Let $\bar{J}^3$ be the functor of semi-holonomic $3$-jets and $\bar{J}^{3,2}$ be the functor of those semi-holonomic $3$-jets, which are holonomic in the second order. We deduce that the only natural transformations $\bar{J}^3 \rightarrow \bar{J}^3$ are the identity and the contraction. Then we determine explicitely all natural transformations $\bar{J}^{3,2}\rightarrow \bar{J}^{3,2}$, which form two $5$-parameter families.
@article{107553, author = {Gabriela Vosmansk\'a}, title = {Natural transformations of semi-holonomic 3-jets}, journal = {Archivum Mathematicum}, volume = {031}, year = {1995}, pages = {313-318}, zbl = {0852.58003}, mrnumber = {1390591}, language = {en}, url = {http://dml.mathdoc.fr/item/107553} }
Vosmanská, Gabriela. Natural transformations of semi-holonomic 3-jets. Archivum Mathematicum, Tome 031 (1995) pp. 313-318. http://gdmltest.u-ga.fr/item/107553/
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