Welcome to my web page. My name is Ashoke Sen and I work at the Harish-Chandra Research Institute in Allahabad.

My area of research is string theory, -- a theory that tries to give a unified description of all matter and the forces between them based on the postulate that the elementary constituents of matter are tiny one dimensional (string-like) objects instead of point particles. My specific research interests include S-duality, tachyon condensation, black hole entropy and superstring perturbation theory.


1. My brief biodata (html version)

2. Full curriculum vitae including list of publications

3. List of research papers from Spires-HEP database.

4. List of research papers from google scholar database.

5. Brief biodata from Wikipedia.


Some lectures at string theory schools

1. Lectures on `extremal black hole entropy' given during January 2012 at the Asian Winter School at Kusatsu, Japan


Scanned copies of some lecture notes of graduate courses

0. Ongoing course on Cosmology

Lecture notes

Lecture 1 Lecture 2 Lecture 3 Lecture 4 Lecture 5 Lecture 6 Lecture 7 Lecture 8 Lecture 9 Lecture 10 Lecture 11 Lecture 12 Lecture 13 Lecture 14 Lecture 15 Lecture 16 Lecture 17 Lecture 18 Lecture 19 Lecture 20 Lecture 21 Lecture 22 Lecture 23 Lecture 24 Lecture 25 Lecture 26 Lecture 27 Lecture 28 Lecture 29 Lecture 30 Lecture 31 Lecture 32 Lecture 33 Lecture 34 Lecture 35 Lecture 36 Lecture 37 Lecture 38

Lecture videos from HRI youtube channel


1. Classical mechanics

Notes taken by Ipsita Mandal and documented by Shweta Srivastava

Part 1 Part 2


2. Quantum mechanics 1 (Notes taken by Sauri Bhattacharyya and documented by Ipsita Mandal)

Part 1 Part 2 Part 3 Part 4 Part 5 Part 6 Part 7


3. Quantum mechanics 2 (Notes taken by Sauri Bhattacharyya and documented by Ipsita Mandal)

Part 1 Part 2 Part 3 Part 4 Part 5 Part 6


4. Atomic and Molecular Physics (Notes taken by Sauri Bhattacharyya and documented by Ipsita Mandal)

Part 1 Part 2 Part 3 Part 4


5. Statistical mechanics (Notes taken by Ipsita Mandal and documented by Avinanda Chaudhuri and Ipsita Mandal)

Part 1 Part 2 Part 3 Part 4 Part 5 Part 6 Part 7 Part 8 Part 9 Part 10 Part 11


6. General relativity

a. My notes (documented by Shweta Srivastava)

b. Notes taken by Ipsita Mandal and documented by Avinanda Chaudhuri and Ipsita Mandal

Part 1 Part 2 Part 3 Part 4 Part 5 Part 6 Part 7 Part 8 Part 9 Part 10 Part 11

c. Video of some lectures recorded by Ankur Das Video


7. Quantum field theory 1

Lecture notes

Problem set

Lecture videos from HRI youtube channel

Older notes (Notes taken by Shankha Banerjee and Ushoshi Maitra and documented by Shweta Srivastava)

Part 1 Part 2 Part 3 Part 5


8. Quantum field theory 2

a. My notes (documented by Shweta Srivastava)

b. Notes taken by Ipsita Mandal and documented by Avinanda Chaudhuri and Ipsita Mandal

Part 1 Part 2 Part 3 Part 4 Part 5 Part 6 Part 7 Part 8 Part 9 Part 10 Part 11 Part 12

c. Video recording of lectures (recorded by Sitender Kashyap)


9. Cosmology: Inflation to Last Scattering (Rough Notes)

page0-36 page37-73 page74-122 page123-157 page158-222 page223-265 References

Video recording of lectures (recorded by Biswajit Sahoo)


10. String Theory 1 (documented by Shweta Srivastava)


11. Superstring perturbation theory

(a) Lecture notes taken by Mritunjay Verma (200MB)

(b) Video recording of lectures (recorded by Sitender Kashyap)


12. Superstring compactification

a. Rough notes

Part 1 Part 2 Part 3 Part 4 Part 5 Part 6 Part 7 Part 8 Part 9 Part 10 Part 11 Part 12 Part 13 Part 4 Part 15 Part 16 Part 17 Part 18 Part 19 Part 20 Part 21 Part 22 Part 23 Part 24 Part 25 Part 26

b. Video recording of lectures (recorded by Sitender Kashyap and documented by Padakshep)


13. Few lectures on quantum field theory at finite temperature

(Based on the review article `Basics of Thermal Field Theory' by Mikko Laine and Aleksi Vuorinen, Lect.Notes Phys. 925 (2016) pp.1-281 [arXiv:1701.01554])

a. Video recording of lectures (recorded by Sitender Kashyap)


Some popular articles

1. Search for a Unified Theory of Matter (postscript file of an article written for high school students and published in Resonance, Vol 5, No. 1, January 2000 )

2. Duality Symmetries in String Theory (postscript file of an article written for physicists and published in Current Science, vol. 77, No. 12, p 1635, Dec. 25, 1999)

3. String Theory and Einstein's Dream , (pdf file of an article written for physicists and published in Current Science, vol. 89, No. 12, p 2045, Dec. 25, 2005)


A note (April 6, 2015)

A few days ago I wrote an essay with the title `Riding Gravity Away from Doomsday'. In this essay I discussed the best possible future course of action for the humankind to prolong its life given two assumptions: 1) that our universe is not absolutely stable and could undergo a phase transition in the future, and 2) that the accelerated expansion of the universe that we see today is due to a cosmological constant. The first one is a theoretical possibility that has been discussed since 1970's by many people and current experimental knowledge could at best put an upper bound of one in ten billion per year to the probability of such an event. The second one is the most widely accepted interpretation of the observed expansion rate of the universe although there are certainly alternative proposals. Both assumptions are natural in string theory, but can be discussed independently of string theory.

Few days after I submitted the essay to the arXiv, one of my colleagues drew my attention to a blog where some discussion on this essay had appeared. Upon visiting the blog, I was amused to see the passionate attack on eternal inflation and the multiverse that the essay had generated, while the essay itself was based only on the assumptions stated above and the standard rules of classical general theory of relativity. Indeed, a word search shows that none of the words eternal, inflation or multiverse appear anywhere in the abstract, text or the figure captions. Of course, many of the physical and mathematical results used in this essay are borrowed from the corresponding results in eternal inflation since our universe is now entering the same kind of accelerated expansion phase that is postulated to exist during inflation.

I do hope that some time in the future I'll be able to make some useful contribution to the subject of multiverse and eternal inflation, but this essay does not count as one such contribution.

The relevant links can be found below.

My article: `Riding Gravity Away from Doomsday'.

The blog with comments on the article.

Back to HRI home page.

sen@hri.res.in