De meningen ge-uit door medewerkers en studenten van de TU Delft en de commentaren die zijn gegeven reflecteren niet perse de mening(en) van de TU Delft. De TU Delft is dan ook niet verantwoordelijk voor de inhoud van hetgeen op de TU Delft weblogs zichtbaar is. Wel vindt de TU Delft het belangrijk - en ook waarde toevoegend - dat medewerkers en studenten op deze, door de TU Delft gefaciliteerde, omgeving hun mening kunnen geven.

Posted in September 2009

Fourth lecture advanced quantum mechanics

was difficult and somewhat technical. Hopefully, it was not boring since I’ve been trying all side stories to keep the audience attending. Besides the material, the microscopic theory of superconductivity being the main topic of it, traditionally interests students. 

There are still many students, more than in years past. They also react differently than in the past. For instance, I used to encounter resistance when coming to work whithin a single Nambu cell, I was requested and had to write the wavefunction as a 2-vector and act with 2×2 matrix thereupon. Today I did not get such request, the students seem to follow. However, just by inertia, I wrote 2-vectors and 2×2 matrix at the blackboard… I’ve thrown a question about contact interaction in completely polarized electron gas where it cancels because electrons cannot come close to each other. Actually, in the past the answer to this question used to come quickly, immediately after the hint that they do not come close to each other. Today there was a significant delay… Why? Luckily, the answer has emerged after a while. A similar question — where did the factor 2 go? — has been answered a way too quickly. So I suspect telepatic abilities in a part of the audience.

As to my telepatic skills, I have to brush them. Close to the end of the lecture, I began to hear very distracting noises from the adjacent room. Bet most students did not hear that and wondered about the reason of my distraction. I tried to send a telepatic message to the noise source. No avail, I had to break the lecture and appear in person. There were four young gentlemen enjoying table soccer match.  While apparently surprised by my request to do it queiter, they were kind enough to accomodate it.

I still have to decide what to do with superfluidity. It looks like I will have to combine with classical description of electromagnetic field. In this case, that’s going to be a mjour pedagogical innovation: do not miss it!

Nativity of the Mother of God

I should have posted this four days ago. However, I was on trip and the internet connection was such that I could not do it. Ok, it’s better late than never.

The feast of Nativity of the Mother of God is celebrated in Orthodox church on Sep. 21 (two weeks later than Catholics do: the calendar is shifted). This is the first feast from the twelve great ones in a yearly cycle of church celebrations that starts on September 1. This is how must people know it.

As to me and my family, this feast has a special significance. On this mere day I was appointed for a permanent position at Delft University of Technology. This has ended a difficult nomadic period in my life. I have got a possibility to do research and support my family, thanks to the Mother.

Why do I write about it now? Well, this took place 15 years ago, a kind of jubilee. Do you think it was a joyfull day for me? Not quite. In this less ideal word, if one gets some, another does not. There was a job search by that time, four people on the list. Me. My student with whom we did splendid physics and were having a good time. He could not find a research job in the Nethrelands and is now a prof in Grenoble, France. My good friend who has actually brought me to Delft and has helped me a lot. He could not stay in research he liked and works for a soft company.   

Fourth lecture quantum transport

was the one I was afraid of.  First of all, the material was a bit "dry" many formulas, although simple ones, less stories to tell. Second, similar to the second lecture, I made rather big changes in the slides and not really in advance. In fact, I have finished the changes at 2 a.m. today.

After all, the lecture have not gone too bad. Or is this just illusion? I was reasonably well on time. In fact, I had to brake in last 15 minutes. There were questions and answers, although not that much I would love. I was a bit dissapointed that nobody answered a control question: what is the combination of two diffusive  conductors? I thought I have said enough to provoke the answer…

I guess the number of students has stabilized, I am with core supporters.

Third lecture quantum transport

was a fulfillment of duty. Most material given was quite difficult to follow, especially at the pace of the lesson. Also it is the most difficult chapter of the book. An easy solution would be just to talk about something else. Or present the topic only partly, just concealing the sharp edges and not drawing conclusions that wait to be drawn. If I do so, I would not be a scientist in a way I understand it. It is my duty to tell about this spectacular line of reasoning that starts from Gustav Kirchhoff, goes through treasures of and ends with curcuit theories of quantum transport. I am afraid if I do not give it nobody would. And this line of research will die replaced by primitive meso-nano-pico-amto incidentalies.

So suffered I, so students did. The first part of the lecture (double junction revisited) get eventually rather good, still felt interaction with the audience. The third (double junction again) was, to my understanding, yet easy to follow. Second (the road from quantum to classical) and forth (quantum circuit theory) are disastrous. I was trying to appeal to previous knowledge, to common sence, to anything: still was hard. Anybody can give me hints?

The student numbers are dropping, how many will I count next Friday? Good news come from problem-solving session of Ciprian. There were many, and many have attempted doing homework.   

Crux II

I’ve already mentioned in this blog that I’m a Christian. The time has come to reveal more: I’m not the only one among the scientific stuff of TU Delft. We’ve a kind of small organization that does not advertise itself. It’s called Crux. Once in a month we meet, trying not to attract much attention.

Why not to attract? For forty years passed since Great Secularization of Dutch society it did not feel quite proper to talk about religion within university environment. The students are of course allowed to have interests, and there are several active student Christian organizations. As to the stuff, the common opinion was that faith is so deeply personal and so irrelevant to any academic acitvies that any mentioning of it is improper, very much like mentioning, discussing and promoting personal physiology. This is why we’re still a bit cautious. Although times seem to change: more and more academics actively and publically discuss questions related to interactions between science and religion and even provoke such discussions. Cees Dekker, prof of molecular biology at our Kavli Institute, is especially famous for this: see his site

So two years ago Cees Dekker and Hans Hellendoorn, prof. in applications of computational intellegence, have founded Crux, In our meetings, somebody usually gives a (short) presentation that ignites a friendly discussion that can be about everything: from the best ways to handle Ph.D, students to what Scriptures say about environmental issues. Starting this year, we also invite postdocs and Ph.D. students: this is called Crux II.  

Today we got very deep in philosophy. Kees Roos told us about Wittgenstein and Goedel. Yet everybody find it interesting and can say something about. Glory to God.


Third lecture advanced quantum mechanics

was a hard one. Today we have switched from "technical stuff" of second quantization to applications: Magnetism. Something about history of teaching attitudes. I have inherited this course years ago from prof. J.J.J. Kokkedee who gave it since 1970, I reckon. The latest "dictaat" of Kokkedee course can be found at the Blackboard. When inspecting this, one finds many similarities in contens. This is natural, because the fundametals of physics have not changed since that. What has changed is the teaching attitude and approach to student — taken the personal differences apart. Namely, the material of the lecture about magnetism was given to students at the exam: just a problem to solve. Modern education is decisively different. Roughly, the students of that time have been taught to less things, but have been expected to know more and to cope with more. A quick pseudo-logical conclusion would be: the students of the past were better prepared and in command of a superior intellengence. Let me say: negative, this is not so, in many cases it is (was) the opposite. Yet the further attempts to comprehend this would lead us to even more paradoxical conclusions, decisively more paradoxical than quantum concepts…

Back to the lecture. The timing was close to the ideal schedule: I was a bit double-crossing in the beginning when announcing the intention to finish the magnetism. Former experience shows that it could go worser: twice I was able to deliver only the second quantization for fermions. Today we stopped just on time: we have stumbled upon a technical problem discussing magnetism, got a prescription to deal with. Homework would do the rest.

Of course it was a bit too fast, I apologize. I hope you appreciate my good intentions. I was trying to tell about many things at once, my speech occasionally got erratic indicating the wandering mind. Must be irritating: Best way to stop it is to shoot a round of questions. Do me a favour.

Before the lecture got a question about my origin. In case more are interested: I was born in Siberia and dwell in the Netherlands since 1993, all time employed by TU. Suppose you like trains. Are you aware of possibility to travel from Amsterdam to Beijing changing trains just twice? If you take this challenge, you’ll pass my native city on the fourth day.

Second lecture quantum transport.

Was embarrasing for me. Was told many times by experience teachers that one should not prepare for the lecture and withstand this tempation provided it arises. Because in this case you want to improve the lecture, thus making changes, thus making errors, thus getting caught afterwards. No use. So I was caught by two students simultaneously: thanks to them for being attentive and bringing the issue.

The start was not very encouraging. A minute before the start I saw only few students that defied all laws of statistical distribution by filling the least probable back rows. Fortunately, it dramatically changed at mere last moment. I was even able to address the audience "ladies and gentlemen" while have already prepared for "gentlemen". Still: two first attemps to get a response from the audience were not accomodated. Luckily, it got to normal a bit later.

The changes made were intended to bring the lecture slides close to the book and to give more physical significance to the phase shifts. First part, multi-terminal scattering, remained almost intact. In future, I shall find a way to present it faster and in a more interesting fashion. It appears I need more time for interference, second part. Although I’ve spent only 4 minutes joking, I have had an acute time problem and finished at 12:33 only.  Sorry, never again. The story "A and B" has been improvised and upon my taste was usefull to illustrate the interference, but I haven’t checked it against other tastes. Please comment on this.


Kavli day

Several years ago I’ve came to Delft to work in the Department of Applied Physics. That sounded almost as Department of Physics and the organization of it was similar to that of a conventional department. There have been many changes. If the organizational changes manifested itself in morfological modifications of the subjects of organization, I would have looked like a violet-pink flying octopus.

What used to be solid-state part of department of physics is now Kavli Institute of Nanoscience, which is commonly misspelled as Kavli Institute of Neurosciene. Kavli is a rich person who likes sciences as much as helping them financially. He kindly gave a donation to us, this is why we are called Kavli Institute.

So Kavli day is kidna birthday of our organizational unit and also a way to make use of the donation. It was centered around a lecture of Michael Roukes. The title contained "Biological Integration" but it was not that bad. He just explained how to sniff with a mechnanical resonator (a kind of nano-violin) which is potentially important for drug development (I guess). It was a high-level presentation with amusing side stories.

There were activities typical for a "bedrijfsfeestje" including lunching, barbequing, exercising, biking etc.  Unfortunately I had to prepare a lecture for Friday and had to skip most of it including beef well-deserved. Yet I was on time to take part in hight-light of the evening: teasing a young (Dutch) bull.  Lieven Vandersypen has emerged as an unbeatable torero: newer knew him from this side.

Everything has been organized by Hans Mooij. He’s made it very instuctive by demonstrativing us hidden treasures of Delftland,real pearls not known even to Delftenaren. The lecture itself was in a 16th century church that has been used as a warehouse since 1963 and promoted to a cafe two years ago ( I recall prosecution of Chirstians by Communists, the cities of my childhood had many warenhouses of the type). A bike ride from Delft to Maasland is a pure pleasure where you discover many such treasures: just make sure that you are on the right (western) side of the channel.

Second lecture advanced quantum mechanics

The events of yesterday, in particular the party, have significantly impeded my teaching abilities as well as willingness to teach. But there are things men must do, so I stood up and was on time in the class.

I started with an honest promise that it will be the most boring lecture in the course. They laughed in disbelief, but I guess I managed to convince them pretty soon. Indeed, the lecture is very technical, and the need of all these technicalities is very difficult to assess without applying those many times. I could only state: bear with me, this is important, makes sense, just wait a week or two. This is how we get through the CAPs, field operators and confusion of the second quantization. It is a meaning of this lecture after all to create a feeling of certain confusion, unsatisfied understanding: what are all these funny things for? It will get easier in a week when we will do the same for fermions and at least repeat the stuff.

The contact and feedback is still good. There were questions, although most of them come from three male students in the class. If I only hear correctly, one always calls me "sir". This does not quite fit my democratic convictions, but I don’t dare to correct him, I like him questioning. After all I have an officer rank, though that of army forces of a non-existing state. A question from another student was a real hit: he managed to follow dimensionality of the resulting expressions, revealed a problem and made everybody attent of that (different dimensions of a quantity and its Fourier transform). The audience also responded well to my questions. When I asked if more explanations are rwequired, the answer was quick and positive.

I did therefore more side explanations than last years. By some good magics, I manage make all in time (though I had to go through Fock space that remained from the first lecture). Bad side of it is using side panels of physical blackboard. Bad writting, oftenly not visible to all students, sometimes confusing notations. Last year I wanted to solve this problem by advanced techiques: I made use of a digital tablet where my writtings were directly projected onto the screen. I do not do this this year because of the problems I had. First hardware: I had to bring the tablet along with the laptop and connect six cables, in most cases yet to reboot computer and adjust the resolution to get it working with the tablet. Second, sofware: from time to time, it gave a buffer overflow and there was always a chance that the writting dissapears before it is finished. Third, me: computer pen is slower than chalk and requires better control, one who forgets about writes as a pre-pre-school kid. I don’t know what to do: perhaps I have to find just better software and hardware (better me does not seem a feasible option).

For those who could be offended/confused by explanation about creation/annihilation operators: I’m a Christian, I do believe that (cross) death is a new beginning, no joke is meant.

To summarize, I’m reasonably satisfied with the lecture. How about you, the reader? Still nobody comments …




A very big day today

Today was a really big day: Ph. D. defence of Jeroen Danon where I happened to be a promotor.

The day has passed in an unbelievably smooth fashion. I got up early and finally have had time to read the thesis and devise a question. The commitee members who had to come from five different cities today all did it on time and have gathered in a correct place. The rector has been very considering. The only really foreign guest we have had has managed to understand and perform all complicated manipulations with hat, did not stamp on his gown and has uttered "waarde promovendus" without any hesitation. All commitee members had polite and sensible questions. The candidate has not collapsed in the course of the event nor he even got pale. Contrary to expectations, he was polite with commitee members even in cases he did not know the answer. In last several minutes, he was kind enough to outline a theory of ideal goverment: thing we all miss. To make my day prefect, he complimented me on my speech.

So it was all good. The only sad thing is of course that Jeroen has finished. We have been working together for five years, and I will miss him. He will go to Berlin to proceed with post doctural studies and thus become a real German Beamte. We still have unfinished projects, most importantly, a textbook on Advanced Quantum Mechanics. 

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