John C. Baez's Blog, page 68

Azimuth Backup Project

This blog page is to help organize the Azimuth Environmental Data Backup Project, or Azimuth Backup Project for short. This is part of the larger but decentralized, frantic and somewhat disorganized project discussed elsewhere:

• Saving Climate Data (Part 2), Azimuth, 15 December 2016.

Here I’ll just say what we’re doing at Azimuth.

Jan Galkowski is a statistician and engineer at Akamai Technologies, a company in Cambridge Massachusetts whose content delivery network is one of the world’s lar...

Saving Climate Data (Part 2)

I want to get you involved in the Azimuth Environmental Data Backup Project. But first here’s a post with some background.

Starting a few days ago, many scientists, librarians, archivists, computer geeks and environmental activists have started to make backups of US government environmental data. We’re trying to beat the January 20th deadline just in case these backups are required.

Backing up data is always a good thing, so there’s no point in arguing about politics or the likelihood that th...

Globular

One of my goals is to turn category theory, and even higher category theory, into a practical tool for science. For this we need good scientific ideas—but we also need good software.

My friend Jamie Vicary has been developing some of this software, together with Aleks Kissinger and Krzysztof Bar and others. Jamie demonstrated it at the Simons Institute workshop on compositionality. You can watch his demonstration here:

But since Globular runs on a web browser, you can also try it out yoursel...

Saving Climate Data (Part 1)

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I try to stay out of politics on this website. This post is not mainly about politics. It’s a call to action. We’re trying to do something rather simple and clearly worthwhile. We’re trying to create backups of US government climate data.

The background is, of course, political. Many signs point to a dramatic change in US climate policy:

• Oliver Milman, Trump’s transition: sceptics guide every agency dealing with climate change, The Guardian, 12 December 2016.

So, scientists are now backing...

Saving Climate Data

[image error]

I try to stay out of politics on this website. This post is not mainly about politics. It’s a call to action. We’re trying to do something rather simple and clearly worthwhile. We’re trying to create backups of US government climate data.

The background is, of course, political. Many signs point to a dramatic change in US climate policy:

• Oliver Milman, Trump’s transition: sceptics guide every agency dealing with climate change, The Guardian, 12 December 2016.

So, scientists are now backing...

Modelling Interconnected Systems with Decorated Corelations

Here at the Simons Institute workshop on compositionality, my talk on network theory explained how to use ‘decorated cospans’ as a general model of open systems. These were invented by Brendan Fong, and are nicely explained in his thesis:

• Brendan Fong, The Algebra of Open and Interconnected Systems. (Blog article here.)

But he went further: to understand the externally observable behavior of an open system we often want to simplify a decorated cospan and get another sort of structure, which...

Semantics for Physicists

I once complained that my student Brendan Fong said ‘semantics’ too much. You see, I’m in a math department, but he was actually in the computer science department at Oxford: I was his informal supervisor. Theoretical computer scientists love talking about syntax versus semantics—that is, written expressions versus what those expressions actually mean, or programs versus what those programs actually do. So Brendan was very comfortable with that distinction. But my other grad students, coming...

Compositionality in Network Theory

Here are the slides of my talk at the workshop on compositionality at the Simons Institute for the Theory of Computing next week:

• John Baez, Compositionality in network theory, 6 December 2016.

Abstract. To describe systems composed of interacting parts, scientists and engineers draw diagrams of networks: flow charts, Petri nets, electrical circuit diagrams, signal-flow graphs, chemical reaction networks, Feynman diagrams and the like. In principle all these different diagrams fit into a...

Compositional Frameworks for Open Systems

Here are the slides of Blake Pollard’s talk at the Santa Fe Institute workshop on Statistical Physics, Information Processing and Biology:

• Blake Pollard, Compositional frameworks for open systems, 17 November 2016.

He gave a really nice introduction to how we can use categories to study open systems, with his main example being ‘open Markov processes’, where probability can flow in and out of the set of states. People liked it a lot!

Under2 Coalition

I’ve been thinking hard about climate change since at least 2010. That’s why I started this blog. But the last couple years I’ve focused on basic research in network theory as a preliminary step toward green mathematics. Basic research is what I’m best at, and there are plenty of people working on the more immediate, more urgent aspects of climate change.

Indeed, after the Paris Agreement, I started hoping that politicians were taking this issue seriously and that we’d ultimately deal with i...