Maynooth University Library Cat Update

Posted in Maynooth with tags , , on December 15, 2025 by telescoper

I saw Maynooth University Library Cat on the way to my office this morning. Most students I saw were heading in the opposite direction, in their Christmas jumpers, to pubs, or at least to queue outside them as they weren’t yet open. I think it will be a quiet day on campus, if not in town. Such is the Maynooth Student Xmas I blogged about yesterday.

Anyway, as you can see, Séamus was looking a bit disgruntled, though as usual he was receptive to a stroke or two and a head scratch. It had been raining overnight and such food as was in his dish had turned to mush and was in need of replacement. At least his water bowl was full.

Leave a comment »

Four Teaching Days to Christmas

Posted in Biographical, Maynooth with tags on December 14, 2025 by telescoper

The week ahead is the last week of the teaching term at Maynooth and, since I don’t have any sessions scheduled for Friday 19th December, I will finish on Thursday 18th and take the Friday off. I don’t think there’ll be many people – either staff or students – around on Friday anyway.

Tomorrow (Monday) is the infamous “Student Xmas” in Maynooth where many undergraduates spend the day getting drunk rather than attending lectures or tutorials. Many start drinking in the morning and carry on until the pubs close in the early hours. I wouldn’t mind this excess too much, but the town is usually in a terrible mess on Tuesday morning, with fast food containers, broken bottles and vomit littering the streets. I have a lecture at 2pm on Monday (tomorrow) which will go ahead and a telecon at 4pm. After those I’ll be making my way home and keeping well out of it until I have to navigate a passage through the debris on Tuesday morning.

Two pubs, Brady’s amd The Roost promote this pre-Chrtistmas celebration vigorously on social media. I imagine their takings are substantial. I wonder if they – or indeed the Student’s Union – pay a little to help clear up the aftermath?

On Tuesday I have three lectures, but one of them (at 11am) will be the final class test for Differential Equations and Complex Analysis so there’s little for me to do but sit there, invigilating. I have promised to get the answers corrected and returned before the break so I’ll have to do them by Thursday, the date of the last tutorial. Our Department Christmas Celebration is on the afternoon of Wednesday 17th, so I’ll have to fit the grading in on Tuesday evening or Wednesday morning.

The other two lectures on Tuesday are Engineering Mathematics, followed by another on Wednesday. I was going to use one of the Tuesday slots for the final class test for this module, but a number of students asked me to postpone it because they anticipate being hung over. I don’t mind but the only available time with a suitable room is Thursday, so they won’t get their marks until after the holiday, for which I feel no need to apologise. It’s good to have the three lecture slots because I missed an hour last week because of the power cut owing to Storm Bram.

1 Comment »

Everything is a Simple Harmonic Oscillator

Posted in mathematics, The Universe and Stuff with tags , , , on December 13, 2025 by telescoper

Anyone who has studied theoretical physics for any time will be familiar with the simple harmonic oscillator, which I will call the SHO for short. This is a system that can be solved exactly and its solutions can be applied in a wide range of situations where it holds approximately, e.g. when looking at small oscillations around equilibrium. I’ve often remarked in lectures that we spend much of our lives solving the SHO problem in various guises, often pretending that the difficult system we have in front of us can, if looked at in the right way, and with sufficient optimism, be approximated by the much simpler SHO. Cue the old joke that if all you have is a hammer, everything looks like nail…

That rambling prelude occurred to me when I found this little problem in some old notes. It is a cute mathematical result that shows that the Friedman equations that underpin our standard cosmological model can in fact be written in the same form as those describing a Simple Harmonic Oscillator. In what follows we take the cosmological constant term to be zero.

The resulting equation is the SHO equation if k>0. I’m not sure whether this result is very useful for anything, but it is cute. It also goes to to show that, if looked at in the right way, the whole Universe is a Simple Harmonic Oscillator!

Leave a comment »

Weekly Update from the Open Journal of Astrophysics – 13/12/2025

Posted in OJAp Papers, Open Access, The Universe and Stuff with tags , , , , , , , , , , , , , , , , , , , , , , , , , , on December 13, 2025 by telescoper

It’s time once again for the usual Saturday morning update of the week’s new papers at the Open Journal of Astrophysics. Since the last update we have published a further five papers, which brings the number in Volume 8 (2025) up to 195, and the total so far published by OJAp up to 430.

The first paper this week is “Cosmic Rays Masquerading as Cool Cores: An Inverse-Compton Origin for Cool Core Cluster Emission” by Philip F. Hopkins (Caltech), Eliot Quataert (Princeton), Emily M. Silich, Jack Sayers, Sam B. Ponnada and Isabel S. Sands (Caltech).  This was published on Tuesday 9th December 2025 in the folder marked High-Energy Astrophysical Phenomena. It presents an argument  that cosmic-ray inverse-compton emission could contribute significantly to the X-ray surface brightness (SB) in cool-corre clusters, implying that gas densities may have been overestimated therein.

The overlay is here:

You can find the officially accepted version on arXiv here and the Fediverse announcement is here:

Open Journal of Astrophysics

New Publication at the Open Journal of Astrophysics: "Cosmic Rays Masquerading as Cool Cores: An Inverse-Compton Origin for Cool Core Cluster Emission" by

Philip F. Hopkins (Caltech), Eliot Quataert (Princeton), Emily M. Silich, Jack Sayers, Sam B. Ponnada and Isabel S. Sands (Caltech)

doi.org/10.33232/001c.154053

December 9, 2025, 7:22 am 1 boosts 0 favorites

The second paper of the week is “Detecting False Positives With Derived Planetary Parameters: Experimenting with the KEPLER Dataset” by Ayan Bin Rafaih (Aitchison College, Lahore, Pakistan) and Zachary Murray (Université Côte d’Azur, France). This one was published on 9th December 2025 in the folder Earth and Planetary Astrophysics. It is an investigation into the performance of a range of machine-learning algorithms on the KEPLER dataset, using precision-recall trade-off and accuracy metrics.

The overlay is here:

You can find the official version of this one on arXiv here. The federated announcement on Mastodon is here:

Open Journal of Astrophysics

New Publication at the Open Journal of Astrophysics: "Detecting False Positives With Derived Planetary Parameters: Experimenting with the KEPLER Dataset" by Ayan Bin Rafaih (Aitchison College, Lahore, Pakistan) and Zachary Murray (Université Côte d’Azur, France)

doi.org/10.33232/001c.154054

December 9, 2025, 7:34 am 1 boosts 0 favorites

Next one up is “The role of peculiar velocity uncertainties in standard siren cosmology” by Chris Blake and Ryan J. Turner (Swinburne, Australia). This paper discusses the impact of peculiar velocities on the error in H0 determinations from local distance indicators with observed redshifts, incorporating the effect of bulk flows. It was published on Tuesday 9th December in the folder Cosmology and Nongalactic Astrophysics.

The overlay is here:

You can find the official accepted version on arXiv here. The fediverse announcement is here:

Open Journal of Astrophysics

New Publication at the Open Journal of Astrophysics: "The role of peculiar velocity uncertainties in standard siren cosmology" by Chris Blake and Ryan J. Turner (Swinburne, Australia)

doi.org/10.33232/001c.154055

December 9, 2025, 7:47 am 1 boosts 0 favorites

The fourth article of the week is “Transient QPOs of Fermi-LAT blazars with Linearly Multiplicative Oscillations” by P. Penil (Clemson University, USA) and 7 others based in the USA, Italy and Germany. This was published on Thursday 10th December in the folder High-Energy Astrophysical Phenomena. This paper presents an investigation of patterns of quasi-periodic oscillations in observed blazar systems characterized by periodic multiplicative amplitudes including both the periodicities and long-term variations.  The overlay is here:

You can find the official published version on arXiv here. The Fediverse announcement follows:

Open Journal of Astrophysics

New Publication at the Open Journal of Astrophysics: "Transient QPOs of Fermi-LAT blazars with Linearly Multiplicative Oscillations" by P. Penil (Clemson University, USA) and 7 others based in the USA, Italy and Germany

doi.org/10.33232/001c.154123

December 10, 2025, 12:22 pm 0 boosts 1 favorites

The last paper for this week is “Tidally Delayed Spin-Down of Very Low Mass Stars” by Ketevan Kotorashvili and Eric G. Blackman (U. Rochester, USA). This was published on Friday 12th December (yesterday) in the folder Solar and Stellar Astrophysics. It discusses the effect of tides from sub-stellar companions on rotational evolution of very low-mass stars, suggesting that these may explain the dearth of field, late-type M dwarfs with intermediate rotation periods.

The overlay is here:

 

You can find the officially-accepted version on arXiv here, and the Mastodon announcement is here:

Open Journal of Astrophysics

New Publication at the Open Journal of Astrophysics: "Tidally Delayed Spin-Down of Very Low Mass Stars" by Ketevan Kotorashvili and Eric G. Blackman (U. Rochester, USA)

doi.org/10.33232/001c.154268

December 12, 2025, 10:31 am 1 boosts 0 favorites

 

And that concludes the update for this week. I will do another of these regular announcements next Saturday, which will be the last such update for 2025. Will we make it past 200 for the year? Tune in next week to find out!

1 Comment »

Blue Christmas Again

Posted in Jazz with tags , , , on December 12, 2025 by telescoper

I’ve had a very busy penultimate week of term and am out of energy so instead of attempting a new post I thought I’d repost this “festive” classic. I posted this one during the “festive” season” in 2013 and haven’t posted it since. Until now. The band is led by none other than Miles Davis; the other members are Frank Rehak (trombone), Wayne Shorter (tenor sax), Paul Chambers (bass), Jimmy Cobb (drums), and Willie Bobo (bongos); the arrangement is unmistakably by Gil Evans. The vocalist is the legendary Bob Dorough who also wrote the lyrics.

“Bah Humbug” never sounded so cool!

 P.S. I’m not particularly blue myself, just tired…

Leave a comment »

An Introduction to Philosophy

Posted in Uncategorized with tags , on December 11, 2025 by telescoper
Cartoon from Private Eye

3 Comments »

Around the Circle – Wassily Kandinsky

Posted in Art with tags , , on December 10, 2025 by telescoper

by Wassily Kandinsky (1940; oil and enamel on canvas. 96.8 x 146 cm Guggenheim, New York)

1 Comment »

Storm Bram Approaches…

Posted in Biographical, Maynooth with tags , , on December 9, 2025 by telescoper

The weather is rather strange today, as a result of Storm Bram which is approaching from the South. The storm is bringing warm air with it, so the temperature is around 15°C which is very mild for December. The prevailing winds are usually westerly or south-westerly.

Heavy rain fell overnight, especially in the South. It’s clearer now and the winds are starting to pick up. Although Maynooth is relatively sheltered we’re still expecting gusts up to 100 km/h. As a precaution, the large tent which is usually situated outside the John Hume building has been dismantled to stop it blowing away.

Campus remains open and lectures are going ahead as normal.

At least mine are…

UPDATE: 4.25pm. I spoke to soon. I have a teaching session between 2pm and 4pm on Tuesdays; I usually take a break halfway through, as I did this afternoon. Chatting with some students in the interval we noted the wind was picking up and discussed the possibility of a power cut. We obviously tempted fate, as no sooner had we resumed for the second half when all the power went off. It came on intermittently a few times, but at 3.30pm I called off the lecture. It was too dark to see the blackboard and no other AV equipment was working. When I got back to the Physics Department, where the power was also off, as it appeared to be for the whole campus, a colleague who lives nearby told me that our area of Maynooth still had power. So I headed home, via Dunnes (which has a generator) to buy a few things. As I walked through Maynooth some lights were on, some were off. The worst affected area seemed to be to the north-west and around campus. Anyway, I’m home safely and can continue working here as long as the power stays on.

P.S. The storm is named after Bram Stoker, author of Dracula, who was born in Dublin.

1 Comment »

Nine Teaching Days to Christmas

Posted in Biographical, mathematics, Maynooth, Television with tags , , , on December 8, 2025 by telescoper

This week is the penultimate week of teaching term at Maynooth and, as usual at this stage of the Semester, we’re getting busier and busier. The examinations for January have been sent off for printing and are (presumably) ready to go, and I’m up to date with all my coursework gradin so I am, miraculously, on schedule as far as teaching is concerned. I should finish covering the respective syllabuses by Tuesday 16th, with the remaining teaching sessions devoted to revision. I don’t have any lectures on Fridays this term, so my teaching ends, a day before the end of term, on Thursday 18th December. To celebrate the end of term I’ll be presenting the students in the last session of my Engineering Mathematics module the gift of a final Class Test. I’m not sure when I’ll get to correct it. Oh, and our Department Christmas Dinner is on Wednesday 17th.

I’ll soon have to decide when to pause the publication of new papers at the Open Journal of Astrophysics and prepared for next year’s Volume 9. A certain person is insisting that I take a complete break for at least a week, so I think we’ll probably stop on Christmas Eve and begin again in the New Year.

In the meantime, term goes on. I have three lectures to get ready for tomorrow. Incidentally, my mid-Semester feedback suggested that I start each lecture with an introduction to say what I’m going to be covering. Here are some examples of what I’ve been doing in response:

1 Comment »

Black Holes, Hawking Radiation (and AI…)

Posted in Artificial Intelligence, The Universe and Stuff with tags , , , , , on December 7, 2025 by telescoper

It seems to be a common misapprehension that the energy released by the supermassive black holes in, for example, active galactic nuclei is in the form of Hawking radiation. It isn’t. Hawking radiation is only significant for black holes of very low mass. The radiation produced around supermassive black holes is due to the extremely high density and temperate of matter falling into the black hole through an accretion disk not due to the evaporation of the black hole itself. Hawking radiation has never been experimentally detected.

Hawking showed that the a black hole will produce black-body radiation with a temperature, the Hawking Temperature, given by TH in a beautiful formula below that brings together constants relating to gravity, statistical mechanics, quantum theory and relativity:

You can see that the Hawking Temperature is inversely proportional to the mass of the black hole M so is largest for very small black holes. In fact for a black hole with mass of order that of the Moon, the Hawking Temperature is just 3 Kelvin. Since the Universe is bathed in cosmic radiation with this temperature, such a black hole would not evaporate at all because it would absorb as much radiation as it emits by the Hawking mechanism as would any black hole of mass greater than this. The Hawking temperature for a supermassive black hole is many orders of magnitude lower than this, so Hawking radiation is completely irrelevant.

Notice that if a black hole does start to evaporate then its mass begins to decrease. Its Hawking temperature therefore increases so its mass decreases even more quickly. In the end the mass gets so low and the temperature so high that the black hole effectively explodes. Nobody really knows how to describe the final stage as it relies on physics we don’t understand.

Anyway, this all reminds that years ago I set an examination question that involved applying the Hawking formula above to calculate the lifetime of a black hole of mass M. It’s not too hard to show that it scales as M-3. Another part of the question asked: what is the mass of a black hole whose Hawking Temperature is room temperature (say 300 K), what would be the Schwarzschild radius of such a black hole, and what would be its lifetime?

I’ll leave it to my readers to plug the numbers into the Hawking formula above to derive the mass, etc. Please submit your answers through the comments box below. The first correct entry does not win a prize, not even a joke Peace Prize.

For a laugh I asked Google for the answer. Here is the AI summary:

Bonus marks for pointing out everything that’s wrong in this summary.

Leave a comment »

« Older Entries
Newer Entries »