# CSSS 2009 Santa Fe-Blog

### From Santa Fe Institute Events Wiki

Post your reactions to lecture material, observations about the school and projects, after hours events, and general conversation here.

## Monday 6/8

Lectures:
Geoffery West & Dan Rockmore: Intro to Complex Systems
Peter Dodds: Networks I: Introduction & Overview

jp: We're getting a few suggestions from people: -Wifi on during break/after lectures. -No NASA microphone headsets.

Lucas Lacasa: Regarding Liz talk, we had an interesting debate on lunch time regarding the choice of discrete vs continuous dynamical system when modeling a physical system that I would like to reproduce here. In discrete time systems you don't impose continuity on the variable x: x(n+1) can in principle be arbitrarily far from x(n) (depending on the specific map). Is that a problem? Within population dynamics (as the case of the logistic map Liz talked about), you can say 'ok, I'm coarse graining, between n and n+1 I allow population to vary as much as wanted, so eventually it can vary in the whole range [0,1] between n and n+1'. But if x characterizes a physical observable (thermodynamical quantity for instance such as temperature or pressure), then continuity is mandatory: small changes in time are related to small changes in the variable. Now, since in discrete systems n and n+1 are arbitrary time discretizations, you can in principle define the time unity as small as wanted. So we conclude that, in the limit, discrete dynamical systems do not fulfill the hypothesis of continuously varying variables. So, is it eventually a useless technique for physical modeling purposes? One possible answer could be the existence of different time scales: if the time scale in which a physical observable varies is much smaller than the scale where the modeling is addressed, you could use discrete time dynamical systems, couldn't you? Enough for today, maybe tomorrow I talk about randomness in discrete versus continuous time series!

## Tuesday 6/9

Liz Bradley: Nonlinear Dynamics II: Flows
Peter Dodds: Networks II: Scale-free networks, power laws, history
Nathan Collins: Adaptive Modeling: Aspiration-based Models
Nathan Collins: Reinforcement Learning Methods

jp: Great Soccer game!

jp: This is more like a tweet than a blog entry but: I'm Enjoying Roozbeh's grammar corrections on some of the Wiki pages. Way to go!

## Wednesday 6/10

Santa Fe Institute On-Site Lecture Series

Peter Dodds: "Sociotechnical Data mining for Emotional Content: Measure the Happiness of Bloggers, Song Lyrics and Presidents"
Scott Pauls: "Partition Coupling for Roll Call Data"
Peter Dodds: Networks III -- Randomness and Contagion
Stephen Guerin and Owen Densmore: "Agent Based Modeling - An Introduction"

jpI enjoyed Peter's first lecture throughly. My personal thoughts might lie somewhere along the lines of study bias--studying the lives of bloggers (which certainly match certain demographics) is no more of a broad sample than the surveys that infer population demographics from college students. Still, the project appears to be very much in its infancy, kind of like a rough outline drawn on a piece of marble saying "this is what we could do" or a horribly pixilated image instead of anything anywhere near presentable form... Still, it's a lot of fun to see what you can do with raw data and how the internet lets you grab massive amounts of it very quickly. I personally wouldn't mind working on something like this <hint, hint>.

jp Interesting observation from Stephen during the ABM talk: mathematical vs. algorithmic problem solving. Does anybody have any more information on this? Unrelated: There were a bunch of people that took off from SFI and decided to walk back to St. John's. How did that go?

Roozbeh Daneshvar: I believe that ABM is not really understood unless you get your hands dirty with it. I have several downloaded versions of NetLogo on my laptop and I can give you copy, if needed (it is for Linux, I'm not sure if it works for Windows or not). Also I can provide an unofficial introduction for starting to work with NetLogo. The walk from SFI to St. John's was great. I still have cramp in my muscles. John Paul, is SFI open on Saturdays and Sundays?

jp Oh, I have NetLogo already--I work with Stephen during the year and he asks me to do various learning projects and so forth on it. I also teach some NetLogo in the local high schools. It's one of my favorite programs.

No, SFI is closed on Saturdays and Sundays. The logistics page has been updated accordingly.

## Friday 6/12

Roozbeh Daneshvar: The microphone/speaker system sudden sounds sometimes bother. Are there any approaches to solve the issue?

Roozbeh Daneshvar: I enjoyed Tom Carter lectures. He put things in a straightforward and clear way.

## Saturday 6/13

Bandelier hiking and a Los Alamos visit.

## Sunday 6/14

Rainy day.

Mafia was a blast. Now that you all are indoctrinated, lets do it again soon. It gets more interesting as everyone understand how the game works and gets an idea for how different people play. I will schedule something, probably for next Sunday eve, in the next few days. watson

## Monday 6/15

Nice turnout today at the Information Theory tutorial. That was fun!

I mentioned a paper at the end of my little part which succinctly addresses the topic of Transfer Entropy. To remind, TE is an alternative (but related) method to Shifted/Time-lagged Mutual Information which aims to uncover causal relationships from time series data. The authors claim it is superior. The paper is super readable and I would be up for arranging a time to meet and discuss, perhaps in a week, if there are others into the idea.

I've posted it online, publicly accessible here.

In that directory you will also find another resource on the basics of information theory. Read the first couple of chapters if you want to learn more.

One other great source for learning about IT is slides from Jim Crutchfield's course 'Natural Computation and Self-Organization'. Jim, btw, is a long time external SFI faculty member.

Finally, we talked a bit about causation. I recalled that I had scanned in part of the reference that Tom was referring to. You can find that online here. I definitely recommend reading the interesting history of thinking on causation which is covered with lots of pictures in the Epilogue. It's a cinch of a read...

## Tuesday 6/16

Allison Shaw: The nonlinear dynamics lab was awesome!! Check out this video of cornstarch and water exhibiting cool behaviors.

## Wednesday 6/17

Roozbeh Daneshvar: I really enjoyed the 08:45 to 10:45 time slot in SFI!

jp I'm glad you did. I was wondering how the free time up at SFI would pan out. I should have guessed that with this group you all would have found more than enough intellectual stimulation to fill that time.

## Thursday 6/18

Roozbeh Daneshvar: I liked the idea of setting the tutorial in 215 Evans.

Roozbeh Daneshvar: The movie was good. After a dense day, this was needed. 1) Liliana Salvador, thank you for launching. 2) jp, we missed you. 3) Hamid Benbrahim, it seems that you should see this movie.

Liliana Salvador: You are more than welcome! It was really a sweet movie! :D

## Tuesday 6/23

I've been poking around on this website for the past few days and find it interesting (if not entirely useful). It's a sort of data visualization blog. http://flowingdata.com/

## Wednesday 6/24

1) Working in SFI was really fun. Thank you teammates!

2) I really do not recommend classes more than 75 minutes!