Math Amateur
Gold Member
MHB
- 3,920
- 48
I am reading Paul E. Bland's book: Rings and Their Modules and am currently focused on Section 2.1 Direct Products and Direct Sums ... ...
I need help with Problem 2(a) of Problem Set 2.1 ...
Problem 2(a) of Problem Set 2.1 reads as follows:
View attachment 8049I am unsure of my solution to problem 2(a) and need help in the following way ...
... could someone please confirm my solution is correct and/or point out errors and shortcomings ...
... indeed I would be grateful if someone could critique my solution ...
My attempted solution to problem 2(a) is as follows:... we have to show that $$\prod_\Delta A_\alpha$$ is a right ideal of $$\prod_\Delta R_\alpha$$ ...
To demonstrate this we have to show that $$\prod_\Delta A_\alpha$$ is closed under addition and closed under multiplication on the right by an element of $$\prod_\Delta R_\alpha$$ ...So ... let $$(x_\alpha), (y_\alpha) \in \prod_\Delta A_\alpha$$ and $$(r_\alpha) \in \prod_\Delta R_\alpha$$
Then $$x_\alpha, y_\alpha \in A_\alpha$$ for all $$\alpha \in \Delta$$
$$\Longrightarrow x_\alpha + y_\alpha \in A_\alpha$$ since $$A_\alpha$$ is a right ideal of $$R_\alpha$$ for all $$\alpha \in \Delta$$ ...
$$\Longrightarrow (x_\alpha) + (y_\alpha) \in \prod_\Delta A_\alpha$$
$$\Longrightarrow \prod_\Delta A_\alpha$$ is closed under addition ...
Now ... $$(x_\alpha) \in \prod_\Delta A_\alpha , (r_\alpha) \in \prod_\Delta R_\alpha$$
$$\Longrightarrow x_\alpha \in A_\alpha , r_\alpha \in R_\alpha$$ for all $$\alpha \in \Delta$$ ...
$$\Longrightarrow x_\alpha r_\alpha \in A_\alpha$$ since $$A_\alpha$$ is a right ideal of $$R_\alpha$$ ...
$$\Longrightarrow ( x_\alpha r_\alpha ) \in \prod_\Delta A_\alpha$$Thus $$\prod_\Delta A_\alpha$$ is a right ideal of $$\prod_\Delta R_\alpha$$ ...
Hope the above is correct ...
Peter
I need help with Problem 2(a) of Problem Set 2.1 ...
Problem 2(a) of Problem Set 2.1 reads as follows:
View attachment 8049I am unsure of my solution to problem 2(a) and need help in the following way ...
... could someone please confirm my solution is correct and/or point out errors and shortcomings ...
... indeed I would be grateful if someone could critique my solution ...
My attempted solution to problem 2(a) is as follows:... we have to show that $$\prod_\Delta A_\alpha$$ is a right ideal of $$\prod_\Delta R_\alpha$$ ...
To demonstrate this we have to show that $$\prod_\Delta A_\alpha$$ is closed under addition and closed under multiplication on the right by an element of $$\prod_\Delta R_\alpha$$ ...So ... let $$(x_\alpha), (y_\alpha) \in \prod_\Delta A_\alpha$$ and $$(r_\alpha) \in \prod_\Delta R_\alpha$$
Then $$x_\alpha, y_\alpha \in A_\alpha$$ for all $$\alpha \in \Delta$$
$$\Longrightarrow x_\alpha + y_\alpha \in A_\alpha$$ since $$A_\alpha$$ is a right ideal of $$R_\alpha$$ for all $$\alpha \in \Delta$$ ...
$$\Longrightarrow (x_\alpha) + (y_\alpha) \in \prod_\Delta A_\alpha$$
$$\Longrightarrow \prod_\Delta A_\alpha$$ is closed under addition ...
Now ... $$(x_\alpha) \in \prod_\Delta A_\alpha , (r_\alpha) \in \prod_\Delta R_\alpha$$
$$\Longrightarrow x_\alpha \in A_\alpha , r_\alpha \in R_\alpha$$ for all $$\alpha \in \Delta$$ ...
$$\Longrightarrow x_\alpha r_\alpha \in A_\alpha$$ since $$A_\alpha$$ is a right ideal of $$R_\alpha$$ ...
$$\Longrightarrow ( x_\alpha r_\alpha ) \in \prod_\Delta A_\alpha$$Thus $$\prod_\Delta A_\alpha$$ is a right ideal of $$\prod_\Delta R_\alpha$$ ...
Hope the above is correct ...
Peter