I was taught to make a left subscript as a right subscript to `{}`

. For example, I would use

```
f: {}_RA \rightarrow {}_RB
```

to typeset this:

If you instead use

```
f: _RA \rightarrow _RB
```

the left subscripts end up in the wrong place (because LaTeX thinks they are right subscripts of the object before):

However, this trick doesn't work well with operators like `/otimes`

. The code

```
A {}_\varphi\otimes_\psi B
```

puts too much spaace between the tensor product symbol and the subscript:

One solution I've found is to use spaces (including a negative thin space) to adjust the spacing. The code

```
A \; {}_\varphi \! \otimes_\psi B
```

produces this:

However, this is a kludge and doesn't communicate to LaTeX that `\varphi`

should be attached to the `\otimes`

. Also, the left subscript is still just a tad too far to the left. Does anyone know a more elegant solution to this?

## Best Answer

Try the tensor package. You can just issue

to get what you specified as an example. Note that if you have mixed upper and lower indices, the standard

`\tensor`

command will leave "phantom" spaces. To make all indices flush against the central symbol, use`\tensor*`

.