Latex keeps on getting parsing errors

[andrewkirk]

I keep on getting errors from Latex. For instance the following code looks OK to me but won't parse:

$g(\vec{\bar{V}}_S, \vec{U}(1)) =\ _Sg_{ik}(O) _S\bar{V}_S^i _SU(1)^k$

However if I break it with the insertion of a close and then an open itex delimiter, the first bit parses but the second won't.

$g(\vec{\bar{V}}_S, \vec{U}(1)) =$$\ _Sg_{ik}(O) _S\bar{V}_S^i _SU(1)^k$

Now if I break it yet again, it all parses OK.

$g(\vec{\bar{V}}_S, \vec{U}(1)) =$$\ _Sg_{ik}(O)$$_S\bar{V}_S^i$$_SU(1)^k$

The three strings are identical, except for the insertion of [/itex][itex] first once and then twice.

I have put enough spaces into deactivate the vBulletin 'no more than 50 consecutive nonspace characters' bug, but it still seems to go wrong.

Any help in fixing this would be much appreciated. I have a derivation I want to post, but it's impractical with this amount of latex problems.

Thanks very much.

PS is there any way to get that first arrow to sit over the V rather than off to the left?

 

[AlephZero]

The problem is towards the end of your LaTeX where you have

\bar{V}_S^i _S U(1)^k

And the error message from LaTeX is "double subscript". If you write

A_b^c_d E

LaTeX thinks the "b" and "d" are both subscripts applied to "A".

One way to get round this is attach subscripts to an empty group, for example

A_b^c {}_d E

PS is there any way to get that first arrow to sit over the V rather than off to the left?

I think that is a MathJax problem. It looks OK in "real" LaTeX.

 

[DrGreg]

PS is there any way to get that first arrow to sit over the V rather than off to the left?

For what it's worth, I had the same problem viewing the message on someone else's computer earlier today (IE8 on XP) but I see no problem now on my own computer (FF10 or IE9 on Vista, all MathJax renderers tried).

 

[andrewkirk]

Thanks for the replies. I presume MathJax is the TeX rendering engine for this site.
I tried the empty group suggestion and it worked, after I put in a few extra spaces "\ ", without which it also seemed to get upset.

I downloaded Texmaker and experimented with that and had a lot of intermittent 'double subscript' errors there too, but at least that was user-friendly enough to give an error message saying 'double subscript'.

When working with tensors there's sometimes no easy way to avoid using pre-subscripts (I use them to denote different coordinate systems) so it's good to know how to make it handle them correctly.

PS Texmaker seems to put my vector arrows in the right place.

 

[alphy]

It seems that there may be an issue with the way you are inputting the code into Latex. It is difficult to determine the exact cause without seeing the full code and error messages, but it is possible that there may be a missing or misplaced character or symbol causing the parsing errors. I would suggest double-checking your code and making sure all characters and symbols are correctly placed and matched. It may also help to consult a Latex tutorial or reference guide to ensure proper syntax. Regarding your question about the arrow placement, you may need to use a different command or symbol in order to achieve the desired positioning. Again, consulting a Latex resource may be helpful in finding the appropriate command. If the issue persists, you may also want to consider reaching out to the Latex community for further assistance.