Steve Trettel

@stevejtrettel.bsky.social

Math Prof: Geometry, Topology and Illustration at University of San Francisco. Minnesotan, from the occupied lands of the Dakota people.

Summers here - time to catch up sharing some of what I’ve been up to! First up - *gravitational photography* - using (simulated) black holes instead of lenses to focus an image onto a screen. Can you see the ghostly dinosaur? 1/n

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The regular hexagon can be rolled up isometrically into a flat torus in 4 dimensional space: here’s a stereographic projection of the result. (Can you see the hexagonal pattern in the spheres covering its surface? 😁)

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So honored to have some of my pieces on display at O’Hanlon Center for the Arts in their exhibition “Chaos” this month. This one is titled “Many Paths to the Beach” (explanatory thread to follow once I’m to my office)

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Here's what it would look like to travel in a distant orbit to two extremal charged black holes, which themselves are stationary (grav/electrostatic in balance). As you orbit you see one pass in front of the other and lens it; Ive colored light rays green/red which enter their respective horizons.

Still having fun with Majumdar Papapetrou black holes over here :) This animation shows six such black holes arranged on the vertices of an octahedron, and traces a null geodesic from a nearby observer. The trajectory, and which BH it enters, depends very sensitively on the initial condition

@mseri.me introduced me to Majumdar–Papapetrou black holes through his+collaborators paper on the chaotic trajectories of light around 3 or more such black holes. Here's some intrinsic raytraced views of the N=3 case, where light rays falling into each are colored red/green/blue respectively.

Three black holes with event horizons colored red green and blue, from above the plane they lie inThree black holes with event horizons colored red green and blue, from in the plane.  The blue even horizon is distorted by lensing to form a ring.Three black holes with event horizons colored red green and blue, from in the plane.  The red even horizon is especially distorted by lensing.

Recently learned about Mamjudar-Papapetrou solutions in GR: masses attract but like charges repel, so if you throw enough charge into a collection of black holes they can remain static! Here's such a collection of BHs arranged cubically, and a (numerically found) closed null geodesic.

One of my fav GR pics for you blueskiers! A bit outside the horizon of a nonrotating black hole lies the photon sphere - a “point of no return” for infalling light. Here’s a light ray that makes a brush with death - skimming the photon sphere, doing a loop, then continuing on its merry way

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Heading down to Southern California today to visit UCI and talk about Newtonian physics in the presence of curvature . So here’s a fun fact: there is no Galilean relativity in curved space ! You can do experiments to determine your precise velocity

Hello all! I’m bad at keeping up with multiple social medias but as people move here figured I should reintroduce myself 😃 I’m a mathematician at the university of San Francisco who has gotten himself too deep into a computer graphics hobby. Here’s a couple algebraic varieties to cheer up your day ☺️

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Hello Bluesky! Trying to keep up with the rapidly fragmenting socials landscape over here - so I’m Steve, a mathematician at the U of San Francisco who loves geometry, outreach, and mathematical art! Here’s an algebraic variety in glass to brighten your timelines 😁

Pathtraced image of the Barth Sextic algebraic variety, made of simulated green glass against a primary color background