Geodesic
Smooth invariants of focus-focus singularities
Vestnik Moskovskogo universiteta. Matematika, mehanika, no. 4 (2011), pp. 59-61

Voir la notice de l'article provenant de la source Math-Net.Ru

We consider focus–focus singularities of integrable Hamiltonian systems with two degrees of freedom. It is known that if two singularities of this kind have the same number of singular points, then they are fiber-wise homeomorphic. However, it may happen that this homeomorphism cannot be made smooth. An invariant has been constructed, which makes it possible to classify focus–focus singularities up to a $\mathrm{C}^1$-diffeomorphism. 
@article{VMUMM_2011_4_a12,
     author = {A. M. Izosimov},
     title = {Smooth invariants of focus-focus singularities},
     journal = {Vestnik Moskovskogo universiteta. Matematika, mehanika},
     pages = {59--61},
     publisher = {mathdoc},
     number = {4},
     year = {2011},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/VMUMM_2011_4_a12/}
}
TY  - JOUR
AU  - A. M. Izosimov
TI  - Smooth invariants of focus-focus singularities
JO  - Vestnik Moskovskogo universiteta. Matematika, mehanika
PY  - 2011
SP  - 59
EP  - 61
IS  - 4
PB  - mathdoc
UR  - http://geodesic.mathdoc.fr/item/VMUMM_2011_4_a12/
LA  - ru
ID  - VMUMM_2011_4_a12
ER  - 
%0 Journal Article
%A A. M. Izosimov
%T Smooth invariants of focus-focus singularities
%J Vestnik Moskovskogo universiteta. Matematika, mehanika
%D 2011
%P 59-61
%N 4
%I mathdoc
%U http://geodesic.mathdoc.fr/item/VMUMM_2011_4_a12/
%G ru
%F VMUMM_2011_4_a12
A. M. Izosimov. Smooth invariants of focus-focus singularities. Vestnik Moskovskogo universiteta. Matematika, mehanika, no. 4 (2011), pp. 59-61. http://geodesic.mathdoc.fr/item/VMUMM_2011_4_a12/