# Posted in May 2011

## Getting sick of being busy

(Posting back again)

I can’t believe that: the semester, that was so difficult, time-consuming and seemingly everlasting, is over, but instead of rejoycing I am confronted with a heap of things that I’ve wisely postponed till the end of the semester. Like seven referee reports (with the deadline end of the week). Like preparing talks and promises to review the texts of articles I involed, checking calculations, thinking of running projects…

Unfair it is. Why a prominent scientist like me could not spend time in leisure, playing with thoughts about things eternal? Recall I was able to do it in a younger age. Will have to think about post doc position…

## Twelfth Lecture Advanced Statistical Mechanics

Finally, finally! We did the renormalization, and try to make sense of it with four examples taking from various places of Kardar: gaussian model, 1d Ising, Midgal-Kadanoff, 4 – epsilon. The lecture was highly technical, but the audience was kind enough to persist: I felt glad, and, after all, had a good feeling.

The lecture was at unusual time of monday morning, yet there were more people than expected. I provoked this by a promise to tell more about the examination: and, indeed, many appear to be interested in this information.

## Concluding Lecture Fairy Tales

We theorists of our section have started a new course this year, Fairy Tales of Theoretical Physics. That has been inspired by the course of Khmelnitskii in Cambridge, and we made use of his material. To aim at Delft audience, we have to adjust the manner and content, so now it differs substantially: this is both good and bad. We were lucky to attract a group of enthousiastc students, eventually, bigger group that we initially expected.

I gave this concluding lecture. I wanted to show up a bit, the lecture beared the title “Yours Classically Quantum” and discused analogies between quantum d-dimensional systems and classical (d+1)-dimensional ones, mostly for d=0. I find this topic very instructive for a student, and perhaps it implicitly answers the question: “what is the theoretical physics?”.

While I think I could partially convey the message, and made a couple of instructive jokes, the technicalities and/or their presentation manner were perhaps too difficult for the audience. Yaroslav Blanter that was present pretended it was difficult for him as well, though I rather see it as his attempt for an instructive joke. I’ll need to revise the presentation manner for the next year. And there was this annoying time problem again…

## Eleventh Lecture Advanced Statistical Mechanics

(posting back again)

was devoted to scaling hypothesis and introduction to the concept of renormalization group. I have had a rather popular introduction with fractal pictures and that was a certain sucsess (modern student seems to know everything about fractal and chaos without getting any lectures on the subject). Making the lecture was an interesting task since I did not take to the stuff since my phd years. I guess I did not depart much from the Kardar, and yet the lecture made sense: much progress:)

## Twelfth Lecture Quantum Transport

dissipation, decoherence, dephasing, relaxation… Indeed, the relaxation after the last lecture is what I seem to deserve…

It’s a good reach-context topic: we’ve been taking about very simple classical physics and saw its manifestations deep in quantum mechanics, there was a place for Schimd transition from decoherence point of view and some experiments. I enjoyed giving the lecture, and, again it seems I enjoyed too much. Again the time problem: talk too much about elementaries in the beginning, did not have time to go into details in the end.

I’d like to do something next year that would spare me, perhaps I need to skip a topic or two. I also shall try to re-new the experimental part.

## Tenth Lecture Advanced Statistical Mechanics

(posting back again)

was devoted to fluctuations. I’ve started with critical opalescence, discussed Gaussian model, relation to susceptibility, quantum fluctuations, and then fluctuations near critical point: Goldstone and upper critical dimension.

Quantum fluctuations would have to be done better: I must think how to do this next time. The rest of material went affordable, and I did not have a noticeable time problem. Also I got more positive signals from the audience. My hope is rising: perhaps I finally manage to finish this course.

## Eleventh Lecture Quantum Transport

went on electron/qubit/Cooper pair tunneling in the presence of the environment. It is a complex topic to present and to convey the fascination of the subject. Last year I’ve remade the lecture from scratch and now it is the way I like it. (I mean, I like it this year as well). The students have been following, it seems. However, the response was less active that the last year (perhaps because I’ve made less typos:))

## Ninth Lecture Advanced Statistical Mechanics

was about Landau theory of second-order transitions, a theory that fascinated many generations of students, me including. With no exaggeration, it was the most valueable thing I’ve leaned at university, though, if I recall it correctly, not from the lectures. I wonder if I could convey at least a part of my fascination to the students.

Problem in hand was that one of the important aspects of the fascination is the recognition of the utmost generality of this theory: it can be applied to any type of ordering, to anything and anywhere. The best way to convey this aspect is to illustrate the theory with many and complementary examples and put it in the context of symmetry groups. Kardar is rather half-hearted about this, he lists some examples but basically keeps taking about “magnetization”. He also avoids the discussions of anisotropy of fourth-order terms and any mentioning of irreducible representations in the context of second-order transition. While I could understand his intent to keep things simple, this is rather a castration of Landau theory.

Well, it’s easy to be critical, it’s difficult to talk about these aspects given shot lecture time. I did it by just mentioning symmetries and groups, and considering pyro-electric transition where anisotropy plays an important role. I could put some stress on it letting the students think about possible scenarios of breaking the cubic symmetry. However, I should try to improve on these aspects next year.

## Tenth Lecture Quantum Transport

(Posting back)

was about qubits. I have substantially changed it this year to make it consistent with my book and with some new developments: for instance, I mention Yale quantum processors. I guess I did it more or less ok, though, as in many lectures of this year, the first part was too slow and the second part was too fast. Wonder how did I developed this annoying attitude.

## Ninth Lecture Quantum Transport

is one of my favourite. It is about quantum dots, and it goes through all aspects of those: we discuss definition, levels, persistent currents, the many-electron states, talk about transport concentrating on resonant tunneling, and go to chaos and Wigner-Dyson distribution.

This time I did not manage to reserve enough time for the last topic, it had to go fast. I had to took three minutes after the lecture to finish my favourite illustration of spectral rigidity of Wigner-Dyson distribution that involves barbed wire and German shepherds.

Apparently got too excited with the story: I’ve forgotten my laptop charger in the lecture room an could not recover it afterwards.