Height: Difference between revisions

Roeesi (talk | contribs)
Examples of height functions: Moved from the general complexity article
Sintel (talk | contribs)
equivalence section: no need to talk about p-adic valuations here
 
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Exponentiation and logarithm are such functions commonly used for converting a height between arithmetic and logarithmic scales.  
Exponentiation and logarithm are such functions commonly used for converting a height between arithmetic and logarithmic scales.  


A '''semi-height''' is a function which does not obey criterion #3 above, so that there is a rational number ''q'' ≠ 1 such that H(''q'') = H(1), resulting in an equivalence relation on its elements, under which #1 is modified to a finite number of equivalence classes. An example would be [[octave equivalence]], where two ratios ''q''<sub>1</sub> and ''q''<sub>2</sub> are considered equivalent if the following is true:
A '''semi-height''' is a function which does not obey criterion #3 above, so that there is a rational number ''q'' ≠ 1 such that H(''q'') = H(1), resulting in an equivalence relation on its elements, under which #1 is modified to a finite number of equivalence classes. An example would be [[octave equivalence]], where two ratios ''q''<sub>1</sub> and ''q''<sub>2</sub> are considered equivalent if they differ only by factors of 2.
 
We can also consider other equivalences. For example, we can assume tritave equivalence by ignoring factors of 3.
<math>\displaystyle 2^{-v_2 \left( {q_1} \right)} q_1 = 2^{-v_2 \left( {q_2} \right)} q_2</math>
 
where v<sub>''p''</sub>(''q'') is the [[Wikipedia: P-adic valuation|''p''-adic valuation]] of ''q''.
 
Or equivalently, if ''n'' has any integer solutions:
 
<math>\displaystyle q_1 = 2^n q_2</math>
 
If the above condition is met, we may then establish the following equivalence relation:
 
<math>\displaystyle q_1 \equiv q_2</math>
 
By changing the base of the exponent to a value other than 2, you can set up completely different equivalence relations. Replacing the 2 with a 3 yields tritave-equivalence, for example.


== Height versus norm ==
== Height versus norm ==