Article
Keywords:
Poisson structure; pseudo–Riemannian manifold; natural operator
Summary:
Let $M$ be a differentiable manifold with a pseudo-Riemannian metric $g$ and a linear symmetric connection $K$. We classify all natural (in the sense of [KMS]) 0-order vector fields and 2-vector fields on $TM$ generated by $g$ and $K$. We get that all natural vector fields are of the form \[ E(u)=\alpha (h(u))\, u^H + \beta (h(u))\, u^V\,, \] where $u^V$ is the vertical lift of $u\in T_xM$, $u^H$ is the horizontal lift of $u$ with respect to $K$, $h(u)= 1/2 g(u,u)$ and $\alpha ,\beta $ are smooth real functions defined on $R$. All natural 2-vector fields are of the form \[ \Lambda (u) = \gamma _1(h(u))\, \Lambda (g,K) + \gamma _2(h(u))\,u^H\wedge u^V\,, \] where $\gamma _1$, $\gamma _2$ are smooth real functions defined on $R$ and $\Lambda (g,K)$ is the canonical 2-vector field induced by $g$ and $K$. Conditions for $(E,\Lambda )$ to define a Jacobi or a Poisson structure on $TM$ are disscused.
References:
                        
[1] Janyška J.: 
Remarks on symplectic and contact 2–forms in relativistic theories. Bollettino U.M.I. (7) 9–B (1995), 587–616.  
MR 1351076 | 
Zbl 0857.53027[2] Janyška J.: 
Natural symplectic structures on the tangent bundle of a space-time. Proceedings of the Winter School Geometry and Topology (Srní, 1995), Supplemento ai Rendiconti del Circolo Matematico di Palermo, Serie II 43 (1996), pp. 153–162.  
MR 1463517[3] Janyška J.: 
Natural Poisson and Jacobi structures on the tangent bundle of a pseudo-Riemannian manifold. preprint 2000.  
MR 1871030 | 
Zbl 1013.53053[4] Kolář I., Michor P. W., Slovák J.: 
Natural Operations in Differential Geometry. Springer–Verlag 1993.  
MR 1202431[5] Kowalski O., Sekizawa M.: 
Natural transformations of Riemannian metrics on manifolds to metrics on tangent bundles - a classification. Bull. Tokyo Gakugei Univ., Sect.IV 40 (1988), pp. 1–29.  
MR 0974641 | 
Zbl 0656.53021[6] Krupka D., Janyška J.: 
Lectures on Differential Invariants. Folia Fac. Sci. Nat. Univ. Purkynianae Brunensis, Brno 1990.  
MR 1108622[7] Libermann P., Marle, Ch. M.: 
Symplectic Geometry and Analytical Mechanics. Reidel Publ., Dordrecht 1987.  
MR 0882548 | 
Zbl 0643.53002[8] Lichnerowicz A.: 
Les variétés de Jacobi et leurs algèbres de Lie associées. J. Math. Pures et Appl., 57 (1978), pp. 453–488.  
MR 0524629 | 
Zbl 0407.53025[9] Nijenhuis A.: 
Natural bundles and their general properties. Diff. Geom., in honour of K. Yano, Kinokuniya, Tokyo 1972, pp. 317–334.  
MR 0380862 | 
Zbl 0246.53018[10] Sekizawa M.: 
Natural transformations of vector fields on manifolds to vector fields on tangent bundles. Tsukuba J. Math. 12 (1988), pp. 115–128.  
MR 0949905 | 
Zbl 0657.53009[11] Terng C. L.: 
Natural vector bundles and natural differential operators. Am. J. Math. 100 (1978), pp. 775–828.  
MR 0509074 | 
Zbl 0422.58001