Ever wondered what it's like to be studying String Theory?

[Kalimaa23]

On Tom's advice, I'll be posting the content of my new blog in an ongoing thread here. It follows my final year of my Master's degree, in which I'll be writing my thesis in String Theory.

You can comment on and read the blog at http://stringschool.blogspot.com



This is where it all starts

So, here we are.

Let me first introduce myself, for those of you who don't know me. My name is Dimitri Terryn, 21 years old. I'm currently studying at the Vrije Universiteit Brussel, or Free (as in non denominational) University of Brussels if you will. The translation into English is somewhat discouraged, because there is a French speaking university just next door with the same name, the Université Libre de Bruxelles. Which has the exact same name in English, hence the confusion.
This year, I will be starting my final year of a Master's program in theoretical physics. I will be doing my thesis at the department of Theoretische Natuurkunde (TENA), that's Theoretical Physics in English, with Prof. Dr. Alexander Sevrin as my promotor. I haven't got a concrete subject yet, but I will be able to tell you in about a week.

Why start this blog? Well, the last few years have seen an enormous amount of physics relate blogs being started. I'm a rather avid reader of these blogs, and I have found that they have been very instructive. Not only do people like Peter Woit or Lubos Motl for example post interesting information on a regular basis, they also allow others to get a glimpse of what it means to be a physicist (or mathematician). A master's student blogging away his woes is something that does not yet exist, as far as I'm aware. So maybe young people who browse these blogs will one stumble across mine, and I'm hoping that by sharing my experiences they will get a better view of what it means to be a physics student. And hopefully, in the process, they will realize that if you are interested in physics it is a wonderful life indeed.

So, that's all for now folks.

posted by Dimi at 09:03 | 0 comments

 

[Kalimaa23]

My first teaching experience

This week I got my first taste of what it means to teach a class.

I got e-mail from the physics department head a week ago, explaining that there was trouble this week for a certain "Bridge Course". These are small courses, typically a few days long, that are taught to freshmen before the academic year if they so desire. The aim is to make sure they know the necessary mathematics, chemistry, physics, latin, etc. that they need for whatever it is they are studying. I turned out that there was no one available to teach the exercises for the physics course. So I volunteered to help out, and together with a friend of mine who is into quantum computing took on the course.

I must say that I was a tad nervous. Having 30 18 year old in front of you for the first time is a strange sensation. The little buggers insisted on calling me "Sir", even when I explained to them that, yes I'm just a student like them, and yes, you can call me by my first name. But suppose secondary school habits don't go away that quickly. Once we got underway, the nervosity dissipated and have to admit I found the whole thing thoroughly enjoyable. Helping people understanding something they find difficult is a good feeling, especially if you see that they've got it, and can get along by themselves by the end of the course.

In other news, I've just purchased Zwiebach's A First Course in String Theory. My promotor gave me Superstrings by Green, Schwartz & Witten, but it was a bit heavy for someone who's mastery of Quantum Field Theory is less than complete. To this end, I've been reading quite a lot of Zee's Quantum Field Theory in a Nutshell, and I've been enjoying it to no ends. If you're an advanced undergraduate or a beginning grad student, and want to learn QFT, I cannot recommend it enough.

posted by Dimi at 10:00 | 3 comments

 

[Kalimaa23]

First lecture of the new year

The new academic year has officially started this year, with my first lecture this morning. It was four hour lecture (with one 15min break...) on the Glashow-Weinberg-Salam elektroweak model. Considering that the only field theory we were familiar with was QED, and that we also have had the basics of non-abelian gauge theories and lie groups stuffed down our throats, I think it's fair to say that it has been a fairly productive morning.

I'm going to attempt an excersise later, namely given a lefthanded up quark/down quark doublet, and the righthanded singlets, calculate the weak hypercharges by use of the G-W-S model. Sounds like fun doesn't it?

In case you were wondering, the courseload I have this semester consists of :

General Relativity & Cosmology
Elementary Particle Theory : The Standard Model
Quantum Field Theory : Path Integral Formalism
Mathematical Methods II : Integral Equations

I don't have a title as yet for my thesis, but I'll keep you informed.

-Dimi

posted by Dimi at 17:35 | 0 comments

 

[Kalimaa23]

I've got my title!

Greetings all,

I've gotten my official dissertation title (which I needed soon because of some bureaucratic requirements...), so here it is :

DEFORMATIONS IN GAUGE AND GRAVITATIONAL THEORIES

or in Dutch

DEFORMATIES IN IJK- EN GRAVITATIETHEORIEËN

I'll explain later (i.e. when I figure it out myself) what the point is.

The second week of the semester is now finished. We finished the theoretical work on the SU(2)xU(1) model, and we will proceed to the Feynman rules and some processes next week. Some new faces in the class, apparently two people from the Katholieke Universiteit Leuven are also taking it. Nice to see that scientific persuits take precedence over ideological differences. For the non-Belgian reader, now that Catholic Universities and Free ones aren't too friendly to each other here. Usually.

I also got my first General Relativity lecture, which was pretty boring since the other string guy in the class and myself have been reading Weinberg over the summer, so no new stuff here.

I missed my first Mathematical Methods class due to a meeting. For those of you who don't know, I'm heavily involved in the university administration as a student representative. I'll explain it in more detail later, as it is an important aspect of of my life right now.

I'm formulating a study plan as we speak, and I think in the next weeks I'll be
- Learning Differential Geometry (through some excellent lecture notes that you can find here).
- Getting through Zwiebach, chapters 4-5-6-7-8 & 9.
- Learning some things on QFT path integral formalism through various lecture notes, in preparation of my QFT class.

 

[Kalimaa23]

Thursday, October 20, 2005
Back in business

That damned infection has finally gone away, so I've been able to amuse myself with more interesting things, namely, physics.

Elementary Particles was fun. We discussed spontaneous symmetry breaking, and how the resulting Nambu-Goto bosons get eating by gauge fields to give the gauge bosons mass. I'd read about it in Zee, but seeing it done in the context of the elektroweak model was certainly interesting.

The general relativity lecture was a little less fun. Sure, we derived the Einstein equations, but the people doing their thesis with this prof were giving Weinberg to study over the summer, so not much new here. Or maybe one thing. He mentoined that the curvature tensor is THE fundamental building block of any differential geometry, and that you can derive all other tensor from it. This in any dimension and regardless of topology. Weinberg gives an informal counting argument in his book for the case D=4, but it would be interesting to know more about the general proof. All the more reasons to be studying differential geometry then.

I'm almost done with the parts of Zwiebach that I need to now. I'm currently reviewing the quantisation of closed and open bosonic strings. I think I'll be making some kind of short version of the chapters I've done. If so, I'll post them here.

Lubos Motl has a very exciting post on his blog. It seems that a group of researchers has succeeding in constructing a correct Calabi-Yau (the cute things you see in the background of this blog, basically the extra curled up dimensions of string theory) compactification that gives the familiar particles of the Standard Model. Moreso, they claim the construction is fairly unique (altough Lubos does not adres the point in his post). If this is correct, that this is tremendous news. It means that there is at least hope that what we are doing will give rise to correct physics, and that there is a possibility that string theory will fullfill it's promises.

And that poor graduate students aren't wasting their not-so precious time with this :-)

 

[Kalimaa23]

My thesis
I'm starting to get an idea what my thesis is about.
Back in the days before QED, people were wondering what the charge of an electron was if it was regarded as a point particle. As you probably know, the strength of a sferically symmetric electric field around a point charge goes as 1/r². So what happens at the origin, namely the charge itself? This expression is singular, so we seem te get infinite results.
Several non-linear generalisations of Maxwell's theory were considered. One of them was develloped by Born and Infeld. They modified the standard Maxwell lagrangian to this :
http://en.wikipedia.org/math/03f13c6940e93e39bc397870ce797212.png
If you expand the square root, the first term gives back the usuall Maxwell term. The other terms are an infinite number of corrections to this. This lagrangian is known as the Born-Infeld lagrangrian, and I will be doing something similar but with gravity. A similar lagrangian (with the scale factor b related to the string length) will give rise to the familiar Einstein equations of general relativity, with an infinite number of "stringy" corrections.
I have to figure whether something interesting can be made out of this. I will get back to you when I figure out how :-)

 

[Kalimaa23]

Marshall unveiled results at my university

I found an interesting bit of trivia this morning. It seems that 2005 Medicine Nobel Prize winner Dr. Marshall first showed the results of his research at a congress in 1983, right here at the Vrije Universiteit Brussel. At the time their results were quite controversional, as the common sense view (you can say dogma) was that bacteria could not survive in the acidic stomach envirement, and they were claiming that kinds of ulcers were caused by bacteria. As the story goes, they even went so far as to swallow solutions of the bacteria to prove their point. And lo and behold, the men develloped ulcers...

The point of this post is to show a very important aspect of my university, and one that I'm very proud of. It is a university founded on the principle of Free Research, or Vrij Onderzoek in Dutch. It is based on the following text from French mathematician Henri Poincaré :

Thinking must never submit itself,
neither to a dogma,
nor to a party,
nor to a passion,
nor to an interest,
nor to a preconceived idea,
nor to whatever it may be,
if not to facts themselves,
because, for it,
to submit would be to cease to be.

 

[Kalimaa23]

Interesting read by Weinberg
Greetings all,
During my usual morning surfing during my much appreciated coffee intake, I stumbled across two interesting Weinberg pieces.
The first one is found in the November issue of Physics Today, and is about Einstein's mistakes. In this World Year of Physics, there is a lot of talk going on about Albert Einstein's accomplishments. As Weinberg points out, it is often much more useful to consider the mistakes made in scientific thinking. It's the same as with working out an assigned problem : how you got to the solution is much more instructive than the solution itself.
The second one is an Archiv paper about the dreaded Landscape. For people unfamiliar with this, the basic idea is as follows. String Theory is formulated in 10 spacetime dimensions, 6 of which are made small because obviously they do not show up in everyday experience. The physics of our familiar four dimensional spacetime depends heavily on the manner in which they are made small. There is as of now no principle that show us the correct way of doing this. As a result, String Theory as of now predicts a huge number of possible stable worlds (or vacua), and appartently looses all predictive power. Landscapoligists seem to think this wonderful, and employ all kinds of scholastic nonsense to sell this as legitimate science. It's nice to hear a more common sense reasoning about this kind of talk.
As for now, I've been slacking off lately. No real news on the study front then I'm afraid. More to follow.
-Dimi