Inter-universal geom ..
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553:現代数学の系譜 雑談
20/10/18 12:54:44.43 ZLSkSSTT.net
>>552
つづき
Then, from the
point of view of the length two substring 01 on the left, the digit “1” of this substring
may be specified by means of its “coordinate relative to this substring”, namely, as the
symbol to the far right of the substring 01. In a similar vein, from the point of view of
the length two substring 10 on the right, the digit “1” of this substring may be specified
by means of its “coordinate relative to this substring”, namely, as the symbol to the far
left of the substring 10. On the other hand,
neither of these specifications via “substring-based coordinate systems”
is meaningful to the opposite length two substring; that is to say, only the
solitary abstract symbol “1” is simultaneously meaningful, as a device
for specifying the digit of interest, relative to both of the “substring-based
coordinate systems”.
Finally, in passing, we note that this discussion applies, albeit in perhaps a somewhat
trivial way, to the isomorphism of Galois groups ΨηX : GK?→ GK induced by the
Frobenius morphism ΦηX in Example 2.6.1, (i): That is to say, from the point of view
of classical ring theory, this isomorphism of Galois groups is easily seen to coincide with
the identity automorphism of GK. On the other hand, if one takes the point of view
that elements of various subquotients of GK are equipped with labels that arise from
the isomorphisms ρ or κ of Example 2.6.1, (ii), (iii), i.e., from the reciprocity map of
class field theory or Kummer theory, then one must regard such labelling apparatuses
as being incompatible with the Frobenius morphism ΦηX . Thus, from this point
of view, the isomorphism ΦηX must be regarded as a “mysterious, indeterminate
isomorphism” [cf. the discussion of §2.7, (iii)].
つづく


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