Tuesday, July 13, 2010

Satish Joglekar -- in Memoriam

Satish Joglekar of IIT Kanpur died last Saturday. He was feted as a great teacher, but he had also contributed significant papers on the renormalisability of gauge theories. Here is a little note I sent around:

I knew Satish Joglekar only marginally. We met in a few conferences and I was once on a thesis defence committee with him (where it turned out we both had very similar questions about the thesis, mostly regarding some Field Theoretical issues on which he was an expert!) . This note therefore deals not with him as a person, but with his work in Quantum Field Theory, the grammar of High Energy Physics, of which I came to know when I followed him years later to StonyBrook. A solid grounding in QFT was considered absolutely essential for working at ITP, StonyBrook, and it was not surprising that so many important field theoretical works emerged from that institute in the 1970s.

During his years in Stony Brook he had left his mark at the ITP (headed by C. N. Yang). He had written some seminal papers with his thesis advisor Ben Lee. He was much senior to su, so we never overlapped, but the mid 70s when he was in StonyBrook were the hey days of gauge theories and what we today call the Standard Model (and which was still called Weinberg Salam in those days). Most people know of Ben Lee from his famous review on Gauge Theories in Physics Reports (with Abers) which was the only reference at that time for learning about the structure of Spontaneously Broken Gauge Theories. But Ben Lee is also famous for his series of papers (some with Zinn-Justin) on various aspects of renormalisability of SB Yang Mill theories, some of which we struggled mightily to understand as mere graduate students.

Thus it was when Satish Joglekar joined Ben Lee to continue this work on renormalisability in the mid 70s. His first significant paper was titled appropriately "General Theory of Renormalization of Gauge Invariant Operators" and dealt with the crucial issue of non gauge invariant operators mixing with gauge invariant ones under renormalisation. Put briefly, they managed to show that it is possible to choose a basis in which the gauge non invariant operators decouple from the G. I. ones to all orders, which is crucial if one is not to have to calculate the full renormalisation matrix. Even though by present day standards of 'significant papers' this paper has few citations, a mere 172 (!), it was crucial for various aspects of renormalisation and gauge invariance.

His second set of papers which he wrote by himself were a couple on the renormalisability and gauge invariance of products of operators and their OPE. He considered here an unbroken non Abelian gauge theory and asked the question -- which subset of local operators have the property that their physical matrix elements are independent of the gauge parameter. I don't want to go into the details of these issues which may strike some people today as being too formal and esoteric. But the fact that we blithely use OPEs in our calculations is based on many theorems like those he proved, which clarified the issue of ghost mixing in covariant gauges, which in turn revolved around questions about the gauge invariant nature of the counter terms in renormalisation.

By then, Joglekar had moved to Fermilab following his advisor Ben Lee, from StonyBrook. Unfortunately their fruitful collaboration was to end tragically when Ben Lee died in a traffic accident in 1977. Subsequently he wrote a highly cited paper on Trace and Dilatation Anomalies during his post doc years in IAS, Princeton with Collins and Duncan (438 citations) but it appears that the shock of Ben Lee's death had a long lasting traumatic effect on Joglekar, affecting his steady record of publication for a long time.

Satish Joglekar continued to work on the more esoteric aspects of gauge theories. For many, the problems he tackled lacked relevance and topicality. But as a child of the golden era of the gauge theory revolution in Particle Physics of the 1970s to which he had contributed significantly, Joglekar's primary interest continued to lie in the formal nature of the structure of gauge theories of which he was a master practitioner.

2 comments:

Anant said...

Thank you for the thoughtful obituary. I have linked it to my blog.

Vivek said...

Thank you for bringing Prof. Joglekar's contributions to our attention, especially those of us from the younger generation. We knew very little about his research, except that it always dealt with the more rigorous and deep aspects of field theory. So, I felt quite enlightened by reading your description of his contributions all the way from his days as a graduate student.

At IITK, Prof. Joglekar was an inspiration to all, not just physics students.

The faculty at IITK have set up a webpage in his honour:

http://www.iitk.ac.in/phy/obituary_sdj/

including a link to a page describing his research contributions:

http://home.iitk.ac.in/~purushot/obituary_sdj/research_sdj.pdf

I had the privilege of knowing him and interacting with him, during my undergrad days at IITK, and I will cherish those memories forever. Prof. Joglekar will continue to inspire generations of students in future.