11 thoughts on “Slides for ACP talk

  1. this is a bit advanced for me. (i’m still trying to find the two point propogator (green’s function/path integral for a particle for my coursera.org course, along with figuring out whether presenting more jams is likely to lead to more purchases (dan ariel’s behavioral econ—it’s good to see Duke U is spending that tobacco fortune on something worthwhile (though the jams i really like are the ones prepared by appalachian people tho i always take too much, being a ta(w)ker, i guess ).

    should it be the sqrt(day) or maybe the 4th power of a second?
    i didnt quite get whether thin people have faster metabolisms. maybe i’ll actually have to read the plos paper or look at what the scatter plots mean, but i’m busy being busy. i know i shouldn’t eat until thursday at midnite but i’ll probably break down. (i do find that now, with it being in the 80’s, spending a few hours (say, 6 to 8) ‘swimming’ in the potomac river (still cold and the spring peepers are out) (more like holding on to avoid being swept over the falls) helps lose 5 to 10 pounds in a day. fat, salt, and sugar (a book) may be relevant 2.


  2. Yes, it should be square root for CV, which is SD/mean. The variance goes as 1 over the time constant for uncorrelated noise.

    Thin people do not have faster metabolism. Metabolism is not correlated to BMI. It his highly correlated to body weight though.


  3. i’d have to reason that through or look it up—this seems to imply that BMI and thinness are uncorrelated. i guess you can be thin yet mostly muscle and hence have a high bmi. (i see wikipedia says quetelet devised this back in the day of comte, etc and social physics, wisdom of crowds (le bon), etc. )

    the first equations in the slides remind me of Bentham’s theory of utility=benefits – costs, which later was written in newtonian spirit, as derivative of a potential. (Philip Mirowski criticized this approach, especially as discussed by Paul Samuelson, but Mirowski just comes up with promoting agent based simulations as the correct way to think of economics; i don’t think they are different except in methodology. the one new thing you get from this is considering tractability—‘approach to (an) equilibrium’ a la FPU experiments, sherrington-kirkpatrick, NP completeness—eg most ‘general equilibrium theory’ results in econ are non-tractable, so you can maximize utility, but hardly ever and it may take forever ).

    i wonder if selling junk food is covered, like campaign finance (under citizens united), by the second amendment or some other one. (i prefer the ideas which are strictly academic that favor placing the legal code into an axiomatic form (which could then be automated to avoid the issue of political bias) or else (or equivalently) written as a dynamical system (eg ‘jurisdynamics’ blog, or papers by J B Ruhl on law and complexity theory—mostly common sense, which i gather is a trait on the endangered species list).


  4. No, BMI and thinness are highly anti-correlated. It just implies that high metabolism is not correlated with thinness. People are thin because they don’t eat much compared to how much energy they burn.


  5. i’m wasting your time but—metabolism is correlated with weight. but since its not correlated with either bmi or thinness then weight is not correlated with thinness or bmi? ( that seems somewhat evident—a small person can have low weight and a high bmi and converse) .

    whats the best metric then? (eg make all people equal under a group symmetry/gauge transformation (hermann weyl) ; differences then might be a phase factor represnting some position in a local field—eg mcdonalds accessiblity).

    an interesting idea might be to connect bmi, thiness, metabolism to brain circuits (eg path integral formulation of neurodynamics) and then ‘choice’ (behavioral economics). and then show (a la robert plomin) how people construct their environments.


  6. Yes, BMI is only weakly correlated to weight. In fact BMI is the best scale invariant transform for humans involving just weight and height. There is no theory as to why weight scales with height squared. Thus BMI is the best measure using just height and weight of how much body fat you have, especially for women. It is true that highly muscled people will have high BMI but they are a very small fraction of the population.


  7. thanks for response–i’m slowly getting it. i guess its a square law, but not an inverse square law (newton—not newtown—theories for that based on euclidean geometry i’ve seen; same for boltzmann etc. distributions arxiv.org/abs/cond-mat/0503337). there are also the species/area power law relations, allometry, zipf, etc…. just heard about stuff in boston. i noticed a whole lot of police downtown and i was wondering why (i wonder why i wonder…).


  8. ps i notice now it is an inverse square law, so i guess it can be derived very simply from verlinde’s entropic gravity. (physics forums and physics.stackexchange also have this. you can even get a hamilton-jacobi equation for thermodynamics –rageev (arxiv.org/0711.4319 for example (or try annila in PRSL B, q wang, ao of wash state u, etc ). i always had difficulty with scaling laws (find the critical exponents—didn’t even know what that meant, at least intuitively—except if one thinks (a la renormalization gp theory/feynamn, k g wilson, kadanoff) . its a trick to make your series converge (of loop diagrams eg for the solution of the fokker-planck equation —also called a seond order taylor’s expansion—sortuh like a 2nd-order markov process (van kampen/mazur).
    this explains iq. n-order markov, and everything is markov (shalizi–santa fe institute–now carnegie mellon where my dad went)

    never understood dimensional analyses. (eg mandelbro’–whassup?) darcy thompson, robert rosen, rashevsky.)

    i was doing my coursera with keith devlin; had to prove 2**n>2n for all n (n a natural number). im a naturalist so i know. had a hard time— i start with the basic fact that 1+2+3+4+…= -1/12.
    boundary of a boundary is zero. ola


  9. The inverse square law of gravity is due to the fact that gravitational flux is never lost so the force scales as the surface area. However, for human bodies, a strict geometric scaling would be mass/height^3. The fact that it is height^2 means that humans deviate from geometry. This is why it is hard to understand.


  10. by googling i see there are many discussions of this issue. i iguess bmi is not like a density as one expect, so the analogy suggests maybe surface area of the body might be related to how much weight one loses due to interaction with air. one could see if bmi fails for cold blooded creatures who wouldn’t be affected, and whether different bmis exist for people in different climates.


  11. (that should be different ‘ideal’ or average bmi’s people in different climates, whatever that means if it can be defined—some sort of most probable/adaptive bmi due to evolution perhaps


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