IP 1.4: Beginning strings

Some of the content I covered this week focuses on string theory and not really in a popular science context. You would need a decent understanding of particle physics at the least to get something out of these lectures, some of them you'll need much more knowledge. Nevertheless here's what I've been absorbing (trying to) this week gone.

'The State of String Theory' - Brian Greene (2008?)

Greene is a well known proponent of string theory but this lecture is different from the theatrical pop. sci. he is often known for. A review of the field at the time is present, bare in mind the Higgs hadn't been found yet and low energy SUSY wasn't ruled out yet either.

Greene is confident but at the same time fairer than some string theorists are about the merits and current deficits of the theory. The content doesn't dive too deep, I understood pretty much everything without having formally studied the subject. He can come across as a bit cocky, but plenty of theorists do. His dismissal of LQG didn't exactly sit well with me, he basically said that he hadn't read much about it but didn't like it anyway. But I'm biased here so take that for what you will, I just think one should be open to approaches outside their own.

I found this a really good introduction to strings pre-LHC findings, its by no means an introduction to the mathematics and mechanics of the theory but gives you an idea of current research. Worth a watch for anyone wanting an idea of what's being going on in strings.

String Compactifications (Lecture 1) - Edward Witten (2008)

If the previous lecture was an introduction this is pretty much the exact opposite. I'd be lying if I said I understood more than 50% of this conceptually... probably a lot less, lets not even make an estimate for mathematical understanding. Witten strikes me as very humble and to the point, he gets straight to it and doesn't let up. In spite of the dense mathematics he regularly contextualises the working in particle physics with relation to the underlying group structure of the standard model and GUTs. With my conceptual understanding of differential geometry I was able to get through most of it without feeling completely lost.

I think more importantly for me it was an absolute blast to watch. When a physicist wins a Fields Medal (the only one ever to do so)... you should definitely watch them lecture at least once. Witten is also a really strong speaker, very clear and calm, which gives you the best opportunity to (try to) understand what he's talking about. If you love particle theory, just do it.

Newton Medal Winner (2010) - Edward Witten

This 30 minute interview is interesting, seeing a bit of the life and research history behind one of the biggest names in string theory. Witten (again) speaks very clearly and you can see that he carefully considers what he's saying. But more than anything his humility and causality comes through, he seems very human though un-relatable due to the lightness with which he speaks of his enormous achievements. If you want to see the more human side of particle theory I'd definitely suggest watching this.

'Why Meat is the Best Worst Thing in the World' - Kurzgesagt

Let's preface this with my own relevant opinions: I do eat meat, I don't eat a lot of it though and I am conscious of the impact eating meat has on the environment and animals. At the same time I am also sceptical of a lot of arguments for veganism, less so for vegetarianism.

This is a nice summary video that I feel is relevant for those on either side of the debate. But this isn't so much about whether eating meat is right or wrong and more about the impact of eating meat and what we might do about it. They make a statement I very much agree with, "Eating meat doesn't make you a bad person. Not eating meat doesn't make you a bad person."

They mention the fact that almost all male chicks are slaughtered very soon after birth, the energy efficiency of certain animals etc. The main issues and concepts they covered also feature in the documentary "Before the Flood". It would have been nice if the video also covered some more concrete reasons to carry on eating meat other than enjoyment and social reasons, nutritional value etc. I also thought they could have covered fish as well, though maybe that's enough of an issue itself to be featured in another video. If you're new to this subject I'd suggest reading more widely to supplement this video.

IP 1.3: Black Holes and Pop. Sci.

Sorry for this being a day late, a mix of material this week, some heavier some very light. Covering more interesting stuff this week, expect a string heavier entry next time!

"How We Could Build a Moon Base TODAY - Space Colonization 1" -Kurzgesagt (In a Nutshell):

Another delightful sub 10 minute animated video covering the wonders and potential of science from an easy and accessible angle. Whilst I'm sure the video isn't necessarily immensely thorough in its calculations and research the principle is there. It makes a very good conceptual case for a moon base though I feel it doesn't necessarily address a number of serious issues, such as whether we should colonise other astronomical bodies given our track record of looking after earth...

That said Kurzgesagt videos usually bring a smile to my face and this is no different. Well worth 10 minutes of your day whether you are a scientist or a science fan.

"Inside Black Holes" - Leonard Susskind

I took a break from the GR lecture series for this lighter lecture. I've seen it described as a lecture but it seems more like a talk or open seminar to me. Having some GR and QM under your belt would help you get more out of it but I reckon someone who's read some pop. sci. books at A level would be able to follow a fair amount of this. I'll confess I skipped the questions at the end.

The lecture isn't particularly technical, initially its entirely conceptual and there's not much maths in it at all (though knowing some of the maths behind it helps). He talks about the classical GR picture and then moves on to discuss the integration of quantum mechanics into black hole physics and then some outlook of theory in area at the time the lecture was given (2013). Overall I found the lecture very accessible and a pleasant watch. Again Susskind is a strong speaker, the humour in this one between himself and his colleagues might not be for everyone, I found it got a little in the way but not enough to detract from the talk. His focus on using actual words to discuss the problem is a welcome break from many university lecture courses. If you like GR and black holes this is a nice casual (as in easy not regarding causality) watch.

"Map of Science" - Domain of Science

Taking a nice wide view of, well all formally studied subjects there are, Domain of Science maps a progression from philosophy all the way to the arts. Not only is it fun but it raises an important point, the progression of the complexity of the systems studied in different fields (i.e. physics studies simpler systems than biology) and the fact that less traditional scientific methods have to be employed because the 'science' itself is actually harder. The replicability crisis in psychology is also mentioned though I feel he doesn't give the subject in its current form enough credit for its level of rigour. Apart from that this is a very nice video and I want a copy of the poster...

"Mathematical Physics 02" - Carl Bender - PSI 2011/2012

The first lecture in this series was really good and I decided to pick it up again this week. I think these lectures are really applicable to almost any area of theory, basically anyone who deals in quantum mechanics and quantum field theory. Topics include asymptotics, differential equations, perturbation series and links with complex analysis. These methods are linked back to problems like the Schrodinger equation and related examples like perturb oscillators then some conceptual links to QFT. There are also some really interesting insights regarding quantisation, these stood out to me as being the most interesting material in the lecture. 

I would approach this lecture having a good understand of differential equations, quantum mechanics and perturbation theory if possible, knowing some complex analysis would definitely help you get more out of the lecture as well. The lectures are really well delivered, enthusiastic and detailed. These are actual class lectures so be prepared for interruptions, all part of the fun.

IP 1.2: GR and LQG

Some different material this week, a bit more formal but very enjoyable! This isn't as accessible for anyone below undergrad level physics and I think you might struggle to contextualise some of these materials if you haven't studied  some GR and have some conceptual understanding of QFT (like in a particle physics course). But for those of you seeking to extend yourselves go for it! I also watched a more accessible (kind of popular science) lecture which might appeal to anyone who enjoys science.

General Relativity Lectures by Leonard Susskind - Stanford Series

Plenty of you will be familiar with the Stanford Lecture series' on YouTube, a huge number of courses are there fully recorded. I've been refreshing my GR knowledge (slowly but surely), the course starts off with some SR and slowly gets into metrics and such. Susskind is very eloquent and provides a good level of detail without losing the big picture. It will be interesting to see where this series leads, I'm not that far through the series yet.

Introduction to Loop Quantum Gravity by Carlo Rovelli - Quantum Gravity at CPT Marseille

Quantum gravity is my passion and this lecture series by Rovelli is a real treat. The first few lectures are high conceptual, this is a bonus for me because quantum gravity is such a broad problem that getting into the nitty gritty too early can narrow your view. Rovelli is a first grade speaker and doesn't pull punches. He's quite happy to say that a claim within the community is "bullshit", a level of confidence I appreciate in a lecturer. If you want some lectures on LQG, this is the place to go.

Covariant Loop Quantum Gravity - Carlo Rovelli and Francesca Vidotto

This LQG textbook is (I believe) the second from Rovelli, the first one was published nearly 15 years ago and is a very very high level book that I found pretty inaccessible at the time I looked at it (the best part of 3 years ago). This second text is far more introductory and like the lecture series above starts from a very wide view point. This is incredibly useful in educating people on what quantum gravity is and what it isn't, as well as approaching the topic at an accessible angle and pace. I've been slowly digesting the pages and whilst I'm not far through I'm already happy to recommend this text (and highly as well).

"The Usefulness of Useless Knowledge" (Dr Robbert Dijkgraaf) - Talks at Google

I've mentioned Dr Dijkgraaf before and this lecture is just a strong as his others. A really good talk that looks conceptually at the place of academic research from a historical context and makes a strong case for supporting physics research. This was an easy but pleasant and inspiring watch, worth a view if you've got an hour to spare.


And that's my coverage for this week! If you're looking to learn more (or start learning) about GR or LQG these are a few places to look and a more conceptual lecture definitely worth a watch.

Series Introduction (IP 1.1)

I've decided to start a running series of short articles, a way of generating content more regularly alongside my longer pieces. I might expand the number of the series in the future but we'll start with this one.

As in the title the working title is 'Information Processing', I'm going to discuss any science material I've been reading, watching, listening etc. I'll chat about what it covered, how I thought it was delivered and how useful it was to me.

Let's get started with Information Processing 1.1! I'm not back at uni yet so I'm really just warming up ready for the first term.

"What are quarternions, and how do you visualize them? A story of four dimensions." - 3Blue1Brown:

I've been a big fan of 3Blue1Brown for about 6 months now, his focus on visualisation and trying to make mathematics more intuitive suits me, he exhibits a level of detail which many YouTube creators do not. 

This particular video is on a topic that I wasn't familiar with previously, it's part of a short series of videos that should be coming over the next few weeks. Quarternions certainly have applications in physics but for me the more interesting aspect of this video was the focus on stereographic projections and dimensions. These are subjects I'm more familiar with. The example of projecting a 4D hyper-sphere into 3D space is definitely worth a look at for anyone interested in theory. 

As always with 3Blue1Brown, the animations are on point and as a classical music fan the soft piano in the background helps me absorb the material presented. Definitely worth a watch.

Various presentations by Dr Don Lincoln - FermiLab:

The FermiLab channel offers some nice (if short) introductions to topics in particle physics. I used these for a quick conceptual refresher over a couple of days. They are a lecture style presentation with a few basic animations.

I covered a number of topics, QFT, QCD, QED but the Twin Paradox one probably sticks in my mind most. This had better animations and covered it from the point of reference frames, something I only covered in detail this academic year gone. The ones on general particle physics were a good terminology reminder but I found them too low level personally.

Solid explanations, but the presentation can sometimes be a bit slow and cheesy, only sometimes though. Still a good refresher though.

QFT lecture notes - Imperial College London:

For anyone interested these notes are available on the Imperial theory group page, freely available to anyone, on the 'Information for Current Students' section of the masters pages. I've read through the PhD note-takers material for the first few lectures, their handwriting is very good with clear diagrams as well. The material is reasonably introductory and as yet hasn't got me running scared (I stress yet). The QFT course seems to seen as the most introductory and 'basic' course in the first term, it leads on nicely from the advanced classical physics course I took last year.

I'll try and cover more ground before I start the course next month!


That's it for this week, I'll check in next time with a few more entries!