I regard that as the right way to supervise. I’ve always encouraged my own students to do things their own way rather than try to direct them too much.)
That loneliness is tough in itself, but there’s also the scary fact that you do not usually know whether your problem even has a solution, let alone whether you yourself can find it. There is no answer at the back of the book; if there were you would not be doing research. A good supervisor will suggest a project that he or she thinks is both interesting and feasible, but the expectation is that you will very quickly be in a position where you know more about that topic than your supervisor.
I think almost every research student goes through a phase in which they feel out of their depth. There are times when you get thoroughly stuck and you begin to think you will never crack it. Self-doubt, crisis of confidence, call it what you will, I think everyone who has done a postgraduate degree has experienced it. I certainly did. A year into my PhD I felt I was getting nowhere with the first problem I had been given to solve. All the other research students seemed much cleverer and more confident than me. Had I made a big mistake thinking I could this? I started to panic and began to think about what kind of job I should go into if I abandoned the idea of pursuing a career in research.
So why didn’t I quit? There were a number of factors, including the support and encouragement of my supervisor, staff and fellow students in the Astronomy Centre at Sussex, and the fact that I loved living in Brighton, but above all it was because I knew that I would feel frustrated for the rest of my life if I didn’t see it through. I’m a bit obsessive about things like that. I can never leave a crossword unfinished either…
What happened was that after some discussion with my supervisor I shelved that first troublesome problem and tried another, much easier one. I cracked that fairly quickly and it became my first proper publication. Moreover, thinking about that other problem revealed that there was a way to finesse the difficulty I had failed to overcome in the first project. I returned to the first project and this time saw it through to completion. With my supervisor’s help that became my second paper, published in 1987.
I know it’s wrong to draw inferences about other people from one’s own particular experiences, but I do feel that there are some general lessons. One is that if you are going to complete a research degree you have to have a sense of determination that borders on obsession. I was talking to a well-known physicist at a meeting not long ago and he told me that when he interviews prospective physics students he asks them “Can you live without physics?”. If the answer is “yes” then he tells them not to do a PhD. It’s not just a take-it-or-leave-it kind of job being a scientist. You have to immerse yourself in it and be prepared to put long hours in. When things are going well you will be so excited that you will find it as hard to stop as it is when you’re struggling. I’d imagine it is the just same for other disciplines.
The other, equally important, lesson to be learned is that it is essential to do other things as well as your research. Being “stuck” on a problem is part-and-parcel of mathematics or physics research, but sometimes battering your head against the same thing for days on end just makes it less and less likely you will crack it., I’m sure that I’m not the only physicist who has been unable to sleep for thinking about their research or who has spent hours sitting at their desk achieving nothing at all. The human brain is a wonderful thing, but it can get stuck in a rut. One way to avoid this happening is to have more than one thing to think about.
I’ve lost count of the number of times I’ve been stuck on the last clue in a crossword. What I always do in that situation is put it down and do something else for a bit. It could even be something as trivial as making a cup of tea, just as long as I don’t think about the clue at all while I’m doing it. Nearly always when I come back to it and look at it afresh I can solve it.
It can be difficult to force yourself to pause in this way, but I think it is essential to learn how to effect your own mental reboot. In the context of my actual research this involved simply turning to a different research problem, but I think the same purpose can be served in many other ways: taking a break, going for a walk, playing sport, listening to or playing music, reading poetry, doing a crossword, or even just taking time out to socialize with your friends. Back in Brighton in the 1980s I spent most evenings in bars and nightclubs. I never felt the slightest bit of guilt for having so much fun. Without the nightlife and all that I’m not sure I would have finished my PhD.
So, for what it’s worth, here is my advice to new or prospective postgraduate students: work hard but enjoy the challenges. Listen to advice from your supervisor, but remember that the PhD is your opportunity to establish your own identity as a researcher. So take ownership of it. And never feel guilty about establishing a proper work-life balance. Having more than one dimension to your life will not only improve your well-being but may also make you a better researcher.
It’s Saturday so, once again, it’s time for the weekly update of papers published at the Open Journal of Astrophysics. Since the last update we have published three new papers, which brings the number in Volume 8 (2025) up to 85, and the total so far published by OJAp up to 320.
The three papers published this week, with their overlays, are as follows. You can click on the images of the overlays to make them larger should you wish to do so.
The first paper to report is “Stellar reddening map from DESI imaging and spectroscopy” by Rongpu Zhou (Lawrence Berkeley National Laboratory, USA) and an international case of 56 others too numerous to mention individually. This paper was published on 1st July 2025 in the folder marked Astrophysics of Galaxies. It describes maps of stellar reddening by Galactic dust inferred from observations obtained using the Dark Energy Spectroscopic Instrument, and a comparison with previous such maps. The overlay is here:
You can find the final, accepted, version on arXiv here.
Next one up is “On inertial forces (indirect terms) in problems with a central body” by Aurélien Crida (Université Côte d’Azur, France) and 17 others – again too numerous to be listed individually – based in France, Italy, Germany, Mexico and the USA. This paper discusses the indirect terms that arise the Newtonian dynamics of multi-body systems dominated by a central massive body, upon which other bodies exert a gravitational pull, when the massive body is treated as the origin of the coordinate system. This one, also published on July 1st 2025, is in the folder marked Earth and Planetary Astrophysics.
The overlay is here:
You can find the officially accepted version on arXiv here.
Today is Consultation Day here at Maynooth University and, in the course of being consulted, I was reminded that this period, being immediately after undergraduate final results are released to students, is a potentially a good time to advertise our local postgraduate course to prospective applicants.
I therefore decided o use the medium of this blog to advertise the fact that the MSc in Theoretical Physics & Mathematics at Maynooth University is open to applications for entry in September 2025.
This postgraduate course is run jointly between the Departments of Physics and Mathematics & Statistics, with each contributing about half the material. The duration is one calendar year (full-time) or two years (part-time) and consists of 90 credits in the European Credit Transfer System (ECTS). This is split into 60 credits of taught material (split roughly 50-50 between Theoretical Physics and Mathematics) and a research project of 30 credits, supervised by a member of staff in a relevant area from either Department.
This course is a kind of follow-up to the existing undergraduate BSc Theoretical Physics & Mathematics at Maynooth, also run jointly. We think the postgraduate course will appeal to many of the students on that programme who wish to continue their education to postgraduate level, though applications are very welcome from suitably qualified candidates who did their first degree elsewhere.
You can register your interest by scanning the QR code above or, if you prefer, simply following the link here. You can apply directly to the postgraduate application portal here.
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In the Dark 