2 1. Introduction

1. Introductio n

The name “vacuum“ is usually given to the space, out of which nothing can be taken with known methods. But it is well-known, that this vacuum is not empty, but it contains physical objects [Man 93], [Köp 97], [Lin 97], [Kuh 95]. This is also reflected within the Theory of General Relativity, namely by the cosmological constant

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