Register to reply 
Continuous  how can I combine these open sets 
Share this thread: 
#1
May2112, 12:23 AM

P: 62

1. The problem statement, all variables and given/known data
let ##X,Y## be compact spaces if ##f \in C(X \times Y)## and ## \epsilon > 0## then ## \exists g_1,\dots , g_n \in C(X) ## and ## h_1, \dots , h_n \in C(Y) ## such that ##f(x,y) \Sigma _{k=1}^n g_k(x)h_k(y) < \epsilon ## for all ##(x,y) \in X \times Y ## 2. Relevant equations 3. The attempt at a solution ##X,Y## are compact which means that for all open covers of ##X,Y##, there exists finite subcover. So, i have been trying to think of a way to pick for all ## x_0 \in X ## and ## y_0 \in Y ##, a function ##g_{x_0} \in C(X)## and ## h_{y_0} \in C(Y) ## such that ##f(x_0,y_0) = g_{x_0}(x_0)h_{y_0}(y_0)## then there exists an open subset ##U_{x_0,y_0}## of ##X \times Y## such that ##f(x,y)  g_{x_0}(x)h_{y_0}(y) < \epsilon ## for all ##(x,y) \in U_{x_0,y_0} ##. Then we can form an open cover of ##X,Y## and so there is a finite subcover, ##U_1,\dots , U_n ## but i don't know how I can combine these open sets to get my functions ##g_1,\dots ,g_n,h_1, \dots , h_n## such that ##f(x,y) \Sigma _{k=1}^n g_k(x)h_k(y) < \epsilon ## for all ##(x,y) \in X \times Y ## 


#2
May2112, 04:14 PM

P: 274




Register to reply 
Related Discussions  
3 questions concerning open and closed sets for sets having to do with sequence space  Calculus & Beyond Homework  0  
Can all open sets in R^n be expressed as countable union of open cubes?  Set Theory, Logic, Probability, Statistics  5  
Analysis: continuous function and open sets  Calculus & Beyond Homework  4  
Open sets and closed sets in product topology  Calculus & Beyond Homework  2  
Is the uncountably infinite union of open sets is open?  Calculus & Beyond Homework  8 