Going NUTs

Posted in The Universe and Stuff, Uncategorized with tags , , , on April 5, 2017 by telescoper

If you’ve studied General Relativity the chances are that you’ve come across the Taub-NUT exact solution discussed in this post. It’s generally regarded as something of an oddity in that it’s a bit contrived, but provides a counter-example to some well-known results. For example, in the context of a Black Hole solution, it violates the No Hair Theorem (by violating the assumption of asymptotic flatness).

When I saw this post at CQG, however, I was reminded of a paper published a few years ago discussing this in a cosmological context, where it can be seen as a special case of the Bianchi IX geometry.

Jennifer Sanders's avatarCQG+

By Paul I. Jefremov and Volker Perlick.


Among all known solutions to Einstein’s vacuum field equation the (Taub-)NUT metric isa particularly intriguing one. It is that metric that owing to its counter-intuitive features was once called by Charles Misner “a counter-example to almost anything”. In what follows we give a brief introduction to the NUT black holes, discuss what makes them interesting for a researcher and speculate on how they could be detected should they exist in nature.

paul jefremov-and-volker Volker Perlick and Pavel (Paul) Ionovič Jefremov from the Gravitational Theory group at the University of Bremen in Germany. Volker is a Privatdozent and his research interests are in classical relativity, (standard and non-standard) electrodynamics and Finsler geometry. He is an amateur astronomer and plays the piano with great enthusiasm and poor skills. Paul got his diploma in Physics at the National Research Nuclear University MEPhI in Moscow, 2014. Now he…

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The Word, by R.S. Thomas

Posted in Poetry with tags , , , on April 5, 2017 by telescoper

A pen appeared, and the god said:
‘Write what it is to be
man.’ And my hand hovered
long over the bare page.

until there, like footprints
of the lost traveller, letters
took shape on the page’s
blankness, and I spelled out
the word ‘lonely’.

And my hand moved
to erase it; but the voices
of all those waiting at life’s
window cried out loud: ‘It is true.’

by R.S. Thomas (1913-2000)

 

Easter Fatigue 

Posted in Biographical, Education with tags , on April 4, 2017 by telescoper

This is Week 11, which is the last week of teaching here at Cardiff University before the Easter break. In the early hours of this morning I finished marking my last set of coursework for the term and later on delivered my last (2-hour) lecture on the Physics of the Early Universe.

I’ve booked two weeks of annual leave from Friday and am really looking forward to a bit of rest, though I will have quite a few private matters to deal with while I’m away from work.

Such is the topsy-turvy world we live in that I note that this month’s meeting of the Royal Astronomical Society is  on this Friday, 7th April. This is contrary to the settled order of Nature, as these meetings are always on the second Friday of the month. This year, however, the 2nd Friday of April is Good Friday. This, after all, is Eastertide, when Christians celebrate the invention of the chocolate egg by doing arms deals with despotic middle-eastern governments. 

I’m only joking. Of course. Chocolate eggs have nothing to do with the true message of Easter, which is depicted in the following.

Anyway, it’s the fact that Easter moves about in the calendar that is the reason this term has been so long and I am tired and grumpy. I don’t like chocolate either.

On the bright side I did receive two pieces of good news today in between the other stuff. I hope to be able to pass them on tomorrow, or at any rate before I go off on my hols…

The Bayesian Second Law of Thermodynamics

Posted in The Universe and Stuff with tags , , , on April 3, 2017 by telescoper

I post occasionally about Bayesian probability, particularly with respect to Bayesian inference, and related applications to physics and other things, such as thermodynamics, so in that light here’s a paper I stumbled across yesterday. It’s not a brand new paper – it came out on the ArXiv in 2015 – but it’s of sufficiently long-term interest to warrant sharing on here. Here’s the abstract:

You can download the full paper here. There’s also an accessible commentary by one of the authors here.

The interface between thermodynamics, statistical mechanics, information theory  and probability is a fascinating one, but too often important conceptual questions remain unanswered, or indeed unasked, while the field absorbs itself in detailed calculations. Refreshingly, this paper takes the opposite approach.

 

 

 

Campaigners say right-wing attempts to singe King of Spain’s beard nothing new

Posted in Beards, Politics on April 3, 2017 by telescoper

A bearded perspective on one of the Great Questions of the Day..

kmflett's avatarKmflett's Blog

Beard Liberation Front

Media release 2nd April

Contact Keith Flett 07803 167266

Campaigners say right-wing attempts to singe King of Spain’s beard nothing new

Zimbio

The Beard Liberation Front, the informal network of beard wearers, has warned that the current furore around Gibraltar as Brexit discussions open may be a ploy by right-wing elements in the Tory Party to launch a fresh attack on the King of Spain’s beard.

King Felipe V1 who sports a salt and pepper beard is thought to be the only serving hirsute European monarch.

Francis Drake, after agreement with Queen Elizabeth 1st, launched an attempt to singe the beard of an earlier King of Spain, also called Felipe at Cadiz, prior to the 1588 Armada.

The Daily Mail complained about King Felipe’s beard on his appointment in 2014:

http://www.dailymail.co.uk/news/article-2797591/will-english-singe-king-spain-s-beard-felipe-joins-facial-hair-trend-making-europe-s-bearded-monarch.html

BLF Organiser Keith Flett said, we’re no great fans of Royal Families but…

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Washington Crossing the Delaware 

Posted in Uncategorized on April 2, 2017 by telescoper

No time for a post today so I thought I’d share this amazingly clever poem.

OK, so from a literary point of view it’s not the greatest poem ever written, but what’s “amazingly clever” about it is that each individual line is an anagram of the title…

Tomorrow’s World Live 

Posted in Uncategorized on April 1, 2017 by telescoper

I was looking in my drawers this afternoon and came across this, which is a memento of something that happened 20 years ago. I just missed the anniversary by ten days!

Believe it or not, that’s me at the bottom left sans beard..

I did an item on the Tomorrow’s World Live show – which was not broadcast but performed in front of an audience of a few hundred people in a temporary theatre. In fact there were four shows a day for the period of the event (19-23 March 1997). Each show was only about 30 minutes long, but it was quite hard work as there were many technical things to sort out in between performances.

My role was to do a little piece about the refurbished Hubble Space Telescope and then answer questions on astronomy and cosmology from the audience. I had no script for that bit, as it was impossible to know what would be asked. I answered with varying degrees of success.

Other items featured on the show were a clockwork radio, an  electric sports car, and a device for scrambling an egg without breaking its shell. I couldn’t see the point of the last invention, as one would have to break the shell to eat the egg anyway.

The best bit about being involved in Tomorrow’s World Live was meeting so many of the presenters, all of them proper professionals (unlike me) who were very friendly and helpful. Only two presenters were involved in each show,  and  each pair only did one or two shows, so over the five days I got to work with the whole set, including Craig Doyle, Philippa Forester, Howard Stableford, Vivienne Parry and Shahnaz Pakravan. I didn’t envy them as they had to work not only with amateurs like me, but also had to learn a detailed script and deal with the gadgets. I was relieved that I could basically just wing it.

My clearest memory of the whole event was the technical rehearsal early  in the morning before the very first show. Nothing worked properly, and I was convinced that it was all going to be a complete disaster. Somehow, however, it all came together and there weren’t any major problems in any of the real shows.

Recycled Bach

Posted in Music with tags , , , , , , on March 31, 2017 by telescoper

I had the office to myself this morning so I was listening to Essential Classics presented by Rob Cowan on BBC Radio 3 earlier on. During the course of the programme he pointed out that Johann Sebastian Bach was not averse to a bit of recycling and gave the following example. I’m sure that everyone has heard of Bach’s Mass in B Minor (BWV232), which is widely regarded as one of the greatest works ever composed in the entire history of music.

However, although this work is often depicted as a kind of culmination of Bach’s career as a composer and it wasn’t completed until 1749 (the year before Bach’s death), many sections were in fact recycled from much earlier compositions.

For example, give a listen to this. It is the Aria Ach, bleibe doch, mein liebstes Leben from the Cantata Lobet Gott in seinen Reichen (BWV11), often called the Ascension Oratorio, which was first performed in 1735. Apart from the fact that it sets a different text in a different language – the B Minor Mass is a setting of the complete `Ordinary’ of the Latin mass – and there are one or two musical differences here and there, this is instantly recognizable as an earlier incarnation of the sublime Agnus Dei from the B Minor Mass..

Oh, and if you’ve got half an hour to spare you could watch this video of a sparkly and sprightly performance of the entire cantana.

 p.s. It’s Bach’s birthday today: he was born on March 31 1685.

 

 

A Question of Equilibrium

Posted in Cute Problems with tags , on March 30, 2017 by telescoper

It’s been quite a while since I’ve been able to find time to post any items in the cute problems folder, and I don’t have much time today either, but here’s a quickie. You may well find this a lot harder than it looks at first sight. At least I did!

An isolated system consists of two identical components, each of constant heat capacity C, initially held at temperatures T1 and T2 respectively. What is the maximum amount of work that can be extracted from the system by allowing the  two components to reach equilibrium with each other?

As usual, answers through the comments box please. There is no prize, even if you’re right.

 

 

We’ll Be Together Again

Posted in Jazz, Politics with tags , , , , , on March 29, 2017 by telescoper

So, we’ve come to it at last.

At 12.30 BST the Prime Minister’s letter invoking Article 50 of the Lisbon Treaty will be delivered to the President of the European Council, Donald Tusk. This will begin the process by which the United Kingdom leaves the European Union. It also begins the process of dismantling the United Kingdom itself. Scottish independence is now an inevitability as is, probably on a slightly longer timescale, the reunification of Ireland.

I am sad beyond words that this country has taken this path to self-destruction, but can only hope that we eventually see sense and change or mind at some point in the next two years, or return to the fold at some later stage.

No artist was better at conveying a sense of tragedy and loss through their music than Billie Holiday, and here’s a track by her that perfectly expresses my feelings at this bleak time:

No tears, no fears
Remember there’s always tomorrow
So what if we have to part
We’ll be together again