A generalized version of the rings CK(X) and C∞(X)– an enquery about when they become Noetheri

Sudip Kumar Acharyya, Kshitish Chandra Chattopadhyay, Pritam Rooj


Suppose F is a totally ordered field equipped with its order topology and X a completely F-regular topological space.  Suppose P is an ideal of closed sets in X and X is locally-P.  Let CP(X,F) ={f:X→F|f is continuous on X and its support belongs to P} and CP(X,F) ={f∈CP(X,F)| ∀ε>0 in F, clX{x∈X:|f(x)|> ε} ∈ P}. Then CP(X,F) is a Noetherian ring if and only if CP (X,F) is a Noetherian ring if and only if X is a finite set.  The fact that a locally compact Hausdorff space X is finite if and only if the ring CK(X) is Noetherian if and only if the ring C(X) is Noetherian, follows as a particular case on choosing F=R and P= the ideal of all compact sets in X.  On the other hand if one takes F=R and P= the ideal of closed relatively pseudocompact subsets  of X,  then  it  follows  that  a  locally  pseudocompact  space X is  finite  if  and  only  if  the  ring Cψ(X) of  all  real  valued  continuous functions on X with pseudocompact support is Noetherian if and only if  the ring Cψ(X) ={f∈C(X)| ∀ε >0, clX{x∈X:|f(x)|> ε} is  pseudocompact } is  Noetherian.   Finally  on  choosing F=R and P= the ideal of all closed sets in X, it follows that: X is finite if and only  if  the ring C(X) is  Noetherian  if  and  only  if  the ring C(X) is Noetherian.


Noetherian ring; Artinian ring; totally ordered field; zero-dimensional space; pseudocompact support; relatively pseudocompact support.

Subject classification

54C40; 46E25.

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1. A note on ideals of C∞(X)
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Topology and its Applications  vol: 189  first page: 25  year: 2015  
doi: 10.1016/j.topol.2015.04.001

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