Originally posted by @kazetnagorra
In physics and mathematics, one can and does use any number of dimensions depending on the problem at hand, including zero, one, any finite number, infinite and fractional.
You're probably referring to string theory. While I'm not an expert on the topic, as far as I understand many variations of string theory require more than 4 physical dimensions. ...[text shortened]... case of string theory, this is extremely hard, which is why few people are working on the topic.
Here is a book I read:
The Trouble with Physics, by Lee Smolin:
This Wiki gives a 50 cent tour of the book. He hates string theory, bottom line
And another physicist chimes in: Peter Woit
Woit and Smolin both object to string theory on the grounds it has yet to make a single prediction that can be tested by any kind of technology in the foreseeable future.