# Colloquium for Fall 2019

If you are interested in giving a talk, please email caherrera@csuchico.edu

Colloquia are typically held on Friday in Holt 175. Refreshments are served at 3:30pm and the talk begins at 4:00pm. Everyone is invited to attend.

Past Colloquium Schedules(opens in new window)

#### Friday, September 6th -- Holt 175, 4:00pm

**Corey Shanbrom (Sacramento State University)**

Where do Kepler's laws hold?

Where do Kepler's laws hold?

Abstract: The Kepler Problem is among the oldest and most fundamental problems in mechanics. Its solution describes the motion of a planet around a sun, and famously yields Kepler's Three Laws of Planetary Motion. The problem makes sense in curved geometries like spheres and hyperbolic spaces. Do the laws still hold? We answer this question and investigate the Kepler problem in a new and strange geometry: the Heisenberg group, where a straight line is a helix.

#### Friday, September 27th -- Holt 175, 4:00pm

**Beth Malmskog (Colorado College)**

**Locally Recoverable Codes with Many Recovery Sets from Fiber Products of Curves**

Abstract: Error correcting codes are systems for incorporating redundancy into stored or transmitted data, so that errors can be identified and even corrected. A good error correcting code is efficient and can correct many errors relative to its efficiency. These codes are ubiquitous in the digital age, and many excellent codes arise from algebraic constructions. The increasing importance of cloud computing and storage has created a need for codes that protect against server failure in large computing facilities. One way of approaching this problem is to ask for local recovery. An error correcting code is said to be locally recoverable if any symbol in a code word can be recovered by accessing a subset of the other symbols. This subset is known as the helper or recovery set for the given symbol. It may be desirable to have many disjoint recovery sets for each symbol, in case of multiple server failures or to provide many options for recovery. Barg, Tamo, and Vladut recently constructed LRCs with one and two disjoint recovery sets from algebraic curves. This talk presents a generalization of this construction to three or more recovery sets, using fiber products curves over finite fields. This is joint work with Kathryn Haymaker and Gretchen Matthews.

#### Friday, October 4th -- Holt 175, 4:00pm

**John Lind (CSU-Chico)**

**Abelian Sandpile Music**

Abstract: I will present a new type of generative music based on the "abelian sandpile model"--a discretized model for the flow of heat which is full of interesting combinatorial structures. The music is created by encoding the mathematics into an algorithm which then plays synthesizers according to the rules laid out by the dynamical system. I will explain how this works, and we will listen to examples. I will also discuss how the mathematics behind the music is regulated by a discrete form of the Laplacian operator and an analogy between graphs and Riemann surfaces.