# Forum for matematiske perler (og kuriositeter)

## 2023 - 2024

## Dr. Michael Korey (Senior Curator, Mathematisch-Physikalischer Salon, Dresden): * Heavenly machines of the renaissance: mathematics fit for a prince *

**Sted:** Lunsjrommet i 13. etg., Sentralbygg 2

**Tid:** Fredag 2. februar 2024 klokken 12:15–13:00

Planetary automata, also called planetary clocks, were expensive and rare masterpieces of technical ingenuity, mathematical modeling, and astronomical learning. They were designed to predict and display the subtle motion of the heavenly bodies according to geometrical models received from Antiquity and then refined over the centuries. In particular, the hands on their dials served to visualize the non-uniform motion of the planets in real time, as seen by an earthly observer. These wondrous automata were almost exclusively the reserve of princes and emperors, and within the history of astronomy notice of about a dozen of them has reached us, of which four from the Renaissance survive (one each in Paris, Vienna, Kassel, and Dresden). This richly illustrated, accessible talk presents an analysis of new research on these instruments. Could it be that a careful analysis of these machines allows us to witness in their gearing both a previously unknown mathematical theorem and the birth of a new astronomical theory?

## Mats Ehrnström: * On Euler’s musical function and other topics in the mathematical theory of music *

**Sted:** Lunsjrommet i 13. etg., Sentralbygg 2

**Tid:** Fredag 20. oktober 2023 klokken 12:15–13:00

This talk is about attempts at describing, understanding, and controlling the perception of harmony and tonal congruence through formal mathematical language and methods. In other words – when we perceive some music or voices in a more pleasant way, can that be described mathematically; and how can knowledge of frequency perception and mathematics be combined to produce tones or sound volume that are physically not there?

## Abigail Linton: * Two knots that slice differently *

**Sted:** Lunsjrommet i 13. etg., Sentralbygg 2

**Tid:** Fredag 6. oktober 2023 klokken 12:15–13:00

The Conway and Kinoshita-Terasaka knots are famous for looking almost identical at first glance, but having surprising differences between them. One particular example is “sliceness”: a knot is slice if it bounds a smooth properly embedded disk in the four-dimensional space. Before 2018, sliceness was known for every knot with fewer than 13 crossings bar one, the Conway knot. In 2018 Lisa Piccirillo used her PhD techniques to solve this long-standing and famous problem: the Conway knot is not slice. But the Kinoshita-Terasaka knot is. We will learn some basic techniques in knot theory and take a closer look at this strange pair of knots.

## Alexander Schmeding: * Buttons that do not roll away and Barbier's theorem *

**Sted:** Lunsjrommet i 13. etg., Sentralbygg 2

**Tid:** Fredag 22. september 2023 klokken 12:15–13:00

Buttons are usually round and thus prone to rolling away (which is super annoying). In this talk we shall meet a class of convex shapes which are well suited to be used as buttons, but will not easily roll away. On this occasion we take a stroll through the realm of convex geometry in 2D and 3D. In 2D much is known about these special shapes. We showcase this with one pearl theorem by Barbier. Surprisingly the proof of this pearl will employ Buffons noodle (as in pasta, not needle spelled wrong).