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Gro-Tsen Profile picture
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5 Mar, 4 tweets, 2 min read
Pourquoi est-ce si difficile même pour des gens éduqués de comprendre la morale de l'histoire du garçon qui criait au loup?
Ma réponse de fond à ce fil est ici: — à quoi il faudrait sans doute ajouter la remarque importante qu'il est faux de considérer les variants comme des épidémies indépendantes dès lors que les formes du virus causent une forte immunité croisée entre elles.
Mais à la limite ce n'est pas le propos. Peut-être que dans qqs semaines les variants vont causer une explosion des cas: je ne prétends pas le contraire. D'ailleurs, dans la fable du garçon qui criait au loup, IL Y A un loup à la fin! Ça n'empêche que le garçon avait tort.
Donc la question à se poser est: que cherchent au juste à accomplir les gens qui crient ainsi au loup et répètent chaque semaine que le loup viendra la semaine prochaine sans jamais analyser leurs erreurs? Quel est leur but? Que proposent-ils? Où veulent-ils en venir?

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More from @gro_tsen

Gro-Tsen Profile picture
5 Mar
Some more numerical examples illustrating various possible outcomes of an epidemic with two viral variants — and, ultimately, how impossible to predict these things are. Let me explain what these graphs show. ⤵️ •1/20
Both images illustrate the behavior of an epidemic with two different pathogen forms: one starting with basic reproduction number 1.0 (the “ancestral form”), another starting with basic reproduction number 1.4 (the “variant”). Infection by either induces immunity to both. •2/20
In each scenario we start with the same initial conditions: 0.75% of the population is infected, and ✳︎of✳︎ those, 1% are by the variant, the rest by the ancestral strain. •3/20
Read 20 tweets
Gro-Tsen Profile picture
4 Mar
Hi @jenniferdaniel! I enjoyed your @unicode talk “Race is Not a Skin Tone, Gender is Not a Haircut”, and I have a question: could you tell me something about the decision not to allow skin tone modifiers on smiley emojis like U+1F928 FACE WITH ONE EYEBROW RAISED? Specifically: …
‣ Am I correct in understanding that the choice of which emoji are or are not skin-tone-able is basically just down to the ones which Apple made explicitly Caucasian in their original set? (as opposed to some more carefully considered choice, that is).
‣ Has the success of the skin tone modifiers on emoji like hand gestures (which I feel convey the same kind of feelings / intention as smileys) led to debates, among vendors or inside Unicode, about reconsidering smiley + skin tone combinations?
Read 5 tweets
Gro-Tsen Profile picture
4 Mar
This thread attempts to answer the question “why do we use elliptic curves in cryptography (for things like discrete logarithms)” and I think makes a very good job at explaining it, but there is one point which is a bit glossed over. •1/12
Basically what we want is a group C which is “cyclic but not trivially cyclic”, i.e., that there be an isomorphism ℤ/ℓℤ → C, easily computable (given a choice of generator of C) as well as the group operation in C, but that the reverse isomorphism be hard. •2/12
This is a bizarre quest, because in mathematics we aren't used to distinguishing isomorphic objects, even less the existence of an isomorphism in one direction from that in the other! (Of course here both exist, but one is “easy” and the other is “hard”.) •3/12
Read 12 tweets
Gro-Tsen Profile picture
2 Mar
Ce n'est pas la première fois que je vois passer des affirmations du genre «Macron ignore le conseil scientifique et c'est pour ça qu'il n'y a pas de nouveau confinement / zéro-covid», mais y a-t-il eu des recommandations du c.s. dans ce sens?
L'avis du conseil scientifique du 2021-02-12, solidarites-sante.gouv.fr/IMG/pdf/avis_c… (le dernier à ce jour) ne fait aucune référence au confinement, encore moins au zéro-covid. Il est dit explicitement (page 13) qu'il n'y a pas unanimité du c.s. (moi je devine «grosses engueulades»).
Les avis précédents évoquent les confinements (sans jamais vraiment les recommander explicitement, mais ils sont présentés comme efficaces pour contenir la situation) mais certainement pas le zéro-covid.
Read 5 tweets
Gro-Tsen Profile picture
1 Mar
La séance précédente j'ai parlé de jeux en forme normale et je crois que j'ai été assez mauvais (confus), par contre, cette semaine j'espère m'en être mieux tiré sur les jeux de Gale-Stewart.
Un jeu de Gale-Stewart est défini par un ensemble X≠∅ et une partie A⊆X^ℕ: Alice choisit x₀∈X (sans contrainte) puis Bob choisit x₁ (idem) puis Alice choisit x₂, etc., et au bout d'un nombre infini de coups, si la suite formée appartient à A alors Alice gagne, sinon Bob.
La question est: un des joueurs a-t-il forcément une stratégie gagnante? En général la réponse est négative, mais si on fait l'hypothèse que A est ouvert ou bien fermé («détermination ouverte») elle l'est, ou même si A est borélien («détermination borélienne»).
Read 7 tweets
Gro-Tsen Profile picture
12 Feb
OK, I may be guilty of a DoS attack attempt on mathematicians' brains here, so lest anyone waste too much precious brain time decoding this deliberately cryptic statement, let me do it for you. •1/15
First, as some asked, it is to be parenthesized as: “∀x.∀y.((∀z.((z∈x) ⇒ (((∀t.((t∈x) ⇒ ((t∈z) ⇒ (t∈y))))) ⇒ (z∈y)))) ⇒ (∀z.((z∈x) ⇒ (z∈y))))” (the convention is that ‘⇒’ is right-associative: “P⇒Q⇒R” means “P⇒(Q⇒R)”), but this doesn't clarify much. •2/15
Maybe we can make it a tad less abstruse by using guarded quantifiers (“∀u∈x.(…)” stands for “∀u.((u∈x)⇒(…))”): it is then “∀x.∀y.((∀z∈x.(((∀t∈x.((t∈z) ⇒ (t∈y)))) ⇒ (z∈y))) ⇒ (∀z∈x.(z∈y)))”. •3/15
Read 15 tweets

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