Author: G.V. Pavan Kumar

Namaste, Hola & Welcome from G.V. Pavan Kumar. I am a Professor of Physics at the Indian Institute of Science Education and Research, Pune, India. My research interests are : (1) Optics & Soft Matter: Optically Induced Forces – Assembly, Dynamics & Function; (2) History and Philosophy of Science – Ideas in Physical Sciences. I am interested in the historical and philosophical evolution of ideas and tools in the physical sciences and technology. I research the intellectual history of past scientists, innovators, and people driven by curiosity, and I write about them from an Indian and Asian perspective. My motivation is to humanize science. In the same spirit, I write and host my podcast Pratidhvani – Humanizing Science.

A Twitter thread on my Japan trip that inspired my podcast

Conversation with Snigdha Thakur

Snigdha is a computational soft condensed matter physicist and a senior faculty member at IISER Bhopal : https://sthakurlab.iiserb.ac.in/.

She uses computational physics to explore a variety of soft matter systems including active matter and of late biological systems.

In this conversation, we discuss her journey as a physicist, and how she developed interest in soft condensed matter. We also discuss about leadership in physics, as she has been the Chair of her department and a Dean at IISER Bhopal.

There are many things to learn from Snigdha and I enjoyed this discussion on various topics related to physics and pursuit of science.

Listen, as we humanize science.

Links on Google and Apple podcasts.

References:

  1. “Sthakur Group.” n.d. Accessed April 16, 2024. https://sthakurlab.iiserb.ac.in/.
  2. “‪Snigdha Thakur – ‪Google Scholar.” n.d. Accessed April 16, 2024. https://scholar.google.com/citations?user=q3X-5pQAAAAJ&hl=en.
  3. Fourth Paradigm conference, dir. 2020. Designing Synthetic Nano Motors by Snigdha Thakur, IISER Bhopal. https://www.youtube.com/watch?v=_J8F2Wd9AzM.
  4. “Principal Investigator | Raymond Kapral Research Group.” n.d. Accessed April 18, 2024. https://sites.chem.utoronto.ca/rkapral/content/principal-investigator.
  5. Raman Research Institute, dir. 2018. Biomimetic Behaviour of Synthetic Particles. https://www.youtube.com/watch?v=R9BVx8_4D-k.
  6. “Sunil Kumar’s Home Page.” n.d. Accessed April 18, 2024. https://physics.iitm.ac.in/~sunil/.
  7. Thakur, Snigdha, and Raymond Kapral. 2012. “Collective Dynamics of Self-Propelled Sphere-Dimer Motors.” Physical Review E 85 (2): 026121. https://doi.org/10.1103/PhysRevE.85.026121.

Music beats on a metal water can

If you have a metal water can, what do you do ?…well make a geeky music video🙂

I played the water can to generate beats & recorded the response.

You will see the periodic beats + colour-coded audio-visualisation. 📹

Enjoy !

#fun #experiment

A metal water can was played to generate music beats, and the acoustic response was recorded. You will see the periodic beats in the timeline and a colour-coded audio-visualisation of it. Enjoy !

Conversation with Sudipta Maiti

Sudipata is a molecular biophysicist who uses light and spectroscopy to study biologically relevant questions. He is a Professor at TIFR, Mumbai: http://www.biophotonics.co.in/

In this episode, we discussed what drew him to biophysics, his journey in establishing biophotonics as a research area in India, his motivation to start the FCS workshop and his thoughts on science in India. There are many other branches of discussion related to the pursuit of science, which the listeners may enjoy and learn from.

Listen as we humanize science.

On Google and Apple podcasts.

References:

  1. “Biophotonics Lab.” n.d. Biophotonics Lab. Accessed April 12, 2024. http://biophotonics.weebly.com/.
  2. “‪Sudipta Maiti – ‪Google Scholar.” n.d. Accessed April 12, 2024. https://scholar.google.co.in/citations?user=_exYXS8AAAAJ&hl=en.
  3. “Sudipta Maiti (@SudiptaMaiti13) / X.” 2024. X (Formerly Twitter). February 8, 2024. https://twitter.com/SudiptaMaiti13.
  4. Berg, Jeremy M., Lubert Stryer, John L. Tymoczko, and Gregory J. Gatto. 2015. Biochemistry. 8th ed. edition. New York: WH Freeman.
  5. Eaton, William A., and H. Peter Trommsdorff. 2013. “Robin Main Hochstrasser (1931–2013), Giant of Physical Chemistry.” Proceedings of the National Academy of Sciences 110 (23): 9189–90. https://doi.org/10.1073/pnas.1307692110.
  6. “Fluorescence India.” n.d. Accessed April 12, 2024. https://fluorescenceindia.org/.
  7. “Measuring Serotonin Distribution in Live Cells with Three-Photon Excitation | Science.” n.d. Accessed April 12, 2024. https://www.science.org/doi/10.1126/science.275.5299.530.
  8. “Watt W. Webb.” 2024. In Wikipedia. https://en.wikipedia.org/w/index.php?title=Watt_W._Webb&oldid=1194542920.
  9. “Watt Webb, Biological Imaging Techniques Pioneer, Dies | Cornell Chronicle.” n.d. Accessed April 12, 2024. https://news.cornell.edu/stories/2020/11/watt-webb-biological-imaging-techniques-pioneer-dies.
  10. Zipfel, Warren, Chris Xu, Elliot Elson, and Sudipta Maiti. 2021. “Memorial Viewpoint for Watt W. Webb: An Experimentalist’s Experimentalist.” The Journal of Physical Chemistry B 125 (11): 2793–95. https://doi.org/10.1021/acs.jpcb.1c01045.

Meditation on Questioning

Why do humans ask questions?

This question fascinates me.

Here is what I have been learning from my observations :

1) Children tend to ask questions that are driven by curiosity. If these questions are refined, they turn out to be philosophical. Eg: Why do we live?

2) Adults tend to ask questions that are generally connected to economics. On average, their questions are more on ‘how’ than on ‘why’.

3) A dialogue is actually a volley of questions and answers. We somehow tend to under-appreciate this. What we generally ascribe to Socrates is something present in all cultures. It is worth exploring this questioning tradition in all cultures. Eg.: Tarka shastra.

4) A great way to engage with a book is to read it as a series of answers to implicit questions. I am amazed to see how interesting and active reading becomes. This also works for research papers and sometimes even on fiction.

5) A collection of questions is a sub-set of knowledge. The answers derived from these questions can lead to further questions. Following this process will give you a ‘body of knowledge’. There is some fractal nature to this.

6) Scientific thinking is essentially a systematic way of asking questions. The operational word here is ‘systematic’. The structure of these questions is such that it fosters further enquiry, but it is also open-ended. That way, it gives us room for creative thinking.

7) Creative thinking, in essence, is a question of effective combination. It becomes ‘creative’ when the sum of parts creates something new AND relevant. The conjunction is its vitality.

8) Finding an error in our thinking also originates in questioning. In fact, error analysis is a form of questioning from a different viewpoint. It requires us to shift our perspective, and the central question is where and when to shift?

9) Questioning is an inherent human quality. Fostering this is not only existential but also very useful. Etymologically “systematic treatment of an art, craft, or technique” means technology. If you observe, its roots are connected to scientific thinking (see 6).

10) Questioning is generally considered a part of the means to an end. If you observe, it is a means that never ends. Worth asking – Why?

Conversation with Jayant Murthy

Jayant Murthy is a distinguished Senior Professor at the Indian Institute of Astrophysics, Bengaluru. His research focuses on space missions, interstellar dust, and diffuse radiation fields. With a rich scientific background, a deep love for teaching and notable contributions to the discipline, Murthy’s work exemplifies excellence in astrophysical research.

Explore further at Jayant Murthy’s website: ⁠https://www.iiap.res.in/people/personnel/murthy/Jayant_Murthy/Home.html⁠

In this episode we discuss his biography. He explained how and why he became interested in astronomy and astrophysics. His ventures in teaching and a freewheeling discussion on science, rationality and society.

Jayant was recently commemorated with the naming of asteroid “(215884) Jayantmurthy” by the IAU, acknowledging his significant advancements in ultraviolet astronomy and space missions. We explore how that happened.

There are many other interesting strands in the conversation. Listen, as we humanize science.

on Google and Apple podcast

References :

  1. Jayant Murthy [WWW Document], n.d. URL https://www.iiap.res.in/people/personnel/murthy/Jayant_Murthy/Home.html (accessed 4.2.24).
  2. ‪Jayant Murthy‬ – ‪Google Scholar‬ [WWW Document], n.d. URL https://scholar.google.co.in/citations?user=Gdv6OEsAAAAJ&hl=en (accessed 4.2.24).
  3. Bureau, T.H., 2024. Asteroid named after Bengaluru Professor. The Hindu.
  4. Henry, R.C., 2005. The mental Universe. Nature 436, 29–29. https://doi.org/10.1038/436029a
  5. IIAstrophysics [@IIABengaluru], 2024. We are happy to announce that the asteroid 2005 EX296 has been named as “(215884) Jayantmurthy” by @IAU_org in honour of Prof Jayant Murthy! He is Honorary Prof & former acting director at IIA. @dstindia @doot_iia @asipoec @fiddlingstars @SPG_IIA https://t.co/E1k6MytYsY. Twitter.
  6. International Astronomical Union | IAU [WWW Document], n.d. URL https://www.iau.org/ (accessed 4.2.24).
  7. Jayant’s Class Presentations [WWW Document], n.d. URL https://www.iiap.res.in/people/personnel/murthy/Jayant_Murthy/Teaching.html (accessed 4.2.24).
  8. Kumar, A., Ghosh, S.K., Hutchings, J., Kamath, P.U., Kathiravan, S., Mahesh, P.K., Murthy, J., Nagbhushana, S., Pati, A.K., Rao, M.N., Rao, N.K., Sriram, S., Tandon, S.N., 2012. Ultraviolet imaging telescope (UVIT) on ASTROSAT, in: Space Telescopes and Instrumentation 2012: Ultraviolet to Gamma Ray. Presented at the Space Telescopes and Instrumentation 2012: Ultraviolet to Gamma Ray, SPIE, pp. 455–466. https://doi.org/10.1117/12.924507
  9. Latest Updates | Astronomical Society of India [WWW Document], n.d. URL https://www.astron-soc.in/ (accessed 4.2.24).
  10. Murthy, J., Henry, R.C., Overduin, J., 2023. Dust scattered radiation in the galactic poles. J Astrophys Astron 44, 82. https://doi.org/10.1007/s12036-023-09973-5
  11. Professor Richard Conn Henry [WWW Document], n.d. URL https://henry.pha.jhu.edu/rch.html (accessed 4.2.24).
  12. Singh, K.P., et al., 2014. ASTROSAT mission, in: Space Telescopes and Instrumentation 2014: Ultraviolet to Gamma Ray. Presented at the Space Telescopes and Instrumentation 2014: Ultraviolet to Gamma Ray, SPIE, pp. 517–531. https://doi.org/10.1117/12.2062667
  13. Slide 1 [WWW Document], n.d. URL https://www.iiap.res.in/people/personnel/murthy/Jayant_Murthy/Teaching_files/history_of_astronomy/siframes.html (accessed 4.2.24).
  14. Zachariah, P., 2024. ‘Our world is built on basic science, and part of basic science is rationality.’ The Hindu.
  15. ಡಾ. ನಳಿನಿಮೂರ್ತಿ | Dr. Nalini Murthy – Hemanth Sahitya, n.d. URL https://hemanthsahitya.com/book-author/d-nalinimurthy/ (accessed 4.3.24).

Graviton-like modes – link and some questions

Recently, I wrote a blog on Graviton-like modes in solids.

There is a nice report from the Columbia Quantum Initiative on the Nature paper.

It highlights the role of Aron (a key author in the paper, who passed away in 2022) and his legacy.

Undoubtedly, the graviton-like connection has created a buzz. As the above report mentions, it has also taken a lot of time and effort on the part of the authors to measure it.

Thanks to my colleague Surjeet Singh, I also learnt about the importance of heterostructures in this work and that authors do not oversell the connection to gravitons in the paper.

For me, as an outsider to the field(s), a few questions remain:

  • What lessons can we learn from graviton-like modes in solids that will help us understand the actual undetected graviton?
  • How is it different from the collective excitation of quasiparticles, such as exciton-polaritons in semiconductor heterostructures? Similar experimental methods are used to study them. 
  • Is the prominence only due to spin-2 collective excitation? 
  • Finally – applying Occam’s razor – can there be a simple explanation without evoking graviton-like modes?

It would be great to know the answers, hopefully, in the coming days.

Some policies of my research

In the past 14 yrs of my research group, I have made a few policies for myself, which may be helpful to others:

1) Any group member is free to criticize my input with reason. This has been one of the most liberating experience. Importantly, it has helped me learn.

2) Physical and mental health of group members is of primary importance. Good health and good research is not a zero sum game.

3) Constancy of thought and work is vital. We overestimate work that can be done in short term and underestimate the long term. Constant effort, spread over months and years, can build intellectual and technical monuments.

4) Set internal standards. Let this standard be reasonable and focused towards oneself. The biggest stress in work comes from comparison with others. Instead, compare your past with present, & strive for a +ve difference. Be sceptical of external metrics.

5) Write regularly. Writing is not only about publication in a journal or a book. It is a way to reflect, learn, revise and communicate. Writing is the process. A publication is one of the outcomes, a temporary goal. Focus on the process, goals will follow.

6) Share your knowledge. If possible – TEACH. Teaching informally is very enjoyable. It is devoid of judgements. In the longer run, it is perhaps the most impactful thing you will do, and will be remembered for. Remember Feynman.

7) None of the above points matter if your work does not make you a better human being. Be compassionate to others. The biggest strength of scientific research, if done well is it elevates the individual & collective – both local & global.

8) Academia, in its good form, can feed your stomach, brain and heart. Nurturing and enabling all the three is the overarching goal of academics. And perhaps the goal of humanity.

Graviton modes in solids: Old Argentinian wine in new Bottle ?

Recently, there has been a buzz about a Nature paper titled Evidence for chiral graviton modes in fractional quantum Hall liquids. There has been some media reportage on the paper too.

The paper makes interesting claim on observation of ‘chiral graviton modes’ in certain ultra-cooled semiconductors (Gallium Arsenide – famously called GaAs). The cooled temperature is quite low (~50 mK), which is impressive, and the chirality of the mode is unveiled using polarization-resolved Raman scattering. The observation of this so-called ‘Graviton modes’ is essentially a quasiparticle excitation, and has created some buzz. In my opinion, graviton-like behavior is a bit of an exaggeration.

Anyway, this paper has set an interesting discussion among my colleagues (condensed matter and high energy physics) in our department. To add to their discussion, I wrote on 2 points (and an inference) from optics perspective, which I am sharing below :

  1. The measurement scheme used to unveil the chirality of the quasi-particles is a well-known trick in polarization optics. In fact, I teach it to our undergrads. Notice the use of quarter-wave plates (indicated by the arrow in the figure below). This is also the measurement at the heart of unveiling optical anisotropy. Experimentally, what is impressive is the ultra-low energy excitation captured via Raman scattering. This is again thanks to the excellent cooling of the sample (50 mK).
Figure from the Nature paper.

2. The last author of this paper, Aron Pinczuk, was a well-known expert in light scattering in solids. He was an Argentinian-American professor at Columbia University, and passed away in 2022.

Aron Pinczuk

He and the legendary Manuel Cardona were instrumental (pun intended) in laying the foundation for using inelastic light scattering methods in solids. The first edition of the series “Light Scattering in Solids”, written in 1976, has Pincuk discussing the very measurement scheme used in the paper (see picture).  

The first edition (1976) of a great series : Light Scattering in Solids

My initial inference on the paper : This is an old Argentinan wine of quasiparticles in a new GaAs bottle at ultra-low temperature….and NATURE is selling it as champagne de graviton made in China !