Transcription of Construction - University of Connecticut
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FINITE FIELDSKEITH CONRADThis handout discusses finite fields: how to construct them, properties of elements in afinite field, and relations between different finite fields. We writeZ/(p) andFpinterchange-ably for the field of is an executive summary of the main results. Every finite field has prime power order. For every prime power, there is a finite field of that order. For a primepand positive integern, there is an irreducible (x) of degreeninFp[x], andFp[x]/( (x)) is a field of orderpn. All finite fields of the same size are isomorphic (usually not in just one way). If [Fp( ) :Fp] =d, theFp-conjugates of are , p, p2,.., pd 1. Every finite extension ofFpis a Galois extension whose Galois group overFpisgenerated by thepth power a primepand a monic irreducible (x)inFp[x]of degreen, the ringFp[x]/( (x))is a field of cosets mod (x) are represented by remaindersc0+c1x+ +cn 1xn 1, ci Fp,and there arepnof these.
Proof. Taking our cue from the statement of Lemma2.1, let F be a eld extension of F p over which xpn xsplits completely. General theorems from eld theory guarantee there is such a eld. Inside F, the roots of xpn xform the set S= ft2F: tpn = tg: This set has size pnsince the polynomial xpn xis separable: (xp n x)0= pnxp 1 1 = 1
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