This is the FIRST experimental work of our 'theory-lab'. Obviously, this is exciting.
Thread. @iiscbangalore
![](https://pbs.twimg.com/media/ESHpebvVUAAfOWd.jpg)
Each individual has only limited local information about surroundings. Yet they show these fascinating patterns. 2/n
This has been a question of substantial work over last few decades, and we provide some new insights here. 3/n
They show that organisms don’t need complex rules to exhibit collective motion. 4/n
[Pic below is Fig 1 of Vicsek et al 1995 PRL]
![](https://pbs.twimg.com/media/ESHsofTUEAAaudC.png)
We show that in a species called karimeeen (Etroplus suratensis)
(i) fish just copy the direction of a (nearby) random fish, or
(ii) they turn a bit randomly. 6/n
In fact, fish school studies by @JHerbertread, @GTheraulaz etc also show a similiar simpl rule of interactions in other fish species. 8/n
We show that schooling in this fish is a rare empirical example of a phenomenon well studied in non-equilibrium stat physics: ‘noise-induced phase transitions’.
But what is this? Let's dig in a bit 9/n
We use karimeen (Etroplus suratensis) -- a popular edible fish in western coast of southern India and put them in a fish tank.
![](https://pbs.twimg.com/media/ESHzgHdUwAAzgbc.jpg)
[This is from fig 1 of our paper.]
![](https://pbs.twimg.com/media/ESH1XqeU0AEnu6R.png)
We then plot this quantity as a function of time. Crucially, we retain all information -- not just mean but also how fluctuations are occurring over time.
![](https://pbs.twimg.com/media/ESH12uZU4AA-ai7.png)
I think this is one of the coolest part of the paper - because unlike most papers that intuitively derive a model or equation, here we let the data talk!
![](https://pbs.twimg.com/media/ESH3KOvUUAAZ9cC.png)
i. when fish are ordered, even random things that they do, like copy one other, doesn't change the overall behaviour very much
ii. when the fish are moving in a misaligned state, the fluctuations are actually high.
If you are interested, you can send me an email to get the pdf OR check this link: rdcu.be/b2pgG
All codes/data are available via: doi.org/10.5281/zenodo…