E066: Character partial sums: cancellation profiles.

Preview figure for E066
Preview figure for E066

Tags: number-theory, quantitative-exploration, visualization, dirichlet-characters

Highlights

  • Constructs full character tables for a small modulus q.

  • Visualizes values as phases / real parts to spot structure and symmetries.

  • Checks orthogonality and basic sanity constraints numerically.

What this experiment does

For a Dirichlet character χ modulo q, consider partial sums:

The implementation focuses on a compact, reproducible numerical workflow: deterministic parameter defaults, structured output folders, and one or more figures saved for the gallery.

Outputs

This experiment writes into out/e066/:

  • figures/fig_01_max_partial_sums.png

  • figures/fig_02_example_partial_sum.png

How to run

make run EXP=e066

Notes

  • The gallery preview figure shipped with the documentation uses conservative cutoffs so builds stay fast. If you run the experiment locally, increase the cutoffs to see the asymptotic regime more clearly.

  • Prime-race plots depend on the chosen sampling of x (linear vs. log grid). The qualitative “who leads” picture can change when you zoom in.

Published run snapshot

If this experiment is included in the docs gallery, include the published snapshot (report + params).

Parameters

  • q: 15

  • N_max: 50000

  • include_principal: False

Summary

Computed partial sums S(N)=sum_{n<=N} chi(n) for 7 Dirichlet characters modulo q.

Top characters by max |S(N)|

| rank | index | max |S(N)| | conductor | principal | |—:|—:|—:|—:|:—:| | 1 | 5 | 3 | 15 | False | | 2 | 0 | 2 | 5 | False | | 3 | 3 | 2 | 3 | False | | 4 | 2 | 2 | 5 | False | | 5 | 6 | 1.41421 | 15 | False | | 6 | 4 | 1.41421 | 15 | False | | 7 | 1 | 1 | 5 | False |

params.json (snapshot)
{
  "include_principal": false,
  "n_max": 50000,
  "q": 15,
  "top_k": 8
}

References

Davenport [2000], Niven et al. [1991]