# E115: Hardy Z: sign changes and zero bracketing

```{figure} ../_static/experiments/e115_hero.png
:alt: E115 hero
:class: experiment-hero

E115: Hardy Z: sign changes and zero bracketing
```

**Tags:** `analysis`, `quantitative-exploration`, `visualization`, `riemann-zeta`, `hardy-z`, `zeta-zeros`

## Highlights

- Focused numeric experiment with a small set of figures.
- Parameters saved to `params.json` for reproducibility.
- Defaults are chosen, so the experiment remains feasible for the CI “slow” suite.

## What is computed

- Scan Hardy Z(t), bracket sign changes, and visualize candidate zeros.

## Notes

- This page summarizes the intent; see the generated `report.md` in `out/` for concrete outputs.

## Published run snapshot

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

```{include} ../reports/e115.md
:start-after: "<!-- REPORT:BEGIN -->"
:end-before: "<!-- REPORT:END -->"
```

::: {dropdown} params.json (snapshot)
:open:

```{literalinclude} ../params/e115.json
:language: json
```

:::

## References

- See the zeta / zeros background pages in `docs/background/`.

## Related experiments

- {doc}`e086` (E086: Hardy Z(t) near zeros)
- {doc}`e088` (E088: Zero counting via Riemann–von Mangoldt)
- {doc}`e116` (E116: Gram points and zero-counting heuristics)
- {doc}`e087` (E087: Gram points and spacing)
- {doc}`e081` (Prime race sign changes: first crossings table.)