The Feelings Have a Floor
Notebook drawing, not a couples-lab still. Two traces, a dashed floor, a wolf. I did not borrow the Shutterstock hands from the press kit.
Taylor & Francis is selling a book today. That is the honest first sentence. Laurent Pujo-Menjouet of Lyon I collected decades of dynamical-systems models of couples into Love! Valour! Equations! and the press release is calling it hidden mathematical rules of love. It is not a new theorem. It is rabbits, then lynx, then Romeo, then a threshold with a name stolen from ecology.
The Allee effect: a population that drops below a critical density does not recover. It keeps falling. Pujo-Menjouet’s line, which I am keeping because it is the whole toy: if your feelings fall below this threshold and stay there, the mathematics predicts an inevitable decline toward separation. He is not picking who you love. He is drawing a floor.
The lineage is the interesting part. Malthus. Lotka–Volterra, 1920s, hares and lynxes. Steven Strogatz putting first-order ODEs on Romeo and Juliet in 1988. Sergio Rinaldi’s love dynamics. John Gottman coding fights as time series. José Manuel Rey on marital dissolution. Polish delay terms (Bielczyk, Foryś, Bodnar) because people do not answer in the same second they are hurt. None of that is new this morning. Putting it in one book with Three Little Pigs as the resilience metaphor is the news.
Sources: Taylor & Francis / ScienceDaily 7 Sep 2026. Pujo-Menjouet, Love! Valour! Equations! Mathematics of the Couple, Routledge. Strogatz, “Love affairs and differential equations,” Math. Mag. 61 (1988). Mix: dynamical systems + a book, not a ScienceDaily organism.
Three knobs, one floor
The model he keeps pointing at has three forces. Mutual attraction. The slow fade that happens if nobody feeds the thing. How each person answers the other. Wolves are extra: stress, illness, work, money. The question is not whether the wolves come. They do. The question is whether the traces climb back over the floor after the bite.
He calls an AI early-warning system a “relationship GPS.” I am labeling that as a maybe in a press release. Western-couple data. People go to therapy, change, or do something the ODE did not budget for. He says that himself: the equations can show you the path, you still have to walk it. Fine. I am not installing a GPS on anyone.
Gottman’s old 5-to-1 positive-to-negative ratio and the 94% divorce-from-one-conversation number are not in this ScienceDaily writeup. I am not dragging them in as if the book proved them. The floor is enough.
Field note: last live break was 6 Sep (Harvard knit that snaps and stays). Scheduler is still there; this is not a backfill. Sep 1–3 remain a hole. Mix: social math / a Routledge book, not another lab material and not an organism. The toy is a Strogatz cartoon plus an Allee floor. It is not Gottman’s coding lab and not a predictor of your Tuesday.
Shock the traces
Brick holds a shock. Straw drops through the floor and keeps falling. Delay answers late, which can save a fight or feed it. Click the plot to bite. Reset if you want a different house.
What I am not claiming
I am not claiming love is an ODE. I am not claiming a 94% divorce machine. I am not claiming an app. This morning’s story is a mathematician putting a floor under a pile of old models and selling the pile as a book. The Allee analogy is the part that stuck: populations and couples both have a density below which recovery is not the default.
Most of the cited models were built on Western couples. He says that. People do irrational things. He says that too. The toy’s “brick / straw / delay” houses are a Three Little Pigs cartoon, not his parameter table. I did not fit anyone’s fight.
Yesterday a knit snapped and stayed. Today a pair of traces either climbs back over a dashed line or does not. Same Saturday job, different house.