Ampform

See all documentation for this version [here](https://ampform.rtfd.io/en/0.10.3).

💡 New features

<details>
<summary>Define breakup_momentum function (97)</summary>

It makes more sense to use `breakup_momentum` as an argument to `phsp_factor` in [`relativistic_breit_wigner_with_ff`](https://ampform.readthedocs.io/en/0.10.2/api/ampform.dynamics.html#ampform.dynamics.relativistic_breit_wigner) etc than [`breakup_momentum_squard`](https://ampform.readthedocs.io/en/0.10.2/api/ampform.dynamics.html#ampform.dynamics.breakup_momentum_squared).

</details>


⚠️ Interface

<details>
<summary>Removed sympy.Piecewise from rrelativistic_breit_wigner_with_ff (98)</summary>

The function [`relativistic_breit_wigner_with_ff`](https://ampform.readthedocs.io/en/0.10.2/api/ampform.dynamics.html#ampform.dynamics.relativistic_breit_wigner_with_ff) now produces
<img src="https://user-images.githubusercontent.com/29308176/125973679-8f97ae5d-37f1-4ef0-a018-bdc919b2e4cb.png" width=500>
instead of
<img src="https://user-images.githubusercontent.com/29308176/125973965-008c5036-93a0-43f5-a1a8-cc4a8d4943b0.png" width=700>
The latter was mistakenly introduced because of a wrong parameterization in [`phase_space_factor_analytic`](https://ampform.readthedocs.io/en/0.10.2/api/ampform.dynamics.html#ampform.dynamics.phase_space_factor_analytic) (this one is valid only for equal masses).

</details>

📝 Documentation

<details>
<summary>Colorized extracted amplitudes in formalism notebook (0f913d6)</summary>


</details>

<details>
<summary>Added links to ComPWA organization (a6dd74d)</summary>


</details>

🖱️ Developer Experience

<details>

<summary>Allow 📖 Physics issue label (56cb749)</summary>


</details>

See all documentation for this version [here](https://ampform.rtfd.io/en/0.10.2).

📝 Documentation

<details>
<summary>Added helicity-vs-canonical basis comparison (95)</summary>

Added a notebook that describes the difference between the **helicity basis** and **canonical basis** in the helicity formalism.

</details>

🐛 Bug fixes

<details>
<summary>Required numpy version is limited to v1.20 (91)</summary>

Since [NumPy v1.21](https://github.com/numpy/numpy/releases/tag/v1.21.0) it is required to explicitly define `__array_ufunc__`, both for static typing as for running the code. With the current set-up, `__array_ufunc__` is too problematic. Better solution would be #92.

</details>

See all documentation for this version [here](https://ampform.rtfd.io/en/0.10.1).

💡 New features

<details>
<summary>Implemented HelicityModel.sum_components (90)</summary>

Import [`tensorwaves.physics.add_components`](https://tensorwaves.readthedocs.io/en/0.2.8/api/tensorwaves.physics.html#tensorwaves.physics.add_components).

Note that this allows removing the [`tensorwaves.physics`](https://tensorwaves.readthedocs.io/en/0.2.8/api/tensorwaves.physics.html) module.

</details>

See all documentation for this version [here](https://ampform.rtfd.io/en/0.9.5).

⚠️ Interface

<details>
<summary>AmpForm interface and implementation has been adapted to the new QRules interface (84)</summary>

Adapts the AmpForm interface and implementation to [QRules v0.9.0](https://github.com/ComPWA/qrules/releases/tag/0.9.0).

Naming has been changed accordingly, most notably that graphs become transitions, edges becomes states, nodes become interactions. Some related interface changes:

- AmpForm's own `ReactionInfo` (under `kinematics`) and `State` (under `helicity`) have been removed
- `TwoBodyKinematicVariableSet`:
- `in_edge_inv_mass` -> `incoming_state_mass`
- `out_edge_inv_mass1` -> `outgoing_state_mass1`
- `out_edge_inv_mass2` -> `outgoing_state_mass2`
- There are now also an instance check on its constructor.

</details>

<details>
<summary>AmpForm's helicity module has been split (87)</summary>

Split up the `helicity` module.

Major change: the `generate()` method is now called `formulate()` (97e9ce2)

Related to 61


</details>

<details>
<summary>HelicityModel.generate() has been renamed to HelicityModel.formulate() (87)</summary>

All methods and functions that produce `sympy.Expr`s are now named 'formulate' instead of 'generate'.


</details>

<details>
<summary>Coefficient names have been changed (80)</summary>

**This changes the sum of amplitudes in some cases!**

Fixes 73

New notation:


For comparison, there's also 32bb1b6, which also includes helicity, but which results in 8 unique coefficient names:




</details>




🔨 Internal maintenance

<details>
<summary>Test fixtures are now parametrized (86)</summary>

Some improvements to the test set-up.

</details>


📝 Documentation

<details>
<summary>Links to expertsystem replaced with internal links (82)</summary>

Some links in the `expertsystem`, because [intersphinx](https://www.sphinx-doc.org/en/master/usage/extensions/intersphinx.html) is a bit too eager.

</details>

<details>
<summary>Intersphinx links can now pinned to specific versions of external API pages (83)</summary>

</details>

<details>
<summary>Added explanation for how to substitute parameters (88)</summary>

First step towards 5. Adds a new page that shows some SymPy tricks to modify the `HelicityModel`.

</details>

<details>
<summary>Added explanation of how to couple parameters (89)</summary>

Closes 5

</details>

See all documentation for this version [here](https://ampform.rtfd.io/en/0.9.4).

💡 New features

<details>
<summary>More phase space factor types available (81)</summary>

</details>


⚠️ Interface

<details>
<summary>phase_space_factor_ac has been renamed to phase_space_factor_analytic (81)</summary>

</details>

<details>
<summary>phase_space_factor does not use ComplexSqrt anymore (81)</summary>

**This reverts the phase space factor behaviour to that of version [0.9.2](https://github.com/ComPWA/ampform/releases/tag/0.9.2) and prior.**

</details>

📝 Documentation

<details>
<summary>Improvements to the analytic-continuation and dynamics pages (81)</summary>

</details>


🖱️ Developer Experience

<details>
<summary>upgrade pinned requirements (79)</summary>

Automated changes by [create-pull-request](https://github.com/peter-evans/create-pull-request) GitHub action

</details>

See all documentation for this version [here](https://ampform.rtfd.io/en/0.9.3).

💡 New features

<details>
<summary>Added a new dynamics builder for analytic continuation (78)</summary>

Added a new function `create_analytic_breit_wigner` to `ampform.dynamics.builder` that allows setting a `relativistic_breit_wigner_with_ff` with analytic continuation.

</details>


🐛 Bug fixes

<details>
<summary>Return masses as floats if possible (76)</summary>

Since 75 there is no need to use complex values as input for analytic continuation.

</details>

<details>
<summary>Set relativistic Breit-Wigner with form factor to 0 if 𝑠 below threshold (77)</summary>

A relativistic Breit-Wigner with Blatt-Weisskopf form factor now returns 0 below threshold. See [updated docstring](https://github.com/ComPWA/ampform/compare/sub-threshold-behavior?expand=1#diff-afdef4ce3b18ddf3a238a155accf7d4d304b5a66ec160cf95ae11b3bedb340bdR307).

</details>