MHB Help with Dummit & Foote Exercise 1, Section 13.2 - Algebraic Extensions

Math Amateur
Gold Member
MHB
Messages
3,920
Reaction score
48
I need help with Exercise 1 of Dummit and Foote, Section 13.2 : Algebraic Extensions ..

I have been unable to make a meaningful start on the problem ... ... Exercise 1 of Dummit and Foote, Section 13.2 reads as follows:
View attachment 6608
I have been unable to make a meaningful start on this problem ...BUT ... further I hope to understand why D&F put this exercise at the end of a section on algebraic extensions ... the exercise seems a bit remote from the subject matter ... ...
Hope someone can help ...Peter
 
Physics news on Phys.org
I would start with the definition of "characteristic" of a field. What is that definition?
 
HallsofIvy said:
I would start with the definition of "characteristic" of a field. What is that definition?
Thanks HallsofIvy ...

Thought about definition and its link to the prime subfield ... and had considerable help from people on the Physics Forums ...Have the following solution ... please critique it ...============================================================================

$$F$$ finite field of characteristic $$p$$$$\Longrightarrow$$ prime subfield of $$F$$ is isomorphic to $$\mathbb{F}_p$$ and $$p$$ must be prime ... (Lidl and Niederreiter, Introduction to Finite Fields ... ... , Theorem 1.78 ... ...also $$F$$ finite means that $$F$$ has finite dimension over $$\mathbb{F}_p$$, say dimension of $$F$$ over $$\mathbb{F}_p = n$$ $$\Longrightarrow$$ Basis for $$F$$ over $$\mathbb{F}_p$$ has $$n$$ elements$$\Longrightarrow$$ all elements of $$F$$ are uniquely expressible as $$c_1 v_1 + c_2 v_2 + \ ... \ ... \ \ c_n v_n$$ ... ... ... (1)where $$ c_1, c_2, \ ... \ ... \ \ , c_n \in \mathbb{F}_p$$

and

$$v_1, v_2, \ ... \ ... \ \ , v_n \in F$$
$$\Longrightarrow$$ number of elements in $$F, |F| = p^n$$

since each $$c_i$$ in expression (1) has $$p$$ possibilities ... ... ( and the $$v_i$$ are fixed)=========================================================================Is the above correct?Could someone please critique solution/proof ... is it rigorous ...?Peter
 
Last edited:
Thread 'Determine whether ##125## is a unit in ##\mathbb{Z_471}##'
This is the question, I understand the concept, in ##\mathbb{Z_n}## an element is a is a unit if and only if gcd( a,n) =1. My understanding of backwards substitution, ... i have using Euclidean algorithm, ##471 = 3⋅121 + 108## ##121 = 1⋅108 + 13## ##108 =8⋅13+4## ##13=3⋅4+1## ##4=4⋅1+0## using back-substitution, ##1=13-3⋅4## ##=(121-1⋅108)-3(108-8⋅13)## ... ##= 121-(471-3⋅121)-3⋅471+9⋅121+24⋅121-24(471-3⋅121## ##=121-471+3⋅121-3⋅471+9⋅121+24⋅121-24⋅471+72⋅121##...
Back
Top