Treynor ratio

In mathematics, the Seifert conjecture states that every nonsingular, continuous vector field on the 3-sphere has a closed orbit. It is named after Herbert Seifert. In a 1950 paper, Seifert asked if such a vector field exists, but did not phrase non-existence as a conjecture. He also established the conjecture for perturbations of the Hopf fibration.

The conjecture was disproven in 1974 by Paul Schweitzer, who exhibited a $C^1$ counterexample. Schweitzer's construction was then modified by Jenny Harrison in 1988 to make a $C^{2+\delta }$ counterexample for some $\delta >0$. The existence of smoother counterexamples remained an open question until 1993 when Krystyna Kuperberg constructed a very different $C^{\mathrm{\infty }}$ counterexample. Later this construction was shown to have real analytic and piecewise linear versions.

References

• V. Ginzburg and B. Gürel, A $C^2$-smooth counterexample to the Hamiltonian Seifert conjecture in $R^4$, Ann. of Math. (2) 158 (2003), no. 3, 953--976
• J. Harrison, $C^2$ counterexamples to the Seifert conjecture, Topology 27 (1988), no. 3, 249--278.
• G. Kuperberg A volume-preserving counterexample to the Seifert conjecture, Comment. Math. Helv. 71 (1996), no. 1, 70--97.
• K. Kuperberg A smooth counterexample to the Seifert conjecture, Ann. of Math. (2) 140 (1994), no. 3, 723--732.
• G. Kuperberg and K. Kuperberg, Generalized counterexamples to the Seifert conjecture, Ann. of Math. (2) 143 (1996), no. 3, 547--576.
• H. Seifert, Closed integral curves in 3-space and isotopic two-dimensional deformations, Proc. Amer. Math. Soc. 1, (1950). 287--302.
• P. A. Schweitzer, Counterexamples to the Seifert conjecture and opening closed leaves of foliations, Ann. of Math. (2) 100 (1974), 386--400.

Further reading

• K. Kuperberg, Aperiodic dynamical systems. Notices Amer. Math. Soc. 46 (1999), no. 9, 1035--1040.