Library / Diffusion / SIR Contagion

SIR Contagion

Susceptible–Infected–Recovered with an R0 tipping point. Same math for flu and pop-star fever.

IS ↓R ↑ firewall
R₀ > 1 takes off · recreated schematic
INTERACTIVE LAB

Tolerance sandbox (original recreation)

happy 76% • avg. similar neighbors 49% • red ring = wants to move

DIFFUSION

When to use / misuse

Use → Epidemics, memes, outages. Push R below 1 or segment the network.

Difficulty → Core

REDCAPE → Predict · Act · Explore

agent: sir-checker
family: Diffusion
combine_with: [two other families]
rule: state failure mode before acting

Free sources: ryansmcgee/seirsplus (MIT) • open-sir/open-sir (MIT) • complexity-explorables.org

← LibrarySee Playbook →
◍ Ask mentor about this →See REDCAPE playbook →

Attach to a lattice — combines with

Different families, shared jobs. Click to open alongside.

DYNAMICS
Markov Chain
Next state depends only on now. Run it forward to get the long-run mix.
SHARED JOBS: PREDICT · EXPLORE
LEARNING
Multi-Armed Bandit
Balance pulling the best-known lever against testing new ones. Regret is the score.
SHARED JOBS: ACT · EXPLORE
GROWTH
Capital Share (Piketty-style)
When returns on capital outrun growth, wealth concentrates without any villain.
SHARED JOB: ACT

More in Diffusion

Bass Diffusion (S-Curve)
Innovators plus imitators make the S-curve. Spend early on seeds, later on social proof.
Percolation / Tipping Points
Sparse links suddenly gel into a giant component — bank networks and blackouts tip fast.
Cellular Automata & Game of Life
Tiny local rules aggregate into gliders, blinkers and chaos. Emergence needs no boss.
← Preferential AttachmentBass Diffusion (S-Curve) →