# Montel space

A barrelled space (in particular, a Fréchet space) in which each closed bounded set is compact. The space $H(G)$ of all holomorphic functions in a domain $G$, with the topology of uniform convergence on compact sets, is a Fréchet space and, in view of a theorem of Montel (cf. Montel theorem, 2), every bounded sequence of holomorphic functions is relatively compact in $H(G)$, so $H(G)$ is a Montel space. The space $C^\infty(\Omega)=\mathcal E(\Omega)$ of all infinitely-differentiable functions in a domain $\Omega\subset\mathbf R^n$, the space $D(\Omega)$ of all functions of compact support and the space $S(\mathbf R^n)$ of differentiable functions that are rapidly decreasing at infinity, are also Montel spaces in their natural topologies.

A Montel space is reflexive (cf. Reflexive space). The strong dual of a Montel space is a Montel space; in particular, the spaces of generalized functions $\mathcal E'(\Omega)$, $D'(\Omega)$ and $S'(\Omega)$ are Montel spaces. A normed space is a Montel space if and only if it is finite-dimensional.

#### References

[1] | N. Bourbaki, "Elements of mathematics. Topological vector spaces" , Addison-Wesley (1977) (Translated from French) |

[2] | A.P. Robertson, W.S. Robertson, "Topological vector spaces" , Cambridge Univ. Press (1964) |

[3] | R.E. Edwards, "Functional analysis: theory and applications" , Holt, Rinehart & Winston (1965) |

#### Comments

#### References

[a1] | H. Jarchow, "Locally convex spaces" , Teubner (1981) (Translated from German) |

[a2] | G. Köthe, "Topological vector spaces" , 1 , Springer (1969) |

[a3] | H.H. Schaefer, "Topological vector spaces" , Springer (1971) |

**How to Cite This Entry:**

Montel space.

*Encyclopedia of Mathematics.*URL: http://www.encyclopediaofmath.org/index.php?title=Montel_space&oldid=32479