Prof. V. Balakrishnan in conversation with Prof. Suresh Govindarajan
On behalf of the Heritage Centre, Professor Balakrishnan,
I would like to welcome you to this informal chat.
[Prof. Balakrishnan] Thank you. [Prof. S. Govindarajan] And, the idea is that we go over the history,
your history and your association with IIT Madras.
And so, we'll start with your life before IIT Madras.
So, maybe you can tell us something about
where you lived, where you studied and worked.
Well, I went to school at, primarily in Bombay and Pune.
After matriculation, I had a year of pre-university science
at the University of Pune
and then my father got transferred to Delhi.
So, I joined Delhi university in the Physics Honours Programme
in 1960 and '63, I finished my Physics Honours.
And, in '65 M.Sc. programme and then went abroad
to Brandeis University for a Ph.D.,
returned to India in late 1970
and then spent 3 years at Tata Institute in Bombay
and then joined the then new Reactor Research Centre at Kalpakkam
in the Materials Science division,
I mean what was then the Materials Science lab.
And, after 6 years there, I moved to IIT
and joined in 1980, and then of course,
[Prof. S. Govindarajan] So, RRC is now called IGCAR right?
[Prof. Balakrishnan] RRC is now called IGCAR;
after Indira Gandhi passed away, the name was changed
and it's the second research arm of
the atomic energy department after BARC.
Since you actually had a permanent job
at IGCAR or RRC as it was called,
how did you end up at IIT Madras?
Well, a combination of circumstances,
some intentional, some accidental,
happy accidents in some sense for me.
I always wanted to teach and in fact, in 1976
Professor R. Srinivasan
who was the Head of the Physics Department
invited me to come over here from Kalpakkam 3 days a week
and give a new course on the quantum theory of solids,
which I did during the January to April semester.
And the next year he repeated the experiment.
So, I realized that I really liked teaching.
So, when the opportunity arose I thought.
I would apply and I did and then I came here.
So ... it's true that I did spend
the first decade in a pure research institution,
but I felt always that something was missing, a crucial ingredient.
And then after coming here I realized
it was the presence of young students -
that's generally missing in research institutes
except for a few research scholars or very young scientists.
But being in an institution with
undergraduates and postgraduate students
and a large number of them is a different feeling altogether.
[Prof. S. Govindarajan] So, in 1982 which is probably a year or two after you joined IIT Madras,
I joined IIT Madras as an undergraduate
and by then you were already a legendary teacher.
And I mean it was my great regret that you were not teaching my class
because you were teaching alternate batches.
So, the odd years had you and your team teaching,
but how did you be ... I mean, have such a huge impact
in, I think a year or two?
I don't know if it was an impact,
but you have to remember that in 1980,
'81, the first 4-year batch - B.Tech batch - started,
till then it was a 5-year stream.
So, after I came over, there was this effort to rewrite the Physics curriculum
to compress all Physics so, to speak in 3 semesters.
Professor Indiresan was the Director
who recruited me and I remember even asking him
saying, because, I had been told by people in the Physics Department
that prior to that in the 5-year
stream they actually had Physics for 10 semesters.
So, I even asked him:
how do you expect all of Physics to be compressed in 3 semesters?
And his reply was: that's the mandate, you have to do it;
now everything else depends on how you do it
and surely you can communicate the essentials of a subject
to potential engineers in 3 semesters,
if you can't, it means something is wrong.
So, he was categorical about it, he said you should be able to do it.
So, a team of us: Professor R. Srinivasan who was taking the lead
and then Dr. Swaminathan, Ramabadran and myself,
we handled the first few batches of the new 4-year stream.
And, we wrote out the syllabus,
a curriculum which was used for many years
and we - our philosophy was roughly to say,
we avoid details and focus on principles
and we talk about single particle
or small number of degrees of freedom systems
in the first semester along with ... vector calculus.
So, essentially you are doing mechanics in vectorial form.
In the second semester, we went on to fields
electromagnetism specifically, with a little bit of optics
and in the third semester we looked at
a very large number of degrees of freedom.
So, after a brief introduction to Hamiltonian, Lagrangian mechanics
we did elementary statistical mechanics and ended up with
the fundamentals of quantum physics.
So, that was a very neat package
indeed, in 3 semesters
which kind of summarized what Physics was all about.
And, I must say that the students,
a much smaller number in those days,
I believe that in the early '80s the number was only about 240 or 260.
[Prof. Balakrishnan] Even less - 220 to 230, I think. [Prof. Balakrishnan] Yes.
And then it, of course, has grown since then
but they were split into 4 batches and the 4 of us handled these batches
more or less in synchrony.
And in - in fact, I would say in strong synchrony
because we discussed things beforehand.
And the students were deeply interested, many of them;
as you know very well, including yourself, many people went on
to form in - to careers in science and mathematics.
So, it did make some difference.
Even though I did not have you as a lecturer,
[Prof. S. Govindarajan] I got access to you know cyclostyle notes. [Prof. Balakrishnan] Yeah.
Your legendary cyclostyle notes
and can you tell us something about that?
Well, I - when I joined here, I had a room, an office room
which clearly was a temporary room because
it had a cyclostyling machine at one end of it which was not used
and it had apparently been junked or whatever
and it was still in working condition as far as I know
and there was a technician who would occasionally run things off on it.
And after a while I got this idea that
we could do this stencilling and type and cyclostyling ourselves.
And question papers in those days were cyclostyle,
220 copies made for the quizzes,
for the final exam and so on, and stapled.
So, we set up a kind of assembly line to do this
and I had an old typewriter with me.
So, we'd type on those old stencils, fill out all the equations
using those stencils and then run off;
I even learnt how to use that cyclostyling machine, how to run it off.
And then once that happened, it became easy to
you know distribute handouts, notes, and so on;
because things are much easier,
now we do it by just forming an email group and then
sending out PDF files or whatever.
But...those early days I think it did help
that students had access to notes
because we didn't, in this curriculum it was so mixed
that we didn't really use a single textbook
[Prof. Balakrishnan] and that caused - [Prof. S. Govindarajan] Actually, there isn’t one till today.
And, that caused a lot of difficulty because a lot of complaints
that there wasn't a single textbook from which we were teaching;
unlike the other IITs, I - I guess.
And we insisted that this course was so broad-based
that a single textbook couldn't do justice to it,
it was certainly at a much higher level than
Resnick and Halliday for instance or Bizer or anything like that.
And ... years later, I had opportunity to
compare this syllabus that we had laid out with
corresponding syllabus at Caltech and Cornell and so on
and to a great surprise it was -
there was a very very high degree of overlap.
So in that sense, we had actually modernized the physics curriculum
well before many other places did.
[Prof. S. Govindarajan] One of the funny things is
that with regard to laboratory duty it’s sort of
in - in the Physics Department - as you know most people are assigned
1 session or 2 sessions of lab.
And ... I mean you were assigned a few times,
but then it was decided that it was better not to give you lab duty.
[Prof. S. Govindarajan] Can you tell us what happened? [Prof. Balakrishnan] Might be
you know, realistic assessment of my talents as an
experimentalist which is less than negligible.
But I think for many years through the '80s,
I actually handled 2 theory courses every semester.
And one memorable semester in 1984,
I had 3 and with a little bit of - for a few lectures
I also handled a few lectures of, you know, 4th course
in the same semester.
I wouldn't want to repeat that experience again.
[Prof. Balakrishnan] Because it was a very heavy load. [Prof. S. Govindarajan] Yes.
But 2 was fairly routine and so on
[Prof. Balakrishnan] and then - [Prof. S. Govindarajan] Which is definitely more than most people
because it's usually 1 lab.
[Prof. Balakrishnan] Yeah, 2 and [Prof. S. Govindarajan] And 1 course.
one of them a 4 credit course - it takes takes away some time,
but towards the end in the late '90s,
I did get assigned lab courses, etcetera.
But... I think they found me more useful,
they found it more useful if I gave lectures on error analysis
and statistics and how to analyse data than to
actually go there and supervise experiments,
which I could do, you know, no differently from anyone else.
And one of the big surprises for me at least
is that you know a lot of stuff about materials science
and it is not something you work on day to day,
but I know that you know so much.
Oh. When I - my - my thesis is on elementary particle physics,
theoretical high energy physics of those days
S-matrix theory and field theory, trying to bring them together.
So, that is as abstract as you could have got in those days,
but then when I moved to TIFR, I slowly shifted
to many body theory and did work on the Heisenberg ferromagnet
and statistical physics and so on.
And then when I got this job at Kalpakkam,
it was specifically in the materials science lab.
So, the mandate was to try to understand
from a physical point of view,
fundamental properties of materials, specifically metals.
So I had to learn a little bit of metallurgy
and materials science to be able to work there
and contribute to the research programme.
So, that - my - initially I felt, I mean
this is a subject which would be totally uninteresting to me.
But as I got into it, I realized that it is
a fascinating subject and that sort of ... interest,
cultural interest has stayed with me, you know.
And among the many things you already mentioned that
you were very actively involved in setting up the
physics curriculum for the new 4-year programme in the '80 -'81,
but - but you kept introducing new courses.
So, can you tell us something about the course
called Classical Mechanics II which became Classical Field Theory?
Oh. That was again a bit of an accident,
the very first course that I taught here was in the January -
apart from the '76, '77 brief interlude.
This was a course on Classical Mechanics II
as it was in the M.Sc. syllabus then
and it was from January to J - April or May of 1981.
The class was small and what I didn't realize then was that
it had some exceptionally good students
including some B.Tech. students who were sitting in on the course.
And in all my innocence I went and asked them
what textbook they'd used for Classical Mechanics I
and they said Goldstein.
And I said how much of Goldstein?
And they said all of it
and I was surprised by this
that they had actually covered this entire course,
I found out later that that was a little bit of a hyperbole.
But...I decided that if they had done all of Goldstein,
then the next thing to do was to do - start practically at the last
chapter of Goldstein which is continuum mechanics
and then I looked at it
and said: continuum mechanics is kind of boring;
so, let us make it relativistic.
And then I gave this course on classical field theory.
One of the great advantages of academic freedom is that you could kind of
distort the syllabus in this fashion as you pleased,
the students seemed to like it.
So, I introduced special relativity and tensor calculus
and then did classical field theory.
It went down well, I even wrote a set of notes on it
and distributed it and then in the next few years
occasionally one would come back and give this.
I think it got formalized as classical field theory only much much
later after all of you came in and then
introduced a lot of general relativity and
really made it a proper course on classical field theory.
But I was happy to be able to do things
like spontaneous symmetry breaking
and the Higgs mechanism and so on,
way back then in the context of basic classical field theory.
And ... one course at least for me it’s memorable by its name
and it gave, I - I did not know what that was about;
it was called synergetics.
Can you tell us?
Oh. In the '80s,
when people were beginning to look at complex systems,
what today known as complex systems,
specifically Hermann Haken in Germany, he coined,
I think he coined the name 'synergetics' for this course;
where you have a large number of
effects coming together to produce -
causes coming together to produce an effect,
something like what we would call emergent phenomena
or complex dynamics and so on, today.
And there was a whole series of monographs published on
synergetics with collections of articles in by Springer.
And, I found that one of the lacunae in our M.Sc. syllabus
curriculum was that there was no room for critical phenomena
or phase transitions, the modern period of critical phenomena
nor was there any nonequilibrium statistical mechanics.
And...there was nothing on dynamical systems per se,
although chaos and non-linear dynamics had become quite
popular and they were very very actively
being pursued in the late '70s and '80s
and I thought why not put these together and offer an elective for it?
Strictly speaking it should have been 3 electives,
but the hassle of going through the Board of Academic Courses,
getting permission for all the courses would have been too much
and 3 would have been too much to float at one - one shot.
So, I put the 3 together into 1 syllabus in a little bit of
sleight of hand and called it synergetics.
And, it was approved by the departmental committee and the Board
of Academic Courses and then the course was floated as an M.Sc. elective.
So, for several years to successive batches of M.Sc. students as well as
senior B.Tech. students who'd opted for this course,
I ran this course by focusing on one of these three main topics.
So, it was three kind of different courses but under one umbrella.
Then of course, today we have separate courses on all these subjects.
So, I mean, actually, you have been involved in
creation of dynamical systems.
[Prof. S. Govindarajan] Now, that's two courses, there is advance. [Prof. Balakrishnan] Yeah, there is an advance.
And, then more recently you added two more courses, you know,
which in some sense, seems to have its origins in synergetics;
[Prof. S. Govindarajan] one is Physical Applications of Stochastic Processes... [Prof. Balakrishnan] Yes. Yes.
And Nonequilibrium Stat Mech.
[Prof. S. Govindarajan] And - and in fact, you have actually given NPTEL courses on this. [Prof. Balakrishnan] Right. Right.
So, can you tell us how your NPTEL courses came about,
especially the first two which I think are
wildly popular, I mean to say the least.
For entirely accidental reasons, as usual,
this was around the time that I was actually retiring from the department
formally, a little later in fact, when I was already on ...
[Prof. S. Govindarajan] But your classical physics and quantum physics was given to a real class.
[Prof. Balakrishnan] Yes. [Prof. S. Govindarajan] You were still. They were all.
Yes, they were given as courses
as you know we had a minor stream
which Professor Ananth had proposed early
and the minor stream started off by saying
the physics minor stream, the proposal was 4 courses;
all 4 generally M.Sc. electives.
So, for a few years it was a little chaotic
because different people who would take
different courses or float different courses among the electives,
depending on the interest of whoever taught the course.
And the course wasn't receiving its
due attention from the undergraduates,
it wasn't being opted for as a leading preference.
So, the department decided to do something about it
and then they revamped it,
there were only 3 courses, I think, now...
[Prof. S. Govindarajan] Now, it is 3 but it started off as 4 [Prof. Balakrishnan] Right.
[Prof. S. Govindarajan] with 2 core. [Prof. Balakrishnan] Right.
So, my suggestion at that stage was
to formulate two new courses altogether for the minor stream
and then have the remaining course of two courses
taken from the list of M.Sc. electives.
And the two basic courses would be an overview of classical physics
and an overview of quantum physics, that was agreed to.
And, then I wrote - helped write the curriculum,
the syllabus for these courses
and then it was suggested that they could perhaps be recorded,
that I could give the courses for the - when they were given the first time
and they could be recorded and that was done.
And that was intended entirely as a recording for the local area network,
for internal circulation alone.
They got recorded and I get these series every day and then I decided
just give it to the student representative
which was done and I forgot about it.
And, then when NPTEL came along a few years later,
I was asked whether these courses could be put under part of NPTEL
and I readily agreed because, I didn't see why they shouldn't be.
The only thing is I didn't edit them in any way because, I realized
that to edit an hour of lectures takes 4 hours of work
and that was too much.
So, I said warts and all, let it be there and then, of course,
if there are mistakes in it, it will be detected by the students
and kind of self-corrected and that is how it's remained.
I did do one or two more courses of that kind and then
the last few were recorded, even them -
all the courses I have given there have been
[Prof. Balakrishnan] courses to actual classes. [Prof. S. Govindarajan] Yes.
They happened to have been NPTEL courses which were recorded,
[Prof. Balakrishnan] but they... [Prof. S. Govindarajan] Except for the series you have for high school students
[Prof. S. Govindarajan] Yes. [Prof. Balakrishnan] which is different in character.
[Prof. Balakrishnan] Can you tell us something about it? [Prof. S. Govindarajan] [inaudible] together.
The mandate there was to do half-hour modules on 11th standard physics
and on 12th standard physics in two different courses
and they were supposed to be half-hour modules.
Hm...I was able to do the 11th standard,
but I still haven't been able to do the 12th, yeah.
And ... you started writing articles for this
nice journal of education called Resonance
which is started by the Indian Academy of Sciences
and I really like this series called What Can The Answer
Be and I think of it as vintage Balakrishnan.
In some sense can you tell us a little bit about What Can The Answer Be?
Well, Resonance started in 1996
and they were looking for articles at that time
and one of the thoughts I had was supposed to be pedagogical articles,
supposed to interest students in science and mathematics.
And ... I was on the editorial board at that time
and one of the thoughts I had was why not
put down some of the useful tricks
that one uses in teaching these courses,
kind of heuristic arguments which could be made rigorous subsequently
after you guess the answer into a systematic set of articles on this.
So, I started by writing 1 and then it grew to 2 and 3 and then 4
and then went on for a few more and I titled it What Can The Answer Be?
The idea being - the philosophy being that you
[Prof. Balakrishnan] use very general arguments such as linearity, superposition, [Prof. S. Govindarajan] Isotropy.
scaling, isotropy, homogeneity, dimensional analysis,
order of magnitude estimates and so on;
all the tricks of the trade of a professional scientist
trying to guess the answers to questions.
And then show that it is indeed the the rigorous answer or whatever.
You can move this up to a point, but I found to my great surprise that
you could illustrate fairly sophisticated concepts like
the reciprocal basis for crystallography
not just in 2 and 3, but in n dimensions.
You could then go on to infinite dimensional
Hilbert spaces, vector spaces,
you could talk about basis sets and change of basis
and the idea of completeness and over-completeness, etcetera.
So, fairly sophisticated concepts could be brought in
from very elementary considerations and that's how this series grew.
I must say I regret not having contributed
more towards that set of articles
but they are sort of time-consuming.
Though, I must admit that some of my lectures
now are titled What Can The Answer
Be and the lecture ... proceeds in
[Prof. Balakrishnan] I - I - don't know where I got that - [Prof. S. Govindarajan] a fashion imitating yours.
I don't know where I got that title from - it may not -
it may not be an original thought at all.
So, I always tell them we are going to imitate 'Professor Balki' as you are called,
we are going to imitate Professor Balki today,
[Prof. S. Govindarajan] we are going to say What Can The Answer Be? [Prof. Balakrishnan] Of course, the greats in Physics have always used such arguments.
[Prof. S. Govindarajan] Yeah. [Prof. Balakrishnan] As you know, the Feyn - Feynman and Fermi and so on are legendary
figures who have used such arguments.
Fermi is famous - back of the envelope calculations -
and Feynman’s heuristic way of arguing even complex ... problems...
[Prof. S. Govindarajan] Yeah. [Prof. Balakrishnan] problems out, their object lessons and how to do this.
So, can you tell us a little bit about your family?
I know that your - both your kids, your son and daughter, studied at IITM
and so, I would like your -
you to tell us a little bit about your family and your
influence in them getting into IIT, influence or lack of influence.
Well, my wife is a theoretical physicist.
We were students together at Delhi university
and then at graduate school at Brandeis
and she worked at IMSC till her retirement.
And when our children grew up,
we have a son who is 7 years older than our daughter -
and when he grew up, well, he went to KV IIT here.
One of the things I realized very early on is that
I simply didn't have the patience to be able to teach him anything.
It's just that I think many parents have this problem
with at least the first child.
They think they can download all their information and experience
at several Tera-whatever-it-is -
TeraFLOPS per second into their children instantaneously
and get impatient if they don't absorb all of this at once,
that doesn't work.
It doesn't work that way at all.
So, my wife was very sane about it and she said, well,
let’s give inputs to the kids only when they ask for it
which of course, was not very often
and this this turned out to be very helpful.
So, we really didn't, you know, interfere in any way or
pressure in anyway: as long as they were doing ok, it was fine with us.
It’s only when Hari- that's my son’s name - when he got to about
maybe the 10th standard or something, that he
showed some interest in problem solving in mathematics and so on.
He got into these various quizzes and
then these Olympiad kind of
problem solving with some friends, he had some very good friends.
And so, he wrote the IIT entrance exam and got in here
into the Computer Science programme.
Long after he graduated, my daughter who went to a State Board school,
and we didn't expect that she would be interested in anything scientific at all.
So, she said - she - one fine morning, she told my wife that
she would like to take the IIT entrance exam.
And then - mean - by this time long before, this promise
had been extracted from me that I won't interfere in any way whatsoever
which I was all the more true in her case.
No, but I remember one legendary story
is that you came proudly and announced
to me and Professor Lakshmi Bala
over a tea that you taught -
tried to teach your daughter complex analysis.
[Prof. Balakrishnan] Well - [Prof. S. Govindarajan] and you should tell us your wife’s reaction to that.
[Prof. Balakrishnan] Yes, I - I must say that residue theorem, residue theorem [Prof. S. Govindarajan] Yeah.
it was - it was a mistake because I felt that -
she was probably in her 7th or 8th or something like that -
I felt that talking about real numbers was meaningless without
introducing complex variables.
So, I tried to do that geometrically
and the poor child was totally confused.
[Prof. S. Govindarajan] To do, yeah, equation of a circle in ... in polar coordinates. [Prof. Balakrishnan] Yeah. Right.
So, I said the equations of common curves in
in terms of a complex variable become very simple.
For example, a circle becomes mod z equal to a
very obvious and then of course,
this totally went over her head and it was a disaster.
So, then, I decided to follow my wife’s advice
and not interfere in this matter at all.
I think she told you to stick to being her chauffeur.
Yes. Indeed.
So, I think it's a good - good idea not to interfere till help is asked for
and then to stick to just that.
The other thing I learnt by
getting involved with them was you shouldn't...
it's true you should explain the basics,
but very often they want an instant answer to
whatever the problem is at that moment.
And if you start going too far back and starting from their basics
then they feel their foundations are shaken completely
and then they don't know which way to move,
they don't have a mooring,
so, it's important not to destroy that, you know.
One more thing which I would like to discuss now
is the evolution of the Physics Department.
So, around the time you joined, I remember it was mostly
a department of experimental solid-state physics.
And, today it's evolved to being one of the largest departments in
IIT Madras and having a wide spectrum
of - of topics, I mean it's probably, one couldn't even argue
that it's one of the better Physics Departments among all IITs.
[Prof. S. Govindarajan] So, could you just - [Prof. Balakrishnan] I - I'd go further and say it's the best.
Okay. So - but I know that you were also involved in this
sort of slow but sure shift.
So, could you tell us something?
Well, clearly, historically, the department started with
emphasis in experimental solid-state physics
or what was then solid-state physics of a particular kind;
specifically, things like colour centres and
you know conventional band structure calculations and so on
and Professor Srinivasan had set up very early on
an extremely successful low-temperature physics programme;
cryogenics and low-temperature physics experimental programme
that must - it must be said that
that was one of the country’s first such programmes.
[Prof. S. Govindarajan] That we had a helium plant, right? [Prof. Balakrishnan] There was the helium plant
[Prof. S. Govindarajan] Working helium. [Prof. Balakrishnan] which arrived here, I believe in 1970 or '71
and which was a kind of one-of-a-kind facility
in this part of the country at that time,
apart from maybe BRC or TIFR.
So, that was a very significant achievement of the physics department,
but after that, it focused essentially on one subject,
one part of one subject.
And it was not even geared to
other developments in condense metaphysics such as
the whole theory of critical phenomena and
even the experimental study of critical phenomena and stuff like that.
But then over the years it started slowly expanding
as it should, as it must, inevitably,
and more and more people came in very slowly at first
and then a little faster later on in recent years.
Till today, I think we have a reasonably healthy balance,
certainly the experiment to theory balance was skewed in the early days.
No one knows what the ideal balance is in the Physics Department,
but certainly 2 to 1 ratio would not be too bad.
Which is what it’s roughly now I think.
Which perhaps is what it is now 2 to 1 or even maybe,
you know, 5 to 2 or something like that would be alright.
But that wasn't attained in those days and it did
it - it was a luck, you know, and that I am very happy to say that -
see that it's been kind of addressed.
We have very good people now
and I think the institute as a whole of course,
and then the department in particular is certainly on an upward trajectory.
I would go so far as to - I said this to the review committee when they
came and of course, I'd retired by then
but I said so, I could say this in a very
casual and irresponsible way and perhaps the review committee felt
a little taken aback by this, they smiled.
When they said the department was a good one,
I said it's the best one among the IITs
and then of course, maybe that is arguable.
But I - I would say that we certainly have today
an extremely vibrant department which is extremely
active both research and teaching-wise, yeah.
You are very well known as a teacher but
personally, I think you are even more remarkable as a scientist.
And so, let us just talk a little bit about your research,
I also know that it's not like you be - you worked on one topic,
your thesis was on S-matrix theory high - you know,
theoretical high energy physics.
And, then promptly in your first post-doc you were doing many body theory
and it evolved over the years.
So, could you tell us a little bit of the kind of problems you worked on
and the evolution of your research?
It - I kind of fell into these problems out of curiosity
... more or less by chance, in some sense.
So, when I ... was in TIFR, I slowly shifted out of high energy physics
which had gone in a different direction then
and the reason was that the gauge theories had just come in,
electroweak unification had just been demonstrated,
't Hooft's papers had just come in.
And I didn't have enough field theory
background to be able to follow this
and contribute in terms of research
but by that time I had also found an interest
in many body theory and statistical physics.
So, I did some work on the Heisenberg ferromagnet
Green's functions for it, low temperature properties and so on
and then slowly moved out. When I went to Kalpakkam,
the shift was to materials science
and we set ourselves the task of doing something new
which is to understand mechanical relaxation
using linear response theory.
[Prof. S. Govindarajan] So, that's how you got into linear response theory. [Prof. Balakrishnan] That's right.
[Prof. S. Govindarajan] Through mechanical relaxation. [Prof. Balakrishnan] Through mechanical relaxation,
because there's a well-established
theory of dielectric relaxation and magnetic relaxation
and the idea was there should be a parallel in mechanics and there is
except that it is for very low strains
and it's things like anelasticity and linear viscoelasticity
which are not of direct interest to metallurgists.
It didn't take long for me to realize that the really hard problems in
metallurgy are non-linear,
intrinsically extremely complicated non-linear complex systems.
But as a baby step, one could look at the linear regime,
the time-dependent elasticity in the linear regime.
And sure enough it turned out
that if you looked at the dynamics of defects
using stochastic as well as statistical methods,
you could formulate ... an approach to mechanical relaxation,
things like anelastic creep and stress relaxation and so on
on the same footing as that for dielectric and magnetic relaxation
and you had the same role played by fluctuation, dissipation theorems
in both the first and second ones in this.
So, we developed that for a few years,
that kind of got me interested in random processes
and stochastic processes
and after coming here I looked at the
problem of hydrogen diffusion in metals
which is a very complicated diffusion problem,
its got mixing of classical and quantum properties here, diffusion here.
And that led me to looking at random box
and random box has stayed a kind of recurring interest for the last
35, 40 years now, many years now.
So, that's one aspect of it.
My first students here we did things on random box
and diffusion and generalized diffusion, anomalous diffusion,
continuous time random box, first passage times and so on
for several years through the decades in the '80s and into the early '90s.
So, you were actually being very productive
at a time when you were teaching 2 to 3 theory courses.
Yeah, surprisingly the semesters
I had the maximum teaching load, I also felt
obliged to do the maximum amount of research
because I felt guilty that I wasn't, you know, spending enough time on that.
So, yes, I think when you're kept busy, then you tend to work harder,
when you when you have a lot of things to do.
Then in the '90s, I slowly switched to dynamical systems
and had a few papers on non-linear dynamics,
got into chaos and stuff like that.
And then a little later into - back to quantum physics
to isospectral oscillators, generalized coherent states, things like...
These were all tailored toward students were on at the time and
what their thesis topics would be like.
[Prof. S. Govindarajan] And, now you are working on quantum dynamics. [Prof. Balakrishnan] on quantum dynamics
because there's this fascinating world of quantum optics
and atom optics and kind of coming together of
fundamental quantum mechanics, operator theory
in the behaviour of -
in a nutshell the behaviour of quantum mechanical systems
which show all the normal complexities of quantum physics
like entanglement and multipartite systems interacting with each other,
along with the fact that classically, these are chaotic systems.
So, signatures of chaos as they translate into these systems,
signatures of non classicality
in mainly in photonic systems, etcetera.
So, it’s a hotchpotch of many things,
but there's an underlying method in the madness -
is a theme which Professor Lakshmi Bala
and I have been exploring for many years
which is to understand using expectation values
of physical observables and their higher moments
and the expectation values of - and correlators
and things like that in quantum systems
And your ideas of recurrence from the early days
is coming back in some sense.
Yes, yes, there are deep connections between
revival phenomena in quantum physics,
wave packet revival phenomena,
fractional revivals, full revivals on the one hand,
and recurrences in the Poincaré sense in classical dynamical system.
So, I have got some papers on recurrence statistics,
recurrence time statistics and different kinds of chaotic systems
including intermittent systems and then
ranging all the way from quasiperiodic
to chaotic fully developed chaotic systems.
And, each of them has their own peculiarities
for the recurrence time distributions
and the idea was to explore if
there are connections with revivals and fractional revivals
in the corresponding quantum counterparts to this
and we have some interesting results.
So, the whole idea is to see to what extent
phase-space descriptions can play a role in quantum mechanics.
As you know on the one side,
you have the Wigner distribution and its generalizations,
but on the other side you could also take a more naive approach
and look at expectation values
of observables and their higher powers and cross correlators and so on,
treat them as dynamical variables in some effective phase space
and see what the plots look like
and what signatures of quantum physics they carry here.
That’s been a kind of general programme,
ongoing programme for about 2 decades now.
One feature of your research which I personally
like a lot is the fact that
you come up with exact solutions,
exact by mean there are no approximations
to ... to illustrate non trivial behaviour.
And maybe you can tell us about a couple of them so that -
Well, I think it's just a personal
like in some sense because I'm not very strong in numerics
or in computation - the students are
and I rely on them entirely for this purpose -
but at the same time, I've always felt that if you have a model
which captures some of the essential features that you want to explain
for more complicated systems,
then it’s worth solving the model as exactly as possible
because any reliability that you place on the
results from this model
shouldn’t be dependent on the approximations that you made.
On the other hand, if you start with a model
which is already a caricature of reality,
or a real physical system,
and then you make further approximations to it and they get uncontrolled,
then any results that you get you have no way of deciding
whether it's an artifact of the approximations
or whether the model has captured whatever you wanted to do.
There's this uncertainty and it's difficult to decide
what to do in such a case.
So, it - it would be good to have analytic solutions to simple models
but of course, what happens in most cases is that
these analytic solutions occur for models
are possible only for models which are extremely simple
and oversimplify the real situation.
So, the trick is to find systems which are not oversimplified,
but which at the same time can be analytically solved
like one dimensional models, for example, very often are solvable
but they may not have real features that you may want to capture.
Just to give you an instance, not something I worked on,
even if you know that the one-dimensional Ising model
does not have a phase transition in the standard sense,
you'd still like to understand correlation functions
or the renormalization decimation procedure
from these one-dimensional models,
where it can be implemented exactly.
So, they still have valuable lessons to give
for more complicated systems.
Ok. So, the last part we will just...you've been writing books over the years.
In fact, your first book was written when you were at ... in Kalpakkam.
So, can you just tell us
something about the various books that you've written?
The first book was not written - it was written with -
[Prof. S. Govindarajan] You were already in IIT Madras. [Prof. Balakrishnan] I was already in IIT Madras when it was published,
it was a Springer for book on the Solid-State Sciences.
We had, in Kalpakkam, looked at topological defects in condensed matter
a little bit, didn’t do much original research on it,
but we looked at what kind of arrangements could -
how you could understand the structure of glass.
So, it was basically a disordered system
and there were ideas floating around at that time
due to the French school particularly,
that maybe there are regular tilings in curved spaces and when
projected onto Euclidean space, they looked disordered the way they do.
That’s an oversimplified idea
but in that connection there were proposition,
there were suggestions to have
quote unquote Gauge Theory of Glass,
using the Gauge theory of defects and
dislocations and disclinations which had been developed
by people in continuum mechanics.
Now, that programme didn't really go too far at that time
but we decided to write a short monograph
explaining in very simple terms, the notions of symmetry, broken symmetry,
broken ergodicity
and then give an introduction to gauge theories in this context
and that was the Springer book which came out in '89,
it's called Beyond the Crystalline State,
because it dealt with things beyond the normal lattice dynamics of crystals.
We even included a little bit about quasiperiodicity,
incommensurate phases, Penrose tiling and so on.
Later on, much later, I wrote this book on Nonequilibrium Statistical Mechanics
based on the courses I have given here, basically [inaudible].
[Prof. S. Govindarajan] This was after retirement or - [Prof. Balakrishnan] Book was published in 2008,
but I had the, yeah, in the last year or two of retirement,
I had already started collecting material on this.
It was a set of notes that I had written when I was in Kalpakkam
as a report and then that got elaborated
and the book should have been written earlier but I just didn’t do it.
And then after 2010, I started collecting material
which I had been giving in earlier courses in Mathematical Physics
and it was - that book has been published this year,
late last year - early this year, that was a major effort.
It took me more years than I thought it would,
I thought I'd finish it in 2 years, it took me 4 times as long
or three and a half times as long.
And I know that you are working on
many more book projects and
so, what is your - what are you currently working on?
... When I started this Math Physics book seriously
I put on the backburner a book on problems
and solutions and non-Linear dynamics
which in all these books I wanted to have a - a point of view
before one would start writing a book.
And in the case of this Non-Linear Dynamics book,
the point of view is that I'd like to lay equal emphasis on
Hamiltonian or conservative systems as on dissipative systems
and equal emphasis on discrete time dynamics
as on continuous time dynamics.
So, maps and flows - with that view, I have several chapters already;
I'm well into the book I'd say about - it’s about two-thirds complete
and I hope to finish it fairly soon.
And what are the other projects in the annual?
Well, there are several research problems
which I should pay more attention to,
for which every now and then I get scattered away from it,
there's a kind of desire to write another book of problems and
solutions on conventional statistical physics.
I have the material ready, it's just got to be [inaudible]
I haven’t done that and then it has to be expanded
and that would be one thing which I...
I have a couple more distant dreams
but I am not sure whether - one at a time I think.
[Prof. C. S. Swamy, off-camera] Excuse me, by the time you joined, the Physics Department had
stopped doing demonstrations [inaudible] the first year students.
[Prof. S. Govindarajan] No. [Prof. C. S. Swamy, off-camera] The Physics Lecture Theatre, Chemistry Lecture Theatre,
they used to conduct the
[Prof. C. S. Swamy, off-camera] first year class because they had to show the demonstrations. [Prof. Balakrishnan] Oh yes, yes, oh yes.
[Prof. Balakrishnan] Well, even after I joined, this went on for many years and [Prof. S. Govindarajan] Even in 2014.
[Prof. S. Govindarajan] I actually had demonstrations. [Prof. Balakrishnan] Yeah.
[Prof. C. S. Swamy, off-camera] You had, is it? [Prof. S. Govindarajan] Yeah.
[Prof. C. S. Swamy, off-camera] Ah, because professor - from the time of Prof. Koch, [Prof. Balakrishnan] Yeah.
[Prof. C. S. Swamy, off-camera] And [inaudible], it had started. [Prof. Balakrishnan] Yeah, they...
[Prof. Balakrishnan] And in fact, they used to have the classes only in those days, that's the thing. [Prof. Balakrishnan] Yes.
the - the Lecture Theatre was built specifically
so that they could actually illustrate mechanics.
They had a lot of very beautiful demonstrations equipment,
piece of equipment from Germany
and in particular, they had this huge turntable
on which you could place 2 chairs
and then you could have a rotating frame of reference, illustrate
[Prof. Balakrishnan] all the non - inertial forces and angular momentum. [Prof. S. Govindarajan] Rotating wheel.
Yes, it’s a pity that these went out
partly because I think the curriculum got abbreviated,
got foreshortened; it was assumed.
I remember distinctly that in the '80s,
it was specifically stated almost that
students had already read those who got into IIT had already absorbed
what was in Resnick and Halliday.
And therefore, there was no reason to repeat
elementary mechanics anymore
and it got an early - you know, it - it - it was discouraged to some extent,
the curriculum didn't have space for this and then
[Prof. Balakrishnan] gradually the number of... [Prof. S. Govindarajan] But still there were demonstrations.
We still have and I think it -
[Prof. S. Govindarajan] Few times. [Prof. Balakrishnan] wherever it's possible it should be revived,
but in the presence of - in the availability of
[Prof. Balakrishnan] very good animation and things on - [Prof. S. Govindarajan] And YouTube.
On YouTube, this has become a little per se
but I still think that a live demonstration - nothing like it, I mean.
I remember not too many years ago going to a school and then
they had issues with understanding
the 12th standard electromagnetic waves:
the idea that you have transverse waves
with electric and magnetic fields in perpendicular directions
oscillating and then a propagation in the third direction.
We have a beautiful piece of equipment where you have rods in
two perpendicular directions coloured differently and you rotate a
wheel and there's this beautiful wave
motion which appears to propagate
and that single piece of equipment is worth
dozens of pages in textbooks and explanations,
because all you have to do is to rotate this wheel
and students understand instantaneously
what polarization is and what transverse waves are.
So, in that sense, I think that these demonstrations should be
to the extent possible, revived;
unfortunately, the classes are extremely large now.
And also my experience from 2014
was that we had 850 students
and so, PHLT can hold 200.
So, what we did -
we broke them up into 4 batches
and turns out that many of them were not interested because
attendance was not compulsory.
And ... the - when I mentioned this to
students who graduated maybe you know
6, 7 years ago; they said: sir, we used - may have bunked classes
[Prof. S. Govindarajan] but we never missed the demonstration. [Prof. Balakrishnan] Yeah.
Also you get chocolates, you are asked questions
and you you get chocolates and that was you know they said
you know I remember PHLT would be filled
and people sitting in the stairs,
you know not just - seats were not enough.
And ... but times have changed in some sense.
[Prof. C. S. Swamy, off-camera] I have another question, your notes for the NPTEL.
This is meant at the - for M.Sc. standard, Master's standard
or is it at the - the engineering students only,
the books - I mean, the lectures you are doing under NPTEL.
The courses on overview of classical physics
and overview of quantum physics
were specifically undergraduate courses,
they were part of the minor stream.
On the other hand, I did introduce topics especially
in the second course on quantum mechanics
in - in the course on quantum physics.
I did introduce some topics which were little more advanced
and the notes do contain some material which
is more advanced on operator theory and so on.
The courses on Mathematical Physics and Stochastic Processes.
[Prof. S. Govindarajan] Non-Equilibrium. [Prof. Balakrishnan] Non-Equilibrium Statistical Physics,
these are M.Sc. courses.
Those are M.Sc.-level courses.
Although in all the courses that I have taught throughout my career at IIT,
they've always been open to undergraduates,
I've always given consent of teacher for whatever
to whoever wants to attend these courses.
Although, undergraduates maybe in the first
year or two may not be able to -
wouldn’t have enough background material to take these courses.
But in the third and fourth years I have had large numbers of undergrads
taking these courses as electives.
[Prof. C. S. Swamy, off-camera] The reason I asked you was, you know, Ramakrishnan, Venki.
He talks about the Berkeley lectures which
[Prof. C. S. Swamy, off-camera] he learnt in Baroda University. [Prof. Balakrishnan] Yes.
And of course, IIT Kanpur they were talking about Richard Feynman’s lectures.
And two volumes you know.
So, those are meant for the Bachelor’s level or at the Master’s level?
[Prof. C. S. Swamy] Feynman’s or. [Prof. Balakrishnan] Ok.
[Prof. C. S. Swamy] The Berkeley lectures. [Prof. Balakrishnan] Yeah. Let me take the Feynman lectures first,
he gave them in the early '60s to undergraduates.
But, as is well known from what he has said in - in the book itself,
as the lectures went on, more and more undergraduates dropped out
and more and more graduate students
and faculty members attended the lectures.
So, they were learning.
So, clearly Feynman’s viewpoint was so original
and things were so beautifully meshed together and brought in,
that it's only people who already had a knowledge of
the subject at some basic level could appreciate this.
So, it's like you know an exquisite music concert
and the lectures themselves apart from the
first volume's initial lectures reflect this
because the topics are absolutely eclectic.
Everything is brought together,
you see this incredible unity of the subject,
but it's not a textbook for beginners, certainly.
On the other hand, the Berkeley physics course was a deliberate effort
to have a 5 volume set of books
accessible to undergraduates
and it's my personal opinion that to this day, they remain the very best
set of textbooks for undergraduate physics.
Book 1 is on Mechanics, book 2 is on Electricity and Magnetism,
book 3 is on Waves and Oscillations.
4 is on quantum physics, 4 is on statistical physics
and 5 is on quantum physics or vice versa.
They're all written by extremely competent people,
very very good people and the textbooks are brilliant in their own way
[Prof. Balakrishnan] and they are at a lower level. [Prof. S. Govindarajan] Purcell's introduction.
[Prof. Balakrishnan] Purcell's introduction ... absolutely. [Prof. S. Govindarajan] of magnetism is.
So, each of the books is a gem
[Prof. Balakrishnan] Reif’s book on Statistics Physics is an absolute gem; [Prof. S. Govindarajan] Statistical Physics.
if a student reads - goes through those books,
he or she doesn't need anything else for undergraduate physics.
I would say B.Sc. Physics Theory you have.
Absolutely and I would say good part of the Master's too,
except for specialized subjects.
And in that sense I think the Berkeley Physics Course
which is available in an inexpensive edition in India today
is a great help and you know I very strongly recommend it to colleges,
to students everywhere in the country.
[Mr. Kumaran Sathasivam, off-camera] Professor Balakrishnan, can I ask you about the connection. [Prof. Balakrishnan] Yes.
that you mentioned with Professor Srinivasan, which brought you to IIT.
Can you tell us about that?
How did you brief [inaudible] about that?
I'm not very sure exactly, I don't recall exactly when I met him first.
There was in this of course, I came here in '76 and '77 as I mentioned
and Professor Srinivasan by that time already was well-known
to be the leading expert in lower temperature physics.
So, people in Kalpakkam were interested in this year.
And, on trips to Madras I have visited IIT during that time,
we'd come in a minibus to do various things in - in Chennai.
And, I've spent days in IIT and looked at the lower temperature lab
and got to know him then, we have a working helium plant, I mean.
It was fascinating absolutely.
And I got to know him then and Professor Srinivasan and my old
boss at Kalpakkam, Dr. G Venkatraman, a very well known
physicist from the Atomic Energy Department, they were close friends.
They are contemporaries and close friends,
I believe they were even college mates
maybe not...within a year or two of each other I guess, Presidency College.
And they knew each other very well.
So, I got to know Professor Srinivasan through Dr. G. V. as we call him.
And then he suggested that a course on Quantum Theory of Solids
kind of modernizing solid-state physics be framed
and taught in IIT and I think Dr. G. V. suggested my name for it.
[Mr. Sathasivam, off-camera] Was that for the - I mean, there were only M.Sc. students right?
There were only M.Sc. students in that course.
So, I started giving that course here,
I would come 3 days a week in the minibus
and then give the course and spend the day here and go back in the evening.
And, as the course got given, it - I - I had a full room
of people and they were not all the M.Sc. students,
there were many research scholars here
and there were students from the theoretical Physics Department
at I - at the University of Madras
because Professor Matthews heard that this course was being given
and he suggested I [inaudible].
It was not a credited course.
It was an M.Sc. elective.
So, I didn’t take care of the administrative part of the course,
since I was not a faculty member here. Yes.
So, I do not know who graded the course and who gave, you know,
who gave the grades and so on,
but it was an M.Sc. elective at that time... Oh, it was.
and... But you mentioned university students, how did they
how did the university students - Professor Matthews,
he is a contemporary of Professor Srinivasan and G. V.’s.
So, he heard about this course, I guess
and then he suggested that some of his students attend it here.
[Prof. S. Govindarajan] Just auditing, I guess. [Prof. Balakrishnan] They they would audit, they audited the course.
So, the notes that I made for this course, I did a lot of reading up and so on,
I wrote as a reactor research centre report, a big report
and sent it out to various people.
And I didn't take their suggestion,
people suggested that I should make it into a little book
and I should have done it at that stage, of course.
But the notes, the - the report was quite popular; many
copies were distributed to people and so on.
And then, in the second year in '77, Professor Srinivasan said
I should repeat it since people - it had been favourably received the first time.
And after that...he was - he expressed interest in my coming to IIT.
He said I should really come here and you know teach
and the opportunity didn't present itself till 1980 or so,
and then when I did, I did take his advice and applied.
It’s good for IIT sir,
I - I would like to also ask you about the colleagues
you had in those early years, in the 1980s
and about the facilities of the department at that time.
I'm pretty sure the facilities were nowhere near what they have now,
that's very obvious... As far as
I was concerned since the only facilities I needed were
[Prof. S. Govindarajan] Cyclostyling machine. [Prof. Balakrishnan] Paper and pencil and a waste basket.
So, I didn't feel the need for, you know, I didn't feel any lack of facility,
there was plenty of academic freedom here.
And... Professor Indiresan was the Director
and he essentially I think
had a lot to do with the the credit-based semester system here,
in this institute and he gave complete academic freedom to people
and... he introduced - I think he introduced relative grading,
I wouldn’t know because I don’t know
what the system was before I came here
but the very first courses that I taught in Physics-I, I still remember
we had to fit a Gaussian to it and then there was a...you gave
[Prof. C. S. Swamy, off-camera] Yeah, Gaussian. [Prof. Balakrishnan] You - you put cut-offs and then those who had
[Prof. Balakrishnan] full attendance were shifted into... [Prof. Swamy] Yeah, yeah.
[Prof. S. Govindarajan] That extra marks you had, right, [Prof. Balakrishnan] they were given a little extra thing
[Prof. S. Govindarajan] if you had at- [Prof. Balakrishnan] to move them to - if you were within a certain range.
So, it was an elaborate exercise.
I have one story to tell about
may not - my memory may not be totally accurate
to tell about the grading: the very first course that I taught
in in the undergraduate programme in '81.
It was Physics-I in the semester July to December of 1981
and out of the total number of students who took Physics-I,
the grades in those days were not S, A...
[Prof. S. Govindarajan] Just A B C D E. A B C D U. [Prof. Balakrishnan] A B C D E.
[Prof. Balakrishnan] There was A B C D and F. [Prof. S. Govindarajan] U
[Prof. S. Govindarajan] U for fail. [Prof. Balakrishnan] For fail if I remember correctly.
Yeah, there was an F for fail
and we drew this - I drew this histogram, there were four of us teaching it
and myself, Professor Srinivasan, Ramabhadran and Swaminathan
and we went strictly by the book.
We drew this graph, it was a beautiful Gaussian,
there were 240 students in the class and we gave this.
[Prof. Swamy] It was very difficult to get the Gaussian in this [Prof. Balakrishnan] Yes but the number of days
[Prof. Swamy] Small number. [Prof. Balakrishnan] given in the course was a handful,
like 6 or 7 out of 240 -
this created some comment because they said
I still remember being told this: they said,
well, the number's much larger in Chemistry,
it's much larger in Computer Science,
much larger in Mathematics.
How come it’s so hard in Physics? It’s impossible.
So, I...you know, I kind of shrugged my shoulders and said that’s what the
that’s what it says here, because if you did
1.2 times the standard deviation and you went beyond it
and gave A grades, that's the number and you,
by definition you've said A is outstanding or excellent,
B is very good, C is fair and D is marginal and E...F is fail.
So, I take that literally and the matter was taken up
and then I had to explain that...
I was asked whether physics was different in any way
to which I kind of said maybe intemperately I said: yes, it’s different.
And I was asked how, how it's, why is it so different?
Then I kind of tried to explain that while Mathematics was
something which, there was a set of rules
of calculus or whatever they were teaching, Real Analysis,
and if you mastered those rules, you mastered the subject.
Chemistry likewise, Chemistry they did not try to
explain the Quantum Theory of valence which is very hard.
They said there is this element, has this valence
and this valence and so on and that was the end of it
and Computer Science also was a set of rules.
But Physics was a situation where according to the syllabus we had,
you took a physical system and you changed,
you formulated a physical phenomenon in mathematical terms,
solved the equations that arose using mathematical tools
which the students who were just learning
and then reinterpreted the solution back in physical terms
and this two way translation is hard enough for professionals,
much harder for young students.
So, that's why Physics at that level is more difficult
than Chemistry or Mathematics or Computer Science;
at least so I thought, that is how I felt.
And in any case, this apparently had reached Professor Indiresan’s ears.
[Prof. S. Govindarajan] Wasn’t his daughter part of that class? [Prof. Balakrishnan] Pardon me.
[Prof. S. Govindarajan] His daughter. [Prof. Balakrishnan] I am not sure if she was also in that class.
She was. She was. She was in that class.
[Prof. Balakrishnan] Might have been. [Prof. S. Govindarajan] She is 1 year my senior so,
But in any case the grades
fell where they fell and
Professor Indiresan casually met me one day near the Ad Block
and by this time I realized post facto that it had gone to him
and so on because you know I stuck to the grades
and we - we as a team stuck to the grades and so on.
So, he said: it appears that you are very harsh in grading.
I said - I was taken aback and then he added as he passed by, he kind of said, "but fair."
So, it's ok and then he went off.
I still remember that and...
[Prof. S. Govindarajan] So, Professor Balakrishnan, thank you so much. [Prof. Balakrishnan] Thank you.
For giving the Heritage Centre your time.
[Prof. S. Govindarajan] Thank you very much again. [Prof. Balakrishnan] My pleasure, thank you.
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