models ...

[Nguyen Tien Zung <tienzung@darboux.math.univ-montp2.fr>]

Hi ba'c AiViet va` ca'c ba'c

Tui thi` tha^'y la` models cua? Zeeman (du+.a tre^n Whitney singularity)
co' serious flaw: no' kho^ng thoa? ma~n extension principle (tu+'c la`
ba'c cha.y 1 ddu+o+`ng phia' du+o+'i variables thi` ve^` nguye^n ta('c
pha?i na^ng le^n ddu+o+.c
tha`nh 1 ddu+o+`ng phia' tre^n, nhu+ng theo Zeeman model
thi` ne^'u ba'c cha.y 1 ddu+o+`ng phia' du+o+'i kho^ng ca^`n tha^.n se~
kho^ng na^ng le^n ddu+o+.c dda^u ca? ne^'u kho^ng co' jumps)
Xem ra ca'i singularity ma` Zeeman du`ng too simplistic. It' ra pha?i co'
branching theo kie^?u complex analysis hay du`ng. (Ma^'y flaws kha'c
cu?a models co' the^? xem trong ba`i cu?a Arnold) 

Co' o^ng savant nao ddo' ma` tui kho^ng nho+' te^n (einstein?) co' no'i
mo.i thu+' ca^`n be as simple as possible but not simpler. Ba'c Zeeman
xem ra oversimplified the things. 

Ve^` simple effective model for love there is our ancestors' model of
no^`i va` vung tui tha^'y ra^'t hay (xin ho?i ba'c Tuan V Nguyen xem dda^y
co' pha?i formal model kho^ng). No^`i thi` pha?i ti`m vung vu+`a, vung cu~ng
va^.y. Co' khi ti`m ddu+o+.c ma^'y ca'i vung vu+`a lie^`n, co' khi cha?
ddu+o+.c ca'i na`o. Ma` mo^`i kho^ng co' vung va^~n "sa?n sua^'t" ddu+o+.c,
chu+' vung kho^ng ti`m ddu+o+.c no^`i thi` xem ra "vo^ du.ng" (ca'i na`y
co^ cu+`u Dolly mo+'i chu+'ng minh cha(.t che~, nga`y xu+a dda~ co'
huye^`n thoa.i ddu+'c me.)

Thu+.c ra dynamical systems are complicated anough to model many things
(including love, i hope). will write about it in the next mail. I have
to go to a seminar now.

Cheers, Zung