# physics/poisson-bracket-expand

Expand poisson brackets to explicit brace fences.

https://texform.dev/rules/physics/poisson-bracket-expand

## Metadata

| Field | Value |
| --- | --- |
| Key | physics/poisson-bracket-expand |
| Level | faithful |
| Fidelity | render |
| Enabled by packages | physics |
| Profiles | Faithful, Corpus, Equiv |

## Rewrite patterns

### poisson-bracket-auto-sized

From:

```latex
\pb{#1}{#2}
```

To:

```latex
\left\{#1,#2\right\}
```

### poisson-bracket-fixed-size

From:

```latex
\pb*{#1}{#2}
```

To:

```latex
\{#1,#2\}
```

## Examples

Examples show the rule in isolation, not a complete normalization profile.

### Poisson bracket canonical

Before:

```latex
\pb{q_i}{p_j}=\delta_{ij}
```

After this rule:

```latex
\left\{q_i,p_j\right\}=\delta_{ij}
```

Packages: base, physics.

Rendering verified with the declared packages.

### Poisson bracket star fixed size

Before:

```latex
\pb*{f}{g}=0
```

After this rule:

```latex
\{f,g\}=0
```

Packages: base, physics.

Rendering verified with the declared packages.

## Triggers

- [\\pb](https://texform.dev/latex/commands/pb)

## Eliminates

- [\\pb](https://texform.dev/latex/commands/pb)

## Produces

- [\\left](https://texform.dev/latex/commands/left)
- [\\right](https://texform.dev/latex/commands/right)

## Same family

- [physics/expectation-expand](https://texform.dev/rules/physics/expectation-expand): Expand expectation-value helpers to explicit angle brackets.
- [physics/matrixel-expand](https://texform.dev/rules/physics/matrixel-expand): Expand matrix elements to explicit angle-bracket and bar fences.
- [physics/physics-bra-expand](https://texform.dev/rules/physics/physics-bra-expand): Expand bra to an explicit angle-bracket and bar fence form.
- [physics/physics-braket-expand](https://texform.dev/rules/physics/physics-braket-expand): Expand braket to an explicit angle-bracket form with a middle bar.
- [physics/physics-ket-expand](https://texform.dev/rules/physics/physics-ket-expand): Expand ket to an explicit bar and angle-bracket fence form.
- [physics/commutator-expand](https://texform.dev/rules/physics/commutator-expand): Expand commutators to explicit square-bracket fences.

## Notes

Covers the star branch, where star suppresses automatic fence sizing. Explicit big-size control after the command follows the shared commutator parser and is outside this rule's scope.

## Disable this rule

```python
TransformEngine(profile="corpus", disable_rules=["physics/poisson-bracket-expand"])
```

```javascript
new TransformEngine({ profile: 'corpus', disableRules: ['physics/poisson-bracket-expand'] })
```

[Open in Playground](https://play.texform.dev/?input=%5Cpb%7Bq_i%7D%7Bp_j%7D%3D%5Cdelta_%7Bij%7D)