John C. Baez's Blog, page 17

Negative Prices for Power

Yesterday it was so windy near Edinburgh that the price of power went negative!

Why does the price go negative? Apparently because it costs more to slow the turbines than to let them spin and generate power. And it costs more to dump the power somewhere than to have customers use it.

We get the pricing data in real time from here:

• Energy Stats UK: Octopus Agile Southern Scotland.

Mike Fourman, whose house we are staying in, is really into keeping track of the price of electricity and ch...

Modes (Part 5)

In Part 3 of this series, we figured out all the scales where we choose 7 notes from the 12 notes in the usual chromatic scale, with the property that the biggest step between notes is a whole tone.

We saw these scales come in three sets of 7:

I discussed all but the last seven in Part 4. So let’s look at these now!

Modes of the Neapolitan major scale

The modes of the Neapolitan major scale are all the 7-note scales drawn from the usual chromatic scale where three consecutive notes d...

Agent-Based Models (Part 1)

I’m working with Nate Osgood and other folks to develop better modeling tools for epidemiologists. Right now we’re trying to develop a category-based framework for agent-based models. It’s a bit tough since many different techniques are used in such models, without yet an overarching discipline—Nate likened it to the ‘wild West’. I have a lot to learn, but I thought I should start keeping notes on our conversations.

Agent-based models involve multiple ‘agents’ that have ‘states’ which change ...

Compositional System Dynamics for Public Health

The Topos Institute has a colloquium every week. This time it’s by my old grad school pal Nate Osgood. He’s a computer scientist, he helped lead Canada’s COVID modeling effort…

… and he is now spear-heading a project to develop software that uses ideas from category theory to make it easier to create models of epidemic disease!

I am completely biased, since I’m involved in this—but I am really excited about how category theory, computer science and epidemiology are meeting in this project and ...

ACT 2023 — Registration

6th Annual International Conference on Applied Category Theory (ACT2023)

July 31 – August 4, 2023

https://act2023.github.io/

Due to generous sponsorship from NIST and UFL, registration is completely free! Please register here:

https://www.eventbrite.com/e/applied-category-theory-2023-registration-643212404617

If you plan to attend virtually, you will need to register before July 14 to receive a Zoom link.

The Sixth International Conference on Applied Category Theory will take place at the Univer...

Modes (Part 4)

In Part 3, we figured out all the 7-note scales drawn from the usual 12-tone scale and obeying an extra constraint: there’s at most a whole tone between consecutive notes. We got a total of 21. They come in 3 groups of 7:

• the modes of the major scale
• the modes of the ascending melodic minor scale
• the modes of the Neapolitan major scale

Let’s start getting to know them better! You see, the great thing about modes is that they’re not just mathematical entities: each has its own flavor, i...

Modes (Part 3)

I want to write more about modes! I’ve been playing music and thinking about modes all along, but now I have more to say. In Part 1, I described the 7 modes formed by starting the major scale at various points:

I linked to videos where you could hear samples of music in each of these modes. I showed how to order them from ‘bright’ to ‘dark’:

and I showed that inverting these modes maps the brighter modes to the darker ones, reversing the order of brightness, with Dorian getting mapped to ...

Diberyllocene

Beryllium is the fourth element in the periodic table, giving it many special properties. But it’s surprisingly rare, because stars almost always make beryllium-8, an extremely unstable form. And it hasn’t been studied as much as other light elements—because beryllium dust is so poisonous! It can cause fatal scarring of the lungs.

Now a chemist named Boronski has made some big progress. Yes, Boronski.

• Josef T. Boronski, Agamemnon E. Crumpton and Lewis L. Wales and Simon Aldridge, Diberyllo...

Seminar on Applied Category Theory

On Tuesday June 6, 2023, David Corfield ran a one-day Seminar on Applied Category Theory. He started with a quick introduction to applied category theory for philosophers! Then Toby St Clere Smith spoke about categorical cybernetics and the Bayesian brain. Then I gave a gentle introduction to applied category theory—more about the history of the subject, what people are trying to do, and my own personal involvement than any actual math.

Here are the talks. You can click on the titles to see ...

Seminar on Applied Category Theory

David Corfield is running a one-day Seminar on Applied Category Theory tomorrow, Tuesday June 6, 2023. I’ll give a gentle introduction to applied category theory – more about the history of the subject, what people are trying to do, and my own personal involvement than any actual math.

It’s hybrid – you can attend using MS Teams if you go here, or in person at KS23, Keynes College, University of Kent, Canterbury.

There are 3 talks. Times here are UK time (which is currently UTC +1):

• 15:30-15:...