QFT MarkdownA space for ideas
Made for focusAbout
A little syntax goes a long way

Make room for the idea.

Write in plain text, add structure with Markdown, and typeset mathematics as you go. The preview follows your source; your downloaded Markdown keeps exactly what you wrote.

Math within a sentence

Use $...$ or \(...\) for inline mathematics. Keep the formula next to its opening and closing dollar signs.

A state is $|\psi\rangle$.
Or write \(e^{i\pi}+1=0\).

Give an equation space

Put $$ or \[ and \] on their own lines for a displayed equation.

$$
i\hbar\frac{\partial\psi}{\partial t}
=\hat H\psi
$$

\[
\int_0^1 x^2\,dx=\frac13
\]

A calculation, aligned

Use aligned, &, and \\ to line up steps. Add an explicit number with \tag{1}. Automatic numbering, \label, and \eqref are not supported.

$$
\begin{aligned}
(a+b)^2 &= a^2+2ab+b^2 \\
        &= (a-b)^2+4ab
\end{aligned}
\tag{1}
$$

Words with structure

Headings create the document outline. Lists, links, emphasis, and quotations give your reader a path through the page.

# A clear title

## A useful section

**Bold**, *italic*, and [a link](https://qft.org).

> A thought worth keeping.

1. Start with the idea.
2. Follow the calculation.

Keep values together

Separate table columns with pipes. Colons control alignment. Escape a pipe within a cell as \|, including inside mathematical notation.

| Quantity | Value |
| :--- | ---: |
| $n$ | 3 |
| $E_n$ | $\hbar\omega(n+1/2)$ |

Code stays code

Wrap inline code in backticks, or use a fenced block with a language name. Mathematical delimiters inside code remain literal.

```python
import math

def gaussian(x):
    return math.exp(-x * x)
```

Notes and next steps

Footnotes hold supporting detail. Mark tasks in the source with [ ] or [x]; preview checkboxes show their state.

A useful observation.[^note]

[^note]: Add the detail here.

- [x] Check the assumptions
- [ ] Finish the derivation

Your own notation

Define a macro with \gdef before using it later in the document. Definitions belong to this source and are rebuilt on each preview.

$\gdef\RR{\mathbb R}$

Let $x\in\RR$ and $v\in\RR^n$.

A few things to know

Mathematics is typeset by KaTeX, which supports a large subset of TeX math. A formula that cannot be rendered stays visible with an error; you can correct it without losing the surrounding document. Raw HTML is displayed as text. Scripts, HTML embeds, and MDX are not executed.

Remote images are off by default. Enable them in Settings when you want the browser to contact the image host. For an image contained in the source itself, use an embedded PNG, JPEG, WebP, or GIF data URL.

Drafts save in this browser. Download Markdown for an editable copy, HTML for a typeset document, or choose Print / PDF to use your browser’s print dialog. Clearing site data can remove local drafts, so keep downloaded copies of work you want to retain.

Stay at the keyboard

In the workspace, use Ctrl on Windows or Linux and ⌘ on macOS:

Try the field guide