\wedge is a math mode character, as it's usually intended to show mathematical meaning. That's why you need to use math mode ($ ... $) to display it: this lets TeX sort out spacing in cases such as
$ A \wedge B $
You can use UTF-8 input directly with XeLaTeX to type in special characters. However, for mathematical characters, getting good font coverage can be hard. So it is often easier for these to stick to using math mode even with XeLaTeX.
One reason that you might not see [ is if it is used in a place where LaTeX looks for an optional argument. You can prevent LaTeX getting 'confused' by inserting an empty group ({}) or the 'do nothing' \relax primitive. A classic case is \item:
\item{} [
\item\relax [
The error message you copy&pasted is taken from a Windows terminal, which makes things a little more complex to analyze.
The important line in your error log is:
l.53 ...o ha complessità spaziale e temporale $Ο
(nÔêÖm)$ risulta poco adat...
This line points to the character causing trouble, which is the one at the end of the first line, i.e. Ο (and not the accented letters which appeared before, and caused no trouble).
However, surely you are pretty sure that your document does not contain the offending chars Ο, right? And you are right.
The problem is that Windows console uses the ancient MS-DOS code page, and not UTF-8, so your error message gets mangled. Using some iconv juggling in my (utf-8) linux machine:
$ cat mangled_error.txt
l.53 ...o ha complessità spaziale e temporale $Ο
(nÔêÖm)$ risulta poco adat...
$ iconv -f utf8 -t cp850 < mangled_error.txt > error.txt
$ cat error.txt
l.53 ...o ha complessità spaziale e temporale $Ο
(n∙m)$ risulta poco adat...
Aha! Now the error looks more readable. The offending char was not the à, as you thought, but the Ο, which is a (utf-8 encoded) capital letter Omicron. This character was not set up to be used in latex. Can you replace it by a "normal" (latin) O? See also: omicron not working in LaTeX
Best Answer
A workaround suggested in Antidote 9 guide for windows is to open the
.texfile with another intermediate editor and copy-paste it into Antidote’s internal editor. I had the same problem and could solve it with the default windows notepad.Step by step instructions can be found one the linux guide of the same version of Antidote
Depending on how your latex file is encoded, you may have to first encode it in
utf-8(inTexMaker, go to theEditmenu and selectSetup Encoding...)