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arXiv 1809.08982math.FA
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函数空间的Dunford-Pettis型性质和Grothendieck性质

Dunford--Pettis type properties and the Grothendieck property for function spaces

Saak Gabriyelyan, Jerzy Kcakol

摘要:

对于吉洪诺夫空间$X$,设$C_k(X)$和$C_p(X)$分别是$X$上的实值连续函数空间$C(X)$,并赋予其紧开拓扑和点态拓扑.若$X$是紧的,则A.~ Grothendieck指出$C_k(X)$具有Dunford-Pettis性质和序列Dunford-Pettis性质。我们推广了Grothendieck的结果,证明了当$X$满足下列条件之一时,$C_k(X)$同时具有Dunford-Pettis性质和序列Dunford-Pettis性质:(i)$X$是半紧空间,(ii)$X$是宇宙空间(=可分度量空间的连续象),(iii)$X$是某个序数$κ$的序数空间$[0,κ)$,或(vi)$X$是局部紧的仿紧空间.证明了如果$X$是宇宙空间,则$C_k(X)$具有Grothendieck性质当且仅当$X$的每个函数有界子集是有限的.证明了对任意的Tychonoff空间$X$,$C_p(X)$具有Dunford-Pettis性质和序列Dunford-Pettis性质,并且$C_p(X) $具有Grothendieck性质当且仅当$X$的任意函数有界子集是有限的.

英文摘要:

For a Tychonoff space $X$, let $C_k(X)$ and $C_p(X)$ be the spaces of real-valued continuous functions $C(X)$ on $X$ endowed with the compact-open topology and the pointwise topology, respectively. If $X$ is compact, the classic result of A.~Grothendieck states that $C_k(X)$ has the Dunford-Pettis property and the sequential Dunford--Pettis property. We extend Grothendieck's result by showing that $C_k(X)$ has both the Dunford-Pettis property and the sequential Dunford-Pettis property if $X$ satisfies one of the following conditions: (i) $X$ is a hemicompact space, (ii) $X$ is a cosmic space (=a continuous image of a separable metrizable space), (iii) $X$ is the ordinal space $[0,κ)$ for some ordinal $κ$, or (vi) $X$ is a locally compact paracompact space. We show that if $X$ is a cosmic space, then $C_k(X)$ has the Grothendieck property if and only if every functionally bounded subset of $X$ is finite. We prove that $C_p(X)$ has the Dunford--Pettis property and the sequential Dunford-Pettis property for every Tychonoff space $X$, and $C_p(X) $ has the Grothendieck property if and only if every functionally bounded subset of $X$ is finite.

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