This week, my collaborator/friend from Barabasilab/award winning physicist, Yong-Yeol Ahn (better know as YY) is visiting the Center for Social Data here at DTU. If you’re anywhere near Copenhagen, I highly recommend you stop by to see his talk!

Time: Thursday, May 24th, 13:00 [details here]

Title: Community structure and flocking of memes in social networks

Abstract: Spreading processes on networks (e.g. epidemic outbreak and information spreading) has been one of the most fundamental topics in network science. Information spreading in social networks has often been described by epidemic spreading models but recent studies demonstrated that some contagions (memes) exhibit fundamentally different pattern, where multiple exposure significantly enhances the transmission probability of the contagion. The co-operativity of a contagion makes the spreading process more sensitive to clustered network structure. Here we investigate the relationship between network communities and spreading of hashtags in a Twitter network.

And if we’re lucky, maybe we can even talk him into speaking a bit about his interesting work on food pairings and molecular gastronomy!

This week I’m visiting the Max Planck Institute for the Physics of Complex Systems in Dresden, participating in the workshop Mathematical Physics of Complex Networks: From Graph Theory to Biological Physics. 

It’s quite the honor to be invited to speak at a conference full of real physicists & bona fide graph theorists (although it’s putting my softening brain hard at work: there seems to be a lot more analytical results here than I’m used to these days).

This week I’m heading out to CompleNet 2012 in Melbourne Florida. It looks like a great conference with Laszlo Barabasi, Robert Bonneau  & Sinan Aral headlining.

The conference will also feature an unreasonably high level of activity by yours truly with duties including an invited talk (8:40 on March 8th), chairing a technical session (on network metrics and models, 10:20 on March 7th), as well as a brief talk at the opening of the art exhibition on The Art of Networks at the local Foosaner Art Museum, about the creation of the TwitterMood visualization.

Hope to see you there if you’re in or around the Sunshine State!

Renaud Lambiotte is visiting for a few days. He’s an exciting guy whose work focuses on the relation between dynamics, function and structure in complex systems, with a focus on neuronal and social networks (check his website for more details). He’s an associate professor in Mathematics at the University of Namur (Belgium).

If you’re in the Copenhagen area, I highly recommend going to his talk this friday. Here are the details.

Title: Random Walks on Networks: Dynamics and Teleportation

Abstract:  In this talk, I will focus on two problems related to random walks on networks. First, I will focus on random teleportation, which is a necessary evil for ranking and clustering directed networks based on random walks. Teleportation enables ergodic solutions, but the solutions must necessarily depend on the exact implementation and parametrization of the teleportation. For example, in the commonly used PageRank algorithm, the teleportation rate must trade off a heavily biased solution with a uniform solution. Here we show that teleportation to links rather than nodes enables a much smoother trade-off and effectively more robust results, and discuss the effect of teleportation on clustering. In the second part of my talk, I will focus on random walks on temporal networks, i.e. networks evolving in time. In particular, I will examine the effects of inter-event statistics on the dynamics of edges, and apply the concept of a generalized master equation to the study of continuous-time random walks on networks.

Time & place: 

• Friday 2 March 2012 at 14:00
• Technical University of Denmark
• Seminar room 053, Building 305

Everyone is welcome! 

Three pieces of excellent news since I last posted here:

On December 13th, I received The Jorck Foundation’s research prize, which is awarded to three young researchers annually (as is evident from the photo, “young-ish researchers” might be more appropriate).

I’ve stolen the image from the DTU announcement (in Danish), which lists all names, etc. The gentleman on my right hand side is the Danish supreme court president, Børge Dahl, who is also the director the Jorck Foundation’s board. Justice Dahl awarded the prize in person inside the actual supreme court, at Christiansborg Palace - the proceedings were very old-worldly (is that a word) and fancy.

Then, on January 23rd, I was officially awarded millions in a very nice research grant as a part of the Villum Foundation‘s Young Investigator Program. More information on the content of the proposal can be found here (official DTU page).

In fact, I’m currently looking for a new PhD student (fully funded) to work on this project; should you be interested, you can read the details here.

Finally, effective February 1st, I am an Associate Professor of social informatics, still at DTU Informatics — and this might be the very best piece of news in a great couple of months.

The program for our workshop on December 15th is finally available for your reading pleasure. We’ll be talking about how to design a great sociometer experiment – and what the most exciting research questions are. Note that the workshop is open to the public, so if you’re in (or near) Copenhagen, do stop by!

We do have limited seating, so please send an email to David (ddl@econ.ku.dk) by December 12th, if you plan on attending.

Workshop:

The Copenhagen Center for Computational Social Science Inaugural Workshop. December 15th, 2011. Organized by Anders Blok, Søren Kyllingsbæk, David Dreyer Lassen, Morten Axel Pedersen and yours truly.

Abstract:

At last year’s Techonomy Conference, former Google CEO, Eric Schmidt, noted: “There was 5 exabytes of information created between the dawn of civilization through 2003, but that much information is now created every 2 days, and the pace is increasing”. This massive increase in the rate of data generation has opened up new possibilities for computational investigations of human behavior. We – a multi-disciplinary team of scholars from the Faculty of Social Sciences at the University of Copenhagen and the Technical University of Denmark – are interested in taking advantage of the recent technological developments in order to push the current boundaries of quantitatively based understandings of social systems.

Specifically, the aim of our proposed research program CCCSS (Copenhagen Center for Computational Social Science) is to record the network of social interactions with very high resolution (both in terms of temporal sampling and number of recorded communication channels) by using smart phones as sensors for sampling a variety of communication channels, e.g. face-to-face via Bluetooth, geolocation via GPS, social network data (Facebook, Twitter) via apps, and telecommunication data via call logs. Based on this highly complex and dynamic network, we want to develop computational (mathematical) approaches to describe the underlying social system. In addition to this overall goal, we are interested in a five concrete themes, which will support and inform our efforts to formulate a general theoretical framework spanning across different scientific disciplines:

1. Incomplete data and sampling. The significance of having access to only a small fraction of the full data in a networked system is poorly understood at present. We will use our findings from this high-resolution sample as a tool to understand much larger `low resolution’ data sets describing millions of individuals and billions of interactions.
2. Information stored in relationships. We know, in a casual sense, that it is possible to learn about a person by the company she keeps. We show that we can quantify this notion in a social network and we study to what extent our behavioral patterns are encoded in our social relations.
3. Influence in social systems. We wish to study how influence spreads in social systems, which is a problematic issue in most datasets. Our experimental setup allows us to probe causal issues by running controlled interventions; we will be able to run field experiments to test our hypotheses.
4. Methodological experiments and their epistemological effects. For a long time, social scientific methods have been split according to a qualitative/quantitative divide. Based on our experiment, we want to explore how new high-resolution datasets may shift the terms of this debate. As part of this effort, we also wish to investigate what the increasing use of digital setups in social network analysis means for the nature of the (social) scientific experiment
5. Privacy and ethics in social network research. We explore the question of privacy and develop novel strategies to ensure that our research (and the research of others working on similar topics) does not violate individual and collective rights to privacy.

Program:

Thursday, December 15th, 2011:

• 9.30 Coffee
• 10.00 Sune Lehmann: Introduction
• 11.00 Martin Raubal: Socially informed location-based knowledge discovery
• 12.00 Lunch
• 13.00 Daniele Quercia: Personality and Language in Social Media
• 14.00 Tea
• 14.30 Alan Mislove: Privacy in Online Social Networks
• 15.30 Matt Candea: The quantity and quality of gaps: On the value of not knowing certain things

Note that we’ll follow the format 30 min. + discussion for all talks

Venue:

According to the best of my calculations, the growth of Gmail storage is linear in time. Today, I recorded the amount of storage at two different times and found the rate of storage growth to be about 4.06541 bytes per second. This is consistent with Wikipedia’s report that, as of Jan 18th, 2010 Gmail’s storage was increasing at a rate of approximately 0.000004 MB per second. In other words, Google is giving away space at a constant rate.

Now, since the price of hard drive storage space seems to drop exponentially (over the last 30 years, space per unit cost has doubled roughly every 14 months (increasing by an order of magnitude every 48 months), this implies that Google is paying exponentially less for their new hard drive space [1]. The only reasonable conclusion is that Google’s generosity is rapidly approaching zero!

Just to be extra silly, I actually plugged the growth-data from my own account and used the regression fit from the site above in order to estimate the cost per gmail account as a funtion of time.

Full disclosure: There are a number of problems with the approach of estimating the cost of an account as current storage multiplied by current cost of storage. And let me just mention some of them here for transparency. Firstly, my storage price is based on consumer hardware prices, and I’m betting that Google probably can probably get some kind of bulk deal. Secondly, I assume that Google has some kind of backup system in place, which increases the need for storage beyond the account size reported by Google. Finally and most importantly, the correct price for storage over time should probably be estimated as accumulated price paid for hardware at time t compared with the total amount of storage offered for free at time t.

And there’s one final problem with the linear growth of storage. The issue becomes extra noticeable because all this cheap storage also applies to our personal computers … and to the average attachment size, which is probably growing in proportion to the size of the hard drive it was sent from [2]. What this means is that we’re likely to use up Gmail storage space at a rapid increasing rate.

I’m not saying that this is a violation of the “don’t be evil” maxim. It’s just that I’m running out of inbox space and don’t want to pay for additional storage.

Footnotes

[1] See also http://ns1758.ca/winch/winchest.html for more info on historical hard drive pricing. [2] I don’t really have data to support this claim, but it sounds reasonable to me.