Is there any difference between じゃあない and じゃない?


> これっ！ 石を投げるん **じゃあない** っ！  
>  すいちゃったものはしかたがない **じゃあない** のっ！

I've been reading a light novel called _Slayers_ , and I noticed something
interesting: the author usually writes `じゃあない` and not `じゃない`. I'm curious if
there are any differences between the two. (I think it's clear that they have
the same basic meaning, so I'm mainly asking about differences _other_ than
meaning, like style/formality/dialect.)

Not long ago, I read [a post on
sci.lang.japan](http://groups.google.com/group/sci.lang.japan/msg/a276c9c0c4e5a8e1)
by the linguist Bart Mathias, which I'd like to quote here. He describes the
contraction from ては to ちゃ:

> Because Japanese is length sensitive, it took time to get the two moras of
> "-te-wa" compressed from "-chaa" to "-cha," and the earlier form still
> survives as an option.

My guess is that the same thing happened with じゃ:

[code]

    では → じゃあ → じゃ
    
[/code]

That is to say, I guess that じゃあ is older than じゃ. If that's right, I also
guess that the combination じゃあない is older than じゃない, and since I usually hear
the shorter form, I'm guessing that じゃあない might sound a bit old-fashioned. I'm
curious if this is correct, so I decided to ask here.

Anyway, here are my guesses about じゃあない:

  1. Perhaps `じゃあない` sounds like an older way of talking than `じゃない`.
  2. Perhaps `じゃあない` sounds a bit closer to `ではない` (making it slightly less informal than `じゃない`?)
  3. Perhaps `じゃあない` is a dialectal variation of `じゃない`.
  4. Perhaps the author just likes the sound of `じゃあない`, and there's no real difference.

So tell me, is there any difference between the two? Or are they totally the
same?




It would be interesting/useful to know if the author uses じゃあ over じゃ・では in
other phrases.

I might be completely off-base here, but if we consider the difference as that
between では、じゃ and じゃあ (rather than between じゃない・じゃあない specifically), there is
some info about, for example
[here](http://questionbox.jp.msn.com/qa3369499.html).

Taking some parts of the first answer on that question which I think are
important (ignoring the bits about では for the moment):

First example:

> これじゃ間に合わない ・・・普通  
>  これじゃー間に合わない ・・・強調した言い方

e.g. in this case the じゃあ version is for emphasis.

Second example:

> この雨じゃ出かけられない ・・・普通  
>  この雨じゃー出かけられない ・・・リズムを変えた言い方（人によって好き好きです。）

e.g. in this case it just changes the rhythm (and this is a matter of personal
preference).

Third example:

> 中学生じゃ無理だ ・・・普通  
>  中学生じゃー無理だ ・・・強調した言い方。あるいはリズムだけを変えた言い方

e.g in this case it could be either for emphasis or a change in rhythm. (This
may be the same way that sometimes 二 is read にい in counting out loud, e.g.
いちにいさん). It appears from additional information given in the linked answer
that the difference between the two cases would be distinguished in speech by
the position of the accent.

Incidentally, 大辞林{だいじりん} confirms the origin from では but isn't much help in
terms of nuance:

> 「では」の転。「じゃ」とも

