Wednesday, 12 December 2012

Multidimensional Bigotry

It turns out that everyone's favourite exploiter of xenophobia also has plans for homophobia:
The Conservatives' turmoil over David Cameron's plans for gay marriagehas been compounded after Ukip pledged to exploit their divisions and go after the votes of Tories who abandon the party over the issue.
Amid signs that Conservative associations are losing members in their droves over what is being dubbed the prime minister's "clause IV moment", the Ukip leader, Nigel Farage, warned that gay marriage could "rip apart" the Conservative party. He plans to put the issue at the heart of Ukip's campaign for the 2014 European parliamentary elections.
Ukip stands for the UK Independence Party, an anti-European Union party whose biggest successes have come in EU elections.  While I'm sure the party members themselves would argue that they are not xenophobic, they clearly benefit from anti-immigrant sentiment, which in the UK also includes a certain level of anti-looks-like-a-Muslim totally-not-racism-honest.

Friday, 7 December 2012

Golden Spike and the Private Space Industry

As a follow-up to my post from a couple of days ago, I thought I'd comment on the announcement by the Golden Spike company to land on the moon by the end of the decade.  In a more general sense, there's the question of commercial space travel; I'd somehow missed the news that the SpaceX company successfully delivered cargo to the ISS earlier this year.

Wednesday, 5 December 2012

The Science of the Apollo Missions

On the subject of research papers, I recently came across a paper by Ian Crawford on the science of the Apollo missions.  It's a review written at a non-technical level; it's from the journal Astronomy and Geophysics, but the only link I've found is at the arXiv.  I encourage anyone curious about the scientific merits of the whole affair to read it.  One interesting quote compares what Prof. Crawford achieved on a field trip on Earth to the moon missions, concluding
I do not think that we were inefficient, and we were in fact well-pleased with what we accomplished (which will result  in several peer-reviewed publications), but clearly what we achieved in 42 man-days at one site in Iceland pales into insignificance to what the Apollo astronauts achieved in 25 man-days at six sites on the Moon under far more difficult operating conditions. Based on my own experience I find the field efficiency of the Apollo astronauts to  be simply staggering.

On Reading

Once upon a time, I used to read for fun.

Tuesday, 27 November 2012

A Roguelike Overview

When I started this blog, I had several things I wanted to discuss.  Things like atheism, feminism and particle physics are fairly serious subjects, and writing about them demands time.  So I threw roguelikes in as a more light-hearted subject, figuring that I could write posts about them when I wanted something quick and easy.

Well, that's not how it turned out.

Monday, 26 November 2012

Climate Change Consensus

Via Pharyngula, a post on the scientific consensus in Climate Change from DeSmogBlog:
By my definition, 24 of the 13,950 articles, 0.17% or 1 in 581, clearly reject global warming or endorse a cause other than CO2 emissions for observed warming. The list of articles that reject global warming is here. The 24 articles have been cited a total of 113 times over the nearly 21-year period, for an average of close to 5 citations each. That compares to an average of about 19 citations for articles answering to "global warming," for example. Four of the rejecting articles have never been cited; four have citations in the double-digits. The most-cited has 17.
The study period ran from 1991 to this year.

The Right Thing for Bad Reasons

A story the BBC classifies as Technology, but I prefer Scary as Shit:
A court challenge has delayed plans to expel a Texan student for refusing to wear a radio tag that tracked her movements.
Religious reasons led Andrea Hernandez to stop wearing the tag that revealed where she was on her school campus.
The tags were introduced to track students and help tighten control of school funding.
Ms Hernandez refused to wear the tag because it conflicted with her religious beliefs, according to court papers. Wearing such a barcoded tag can be seen as a mark of the beast as described in Revelation 13 in the Bible, Ms Hernandez's father told Wired magazine in an interview.
So.  Where to begin?

Monday, 19 November 2012

Concern Trolling

I see that the Church of England is to vote on whether to allow women bishops.  Usually in cases like this, my desire for a religious organisation to do the ultimately self-destructive thing is tempered by the realisation that this will cause real, serious harm to members of that religion.  But here the harm is minor, so I encourage the church to stick to its tradition, vote no, and speed its path to irrelevance.

Tuesday, 13 November 2012


There's yet another new observation that agrees perfectly with the Standard Model and shows no sign of new physics.  To quote one of my friends, "this game isn't fun any more".

The process in question is the decay of a bound state of a bottom and strange quarks to two muons.  This decay is heavily suppressed in the Standard Model, happening only three times in a billion events.  The tiny Standard Model rate made it an excellent place to look for contributions from new particles and interactions.  A much higher or lower rate than expected would have been an exciting discovery.

Instead, the results agree well with the Standard Model prediction.  Technically, this is evidence rather than a true discovery (3 sigma instead of 5), but at this point it's unlikely that we'll see anything radically different.  And we have one more piece of evidence pointing towards the Standard Model and nothing else.

Monday, 12 November 2012

An Odd Political Feeling

So, I was reading in the Guardian online about the issue of boundary reform.  This is the Conservative party's desire to reduce the overall number of MPs and change how they are divvied up.  However, they are facing a revolt (or at least resistance) from their nominal coalitian partners, the Lib Dems:
The Conservatives are in talks with the Democratic Unionist party (DUP)to win their backing for moves to cut the number of MPs at Westminster, Tory sources have told the Guardian.
The party is also looking to win the support of one of the nationalist parties in a bid to keep alive constituency boundary reforms that would improve Tory chances of securing an overall majority at the 2015 election. Prime minister David Cameron fears Labour and Liberal Democrats will combine to defer the boundary reforms until after the election.
The DUP, for reference, are one of the Northern Irish parties.

Usually, I'd enjoy at least a little Schadenfreude at the failings of a right wing party.  That's double in a case like this, which could easily be called gerrymandering (second comment below the article!)  But instead I feel somewhat conflicted.

Saturday, 10 November 2012

Bayes vs Frequentist

I hate to link to XKCD for the second comic in a row, but the most recent one really struck a chord with me.  While it is a little unfair, it hits what is to me the essential weakness of frequentist statistics: that the standard null-hypothesis rejection only considers how unlikely something is to happen by chance.  In contrast, the Bayesian analysis weighs the different possibilities using prior information.

Also, the willingness of the Bayesian character in the strip to place a bet relates to the characterisation of probability as degrees of belief; intuitive, meaningful in a Bayesian approach, but impossible under a strict frequentist interpretation.

Friday, 9 November 2012

What is Seen

So, a couple of days ago I discussed the problem of infinities in quantum field theories (QFTs).  I noted that two types of infinities exist, infrared (where we get a 1/0 in our perturbation expansion) and ultraviolet (where an integral to infinity diverges).  Today I'll discuss the resolution to the former, which is conceptually easier to grasp.  What makes this question interesting is that the answer forces us to think about what we can actually hope to measure in an experiment.

Wednesday, 7 November 2012

No Surprises

So apparently there was an election today?

As so often, Randall Munroe of XKCD gets to the point:
Props to Nate Silver, Sam Wang and especially Drew Linzer, who's been predicting this outcome since June.  Scorn to the media pundits and conservative bloggers who attacked Nate Silver for the temerity to suggest Obama was ahead on the basis that the polls showed Obama was ahead.  Relief for me, that my USAlien friends can live in a country that is still at least partly sane.

Tuesday, 6 November 2012

Juggling Infinities

In the introduction to his textbook on quantum field theory, Steven Weinberg recounts a saying from his days as a (post-)graduate student:
Just because something is infinite does not mean it is zero!
The infinities here show up in quantum field theory (QFT) when we look at the perturbation series beyond leading order.  They confused people a lot during the development of QFT, but their resolution is physically interesting, and something I've been meaning to talk about for a while.  Today, I'm only going to be able to set up the problem; I hope to get to the solution by the end of the week.

Monday, 5 November 2012

Taxes are Optional

Another day, another story of massive tax avoidance:
Apple paid less than 2% corporation tax on its profits outside the US, its filing with US regulators has shown.
The company paid $713m (£445m) in the year to 29 September on foreign pre-tax profits of $36.8bn, a rate of 1.9%.
 The key line comes later in the report, though:
It has not been suggested that any of their tax avoidance schemes are illegal.
It's okay, though.  It's not as if countries around the world are in some sort of budget crisis, or anything.

Monday, 29 October 2012


All right.  Let's do this.

Way, way back in March, I talked about Roguelikes in general, and gave my opinion of one of the main examples of that genre of game, Angband.  I followed this up with a review of probably the most famous example, NetHack, in April.  I originally intended to these reviews a regular series, and planned to review another major variant, Crawl, a week or two later.

Well, only six months late.

Thursday, 25 October 2012

Who the Hell is Mallory?

Via the BBC, worrying news for Android users like me:
Our analysis revealed that 1,074 (8.0%) of the apps examined contain SSL/TLS code
that is potentially vulnerable to MITM [Man in the Middle] attacks. Various forms of SSL/TLS misuse were discovered during a further manual audit of 100 selected apps that allowed us to successfully launch MITM attacks against 41 apps and gather a large variety of sensitive data.
Now, I don't use my Android phone for anything sensitive.  Further, the Android marketplace is open, so you'll have good and bad software there; in that sense there's no surprise that some of the apps have security flaws.  I've only skimmed the relevant paper, but I didn't see any list of who these troublesome programs were from.  The authors do observe that the insecure apps include mainstream ones, with tens of millions of installations, but at first glance this seems to be what you'd expect in an unmonitored market.  In short, caveat emptor and be careful with your data.

What I found most confusing, though, was the title of the paper: "Why Eve and Mallory Love Android".  Eve of course is the common name for the eavesdropper in cryptographical circles, but I've never heard of Mallory, hence my question above!  Some wiki-ing gives the answer (the malicious attacker) and a long list of names that makes it clear I know much less about cryptography than I though...

See Ceefax No More

So I find to my surprise that Ceefax has been officially turned off:
BBC Ceefax, the world's first teletext service, has completed its final broadcast after 38 years on air.
Ceefax was launched on 23 September 1974 to give BBC viewers the chance to check the latest news headlines, sports scores, weather forecast or TV listings - in a pre-internet era where the only alternative was to wait for the next TV or radio bulletin to be aired. 
I say surprising not least because I wasn't aware it was still running.  Indeed, during my entire time as a student (under- and postgrad) I never owned a TV and rarely watched one, and I pretty much forgot the whole concept of teletext existed.  I guess it's like returning home and finding that one of the playgrounds of your youth that'd faded from your mind was torn down and rebuilt; makes you feel old.

Tuesday, 23 October 2012

Because Predictions are Never Wrong

Ominous news from Italy:
Six Italian scientists and an ex-government official have been sentenced to six years in prison over the 2009 deadly earthquake in L'Aquila.
A regional court found them guilty of multiple manslaughter.
Prosecutors said the defendants gave a falsely reassuring statement before the quake, while the defence maintained there was no way to predict major quakes.
It is important that the government, including government scientists, should be held accountable.  But the case here is not good.  The prediction of earthquakes is an inexact science; with current knowledge, we will always make mistakes.  And yet that seems to be all these people have been found to have done, made an error.

Monday, 22 October 2012

Three is a Large Number

One thing I sometimes like to joke is that in  physics, there are only three numbers: zero, one and infinity.  By that I mean that you can get a decent rough estimate in many cases by treating the relevant parameters as one of those three values.  The entire field of dimensional analysis involves setting numbers to be one in the appropriate units; for example, consider atomic physics.  We are in the quantum regime, so we need Planck's constant h; the dominant force is electromagnetism, so we'll need the vacuum permittivity ε0; and the electrons form the "outside" of an atom, so let's also consider the electron charge e and mass me.  There's only one way to combine these objects to have the dimensions of energy:
$\frac{m_e e^4}{\epsilon_0^2 h^2}$
Up to an overall constant, this is the Rydberg, which indeed characterises the energies of atomic physics, and which is normally derived after several weeks of quantum mechanics.

Setting things to be zero is fairly intuitive.  Small things normally have small effects, and can be ignored at first.  Correcting for them being non-zero is then precisely a perturbation series.  Interestingly, setting numbers to infinity is pretty similar; there are plenty of situations where the mathematics can be exactly solved when a coupling g goes to infinty, and then corrections come as a series in inverse powers of g.  A somewhat different example is in the strong interaction, which has three colours (analogous to the single electric charge).  Before I was born, Dutch physicist Gerard 't Hooft was able to successfully analyse the strong interaction by setting the number of colours to be infinity.  Despite three not being very big, the approximation was successful.

In a similar vein, we have the paper I want to discuss today.  Like 't Hooft, Bai and Torroba are approximating a number that equals three by infinity.  Instead of gauge interactions and colour, they have chosen to look at flavour and the number of generations.

Friday, 19 October 2012

Homophobia in England

Apparently, the far right are a bunch of bigots.  Shocking, I know.
Police in Cambridgeshire have said they are investigating complaints made after the leader of the far-right British National party, Nick Griffin, posted the address of a gay couple on the internet and appeared to urge his supporters to demonstrate outside their home.
This relates to a recent case that was actually quite pleasant and uplifting.  An elderly gay couple tried to stay in a bed and breakfast, but the owner refused to let them share a bed.  They sued and won, which shows that the British courts do get things right sometimes.

Of course, to the BNP demanding you are treat fairly is "bullying" if you're not a straight white English man.  Posting someone's address online and asking your followers to harass them is not, though.  We even got an accusation of "heterophobia", which I think completes the bigot bingo.  Still, one thing did make me laugh; after it emerged that Griffin might face criminal prosecution for his acts, he immediately started whining:
Griffin then wrote: "Why don't left & gay activists confront Muslims instead of picking on meek & forgiving Christians? Bullies are always cowards!"
That last line is just precious, given that Griffin has now exhibited both behaviours—bullying and cowardly whining—in this single incident.

Lines and Boxes in the Sky

I've talked recently about the potential signal of dark matter found from gamma ray photons with an energy of 130 GeV.  One paper from a several weeks ago that I've wanted to discuss made a simple but interesting point.  You see, the most obvious interpretation of this signal is from dark matter self annihilating directly to a pair of photons.  This direct production gives us a mono-energetic spectrum.  But instead of a line, we might have a really narrow box, coming from a two-step process.  And this is actually quite natural in certain types of models.

To go into more detail, we'll need to cover some basic kinematics.

Thursday, 11 October 2012

Gay Rights in Ukraine

Courtesy of the BBC, it looks like LGBT rights are in danger in Ukraine:
The Ukrainian parliament could give final approval next week to a bill that aims to outlaw "pro-homosexual propaganda" - any "positive depiction" of gay people, gay pride marches, or even the screening of a film like Brokeback Mountain.
The story is a depressing parade of the usual, such as this guy:
Supporters of the bill, like Ruslan Kukharchuk, a founder of the local group Love Against Homosexuality, deny the accusation of intolerance. They say they too condemn the violence against homosexuals. What is more, they add, gays are free to do whatever they want "in the privacy of their room".
Kukharchuk, however, has also written about what he calls the "homo-dictatorship" which he claims dominates Western society and persecutes religious, anti-gay proponents like himself. He strives to counter "aggressive" gay propaganda, he says - in other words, public discourse that implies that homosexuality "is normal, is good, is part of democracy".
 Yes, it's not intolerant to want to outlaw any positive representation of 10% of the population; but it is intolerant to object to such rampant bigotry.  And we also get some fun talking about offense from, of course, some religious shithead:
"Here's the issue," says Pastor Reshetinsky, a large-boned man with a slight moustache, tells me. "In a real democracy, my freedom and rights are limited by the freedom of someone else."
In his opinion, freedom of speech for sexual minorities is a violation of what he considers his inalienable right not to have to hear something he finds offensive.
Pastor Rechetinsky, let me say with all sincerity, fuck off you despicable example of humanity.  Your "inalienable right" is bullshit, an attempt to oppress people for no reason other than your own petty bigotry.  Oddly enough, the comment about how individual rights are limited by other people is correct; but you think this means your own right not to be disconcerted is more than other people's rights to live their lives normally.  Egocentric bastard.

There's some pretty depressing stuff in that article, such as the poll on Ukrainian's attitudes towards homosexuality.  Over 70% reported a negative opinion.  Not to mention attacks on gay activists, though I must admire one guy:
Despite the formidable pushback - and the threat of physical assault - LGBT activists are undaunted. Karasiychuk, who suffered a broken jaw and concussion in his attack, says gay people cannot retreat into the woodwork.
"We need to be more visible in everyday life. We have to provoke this conversation. Everyone has to ask themselves, why they don't like gays."
I can only wish these people the best of luck.

Wednesday, 10 October 2012

Some thoughts on the Nobel Prize

One of the dangers of working in a scientific field is becoming short-sighted, and thinking that it is automatically the most important area of research.  That is something I think many of us in the particle physics community have been guilty of with regards to the Nobel Prize in Physics this year.  The discovery of a Higgs-like particle at the LHC has been of great significance to us.  It justifies the construction of the LHC, meets the predictions of almost fifty years and opens new doorways to future physics.  For most of us, the only question was how the Nobel committee would resolve the problem of too many candidates; do you award it to the experimental collaborations?  Who among them?  What about the theorists; it's now properly recognised that in addition to Peter Higgs, several other people offered essential insights to the theoretical framework of the "Higgs mechanism".

Of course, the committee resolved this issue by giving the prize to a different field of physics, quantum optics.

Sunday, 30 September 2012

Accommodation and the Provision Thereof

So I've finally found a permanent place to stay here in Australia.  I signed the lease on Thursday, and move in next week.

Once I've settled in, I'll be able to enjoy living in my own place for the first time in a month; but if you consider all the stress I had during my last month in Vancouver, it's really longer than that.  I still need to convince myself that my new place is home, but I've done that before and it shouldn't be too hard.

All this leaves me with no more excuses about getting work done; nor for blogging.  I have several things in the mix, including the long-postponed review of Crawl that's about one-third done.  I hope it will be a productive Spring and Summer!

Saturday, 29 September 2012

Michael O'Hare Dies

Apparently, Michael O'Hare, who played Jeffrey Sinclair on Babylon 5 among other roles, has died today after suffering a heart attack on Monday.

I'm a huge Babylon 5 fan.  I got into the show at the right age, when I was an undergraduate, though by then the show had actually finished and I was catching repeats.  And I always preferred Sinclair to Sheridan.  It's not that I disliked Sheridan (and I have a lot of respect for Bruce Boxleitner, after seeing his contribution to the DVD extras).  But Sinclair seemed more interesting as a character; more of a diplomat, while Sheridan was more of a warrior.  It's common to criticise O'Hare's acting in the role, but I never had a problem with it.  And one thing that he could do better than Boxleitner was deliver speeches, a useful trait on that show.

Plus, whatever complaints might be raised about O'Hare during the first season can't really hold to his return as a guest in the third.

Wednesday, 19 September 2012

Romney's Video

I imagine you've already seen the recent news about Romney's speech at a fundraiser that was secretly recorded.  It's all kind of depressing.  Not that he would hold such views; I may have called Romney the least evil of the Republican candidates, but that's very much damning with faint praise.  Not to mention that the idea that a rich business owner who'd outsourced jobs and paid little in tax should look down on the poor is less shocking, more expected.

It's not that Romney has defended his views once they've been made public.  That was pretty much forced; apologising would appear weak without convincing anyone.

No, what depresses me is that it probably doesn't matter.  The Republican base will, if anything, think better of him for this.  And swing voters either don't care, won't remember or won't even notice.

Tuesday, 18 September 2012

ID Problems

I've been in Australia for two weeks now.  Much as I expected, the stress and worry I was feeling prior to the move evaporated almost as soon as I got here.  That's not to say that looking for a permanent place to stay and wading through the new-job bureaucracy has been easy, but it hasn't put me on edge to nearly the same degree.

One thing that has come up is the issue of ID.  I'm not sure if I just had good luck in North America, but the requirements here for apartments or phone contracts seem perverse.  In general, I'm poorly disposed to any demands more stringent than I needed to enter the bloody country.  But it seems to be popular to use a points-based system where a passport is only half the required number of points.  When I inquired about a mobile phone contract yesterday, I was told I would need:

Wednesday, 12 September 2012

Race for the White Pillow

Back in March, I wrote a couple of blog posts about the Republican presidential primary for the US.  If you'd asked me then, I probably would have expected I'd write a lot more about that election.  But as the months have passed, I've found myself pretty uninterested in the whole affair.

You might say that's not too strange, since as a Brit I don't get to vote.  But the 2004 and 2008 elections grabbed my attention throughout the whole messy campaign.  Of course, I was living in the US back then; but I wasn't in a swing state and saw few adverts or other campaign literature.  I wasn't watching the national news, but looking things up online.  I went out of my way to get information, especially in 2008.  This time around I find it hard to care.

Tuesday, 11 September 2012


Way back at the beginning of August, I spotted a paper proposing a new experiment: LEP 3.  This struck me as somewhat amusing; you see, LEP—the Large Electron Positron collider—was the predecessor to the LHC.  When LEP finished its second run, it was dismantled and the LHC built in its tunnel.1  But the idea is serious, from the people at CERN no less.

To understand why, we need to consider the fundamental difference of the LHC and LEP.  As the name states, LEP collided electrons and positrons (anti-electrons).  The LHC collides protons.  There are two relevant differences: protons are much heavier, but are composite objects made up of quarks and gluons, while we believe electrons to be fundamental.  These have the consequence that the LHC (and similar proton machines) can reach higher energies, but with less precision.

Thursday, 6 September 2012


So.  I've made it to Melbourne.

So far there's nothing about this city to mark it any different from the rest of the English speaking world, but I expected that; such is the nature of globalisation.  And I've barely explored the place, just a few areas around the University.  No killer spiders so far!

Also as I expected, I feel much happier to have finished my travelling without incident.  Even with all the quarantine warnings, the Australian customs and immigration services were friendly (if a little slow).  I flew through LAX, and was questioned more closely by the Americans just for that short trip.  Of course, saying that immigration officials are nicer than the US is very much a low bar to pass; I had to pass through less security to enter a UK naval base than to enter the US!

The one big shock has been the prices here, which are pretty high.  Also, there's one obvious thing that marks being in a different country, the money.  The Australian 2 dollar coin is one of the smallest, which is just weird (compare the Canadian toonie or the UK two pound coin).  But in all, I am feeling optimistic about the next year or three I'll be spending here.

Tuesday, 4 September 2012


I'm currently sitting in Vancouver airport (yay for free wifi!) waiting to board the plane that will take me away from Vancouver for the last time.

It's always very hard for me when something comes to an end.  I've enjoyed the last three years, settled into a nice routine and made more than a few friends.  I've come to think of this place as home, to a degree I haven't really felt since Cambridge.

But the time has come for me to move on.  My job in Vancouver was always temporary, so I knew this day would arrive.  That doesn't make it any easier.  For the last few weeks, I've often done something and noticed that I will never do that thing in quite the same way.  Throw in the stress involved in trying to get all the packing and shipping finished, and I've felt less than sanguine.

Beginnings are easier.  So once I make it to Australia, I expect to feel better.  Sure, there are still lots of things I will need to do (like find an apartment), but with a better frame of mind and less of a hard deadline I should be less stressed with it all.

Wednesday, 15 August 2012


Just a note to explain the lighter than usual posting over the last couple of weeks.  I'm packing stuff up to ship for when I leave for Australia in a few weeks, and this has taken up a lot of time.  I should have that finished soon, which will hopefully let me finish off a couple of posts I'm working on.

While this is necessary, my apartment is looking increasingly empty, which does make me feel a bit sad.  I've enjoyed my time in Vancouver, and will definitely miss it.

Thursday, 9 August 2012

Armstrong in Hospital

Neil Armstrong has just had heart surgery.  The reports suggest that he's recovering well, and cutting into your heart is almost routine these days.  But I couldn't help but be reminded of this old XKCD comic.

Wednesday, 8 August 2012

Shiny Dark Matter

A couple of months ago, I discussed a recent paper by Christoph Weniger that claimed strong evidence for dark matter from the Fermi Satellite Large Area Telescope.  In short, the Fermi LAT detects gamma rays, light of very short wavelength/very high energy.  Looking at gamma rays from the centre of the galaxy, Weniger claimed to see a feature in the spectrum:
Weniger's main result: black points are data with error bars; the green line is a featureless background; and the red line the combination of that and the proposed signal, shown in blue at the bottom.
Such a feature is difficult to produce by conventional astrophysics (stars, pulsars, etc).  It can be easily produced from dark matter.  For example if two dark matter particles annihilate into two photons, then conservation of energy and momentum forces those two photons to have the same energy, equal to the mass-energy of the dark matter.  Throw in the effect of experimental resolution and we get something that looks like the above, a small peak in the spectrum.

Since Weniger's original paper there has been a lot of work done.  In summary, this feature stands up to reanalysis but is not statistically strong enough to claim a true discovery.  Non-dark matter explanations have been offered, but are not compelling.  However, the dark matter explanation has problems of its own; the signal seems to be too big.

Thursday, 2 August 2012

Feynman Diagrams

In an earlier post, I talked about perturbation series, one of the most important tools in physics calculations.  In brief, there are very few problems in science that we can solve exactly.  Instead, we approximate the problem we have as a simple one that we can solve, plus terms that are "small".  The real solutions are the solutions of the simpler problem, plus an infinite set of corrections.

In that earlier post, I was pretty general.  In a sense this made things harder for me than necessary.  In particle physics, or relativistic quantum mechanics, there is a nice intuitive split between things we can solve exactly and things we can't.  The only problems we can solve exactly are non-interacting.1  We could only describe an electron exactly, if we turned of electromagnetism.2  The small numbers that we make our expansions in are the coupling constants.  For example, the natural definition of the charge of the electron is the through the fine structure constant,
$\alpha \equiv \frac{e^2}{4\pi\hbar c} \approx \frac{1}{137}.$
Here, e is the electron charge; h is Planck's constant; and c is the speed of light.

While the idea of a perturbation series is relatively simple, actually constructing one can be a bit tricky. The main problem is to ensure that you get all the relevant terms with the right factors.  This is where Feynman diagrams come in.  They are a concise way to construct perturbation series from a simple set of rules.  They can be easily coded into software programs, and a number of options exist.  And they have a really nice intuitive interpretation.

Saturday, 28 July 2012

Fingerprinting the Higgs

This blog post title stolen from Christophe Grojean and his collaborators.

With Thursday's mammoth Angband post finally finished, I figure it might be a good time to talk about physics instead.  And what better thing to talk about than what the theory community has been up to in the last three and a half weeks?  Yes, as expected there have been an abundance of Higgs-related papers of varying quality since the discovery announcement back on the 4th.  Thankfully, since many of them tread over similar ground I can cover multiple papers at once!

Thursday, 26 July 2012

Return to Angband

It's been a long time since I talked about a roguelike, hasn't it?

I do intend to get back to reviewing more examples of this fun class of games; indeed, I hope to get one of Crawl out soon.  That is not what this post is.  Rather, I want to go back and talk about Angband again.  I want to go into the mechanics in more detail than in my original post, and also offer some strategy and tips.  This will be the first post in a short series looking at Angband; if this goes well, I might give NetHack the same treatment.1

Before giving my own opinions, let me mention some other useful places to look around the web.  First off, the official forum is one of the best places to get information, strategy and reports of games.  The ladder can also be helpful; in particular, you can see what kind of gear winners tend to have.  You can also look into the spoilers, either in the /lib/edit/ subdirectory or online here.

Monday, 23 July 2012


A global super-rich elite has exploited gaps in cross-border tax rules to hide an extraordinary £13 trillion ($21tn) of wealth offshore – as much as the American and Japanese GDPs put together – according to research commissioned by the campaign group Tax Justice Network.
We all knew that tax evasion was a serious problem, but this is just fucking ridiculous.  Just what could we do with that money?1  How many hungry could be fed, how many sick treated, how many educations provided?  Pick your social worry of choice, and wonder what could be done with a little wisdom.  But no, it's more important that a billionaire keeps an extra million.

I'm reminded of a comment I saw a few years ago, in response to one of the standard cliches that asking the rich to pay their fair share is class warfare.  This is class warfare, launched by the rich, and right now they are winning.

1. Okay, in practice governments would probably blow it all on military hardware, but let me fantasize for a moment.

Friday, 20 July 2012

Climategate Crooks to Avoid Justice

As per the BBC:
The police investigation into the so-called "ClimateGate" affair is over. 
Norfolk Constabulary says there is no realistic prospect of finding the culprit within the statutory time limit of three years since the 2009 offence.
In a sense, the crime of hacking into people's emails is not that serious.  But the damage done by this theft and its resultant distortion by anti-science elements of the media could be severe.  How many people know that eight separate investigations exonerated the researchers?  (Even I didn't, I thought it was only three.)  Criminal prosecutions for those responsible might have served to send a message to those who try to twist science for their own political ends.

Tuesday, 17 July 2012

The Ontological Argument II: Anselm

This is the second article in a series of posts addressing arguments for the existence of any god or gods.  See my first post here.

Anselm was an eleventh century Monk whose version of the ontological argument may well have been the first, and in my experience is the best known.  At this point, I must reiterate a point from my original post: I am not a physicist, not a philosopher, so my opinions here are more that of the educated layman.  I certainly welcome comment on what will follow.

Monday, 16 July 2012

Branes! Branes!

Yes, it's a cheap and old pun.  I don't care.

I've mentioned how extra dimensions are one of the main ways particle theorists pad out their publication list conjecture new physics might arise.  But I spoke mostly in generalities, about the basic concept of more dimensions, and how it differs from the pop scifi ideas.  But there's lots of fun to be found in the details!

The idea of extra dimensions goes all the way back to 1921, when Theodor Kaluza suggested identifying electromagnetism as the gravitational effect of the extra dimension.  Five years later, Oskar Klein expanded on his idea, which is thus known as Kaluza-Klein theory.  More generally, the process of taking a five- (six-, etc) dimensional theory and figuring out what it looks like in four dimensions is known as the Kaluza-Klein expansion.  The specific model of these two men is no longer in favour, as it implies that electric charge and mass should be correlated (they are not).

Modern theories relevant to experiments like the LHC go back to only 1998, when Nima Arkani-HamedSavas Dimopoulos, and Gia Dvali proposed the existence of large extra dimensions.  They where inspired by string theory, so large means at most millimetre-sized.  This is still much, much bigger than the Planck scale; more to the point, it can lead to phenomena observable at current experiments.

British Science to be Free to All

From the Guardian:
The government is to unveil controversial plans to make publicly funded scientific research immediately available for anyone to read for free by 2014.
The specific approach is to require researchers to pay journals a fee upon acceptance of their work.  As I noted in an earlier post, at the moment Universities pay journals anyway, they just do it in the form of subscription fees.  So this move is a good one, and to be applauded in making science more accessible to the general public.

There are only two problems with this plan.  The first is that there are no proposed increases in the research budget; while this should be made up in reallocating existing University budgets, there's no guarantee of this.  A bigger one is that this constraint will only apply within the UK.  Hopefully it will bring pressure on other countries to follow suit; but as long as the UK is alone, it will effectively be subsidising the research of other nations.  (Many if not most journals present research from many countries, so they will still have to be paid for.)

Still, these drawbacks should not outweigh the benefits and, in any case, should only be temporary.  So I'll raise a glass to the government---for one day, at least!

Science is Not a Matter of Opinion

Over at Irregular Webcomic, David Morgan-Mar has an excellent piece about science and the scientific method.  Specifically he shows how science is not just another belief, and it's ultimately irrelevant if you think scientific conclusions don't make sense; only that they agree with, explain and predict experimental results.  To quote from his conclusion,
[Scientific theories] do not explain our world because a bunch of people believe in them. They do so because they reflect deep, underlying truths about how our universe works.
Go read the rest.

Thursday, 12 July 2012

A Little Good News

It's always good to celebrate the small victories in life:
A Mississippi judge has kept in place a temporary block on a law that could see the state's only abortion clinic close its doors.
Of course, the idea of there being only one clinic in the whole of Mississippi is hardly to be filed under "good", but at one is better than none.

This article from the Guardian, written before today's ruling, points out that the anti-abortion groups have gotten smarter.  They've more or less realised that outright evil actions---killing doctors, bombing facilities---don't actually win for them.  If they want to succeed in their goal to end women's control over their own bodies, they need to present things with a more reasonably facade.  Hence the law that is trying to shut down Mississippi's last facility claims to be about women's health.  Of course, in a sick sense it is; it's about making it worse.

There's a parallel to another cause celebre of the religious right, creationism.  The wedge strategy is an attempt to push religion into science classes under the fraudulent banner of academic freedom, much as this law pushes religion under the pretence of health.  The only good thing about that comparison is that the attempts to push creationism have failed; I'm not optimistic enough to think the same will happen in Mississippi.

Wednesday, 11 July 2012

The Ontological Argument I: Overview

In an earlier post, I discussed my path from moderate Christianity to atheism.  In that post, I talked about things that influenced me personally, but I did not get into actual arguments in much detail.  I think I'd like to do that, for several reasons including the opportunity to clarify my own thoughts on the matter.

This post will be the first in a series of posts, where I attempt to address as many of the arguments that are offered to support the existence of a god or gods as I can.  I am a physicist, so in many cases my position is that of an educated layperson rather than an expert.  Still, I hope to be able to say something new and accurate.  I also intend a parallel, and probably shorter, series of posts covering arguments against the existence of any gods.  The two sequences will be complementary, since a big reason for my atheism is simply that there are no good arguments to believe.

I'll start with Ontological arguments.

Tuesday, 10 July 2012

Approaching the Truth, Term by Term

When I was younger, I had an odd misconception about science: I believed it was all about exact expressions.

Part of the reason I though this was that textbooks would have these nice expressions, and it seemed obvious to me that they could be solved exactly.  Part of it is for the same reason I sometimes call myself a failed mathematician.  Part of it is undoubtedly the same reason so many of my students would quote ten significant figures in lab classes, when their measurements were only accurate to two.

The truth is, there are very few problems in nature that can be solved, even after making reasonable simplifications.  One important tool to get around this problem is the Perturbation Series, where instead of a simple exact result we have an infinite sum that, for practical purposes, is good enough.  In my field this is ubiquitous.  For example, the recent Higgs discovery is based on perturbation theory, in that the theoretical predictions for the rates of Higgs production where calculated that way1.

A Few More Thoughts on the Higgs

It's been almost a week since ATLAS and CMS announced their discoveries.  Even within the field, not much has changed.  What has is mostly a perspective; we have a Higgs, probably, so it becomes an input to our models instead of an output.  There have been a lot of new papers on the arXiv, especially this week, but the biggest splurge came with the hints last December.  So far I haven't seen anything really notable, though I'll admit I'm a bit behind on my reading.

What do we know about the discovery?  It looks very much like a we would expect.  The nice thing about the Standard Model is that when it comes to the Higgs, it is highly predictive.  All the relevant couplings relevant were known long ago; only the mass and the Higgs self-coupling were not predicted.  Now that we know the mass, we also know the latter value too, but this cannot be measured at the LHC.  When we compare those predictions to the data, everything more or less agrees.  Only the Higgs decay to two photons is not within the error bars, but the difference is still small.  The most interesting hint is that the decay to W bosons is small, but the Higgs-W coupling is also relevant for Higgs production, and the evidence there is consistent.  Of course, the fact that the differences are small won't and hasn't stopped people writing papers!

Wednesday, 4 July 2012


So.  The LHC has found something.

Watching the webcast now, CMS claims 5 sigma combining the diphoton and ZZ channels.  It looks very compelling.

Of course, there's some way to go to confirm that what's seen is actually the Higgs.  But all the different decay channels seem to match up as expected, within the errors.  It looks very Standard Model like.

Update: Nothing in ditau.  That might be interesting.

Update 2:  ATLAS comes in with 5 sigma excesses in the same channels, at the same points.  That's pretty much unequivocal.

The biggest thing missing is Higgs to WW.  Neither experiment saw much of an excess there, and that's the key to proving the new state is the Higgs, in that it is responsible for giving mass to the W and Z bosons.  Then, a longer period of measuring the fermionic branching ratios, and maybe the total width in the diphoton and ZZ channels.

Still, I think we can safely predict Nobels for the collaborations and/or Peter Higgs this year.

Tuesday, 3 July 2012

The Tevatron Higgs Announcement

The Tevatron today announced stronger evidence for the Higgs from its own searches.  There had been rumours that such an announcement would be made before the LHC likely claims discovery on Wednesday.

The Tevatron results are not enough, by the standards of the particle physics community, to claim discovery.  They are not even enough to claim "evidence", a lower standard where people tend to start getting excited.  But the results are very interesting and useful, even so.  A big part of this is because the Tevatron search channels are different to the ones currently used by the LHC.

Monday, 2 July 2012

Challenging Dimensions

It's time to talk about ... The Fifth Dimension! <Cue Tw- oh, I've already made this joke.

Yes, I want to talk about a popular model of theoretical physics that isn't supersymmetry: extra dimensions.  Actually, this is really three classes of models, with different motivations and features.  In subsequent posts, I will get into those details.  But here I want to talk about the idea in a very general context.

In my earlier post, I defined the number of dimensions of a thing as how many different coordinates you need to uniquely identify a point on that thing.  I contrasted the two numbers needed to locate a point on your computer screen, to the three numbers (e.g. longitude, latitude and altitude) to find a point near the Earth, to the four numbers to additionally specify the time an event happened.  So if there are five dimensions, then we would need five numbers to locate objects in space and time.

And yet, we seem to get by perfectly well with three spatial and one time coordinate; that was the very example I just used.  How can this be resolved?

Two Months

I finish my current contract on August 31st.

It always sneaks up on me.  Only two months left before I leave Vancouver and head for Melbourne.  Among other things, I need to start seriously packing.  But simply the realisation of how little time I have left here has made me suddenly sad.

Friday, 29 June 2012

The Role of Academic Journals

The Wellcome Trust intends to use its money to encourage open access science:
The Wellcome Trust plans to withhold a portion of grant money from scientists who do not make the results of their work freely available to the public, in a move that will embolden supporters of the growing open access movement in science. In addition, any research papers that are not freely available will not be counted as part of a scientist's track record when Wellcome assesses any future applications for research funding.
 As one of the major donors to scientific research in the UK, this is bound to have an effect.  I support this; science requires that knowledge is shared, so that advances can be checked and built upon by multiple researchers.  Repeatability is at the heart of the scientific method; while the possibility that anyone can contribute ensures both the highest level of scientific development, and protects science against cultural biases and blindspots.

The problem is the position of scientific journals as the gatekeepers of the knowledge.  Published work remains the gold standard for assessing a scientist's output.  The review process serves to catch and correct mistakes and omissions, and to check that a research paper says something genuinely original.  The journals in turn need funding to maintain themselves, so must charge a fee.  The low print runs mean that the cost of a journal is quite high, and if the work in a journal is freely available elsewhere, there is little incentive to buy them.

Good News, Everyone!

So to my surprise, the US Supreme Court ruled that Obama's health care plan was constitutional.  Apparently, the US Constitution does allow for the government to look after its citizens; who knew?

Dimensionally Challenged

Prepare yourselves, as I take you into ... The Fourth Dimension! <Twilight Zone Music>

Thursday, 28 June 2012

Why I Am an Atheist

PZ Myers over at Pharyngula has been running a regular series with the title of this post.  It's based on reader submissions, and each day he selects one at random.  With his readership he has a lot of submissions, so if I send this to him it might never get posted.  If only I had my own place to put my thoughts ...

My parents are not religious.  I'm not actually sure if they are agnostic or not, but we would only go to church for, in my father's words, "hatches, matches and dispatches": Christenings, weddings and funerals.  We didn't even hit Christmas and Easter.

Wednesday, 27 June 2012

How Constrained is Constrained SUSY?

It has become standard lore in the theoretical physics community that the fact that the LHC is already on the edge of ruling out Supersymmetry (SUSY).  The reason is quite simple: the standard argument for SUSY, the hierarchy problem, would suggest that the supersymmetric partners (superpartners) of the Standard Model should have masses less than about one thousand GeV (where the proton has mass of about one GeV).  The LHC has not found those partners, and has published exclusion plots like this one:
ATLAS LHC limits on Supersymmetry; stolen from Michael Kobel's talk at Planck 2012.
The different coloured lines correspond to the limits from different types of signals that could have been seen.  The areas below the lines are ruled out.  The coloured regions were either ruled out from earlier direct searches or theoretically.  The grey dashed lines correspond to superpartner masses in GeV; horizontally for the gluon superpartner, vertically for the quark superpartners.  Note that the regions for masses less than one thousand are almost entirely within the excluded region.

Now, there are a number of caveats, and a lot of work has been done in the last year to eighteen months exploring ways to get around these restrictions.  However, a recent paper by Balazs and his collaborators went back and examined the simplest situation more rigorously, and suggested that the LHC results have not actually had that much effect on the allowed parameter space.  How did they conclude this?  Join me below the fold!

Tuesday, 26 June 2012

The Good and Bad Side of Finding the Higgs

In a previous post, I commented
Of course, in some respects it would be more interesting if those hints are wrong and there is no Standard Model Higgs ...
I thought I'd expand on this a bit.  You see, the LHC is a multi-billion dollar, multi-national enterprise.  Finding the Higgs would justify the whole endeavour, and should ensure funding for the next round of experiments, be it a linear collider, muon accelerator or whatever.  So why would I want there to be no Higgs?

Monday, 25 June 2012

Italy 0 - 0 England

So, as I predicted before the tournament began, England fell at the last eight.  I've also explained previously why that's not a very bold bet.  In the end, the old failings doomed us; an inability to keep possession or take penalties.

As for the game itself, few of England's players performed well.  Rooney looked consistently off the pace and lacking match practice (as he is).  Young had another bad game to round out a bad tournament for him.  Gerrard has had a good tournament, but didn't do much tonight.  England's back five did manage to show up.  Johnson in particular put in another excellent performance to justify his place in the team, and had probably England's best chance of the match early in the first half.

For Italy, Pirlo was unsurprisingly the maestro, pulling all the strings.  Balotelli was unpredictable, but ultimately ineffectual.

The problem I find is that as much as I don't expect England to win games like this, I do hope that they might.  And that hope, that stake makes watching them play very tense.  Indeed, I had to pass on the shoot out, and just look up the result later!

Saturday, 23 June 2012

Higgs Discovery on the Horizon?

A CERN press release confirms what I think most people in the field expected:
CERN will hold a scientific seminar at 9:00CEST on 4 July to deliver the latest update in the search for the Higgs boson. At this seminar, coming on the eve of this year’s major particle physics conference, ICHEP, in Melbourne, the ATLAS and CMS experiments will deliver the preliminary results of their 2012 data analysis.
 If the hints of a Higgs that were seen in last year's data are true, it is likely that this seminar will serve to announce that fact.  This would be the first discovery of a new fundamental particle since the top quark in 1995, and would essentially justify the LHC.  Exciting times!  Of course, in some respects it would be more interesting if those hints are wrong and there is no Standard Model Higgs ...

Friday, 22 June 2012

Atheism and Feminism

One of the hardest lessons I ever had to learn was that just because someone agrees with you on one thing, no matter how important that thing is, doesn't mean they can't be a complete shit in some other way.  And even knowing this doesn't stop it being disappointing when it happens.  I bring this up because I want to talk about the arguments that arose out of ElevatorGate in the skeptic/atheist community over the last eighteen months or so.

Now, after all this time I don't have too much to add to the substance of the "debate" itself.  From the links to the right, it should be easy to see that I come down on the side of Rebecca Watson and her allies in the whole affair.  Really, I want to focus more on the fact that so many self-professed atheists proved to be uninterested or even hostile to feminism from a personal perspective.

Wednesday, 20 June 2012

Brought to You by the Letter S

Ah, Supersymmetry.  I've been meaning to talk about Supersymmetry, or SUSY for short, for some time.  I was obviously setting things up in this post from almost a month ago, back when I was in England, but I've been planning this post for longer than that.  SUSY is the most popular theoretical framework for new particle physics, and as much as I'd like it not to be true, I need to worry about it all the same.1

England 1 - 0 Ukraine

Sadly, I wasn't able to see the last match of the group stages, because I'm at work.  So I can't offer any meaningful thoughts on the game itself.  But we see that England have qualified for the quarter-finals, as I predicted, and won the group, as I did not.

In the build up to the tournament, there was a lot of pessimism about England's chances.  In particular, many people seemed to predict that they would fail to make it out of the group.  My prediction was bold in that it went against that consensus, but conservative in that it followed history.  In the nine European Championships since the finals were expanded to eight teams, England have reached the last eight six times; only Germany, the Netherlands and Spain have a better record (and France and Portugal an equal one).  The problem with England has always been getting beyond that stage, which we only managed in 1996.  The five other teams I mentioned have all made the semi-finals at least three times, with the exception of Spain who only managed it twice (again, only counting finals since 1980).  In short, getting to the quarter-finals is the "typical" English performance.

Saturday, 16 June 2012

Sweden 2 - 3 England

Well, that was an unexpected game.  Weren't England under Hodgson supposed to be stogid and boringly defensive?

While this game must have been fun for the neutral, it was nerve wrecking to watch with a horse in the race.  Sweden become the second team to be eliminated from the finals, somewhat unluckily as they lead in both their matches so far.  England, meanwhile, go into their last match with their destiny in their hands.

Friday, 15 June 2012

The Falkland Islands

I was not even two years old when Argentina, then under a military dictatorship, invaded the Falkland Islands.  Today has marked the 30th anniversary of the end of that brief conflict, which ended with the  islands remaining under British rule.  As such, I have no understanding of how things were at the time even in the UK, or controversies such as the sinking of the Belgrano.

The anniversary has seen tensions between Britain and Argentina rise.  It's sad to me, but also somewhat annoying.  Today, the Argentinian president has demanded that Britain enter negotiations over the island's sovereignity:

Thursday, 14 June 2012

Ignorant Commentators

I've been watching the Germany-Netherlands game on TSN, and the commentator has on several occasions talked about the importance of goal difference.

The first tie breaker in European competitions is head to head results.  In particular, in the relevant cases for Group B---where Germany, Portugal and Denmark end on 6 points; or the Netherlands, Portugal and Denmark on 3---the scoreline in this match will only be relevant if either Denmark beat Germany 3-2, or the Netherlands beat Portugal 3-2, and the other results go appropriately.

I mean, this is only the way UEFA has done things for at least a decade, I can see why it might be hard to figure out.

Another Christian Whining About Persecution

While looking up the news article I commented on in my last post, I came across this little gem:

A Kent GP has accused medical watchdogs of persecuting Christians after denying trying to convert a patient.
He is before the GMC accused of breaching medical rules by refusing to give a patient medication at his Margate surgery, in August 2010.
I guess in honesty I should point out that the accused, Dr Richard Scott, is still being tried.  But he is definitely guilty of magical thinking:
He told the council scientific studies, mainly carried out in the United States, showed faith benefited patients.
"Spirituality and faith is now becoming a new angle with medicine," Dr Scott told the hearing.

Marriage Again

Oh look!  It's another group of Christians complaining about gay marriage!

The Church of England has warned that proposals to legalise gay marriage could undermine its status.
It says giving civil ceremonies the status of marriage would "alter the intrinsic nature of marriage as the union of a man and a woman".

What intrinsic nature?  Marriage is a human construct.  Historically it has been about inheritance and property rights, and polygamous marriages have been common.

...the Church of England said government proposals to allow same-sex marriages by 2015 would "alter the intrinsic nature of marriage as the union of a man and a woman, as enshrined in human institutions throughout history".
It said marriage acknowledged "an underlying biological complementarity which, for many, includes the possibility of procreation".
So, obviously, any heterosexual couple who get married and don't intend to have children are wrong to do so.  For fuck's sake, do these people ever think about what they are saying in their rush to be homophobic?

England 1 France 1

I know I'm a bit late, but I thought I'd comment on England's Euro 2012 opener.  In general, I though England's performance was okay; not great, certainly room for improvement, but not bad either.  In particular, it was good to see England play like a team rather than eleven individuals.  I also thought Gerrard had one of his better performances in an England shirt for a while.  Defensively, England were pretty solid.  Despite the French dominating possession, they had few real clear chances and only scored through a moment of brilliance from Nasri.  Offensively, England did not show too much but did have probably the best chance of the match, when Milner was put through by Young.

Conference Talks

I've been in Calgary since Sunday, and most of my time has thus been spent either listening to talks or writing my own.  Sadly, this means all I've seen so far is the University, though I will have time to do some proper exploring before I return home.  The one nice thing about this conference has been the weather, especially compared to the same conference last year or even Pittsburgh in May.

Friday, 8 June 2012

Euro 2012

The European Championships start tomorrow (in my time zone).  I've been looking forward to this for some time; for one thing, international tournaments are easy for to find (legally) online.  (In contrast, my home team -- Plymouth Argyle -- aren't easy to watch regularly in Vancouver).  Also, the last European Championships four years ago was one of the best tournaments I've ever seen, only beaten by Euro 96 for personal reasons.  So, with everything about to kick off, I thought I'd offer a few predictions to embarrass myself with later.

Tuesday, 5 June 2012

Cubic Zirconia

This year is the Queen of England's Diamond Jubilee.  Right now, more or less, are the main celebrations.  Despite being British, I really don't care.  Indeed, I am a republican, in the sense of being opposed to monarchies.  There is simply no reason to raise some family as special simply on the grounds of their heredity.  There's no magic that makes the Royal Family intrinsically bettter than me, or anyone else.

Back in Canada

My long trip has finally ended, and I'm back in Canada.  This should mean that I have no more excuses not to get back to things I've neglected, like this blog.

I am still quite jet lagged, despite having been back for two days; there's a nine hour time difference between Warsaw and Vancouver, and I'm too old to shrug that off, it seems.

I will be off to Calgary next week, for another conference.  This one is more general physics, rather than particle physics, so I expect to have more free time (in the form of skipped sessions).  In theory, this means that I'll be able to update with some regularity then!

Friday, 25 May 2012

Mirror, Mirror, On the Wall

One of the most useful, general tools in physics is symmetry.  To a scientist, a symmetry is any change we can make to reality that is undetectable.  For example, if I moved the entire universe five metres to my right, how would anyone know?  All we can measure are the relative positions of objects, e.g. the Earth relative to the Sun.  If I move the everything the same amount, then relative locations are unchanged.  This is then a symmetry of nature.  Hopefully, it is clear that there is nothing special about the distance and direction I chose; all such shifts are unobservable.

Why is this helpful?  The key lies in Noether's Theorem, named after the German mathematician Emmy Noether.  This states that whenever we have a symmetry in nature, there is a conserved quantity associated with it.  Conserved quantities make our lives easier, since they simplify calculations.  Amount in equals amount out is a pretty easy expression, after all.  (Not all physics demands advanced mathematics!)  For example, the symmetry I mentioned in the previous paragraph leads to conservation of momentum, while the fact that physics is constant in time means energy is conserved.

Sunday, 20 May 2012


I'm planning another post on a recent research paper, but in preparation I want to talk about statistics.  Specifically, I want to talk about Frequentist versus Bayesian perspectives for the interpretation of experiments.  I won't get technical, or go into the actual details about how calculations are done, but rather talk about philosophy.

My casual impression, based on reading papers to stay abreast of the field, is that most experiments use Frequentist methods in analysing their data.  In this approach, discovery of new phenomena is based on disproving the null hypothesis, the assumption that there is nothing to discover.  In this sense, Frequentist methods are very Popperian.  Frequentists will argue that this ensures their methods are objective, which is more or less true.1

The problem with Frequentism is that it has a tendency to be misinterpreted.  For example, let's say in a particular experiment we can exclude the null hypothesis at 95% confidence level.  What does that mean?  It is tempting to interpret it as saying that there is a 95% probability that the null hypothesis is false.  However, this is wrong.  The strictly correct statement is: if the null hypothesis is true, the probability of getting this experimental result is 5% or less.

The Trouble With Travel

This little corner of the internet of mine has gone quite quiet for the last couple of weeks.  The reason is simple; I've been travelling, and between the travel time itself, the jet lag and the things I've been up to at the places I've visited (conferences, meeting old friends) I've been unable to find the time to write anything worth publishing.

I'm currently in a relatively calm period, where I'm spending two weeks in the same place (visiting family).  So I hope to get back into a somewhat regular publishing schedule for the next week.  After that, I'm off to Warsaw for another conference, followed in turn by conferences in Vancouver and Calgary.  So I likely will be posting rarely during those three weeks.

Monday, 7 May 2012

Hollande wins French Presidency

I haven't said anything about the French presidential elections, not least because I know little about French politics.  However, the election of a socialist president for the first time in 24 years will be interesting.  According to the BBC, Hollande describes himself as a moderate and was praised by former conservative president Jacques Chirac.  Of course, this is France; Hollande has proposed a 75% upper income tax bracket (to apply to incomes above one million Euros).

I don't describe myself as a socialist, but I do tend to broadly align with socialist economic opinions.  So I'm tentatively welcoming of this result.  In particular, I hope it will encourage a reconsideration of the politics of austerity that have hit Europe in recent years.  Times of economic recession are exactly the times that governments would be expected to run deficits.  High poverty and unemployment mean that welfare spending should increase, while low tax returns cut government income.  To be sure, too much government spending can lead to excessive inflation and make things worse.  But I think things have swung too far against this.

Of course, ignoring Hanlon's Razor it's easy to believe that this is deliberate.  The push for austerity and tax cuts by the IMF and other organisations seems tailor-made to benefit powerful corporations and wealthy individuals, at the expense of the poor.

Sunday, 6 May 2012

Dark Matter Found (or not)

So earlier this week I offered a brief overview of the Dark Matter problem.  (See also the Font of All Knowledge for more.)  Today I want to talk about a paper from two weeks ago relating to a possible discovery (or more accurately, hint of a signal).

Now, this is far from the first time such a hint has been found.  The DAMA experiment is perhaps the longest-standing claim of discovery; that question, and why it's not widely accepted, is a whole blog post in itself.  I want to start with this one because it is recent, and also most closely related to the work I have done in dark matter detection.

The Heartland Institute Climate Denial Ads

Yesterday, the Heartland Institute put up some billboards comparing Global Warming to mass murder:

Thankfully they've already taken them down in the face of a torrent of criticism.  But I couldn't comment on this yesterday, I was too angry and needed to calm down.

Wednesday, 2 May 2012

The Dark Matter Problem

One big and as-yet unanswered problem in modern physics is the dark matter problem.  The problem is astrophysical: a number of observations, from galactic to universal scales, show a difference between the mass distributions observed directly (in visible stars, galaxies etc) and indirectly (through its gravitational effects).  As the name of the problem suggests, it looks as though there is a lot of extra matter that we can't see (because it's dark).

The canonical example of such an observation is also the first one made (by the brilliant but prickly Zwicky), that of galactic rotation curves.  In particular, let us focus on objects (stars, globular clusters) orbiting a galaxy but not really part of it.  We are in the limit of weak gravitational fields and small speeds, so Newtonian mechanics is adequate.  The gravitational force due to the galaxy drops off with the standard inverse-squared law:
$F = \frac{G M m}{R^2}$
Here, G is Newton's constant; M and m are the masses of the galaxy and the object orbiting it, respectively; R is the distance between them and F the force.  Using Newton's second law of motion gives us the acceleration:
$a = \frac{G M}{R^2}$
Lastly, we use the relation between acceleration and velocity for objects moving in a circle:
$a = \frac{V^2}{R} ; \therefore V = \sqrt{\frac{G M}{R}}$
The main point is that we expect the speeds of objects orbiting a galaxy to decrease as they get further away from it.  We can extend this for objects within the galaxy itself, but then we need to take the finite size of the galaxy into account.  The result is that we expect the orbital speed to increase with distance within the galaxy, then decrease with distance outside it.

What we see looks like this:


Obama has pledged to end the war in Afghanistan.

Presumably the same way he closed Guantanamo.

Monday, 30 April 2012

Religious Schools and Bigotry

The UK has seen a noticeable push towards state support of religious schools over the last ten years or so.  I don't want to get into the various economic reasons that underlie this; the point is that government-supported schools should be welcoming to all citizens.  And as we all know, if there's anything known for being open and welcoming, it's religion:

It emerged this week that the CES wrote to nearly 400 state-funded Roman Catholic schools inviting them to back a petition against gay civil marriage.
Earlier this week, reported that students at St Philomena's Catholic High School for Girls in Carshalton were "encouraged" to sign the anti-equality pledge by the school's headmistress.
I'm sure that gay and lesbian students will feel right at home!  Certainly, we shouldn't let our concerns for them get in the way of Catholic's right to advocate for traditional marriage (one man and one or more chattel).

The only good news about this whole thing is what the bigots are opposing; full marriage equality, which is being introduced by our main Right Wing party.  Even the Conservatives have figured out to get on the correct side of the issue.

Also, only tangentially related but it really pisses me off when people try to justify bigotry with religion.  If I believed in a god with such a flawed morality, I wouldn't worship it.  Indeed, the fact that so many religions depict their god as a ethically primitive barbarian really makes me wonder.  Am I supposed to be impressed?  Really?

I'm Really Not Dead...

I know, I know, I promised something new almost a week ago.  Still, between the travel plans, shifting money around so I can afford the travel, trying to get something sufficiently finished to talk about at conferences, and writing my talk, I've been quite a bit busier than normal.  If anything, I might actually be less busy once I'm actually travelling; we'll see.

Still, I will try to post more regularly, starting today.

Tuesday, 24 April 2012

I'm not dead ...

Only resting.  I'm busy with large stacks of papers to read and travel plans to finalise.  But I should be able to get something substantial up tomorrow.

Wednesday, 18 April 2012

Last Flight of the Shuttle

The Discovery has made its last flight, on its way to the Air and Space Museum.  Much has been written about the end of the Shuttle program.  To me, the sadness is not the end of the program, but the lack of anything to directly replace it.  And I'm looking forward to seeing it in reality, too.

I wish they could have delayed this flight till I'll be in DC in a couple of weeks, though!

Tuesday, 17 April 2012


Today's been one of those days.  Little accomplished, certainly nothing I planned to get done.  In fact, it feels like I've gone backward thanks to finding an error in a calculation I did last week.

At times like this, when the world seems set against you, there's only one thing any self-respecting Englishman can do.  Make some tea.

Monday, 16 April 2012

Majorana Fermions

A Dutch team of researchers are claiming to have seen evidence for the existence of Majorana fermions in superconductors:
Majorana fermions are particles identical to their own antiparticles. They have been theoretically predicted to exist in topological superconductors. We report electrical measurements on InSb nanowires contacted with one normal (Au) and one superconducting electrode (NbTiN). Gate voltages vary electron density and define a tunnel barrier between normal and superconducting contacts. In the presence of magnetic fields of order 100 mT, we observe bound, mid-gap states at zero bias voltage. These bound states remain fixed to zero bias even when magnetic fields and gate voltages are changed over considerable ranges. Our observations support the hypothesis of Majorana fermions in nanowires coupled to superconductors. 

(That's the paper's abstract).  I originally read of this at a reasonable article over at the BBC, but I felt there were a few things I wanted to say.  One thing that could easily mislead the lay person is that Majorana fermions are far from the first particle to be its own antiparticle.  Photons, the particle of light, are a simple example.  Rather, Majorana fermions are there own antiparticle and have not been discovered yet.

Friday, 13 April 2012

The Hierarchy Problem

I've got several drafts in progress, but none of them look like getting finished soon and I wanted to get something substantial out today.  So I thought I'd talk briefly about an important concept in theoretical particle physics, the hierarchy problem.

The Big Lie

Personal Headphones.

If you're going to claim the right to listen at volumes I can hear on the opposite side of the bus, I'm going to claim the right to beat you round the head with a nine iron.  Or at least not pay for your hearing problems later in life.  I'm just saying.

Thursday, 12 April 2012

The Theorist's Pleasure

So you're working on a physical problem, and you need to calculate some physical quantity.  So you sit down to start writing, and it's soon clear that this is going to be a tricky calculation.  But that's no reason to quit; you are confident you can overcome any challenge.  So you keep going, but the intermediate expressions are getting long and unwieldy, and you are faced with the question of errors.  It begins to occupy all your thoughts, and you work to seek and implement checks to catch mistakes.  When you do, you feel frustrated and return to hunt them down.  When you don't, you can only feel temporary happiness because you must press on in search of the goal.

As things continue, you hit that crucial point where expressions start to simplify, rather than the reverse.  With the end in sight your anticipation of success grows, but you must control yourself, holding back to avoid going of prematurely and letting a mistake slip in.  But the emotional excitement grows, as the hours, days or even months of work look to pay off, line by line as things simplify till, finally, you get to spurt out the result in a short, beautiful expression...

Then, afterwards, you feel really mellow and relaxed.

Wednesday, 11 April 2012


A couple of weeks ago, I talked about Angband, my introduction to Roguelikes and the iconic *band.  However, the most famous descendent of Rogue is probably NetHack, which is derived from Hack and is the iconic Hacklike.  It is renowned for the huge number of item interactions, powered by a flexible and powerful control system.  As a simple example, in Angband, the only things you can equip as weapons are actual weapons---swords, maces etc.  In NetHack, you can equip anything as a weapon; and there are times when you'll want to.

I'll be honest.  I'm not a huge fan.