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This paper has been temporarily withdrawn for corrections.

This paper has been withdrawn by the authors. It has been superseded by hep-th/0309154

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This paper has been withdrawn by the author due to some errors.

This paper has been withdrawn by the author

This paper has been withdrawn by the author, due a crucial error in the optimization. For the last one month I have been trying to remove the error, but it seems to take a lot of time so I decided to withdraw this paper for the moment.

This paper has been withdrawn by the author due to a crucial sign error.

This paper has been withdrawn by the author due to similarity to Author's other paper

This paper has been withdrawn by the author due to inconsistency of the considered working hypothesis. The consistent treatment is presented in the last publications of the author.

This paper has been withdrawn temporarily.

This paper has been withdrawn.

This paper has been withdrawn by the authors due to some fatal errors in the analysis.

The paper was retracted.

This paper has been withdrawn by the author because Lemma 3 is incorrect. This mistake is crucial in this paper.

This paper has been withdrawn due to disagreement of suggested results and methods between authors.

This paper has been withdrawn by the authors; the main conclusion is incorrect, as some of the crucial calculations were not properly converged.

This paper has been withdrawn by the author.

This paper has been withdrawn by the author, due to the fact that a similar paper (quant-ph/9904075) has been published.

This paper has been withdrawn by the author(s) in the light of several other works available and due to a misunderstanding in the authorships.

This paper has been withdrawn.