Tag Archives: Physics

Physics and the Earth

As I delve deeper into the context of the physics I’m doing at the moment, all I seem to find is more and more information about the really serious state that the oceans are in.   I’m not sure whether this is just because I automatically hear much more about it now that I work in this field, or because it’s finally getting the much-needed press and so this stuff is being found out in the public sphere more and more.

In one way, I’m lucky because at least the physics I do is contributing to knowledge of the way the earth’s systems work, and in that sense I feel that I’m at least doing something positive about this issue on a daily basis.   Bubbles are at a crucial place on the boundary of the ocean and atmosphere and better knowledge of how many there are and where they are can only improve our understanding of the exchanges between these two great reservoirs of air and water.    On the other hand, all this will have a benefit a long way in the future (it’ll probably be ten years before models that incorporate this sort of data are really being used regularly), it seems that there is less I can do on a daily basis.   I choose stuff in the shops that has travelled as short a distance as possible to get there, I limit travel by car as much as possible, I don’t buy stuff I don’t need (like silly plastic toys that are only going to get thrown away), and I try to be aware of the consequences of my choices in life as much as possible.   I truely believe that all of those are important things to do.   And many people could do more of them and I could do better – it’s all dependent on the availability of information and the availability of real options.

However, I also feel that as a scientist, there should be more I can do.   After all, I understand the issues better than most people, because it’s part of my job to do so.   I understand how science works and how the evidence leads to these conclusions.   I have spent time in the oceans, and I’ve seen some of the effects of environmental changes (and I can imagine more).   Maybe I need to have more patience, and I’ll see places to do something extra soon.   But I feel that one of the biggest motivations for really changing your life to at least stop the problems getting worse, if not to start to reverse the recent trends, is knowledge and understanding of what is happening.   Really understanding it, not just looking at a picture of an ice floe and thinking “well, that won’t be there in the Arctic in the summer in ten years time”.    People really need to understand what it is that has been done, and then very quickly get over most of the anger and sadness that this knowledge causes and move on to actual changes that can be made.   Many of them are personal and they start with better informed consumers and voters.

Some days, when physics is a hard thing to do, when there are tough deadlines and a lot of responsibility for creating my own projects and direction, and when I’m floundering in new understanding of something, I wonder why I do what I do.     And then I realise that I’m one of the few people that really has a unique role here, to communicate what is happening from direct scientific knowledge and to convince people that these changes to their outlook and lifestyles really are important, and that they do make a difference.   There needs to be a connection between the scientific facts and the individuals whose actions have caused those facts.   And that divide should be bridged by a scientist.  Maybe people don’t really think about physicists as being those who are working in this area, but there is as much physics in all this as biology and ecology and chemistry.   I think that all scientists should do what they can here.   Just understanding how science works is something that you can try to share with other people, which may help them digest the information about the environment in the news.

If you’re interested, a great place to start informing yourself about ocean-related issues is the Shifting Baselines project and also the blog below:

http://www.shiftingbaselines.org/index.php

http://scienceblogs.com/shiftingbaselines/

And number one thing (in my opinion) on the list of “things that you could change but you probably don’t really know about” is to think very hard about any fish you may eat.   Overfishing is causing tremendous damage to the ocean, not just because of the removal of fish but because of the massive habitat destruction that dredging causes.   There are some fish that are still sustainably harvested, and try to find that out.   In the UK, I’m not sure about the best sources, but the Monterrey Bay Aquarium has  a great website with recommended alternatives to some of the fish that are found in the US:

http://www.mbayaq.org/cr/cr_seafoodwatch/sfw_sushi.aspx

I think that physicists really have a role to play here…   I took a course called “Systems” in the third year of my undergraduate degree, and the much of same thinking really applies to environmental phenomena.     We may feel that because our academic work doesn’t relate directly to environmental stuff, we are not in a position to talk about it.   But sharing our understanding of science itself is really invaluable.

Where’d You Get That Supercollider Shirt?

I was skimming an old review of the Coachella Festival today and I couldn’t help but notice that a singer from the band MGMT was wearing a Supercollider shirt on stage. The Superconducting Supercollider was a proposed hadron collider in Texas, and was cancelled after about a quarter of the the tunnels were dug due to US federal budget limitations. It would have been bigger than the LHC, explored higher energies, and been running by now, but so it goes. Construction started in ’91 and terminated in ’93, so that’s probably when the promo shirts were made. I’ve got one too, which I discovered in a box in the server room in at the Pheno Institute in Madison a few years ago. I keep it in a nitrogen vault to preserve it, and mostly only wear it to conferences. I’ve been debating scanning it and getting it reprinted or recreated, just ’cause its so ridiculously awesome.

Particle Flow Calorimetry

I took a break today from thesis writing to attend the weekly computing seminar, since it had calorimetry in the title, which should supposedly be one of my skills. The slides aren’t posted yet, but whenever they are you can find them here. Mark Thomson was the speaker, who also has a few papers out on the same subject on the web, this one seems to have the most overlap with the talk.

The idea goes a bit like this: If you want to test new physics at a collider, you need to measure collision products very carefully. Specifically, testing electroweak sector models (all this higgs hubub) requires identifying and differentiating Z and W bosons real well. Single production Z and W’s both decay in to quark-antiquark pairs. We can’t see quarks in detectors directly, but we observe sprays of particles called jets which have basically the same energy and direction, etc. So they want to measure jets real well at the proposed and under-development International Linear Collider (ILC), and the main technique to do this that they are trying to develop is called Particle Flow Calorimetry (PFC).

Continue reading

NeuroBayes: Sometimes sans Neuro

I went to the weekly computing seminar yesterday, because it was on a statistical data mining tool that is being simultaneously used by physics experiments and marketing firms. The speaker is a physics professor, used to work for the PLUTO Collaboration, DELPHI, and now is variously associated with CDF and CMS. The company, Phi-T, is now totally private, and employs a couple dozen ex-physicists, or physicists, depending on how much of a purist you are. The software is proprietary and closed source, and the speaker was severely vague about what specific tools were actually used, but there is an interface in C++/ROOT/C#/Lisp already made, so its (supposedly) trivial to use, with a discounted academic licence.

So what is it? Basically, you have a vector of measureables, like detector channels, and some target, like say Resonance mass. Or Age, profession, #kids, and your target is “How much will this person cost us in Health Care in the next n years.” You then train the thing on your historic or simulated data, and it generates Bayesian posteriori distributions for new data. This is pretty common in neural computing literature, but this thing seems actually practical.

The only really fascinating thing is the generality of the thing, which was (supposedly) applied with minimal expert consultation on problems like car insurance premiums, to B_s mixing at CDF. Here’s a list of referred journal articles with their stamp. So whats inside? A neural network you say? No! The guy said in most applications they skip the neural net entirely and just use “Other” statistical methods. It’s clear that he was using some kind of input decorrelation like principle component analysis, but he wouldn’t say what specifically. He used a bunch of phrases that were cryptic to me like “zero layer network” to mean something other than a perceptron (I asked), and “zero iteration training” of a network. Maybe these things mean something to yall statters, but nothing to me. Anyways, the output of whatever was a discretized probability histogram that got splined together.

I’m unconvinced that the “default settings” he mentioned could schedule re-stocks for the largest book distributor in Germany AND find the X(3872) resonance, but what do I know? He also said that the companies own stock were controlled by this thing, but that selling it for this purpose is somehow illegal. Anyone know what he was talking about? Here’s a paper on it, by the speaker.

In the end, the talk was a sales-pitch/head-hunt, but if anyone out there needs to solve a highly nonlinear problem and has a cushy grant, go nuts.

Download Hermann Weyl’s 1919 Book For Free

If you speak German, and like science history, you can download Weyl’s 1919 Zeit, Raum, Materie book in PDF for free from The Internet Archive. I wanted a sort of journalistic, “this is how it went down” kind of book, but that doesn’t seem to be the case. There’s some nice first person stuff in the forward, and some nice philisophical musing at the end, but mostly is seems textbook stylie. I just skimmed it a bit, so maybe the gems are buried deeper.

If anyone can find anything on his early attempt at gauge invariant therory of unified electronmagnetism and gravity, I’d be grateful to hear from you.

You can also check out a collection of original papers on Relativity from before 1920, too. These are all translated into english.

The end of the affair….

I’m part of a collaboration that built and operated a particle detector at a collider which finished taking data in July of last year. I wasn’t here to build it by a long shot, but I did run and repair part of it during last two years of data taking. Now I’m only analysing data for my thesis, not doing any hardware work anymore, and I’m finding its a mixed blessing. Continue reading

Generalized PDFs Imply a Gravitomagnetic Moment!?!?!?

Today I’m writing conference proceedings, which are boring me to write, so they will probably be inhumanely boring to read, and lethally boring to publish. I may try to write them so the first letters spell out a hidden message, just to stay focused.

Part of the way I’m constructively procrastinating is skimming a review paper on Generalized Parton Distributions. They’re a pretty cool idea. So QCD can’t be perturbatively calculated at arbitrarily soft scales, so nobody knows how to directly calculate from first principles whats happening inside of hadrons. The lattice folk are making progress here, but that technique takes a lot of power, so those calculations can’t easily get incorporated into general calculations.   You can parametrize what’s happening in a hadron, measure it, and the factorization theorem tells you your resulting functions are universal, modulo an evolution of the factorization scale. So we can measure parton distributions functions here at HERA, and then you can roll them up to the LHC/TeVatron scales or down to a fixed target, and everyone agrees on what these functions are and do. If you are operating at first order, the vanilla type of PDFs naively tell you what the probability of finding a quark or gluon of a certain type and certain longitudinal momentum is. At higher orders the interpretation isn’t so clear, but they still return a real scalar. There’s no interference, no helicity, no transverse momentum. You can tack on spin or other stuff, but its always a bit of a blunt object.  How the proton gets its spin out of the quark-gluon shimmy is still a big mystery, so theorists have been experimenting with difference ways to combine PDFs and form factors, to include interference terms, and understand all components of nulceon spin. The situation is stabilizing a bit, and this paper seems to imply that the parameterization they describe is widely used.

I got a bit shocked by the following couple of lines:

…according to an extension of the equivalence principle of general relativity to describe the interaction of the nucleon with the external gravitational field one arrives to the interpretation of B(0) as an anomalous gravitomagnetic moment being the analog of the anomalous magnetic moment [47]. There is also evidence supporting the conjecture that the equivalence principle is valid separately for quarks and gluons resulting in exact equipartition of momenta and angular momenta in the nucleon. The most precise numerical support comes from lattice calculations [48].

AH!  What!!?!?!  Who said anything about gravity!?!?!  But it’s not really what it looked like at first glance.  B(0) is zero, btw, so whatever you want to call it is moot, but the cool thing is that [47] paper, where the author sees a relationship similar to the equivalence principle, and this cancels out that B(0) thing at all orders.  I can’t do GR, so I can’t comment on the validity of the approach, but its a cool idea…..