From Black Holes to Anti-Superstition – Interview with Dr Atish Dabholkar (Tamil version of this interview is published in April 2019 issue of Puthagam Pesudhu)

Interview By : Subashree Desikan Transcribed by : Ma Sivakumar

First, I would like to know about your personal life. Narendra Dabholkar is very famous. We know so much about him. In a sad way his life ended. Can you talk about your relationship with him? Did you imbibe his rationalism as a youngster? Did you interact a lot with him?

Dabholkar : We are a quite close family. He was a very dear uncle, he was a very nice uncle. Take us to movies and things like that. Both my parents are also rationalists. My mother is an atheist without any compromise. My rationalist approach started there. I was particularly interested in Narendra Dabholkar as I became a scientist. I came to appreciate what he has been doing. I argued with him and talked with him quite extensively over the years. I did take part in some of his campaigns.

Later, after his death I got more seriously involved in a signature campaign. We had a website to collect signatures of some 3,000 scientists and 100,000 citizens. We succeeded in getting the support. Of course, this movement was going on for many years and people have been working on it. My colleagues worked a lot on this, they drove this and deserve the credit. But, this campaign played a role in getting the law passed. Especially, in making this issue known to the scientific community.

I would not say that I necessarily learnt my rationalism from him. But something I felt intellectually close with. He was a close uncle.

Did you do any activities with him as a child or as a youth?

Dabholkar :

I went for a couple of programs and they used to have camps for various things. But not very significant way, only marginally. But I did read and discussed with him a lot. My own interest was not in the direction of social, I was certainly interested in making a commitment. The focus of my work was mostly in science which is more academic.

As a citizen, I am certainly interested in these issues. These are very important s. Somebody at home was making a very big contribution. I was certainly involved in that.

Was he celebrated in your family?

Dabholkar : Not particularly. Everybody in my family is kind of unique, I would say. My father got the Bajaj award. He was a mathematics graduate, a professor in college. But he was interested in people science, farmers. My various other uncles also have their own peculiarities.

About your education. You passed Masters in Physics from IIT Kanpur in 1985. Then you went to the to do PhD. Was it at that time, RR and HS Mani were professors there. It was considered to be the best Physics department in the country.

Dabholkar :

That was one of the reasons I went all the way to Kanpur. My parents were worried. They wanted me to go just to Bombay. In those days to make a phone call, you have to book a trunk call. Sending letters use to take several days. They never pushed us, they gave complete freedom to pursue what we wanted to do.

Many parents were against going into pure sciences when you have an IIT admission. I was quite sure I wanted to do physics. They completely supported me. If you think Kanpur is the best place, you think, you go. Whatever happens to your it is your decision. I think that was the right decision. It was quite an inspiring place in those days, because of very good professors.

When you prepared for IIT itself you prepared with a view to go into Physics?

Dabholkar :

1/6 Yes, I was quite sure that I want to do Physics. I did not prefer IIT. I sort of took it on the side. I did okay, not particularly brilliantly. Both my parents were not particularly oriented in one direction. They were not pushing to go to IIT.

I was thinking of this curious co-incidence. also went to IIT Kanpur. He also topped in IIT JEE and went there. He took up later on. Is there something about IIT Kanpur which makes you go towards String theory.

Dabholkar :

Particle physics and string theory were exciting that time. Things have changed now, people prefer different fields now what become fashionable. I think some of the professors were more oriented towards theoretical particle physics. Later there are very good professors who do theoretical condensed matter. More students went into condensed matter physics in the 1990s. Rajesh was 6 years junior to me, I think. He sort of followed me. When I finished in Princeton, he joined a year later.

Who was you thesis advisor in Princeton?

Dabholkar : Jeffrey Harvey. He was one of the Princeton String Quartet. The famous paper on Heterotic String theory.

Who are the four?

Dabholkar : David Gross, he was the Nobel laurate, Emil Martinec and Ryan Rohm.

How was Princeton after the IIT-K experience. Did it adequately prepare you for it?

Dabholkar :

Yes, I was adequately prepared. There are a lot of cultural issues. In those days they were more severe than they are now. Even things like washing machine I have not seen in my life. Landing at midnight in Princeton was an experience. There were no phones, connectivity was not like today.

Scientifically I was very happy. IIT education has very well prepared me for it. Quite solidly I would say. There were a lot of students from Harvard and so on, top places in the US. I actually was probably ahead of them. I cleared by qualifying exam quickly.

You came back to work at TIFR after that?

Dabholkar :

Yes, because of my family background, I was quite keen to come back. Because of my family background I always felt a social commitment towards India. I have always felt that we have benefited from such excellent free education in IITs. It was always a thought in my mind to find a way to give back.

TIFR offers that kind of opportunity without compromising on science. It was a very strong group in those days. I think during our time it became stronger. It has an International profile, it was not like we were. It was among the top 10 places in the world. Many post docs from abroad used to come. We organized string conference in 2000, I was one of the organizers. Hawking had come. He was in India to talk to us. The level of the group was high enough. It was not like we were travel agents.

After that why did you leave Bombay?

Dabholkar :

Mainly for personal reasons, my wife is from Europe. Otherwise I was quite happy. I would not have left. I was very happy. I felt good about whatever little contribution I was able to make to Indian science. Just lecturing at various places, training students, being there, organizing conferences and giving some profile to these places. That was very satisfying.

Recent times, do you feel the need to get involved in social mobilizations? Apart from physics, academically.

Dabholkar :

As I said, I did get myself involved personally. For six months I sort of put Physics on hold. I sort of got this website designed. I really knew nothing about website. For 6 months, I came here. We marched on the streets of Bombay. I really took time off. But you can not do science at very high competitive level and do this at the same time.

But at the same time, I think, people like me or whoever are privileged enough to do, it is there responsibility. I think everybody should find a balance in where you can contribute. We don’t want to also dissipate your energy. Pick some thing where you can make a contribution. For six months I was working on this and then I switched back to Physics. Whatever little contribution I could make I had done. There are other things. Implementation of this law is an ongoing battle. There, all the activists – Andha Shraddha Nirmulan Samidhi (AniSa – Anti Superstition Forum) are in the front. They are the ones who are pushing this forward.

2/6 But I was not in a position to make a contribution at that level. But there was a different place. I helped them to raise money for a science van. It was Rs 50 lakh. Those are the kind of places where I found a role of for myself.

[AniSa was founded by Dr Narendra Dabholkar]

We will go on to the string theory questions. Can you explain to a lay person, what is string theory and why it is so important in Physics?

Dabholkar :

At the moment string theory is a theory, not an established fact of nature. It is an exciting theory where some of the very long standing difficulties in theoretical physics. There is a hope to resolve them in a consistent way. One of the big long standing difficulty is the conflict between General Relativity and Quantum Mechanics . Both them work very nicely, in their respective domains. But they are inconsistent with each other. And in science we can not tolerate such situations where we have inconsistent theories. It is a kind of, no option. We have to find.

Our means are limited, our brains are limited, our resources are limited. May be we can not go beyond the LHC (Large Hadron Collider). When this will happen is not clear. Unlike in the early 20th century, when there was a huge amount of data. Or in the mid 1970s when a huge amount of data was coming from particle accelerators. That kind of situation doesn’t always arise. We are also in a different point in the history of science. One should not try to follow the earlier methods.

For example, the Higgs Boson took 50 years to discover. To establish that it is a fact of nature. There is no doubt that spontaneous symmetry breaking, Higgs mechanism are clearly correct ideas. They will get incorporated in some way in the final theory.

String theory is a bit like that, it is a lot harder than discovering Higgs Boson. That took 10 billion euros, LHC and thousands of scientists. String theory is going to take even longer. But, some of the early promises of string theory on particle physics has not worked now. There are issues about finding the correct vacuum of the theory and so on.

But other hand, String theory has made very surprising and dramatic advances on conceptual frames like blackhole physics, holography etc. Very surprising and so remarkable that I don’t doubt it captures some element of truth. For example, holography is a very remarkable equivalence between theory of gravity with a theory without gravity. This sound almost like impossible. How can this happen? Because in one theory things fall, In the other theory things do not fall. But somehow strong coupling and the other theory starts look like a theory of gravity. There are such non trivial checks of this equivalence that we can not dismiss it.

It is a little bit like the analogy I gave. You can find it in the internet also. I gave in an interview for ICTP when I became the head. I gave this kind of analogy.

You are in some archaeological expedition. And suddenly, you find very beautifully carved pillars. But you really don’t know whether there is a sanctum santorum or whether there is a big temple or what. But if you are an archaeologist it is foolish to stop digging. There is something there. We need to find out what it is. May be it is not what we are after. But it is interesting enough that ignoring it is not an option.

How many people are going to string theory? That is a matter partly decide by market, availability of funds and so on. Or how productive these ideas remain. But I think it may happen that fewer people may work on string theory. That may be completely possible. But I think that our scientific community has sufficient integrity to control it. It is not that string theory work will keep on happening even if no progress takes place.

Super symmetry is supposed to be a very important concept in string theory. Why is it important? Can you give an idea?

Dabholkar :

Super symmetry is an unique extension of all the known symmetries, that is allowed by the principles of quantum field theory. We have some symmetries like translation invariance is a symmetry. Laws of Physics don’t change whether you look at them here or in London. Stones fall in the same way. That is called translation invariance.

3/6 Similarly, time translation invariance is a symmetry. Laws of physics don’t change between today and tomorrow. There is an extension of this symmetry translation that is called super translations.

Translations in additional odd dimensions, fermionic dimensions. What is interesting is that Quantum Field Theory allows only a very small number of symmetries. Super symmetry is the only one we have not found in nature. All other symmetries we are able to implement. Since it is the only theoretically allowed symmetry that is missing, it is a very good guess to think that it is there. It may turn out that it is not there. But usually, this kind of theoretical principles are so powerful nowadays, if they tell you that something is possible, it is almost always possible.

Guage theory was an example. Theory of strong nuclear interactions and electolyc theory. They were explored only by consistency of guage theories in the beginning. There was no direct strong experimental motivations to begin with. But, the structure of the theory was so constrained that this was the only way you could quantize spin 1 particles. Spin 1 particles are like vector bosons, photon is an example.

Similarly string theory is the only known way to quantize the spin 2 particles. Spin 2 particle are like graviton. Since there is not other option and this option is so deep and constrained, it is worth taking seriously. But one should keep an open mind, if we are in the wrong track, it can happen.

But, if you don’t find super symmetry, does it mean string theory will break down?

Dabholkar :

Not really. String theory does not necessarily require a low scale super symmetry. For some other problems like, in particle physics super symmetry is required at low scales. For the consistency of string theory super symmetry is not required in low scales. It is possible to imagine situations like super symmetry is at say 100 times the energy scale explored by LHC or 10 times. So we would not see any evidence for it now. But it will still be required for the very high energy where string theory comes into play.

There is no absolute. Ofcourse, if super symmetry was discovered it would have been a huge boost not only for string theory but for all of particle physics and for LHC. It was a bit disappointing, we are sort of around the corner and there is no super symmetry. That is life. We have learnt something.

If there is no super symmetry it tells us something that there is a real gap in our understanding of electrolyc symmetry breaking. Such things are interesting. As I said in my talk, such conflicts are interesting. Because that is what you try to resolve, new ideas will come. It is super symmetry.

I attended a talk Strings 2012. You were there. Nima Atkani Hamid gave a talk. He was talking about some new way of convincing yourself that Super Symmetry exists by looking at the distant galaxies or something. Do you remember that?

Dabholkar :

I don’t remember that. But there are many speculative ideas in that direction. It is one of them. I don’t think that there is any particularly special or importance about that. We will not go into that.

To move on to the other thing. How does quantum theory modifies the entropy of black holes?

Dabholkar :

That is also a fascinating subject, I have been working on this for the last 10 years. Hawking had this famous calculation for the entropy of . Beckinston and Hawking. But that is for the black hole whose area is large. But ofcourse black hole with small areas can also equally well exist.

And then Hawking’s famous formula which is entropy is area divided by 4 is expected to received corrections. Because quantum physics becomes important. And how to calculate. In physics if you have very nice formula, one should ask what are the corrections to it. Are they big, are they small, are they controlled, are they meaningful, how to calculate them. That was the kind of I was interested in.

It was all kinds of interesting connections with mathematics, interesting connections with the idea of holography I mentioned about. It really proves , because we are computing quantum corrections to some classical answers. From that point of view, it is an interesting to learn about quantum theory of gravity.

What is the Ramanujan connection here?

Dabholkar :

4/6 Ramanujan connection is that when you try to study, explain the entropy of black hole as part of counting problem. It is counting of some dimensions, hilbert space. Basically counting some number of configurations of the system. Those configurations can be obtained, related to a kind of counting problem.

Ramanujan was very interested in some of the counting problems. How do you partition an integer into smaller integers? If you take 3, you can write it as 1+1+1, or 1+2, or, 2+1 or just 3. There are so many ways of partitioning the integer.

That problem is directly related to the problem that arises in explaining the entropy of black hole. Ramanajan’s work has turned out to be quite influential. For the methods he developed. Later on, some of the more exotic things he talked about, called mock modular forms also very surprisingly involved in our exploration of multi centered black holes. So, somehow, the power of his ideas was such that they found a way to be useful.

The mock modular forms are different from mock theta forms?

Dabholkar : Yeah, they are related. Mock modular forms are generalisation of mock theta forms.

Did this just happened that you got these forms and you realized they are Ramanujan’s work?

Dabholkar:

I had read about mock theta functions when I was undergrad. There was a very nice lecture in 1989, I remember, something Dyson, Ramanujan’s centenary, he gave a beautiful lecture. Later on I had the opportunity to give our paper to Human Dyson, he was with institute of advanced studies. I got a very nice letter from him. The talk was called “A walk through Ramanujan’s Garden”. He talks about all these weird things.

Our paper actually starts with his quote “one day I hope, these are very beautiful things, but I don’t know, some day some bright young physicist will find use for it. One day I will.

We actually did. I was very thrilled, I sent him the paper and met him when I was in Princeton. And in the beginning he took some time to really understand it. Then I got a very nice letter from him saying that you have really developed a much beautiful structure based on my very simple comment. I really enjoyed it. I really did not understand all of it. But I can see the connection with what I had worked on.

Actually, you showed clipping from Man who knew infinity movie. At the end of the movie there is a slide which says now even mock theta functions are even applied to black holes? Is that reference to your work? When I saw that I wanted to find out.

Dabholkar : Yes, it is reference to our work actually. It made to the popular culture. Nobody else has done this, it is our work.

What is the next step in your work?

Dabholkar:

I am working on many other things, they are related mostly to problems in quantum gravity. One is the issue of entropy of – can we calculate the entropy of non super symmetric black holes, there are very interesting connections with entanglement and quantum information. People are exploring holography. There are many. There is no huge big problem on the horizon. But there are a lots of very interesting directions to pursue. That is a good time, often times new things come.

Do you have to do a lot of administrative work as the head of high energy physics lab?

Dabholkar :

Fortunately ICTP is a very well organized and well run place. It is more like providing some directions to the hirings we do and I think you can play an important role there. Administratively it is not onerous. It is not taking time away from my research.

Do you get a lot of Indian visitors?

Dabholkar :

ICTP has 6000 visitors every year from all over the world. Half of them are from the developing world and a good fraction of them are from India. That was ICTP is a very international, very dynamic place. Often times, both from developing and developed world. Many of friends, condensed matter who are in different places in the US, France. I meet them more often in ICTP than anywhere else. Because they usually come for some event.

Do you visit India often?

Dabholkar :

5/6 Once in a year, I try to visit my mother who is in Maharashtra. Also usually visit Tata Institute and many places like IMSc, ICTS.

Is there anything else you wish to say?

Dabholkar :

I would say that Indian science is at a special juncture at the moment. Some of the goals people like Baba have been accomplished. We have quite good quality institutes, we should have the ambition to take the next step forward. Try to be a center in some fields.

It is not easy, just like cricket it has happened. Ofcourse money is different in cricket than in research, but it is conceivable that as the center of cricket shifted from England to India, I think countries like India and China have the potential. China has a much bigger pockets, India should not.

Ofcourse, as a socially concerned scientist we also have to prioritise other things like primary education and drinking water for everybody. But even so I think our investment in science and our attitude toward science have taken a hit. If you look at the Indian National Science Congress yesterday, it was a kind of embarrassing. Kind of things people are talking about.

I think, Human resource in Indian are in some way better developed than in China. Atleast in my view, I know that, I have visited Shanghai and places like that. We have very high quality people in India. I dont know we can leverage that to what extent. But, we should aspire to do better that what we have done so far.

1. String Theory

Matter is composed of atoms, atoms of Protons, Neutrons and Electrons, they in turn are made of quarks. String Theory considers quarks as strings and investigates their properties.

2. Condensed Matter Physics

The study of how the fundamental particles created by energy in Big Bang combined to form liquid and solid matter.

3. Symmetry Breaking

In Big Bang Theory matter and antimatter were created in equal quantities symmetrically. Then, matter and antimatter annihilate each other. But today we have matter, i.e the symmetry between matter and anti-matter is broken. This is called Symmetry Breaking. Why and how this happened is an unanswered question in modern science.

4. Super Symmetry

Theoretical Physics postulates that just after Big Bang each fundamental particle found in today’s universe would have had a super particle. This is called Super Symmetry. Research into this is called uper Symmetry Studies.

5. Entropy

Entropy is an important concept related to energy. Simply put, it states that omlette can not be turned back into eggs. In the universe we can move from certain energy states to certain other energy states only.

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