Rahul gives unsolicited advice

I got lucky in March 2022. I happened to be in Bhopal for two weeks. Specifically, I was at the Indian Institute of Science Education and Research (IISER) Bhopal with my wife. She was wrapping up some work at the TrEE lab in the Biology department. She successfully defended her PhD thesis in 2021 but she needed to go back to wrap up some loose ends. I went along with her and I got to meet her labmates. That's how I came across Improbable destinies by Jonathan Losos . As far as I can remember, it's the first biology/ecology book that I have read. It's technically a popular science book but it's not something that a school student can read and understand. But, it's damn good. I would definitely recommend it to biology and science undergraduates who are yet to understand and decide where their interests lie in. Preeti likes the fact that I can atleast know of and can use some of the vocabulary she works with on a day-to-day basis. The book introduces the reader to con...

Well, I sat through a seminar during which a post-doc was talking about how many body systems can be understood using numerical simulations of their behavior, using density matrix formalism or the wavefunction formalism. He then went on to talk about how they studied various theoretical and (very) real systems and showed how their properties arise from ab-initio calculations. Although much of the talk went over my head, the one thing that was running through my mind was how I was taught the Hartree-Fock method in my second year, as part of a course on physical chemistry, and how it's seemingly invincible power went right over my head. This is pretty much what I've been doing most of the summer. I am doing a course on numerical methods in programming and apart from the examples the prof mentions in classes and in our programming lab session, I've been trying to come up with or formulate computational problems related to physic topics that I've been learning over the l...

The day was spent rewriting notes of the course on General Relativity. The professor has structured the course to take advantage of the assignments, teaching the necessary concepts and putting them to good use soon after by working out some problems. I wanted to keep a copy of the assignment solutions so I can refer to them during the exam but I thought I'd go one step further and fill all the gaps between the assignment sheets by rewriting the notes. The professor also leaves behind incomplete derivations for us to complete so it was good practice overall. One other thing that came to my mind during the day was regarding Pocket, the offline reading app. I love it and I've been religiously using it for about 4 months now. Pocket tags article as 'Best Of' or 'Long Reads', and I'm guessing it creates the former label depending on how many people star the article in their library. Also, at the end of the year, Pocket tells you how many articles you've re...

Compared to the rest of the saturdays I've spent so far, I'd have to say that today was the most eventful. From 2 till ~4:30, I was at a panel discussion on research in basic science in India, with panellists mostly from the physics community, with the exception of one professor from the EE dept. Some really interesting points were raised on why Indian research isn't on par with the research output of western universities, how this can be tackled and overcome, how research in basic sciences can help the society and the country as a whole and the measures one needs to take to increase the research output of Indian institutes. With veterans and young researchers on the panel, it was a lively talk with a good amount of cross talk, a lot of anecdotes and lots of humour. I wanted to ask the panellists what role science popularization plays in increasing public and government interest in science as a whole and in drawing more students towards basic research in the sciences. I al...

I spent about an hour writing code that computes the trajectory of a particle in constant electric or constant magnetic fields, the first of which is available here and the second here . I apologize for the incomplete code that computes the motion of a particle in a magnetic field, I am still trying to figure out how to plot two different data sets with different x and y ranges on the same figure. There are convenience functions to duplicate the x axis or the y axis but not both, which is what I'm looking for. Either way, the codes are still rough, in the sense that I used euler's method to do solve the differential equation that governs the motion, which is known to be errenous. I will have to implement one of the Runge-Kutta methods if I want better accuracy in position and velocity measurements. Moving further, it's a bit harder to solve the case of a particle in a magnetic field as there are cross terms i.e the force in the x direction depends on the velocity in the...

Today was a wonder colloquium by Prof. Sir Michael Berry on the effect that science and research have on our day to day lives, on technology and on science as a whole. He started talking about how CD players have democratized music and made it available to the millions. Sure, gramophone had been invented and the radio was also prevalent. But only with the advent of compact disc players did people get a portable device to listen to music. He then talked about lasers, without which there wouldn't be any CDs and digging deeper, quantum physics, without which we wouldn't have the theory of how lasers work. He talked about how Einstein couldn't have imagined that his theory explaining atomic transition using spontaneous absorption and spontaneous and stimulated emission could've led to the laser. And not just that, he gave many accounts of scientists who pursued research without worrying about applying them to *real world problems*, who would be surprised knowing how much...

I finally got off my ass and figured out how to use arrays and matrices in fortran, beginning from how to write them and read them and so on. I was trying to implement a simple linear algebra solution, that we had already done in C and python. I was frustrated most of the time because of the inconsistency in using the various loops, in defining variables and so on. I don't know how much ANSI C has changed in the last 10 years but from the looks of it, Fortran has. But I did find an interesting implicit method to read arrays in the in the mess, very functional and minimalistic. On the other hand, as I've been doing over the weekend, I shall continue to write about the various metrics used in GR and their relevant christoffel connection symbols, reimann tensors and ricci tensor and ricci scalars. I read grtiny.pdf or the No-Nonsense introduction to general theory of relativity by Sean Carroll and was spurred on by it a little. But in general, I want to document all of this, pr...

I wanted answers to two questions at the beginning of the semester, both of which are related to general relativity and cosmology. Both of the questions are related to gravitational lensing, a phenomenon where light bends around massive objects. Gravitational lensing was one of the predictions of Einstein's General theory of relativity and was observed during a solar eclipse. The first of my questions is related to how distant galaxies are lensed by galaxy clusters in our line of sight. Conventional optics governs that if two sources of light are placed behind one another, the farther one will be obscured by the closer one. General relativity, on the other hand, allows for light emitted by the distant source to get bent around the closer source to reach us. It has been observed to happen that multiple images of the distant galaxy are formed due to a lens in the line of sight. Einstein's cross is one such example. Now, having covered the topics of curvature and geodesics in t...

To be exact, it's been almost 10 days since I last wrote. It's not that I don't have anything to say anymore, I've been talking about menial, day-to-day, conventionally boring stuff all along, it's just that I lost interest in telling people how (conventionally) boring my days were. I can say that I needed a break from writing. I can say that I was busy with work. I can say that I was not interested in writing anymore but I guess none of them are the true reason. I guess I just stopped caring. I don't really have much of a reason as to why I stopped writing and why I am starting again. It's been a productive week I guess, compared to the same week last year that is. I got tired of having to solve the same problem over and over again so I decided to latex my solutions. I was also getting frustrated/irritated because I wasn't finding practice problems at my level. And because most textbooks don't have a solution sets. One long term goal that I'v...

Not much to say today other than for the fact that there were a couple of interesting classes in the morning, one on estimating the fraction of radiation emitted by a body that is received by another (referred to as view factor) and another on ultra-short pulses and how they can be characterized in the frequency space using phase which is a linear, quadratic or higher order functions of time. It's hard to put in words but I'll try make a simulation as I have earlier. I am still trying to swallow the fact that the leading and the trailing edge of the pulse can be at a different frequency!

I now have a working code that can compute the christoffel symbols for a given metric. I have computed them for two kinds of metrics here . I intend to extend it to be able to compute the riemann and the ricci tensor and eventually the ricci scalar, which is representative of the curvature of a manifold. Hopefully. I will need some help though. Well, I wouldn't mind help...

Since I learnt how to use ipywidgets to make small visualizations, I've wanted to make a model of simple and damped harmonic oscillators, using euler's or runge-kutta methods to solve the second order differential equation. And I finally make them, here and here . Otherwise, it's been a week filled with popular science talks. I attended a talk on tuesday on the landau theory describing fermi liquids. On wednesday, there was a talk on light that twists inside optical fibers, followed by a talk on particle physics and the Belle detector in Japan. The first talk was about modes of polarization and the methods to be able to generate vortex beams in fibers. He then talked about how vortex modes can be used advance communication technologies. In the following talk on high energy physics, the speaker talked about how the BELLE detector upgrade will help in understanding the CP violation, to study dark matter and how the new instrument is a huge upgrade on it's predecessor....

It took a while but I finally figured out, after almost 3 days, as to how to visualize a travelling wave using the method I've been using so far  using ipywidgets on an ipython notebook! And here is the result of it. The first plot shows how the envelope of the pulse as a whole changes with change in the total number of modes added in phase and the second plot shows how the pulse moves along the x-direction in time. So far, I'm pretty happy with the incremental progress I've made and my resolve to build something on a solid foundation has strengthened over the last month. I will keep pushing this further, at whatever slow pace I can, adding more and more complexity to it. Let's see where the rise takes me. Otherwise, the interesting thing today was the bi-monthly departmental colloquium, delivered this time around by Prof. Anil Kumar from IISc, Banglore. His research interests include spintronics, nano-magnetization, and spin polarized electron scattering. He talked...

Count Photon is a very witty nick name. I wish I'd thought of that! Either way, back to hearing me instead of my friends. Today just passed by thinking about general relativity, lasers and cython. I finally figured out why my cython code was giving seemingly errenous results, because I had forgotten to implicitly typecast a specific constant that I was in the earlier buggy version, calling directly from the function. Every numeric operation in cython has to be between values that are typecast is something that I learnt out of this so far. The morning was spent in awe at what was being taught as part of a general relativity and cosmology course that I am taking this semester. By simply varying/extremizing the action of a free particle in space, we arrived at the equations of it's motion. No field, nothing! It was beautiful to see that a function derivative of the metric that describes the space(time) describes the equations of motion. It was also interesting to note that the ...

The speaker at the physics colloquium this week was Prof. Manu Jaiswal from the Dept. of Physics, IITM and his talk was about graphene, exciting research on the elasticity of graphene coatings/layers and on the recent developments in the field. The talk started off with Zidane's penalty kick of the football world cup and at the end, he pointed out how the shape of the goal net has changed. He mentioned that physicist and mechanical engineers aren't the only people working on material elasticity, so are footballers, so to speak. The goal net design changed in 2002 from being a square net to a hexagonal net. It was shown, through simulations, how stress propagates along the two structures and how hexagonal structures behave like a 2D isotropic body where as square nets have local minima along the grid outlines. Moving on the talk, he mentioned how he himself got involved in understanding the elasticity of graphene. As is the case with many-a-stories in science, results that...