Posted in 2009
Thanks for 8000 views
It appears the blog is getting centred around a single dull topic: quickly increasing number of views. I apologize for an inconvenience. Let me explain.
Firstly, the number displays an unusual and interesting dynamics that I can not rationalize or predict. This activates my research instincts and I redard reporting the phenomenon as a part of my scientific duty. Second, let me confess, I like very much to get noticed and appreciated, especiallty if this attention is not deserved or expected (since I’ve abandoned any hope to get appreciated for things deserved).
Thank you very much for this! So I will keep reporting every doubling of the number of views.
Sixth lecture advanced quantum mechanics
was given in exceptional circumstances of fair weather. I could not recall this occasion for the last lecture before the semester break for all years of my service. Believe me or not, I managed to say more than I was going to. We have started with e.m. field as collection of classical oscillators, a debt from the weeks past. I gave the material in more or less reverse order: first explained the result of the activity, them the activity. Unexpectedly, this appeared to be rather convenient, and I moved reasonably fast. I wonder if the students liked it, yet they did not protest. So accelerated, we have accomplished our main task: field quantization – just before the semester break.
I expected the classical oscillators to be the most boring part of the lecture. Unfortunatelty, I was wrong. The most boring part appeared to be the last one where I talked about zero-point energy, uncertainty relations and vacuum fluctuations. I do not know why. Usually it’s rather interesting, since it goes over "fancy" subject the students have heard about but would like to hear more. Usually the audience is more interested so I also talk in more detail. Perhaps it was unwise to hurry up with this, I could have postponed the discussion till the second half of the semester. However, it’s done, and frankly I am happy to get over with.
There was an interesting discussion afterwards. The idea of a student was that the uniform mass background arising from the zero-point energy should lead to a uniform gravitational potential. So no gravitational field would have been felt. We had to write down an equation to figure out that it can not be true: the gravitational potential from a uniform mass distribution can not be uniform. Yet perhaps such reasoning is a step towards true solution of the problem?
The Protection of the Mother of God
is a feast of Orthodox churches.
On Oct. 1, 911, Constantinople was besieged by a viking-style gang consisting mostly of Russians. The fall of the city seemed inevitable. Most non-military population gathered in churches where the services had been conducted day and night. At four o’clock in the morning st. Andrew, the fool-for-Christ, and his disciple Epiphanus, came to see Our Lady praying in the altar. After the prayer, She has covered people gathered in the church by Her veil, as if protecting them from cold or cloaking from the enemy.
The city was spared by the time. The gang turned away satisfied with a modest tribute. Since that the orthodoxes celebrate the feast of Protection, or Intercession, or Veil: Greek word ÓêÝðç can mean all of above. It may seem strange that the feast is most loved by Russians, wrong side in the story. It requires some reasoning to gasp that the violence and terror inflicted by Russian gangs (either state-owned or private) abroad must be a minor fraction of that inflicted on their own soil. The conclusion is that Russians need the protecting veil most: to cloak from themselves.
Anyway the protection, the mercy comes to everybody. Mostly undeserved. Glory to God.
Thanks for 4000 views
it took my blog a month to get first 2000 views and a week to get second 2000. I’ve no rational explanation to this fact, blog stats available to me do not provide one.
There must be some magics involved, and I was trying to recall the tales my grandma used to develop my social skill. There were three magical spells in the tales, "thanks", "please" and "I promise". If I got it right that time, the first you use if you want something, with the second you politely refuse, and the third you just never-never use cause the powers unleashed can not be controlled by human beings. So it looks like I occasionally made use of the first spell.
So I shall thank you for 4000 views, and I promise …
Sixth lecture quantum transport
was about Josephson effect in the context of quantum transport. Theoretically, it can be one of the best and useful lectures in the course. It combines information of general use (superconductivity, josephson relations) with something that the students can do with their "own hands", in our case, evaluate step by step, and some fascination about "unusual" processes discussed. This assumes students rady to work with "own hands" and teacher able to fascinate keeping things comprehensible and logical. To my estimation, both resourses were present but not abundant.
Right after the break we get a control question and concentrated on it. The answer has emerged, though slower than I would like it to happen. A "fascinating" introduction to superconductivity meant to provoke a discussion was listened to with attention but did not give rise to a sinlge question. Perhaps the mood was "he speaks riddles, but may be I understand it later. In case it’s worth understanding".
And I get to generation gap with both feet. The essence of Josephson dynamics is explained with two words: "pendulum" and "washboard". I’ve heard "washboard potential" from many young people but actually never checked if they think that Washboard is a family name of XIX century mathematician. Can somebody become a good physicist without trying to swing a pendulum with hand? Sometime ago I have tried to explain a non-linear second order differential equation to my phd student by saying "it’s like a pendulum, you know…" This did not work. Naively I thought there are some pendula left in physical practicum. It came out today that this does not seem to be the case anymore.
So let me finish this post with providing proper references for washboard
www.nps.gov/fosc/forteachers/laundress8.htm
and pendulum (this is with equations:))
Fifth lecture advanced quantum mechanics
was a kind of experimental: it combined a story of superfluifity with refreshing the concepts of classical electromagnetic field. Never did it before. The lecture has started with another experiment not set by me. Somebody has experimented hard with the beamer settings. As result, the projection i. caught only a part of my computer screen ii. was a meter below its usual position. I’ve fixed i. but could not deal with ii. after 10 minutes of trying. It looks like my remote control does not give me sufficient priviledges in changing the settings. And I missed by smoking break. So when the lecture has started, steam was hissing from my ears.
To let off the steam (and explain the disorted projection), I gave a rather inconventional introduction to the lecture. I mention that a university education is very broad, there are many things to learn at a university, those may include the lessons of irresponsibility and negligence and getting away with these indespensible qualities. But I hope that my students will get bad marks in these particular subjects etc… It is my hope that the students did not find this introduction too patronising/irrelevant. Anyway I talked from the bottom of my heart, and most understood this.
And I was back to the subject. We got thru superfluidity with no much viscosity. Both in positive and negative sense. All went smoothly: quantum field theory => almost classical field theory => linearization with operators => wreid terms => Bogolyubov hunch=> particles become quasiparticles, and, look, atoms become a sound. "=>" means a simple calculation, we did not do that: this explains zero viscosity. So the students were rather spectactors, did not feel any interaction with the audience.
And got tired upon switching to the classical field. This is not my favourite topic, but with more energy I could make it more entertaining and not just mumbling "from zis ekwatin" and "substitute"… Sorry for zis. Anyway, almost a half of the course is over, we have completed at least one climbing: from "particles" to a top where difference between particles and fiels is hardly seen.
Next week the students will decide if we go through the rest of classical preparatory stuff or just stat quantizing.
Thanks for 2000 views
When I have started the blog, I did not really counted on any noticeable audience. Well, the blog goes about boring and rather specific stuff, mostly it is a technical dairy of my lectures. I am flattered with the fact that people find it (and perhaps the lectures) interesting. Thank you, your attention is very motivating both for writting the blog and for lecturing, and, let me put it frankly, just for living this life through.
Of course, I’d love to receive more feedback in the form of comments:)
Fifth lecture quantum transport
was a change of the topic: we have departed from the scattered quantum waves and entered the world of Coulomb blockade. I have stressed from very beginning that this is perhaps a boring world, although I myself do not think so. However, I am afraid I was boring at times. Perhaps it was just a matter of mood.
The slides of the lecture, especially the diagramms in the slides are better be updated to match the book. I did not to it this time to avoid, according to the mechanism described earlier, a complete rewritting of the lecture. I would do it next year.
This was I guess the majour problem while taking about co-tunneling. I was trying to explain a cartoon, while the sildes give formulas. That gave this discrepancy between the speech and visual and was bad for explanation.
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.