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Showing posts from May, 2015

29/05/2015

Another day spent putting pen on paper and pouring over the equations in a paper. No corrections made to code yet and it is running at a snail's pace! I remember trying out FSAL methods to solve differential equations, ones  which were as accurate as RK4 but wayy faster. And there's this new C++ library that I found that does symbolic math, the same way the SymPy library does. There wasn't any csympy I could find that I could call from Cython code so I guess I'll have to try the C++ library. June 15 is the deadline to write my project thesis so I guess getting the codes and plots out of the way should be the first thing to do...

28/05/2015

Another day, spent working through tens of pages of derivation and a couple of hundred lines of code. And there was a weird bug that I couldnt repair. Most of the afternoon was spent waiting for help with some derivation and with converting ipynb code to py code, adding comments, savefig and the like.

from __future__ import *

I was going through a code with the statement "from __future__ import division" and I finally asked the question as to what exactly __future__ is and what the hell is it that we're importing. Turns out when there are backward compatability issues with changes made in a release, the revised function can be called using the above statement and if we simply call the function without the above import statement, we will be using the previous form of the function. Read this and this for a better understanding of what i'm talking about.

More sympy and 2 As

I thought I'd hit a wall yesterday on my problem but when I restarted working on it in the afternoon, instead of waiting till tomorrow to ask my professor for help in resolving it, things worked out nice. Well, almost. I'm still stuck on the last but the most important bit of the problem and I dont understand why there's an 'i' in the equations! But i'm getting the hang of using lambda for functions and doing differentiation using sympy.

And I just got the grades for 2 of my courses this semester, an A in GR & Cosmology which I was hoping for and an A in Numerical methods in Programming, which could've been an S if I hadn't been so lazy as to not submit 2 assignments. But hey, it's been 4 years since I saw an A grade on my grade card. 4 years. That's a long time. And I finally know what I was doing wrong all this time. Well, most of it atleast. My mind is swaying between being happy about the grades and being mad at myself for all the time …

Sympy and symbolic differentiation

I am currently porting a code from mathematica to python. As is commonly known, code which is a few tens of lines in a higher level language becomes twice or thrice that in a lower level language. While there are convenience functions in mathematica and python for almost everything imaginable and needed by a student/physicist (except for a theta function!), the one thing that sets mathematica apart from everything else is it's ability to do symbolic math. The fact that the language was built around this (is it?) probably lends to this but nevertheless, it's one of the things that I'm having the toughest time reimplementing in python. I've been working with sympy, picking up the pieces along the way but I've hit a roadblock for the time being. I'm not able to differentiate an expression that contains a theta function! I'll prolly have to rewrite the expressions so that it'd be easier to work in python i.e do sym diff.

The other interesting thing that I&…

-15/05

It's been an interesting couple of days. I've been hanging out with a classmate of mine, who came back to give her PhD entrance test+interview here at IITM. And having finally cleared my course work, I can work full time on my project work. I'm in high spirits, pretty much what I'd be feeling it'd be like to finally get to work on a research topic again. More on what I'm working on later.

It's been an amazing semester. I've learnt a lot, a hell lot, maybe even more than last semester. There's just a buzz of thoughts in my head but the two that stick out. The first is that I'd like to keep doing courses to learn new things, not just in physics but other parts of science. I've learnt that it's hard to learn something new by oneself, it's hard to motivate oneself to keep trying. And personally, I learn a lot more in a classroom that I'd probably do on my own. I'm not saying that I haven't learnt anything on my own, it's…

Computing the non-zero, independent components of the Riemann Tensor

The Riemann curvature tensor is a rank four tensor and it is used to describe space-time. has some peculiar properties i.e

i.e it is anti-symmetric in the pairs and but it is symmetric upon the interchange of the pairs and .
which is referred to as the first Bianchi Identity.Using the above constraint equation, assuming that can take values between and , one can compute that the total number of non-zero and independent components of the Riemann tensor are . In (3+1) space-time, there are twenty, in (2+1) space-time dimensions, there are 6 and in (1+1) dimensions, there is only one.Now that I have introduced what the Riemann tensor and it’s properties are, my question is how does one go about computing these independent, non-zero components i.e what are the different combinations of a,b,c,d!Naively thinking, one can start with for a = 0,3 for b = 0,3 for c = 0,3 for d = 0,3 if a != b if c != d prin…

Keeping track of my finances

I don't exactly live a lavish lifestyle (Duh! I'm still a student) so it's not like I spend a lot of money, but I'd still like to keep track of my expenses. From time to time, I get riled up and try writing down my daily/weekly expenses. I recently downloaded a couple of apps that I can use to track my spending. The thing with these apps is, however beautiful the UX was, I still had to manually enter the amount spent and when, where and what it was spent on. Well, how will the app figure out on it's own you ask? I'll tell you. And no, I'm not talking about talking to the phone to make note of it (Ohh wait! That might work too!). In my case, I get instant messages from the bank as soon as I use a card for a transaction or if I withdraw money (In fact one bank sends me semi aggressive messages telling me to withdraw at select ATMs!). And I thought that it'd be an interesting fix if I can go through messages, or messages from a particular number i.e the b…

(Insert witty title here)

I'm having a tough time in the transition from following a daily schedule that is tailored around coursework to defining a daily schedule on my own. I know it for a fact that I can deal with setting my own schedule because at least in one instant (Melbourne), I was able to give in ~9 hour days regularly. It's a weird tug of war my subconscious has between what I am supposed to be doing and what I want to do. Either way, I can't afford to be in this state any longer given that my end semesters are coming up and all that I've put in during the semester will go down the drain if I act reckless now.

And I don't know exactly when it was that I started feeling this way but I just felt as though there wasn't much happening in my life. Anymore. Although there wasn't much happening to begin with! I used to write about small projects that I'm working on or interesting things I learnt in courses or thought provoking talks. It's not like that stopped happening…