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Astrophysical Institute Neunhof

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			The zero-point energy of elementary quantum fields A comment on the "cosmological constant problem" Since 1925, exactly four arguments have been forwarded for the assumption of a diverging (respectively — after regularization — very huge) zero-point energy of elementary quantum fields. And exactly three arguments have been forwarded against this assumption. In this article, all seven arguments are reviewed and assessed. It turns out that the three CONTRA arguments against the assumption of that zero-point energy are overwhelmingly stronger than the four PRO arguments. → Download the complete article ( pdf, 471 KB ) Zero-Point Energy and Casimir-Effect The essential arguments for and against the assumption of a physically effective zero-point energy Since the invention of zero-point energy in 1911, there is some dispute whether it is really detectable in experiments, or merely a strange artifact of the theory. The discussion is traced in a historical perspective, and the essential arguments, which have been cited in support or in refusal of the assumption of zero-point energy, are sketched. The article in particular is focused on the Casimir-effect, which often is considered to be the most convincing evidence for the measurable existence of zero-point energy. → Download the complete article ( pdf, 463 KB ) What exactly is proved by the violation of Bell's inequality? Bell's inequality has been derived several times from quite different basic assumptions, which imply different conclusions. This resulted into widespread confusion regarding the exact implications of the experimental violations of the inequality. In this article, the structures of Bell's and of Peres' derivations are analyzed, and the title question is explicitly answered. → Download the complete article ( pdf, 372 KB ) Decoherence The decoherence of the state functions of open quantum systems is known already since the twenties of last century. But only since the seventies it found appropriate attention in the debate about the interpretation of quantum theory. In this letter, the basic concepts for the description of measurements of closed and open quantum systems are derived and compared. The density operator is defined, and the notions PVM and POVM are explicated. Also the “measurement problem of quantum theory” and the “problem of the preferred basis” are discussed in this context. In the last section, the essential properties of projection operators and density operators are evaluated. → Download the complete article ( pdf, 430 KB ) The discovery of Bose-Einstein-statistics Half a century passed inbetween the first appearance of Bose-Einstein-Statistics by 1877 and its completion by 1926. In this article, the historical evolution is traced, and the implications of this quantum statistics for the physical world view is discussed in detail. This article is written in german. → Download the complete article ( german, pdf, 426 KB ) Interaction of 2-level systems and electromagnetic radiation Rabi-Oscillations, Bloch vectors, and Ramsey fringes The interaction of quantum mechanical 2-level systems and electromagnetic radiation is outlined in detail. Rabi-oscillations and the dynamics of the Bloch vector are described for coherent and incoherent systems. Eventually we deal with Ramsey interferences and their practical use for precise time measurements by means of atomic clocks. → Download the complete article ( pdf, 434 KB ) Robertson’s Derivation of the Indeterminacy Relation Heisenbergs Relation of Indeterminacy was reformulated with quantitative precision in 1929 by H.P.Robertson. When Heisenberg introduced the relations of indeterminacy in 1927, he used a description which attached more importance to physical clarity than to mathematical precision. In 1929, Robertson found a more abstract and quantitative exact formulation of the indeterminacy relation. In this article, we derive Robertson’s formula, and prove it’s validity for arbitrary hermitian operators and arbitrary state functions of quantum theory. → Download the complete article ( pdf, 274 KB ) Quantum Jumps Planck’s radiation law, and its statistical derivation due to Albert Einstein Planck found by guessing his law of blackbody radiation, which marks the historical onset of quantum theory, when he analyzed the radiation’s entropy. Einstein found a significantly simpler and clearer access due to statistical analysis of the absorption’s and emission’s equilibrium. We describe and discuss the radiation laws of Rayleigh-Jeans, Planck, and Einstein. This article is written in german. → Download the complete article ( german, pdf, 407 KB ) The Casimir-Effect: No Manifestation of Zero-Point Energy The attractive force between metallic surfaces, predicted by Casimir in 1948, seems to indicate the physical existence and measurability of the quantized electromagnetic field's zero-point energy. It is shown in this article, that the measurements of that force do not confirm Casimir's model, but in fact disprove it's foundational assumption that metal plates may be represented in the theory by quantum-field-theoretical boundaries. The consequences for the cosmological constant problem are discussed. → Download the complete article ( pdf, 343 KB ) Can quantum theory not consistently describe the use of itself ? A comment on an article of Frauchiger and Renner In 2018, Daniela Frauchiger and Renato Renner published an article titled "Quantum theory cannot consistently describe the use of itself". Their argument is wrong, for reasons explicated in this comment. → Download the complete article ( pdf, 298 KB ) What the Casimir-effect really is telling about zero-point energy Casimir predicted an attractive force between metallic surfaces, which according to his model is caused by the zero-point oscillations of the quantized electromagnetic field. Following a suggestion by Casimir, we assume in this article that the reflection spectra of metals are at least approximately identical for the reflection of photons and the reflection of zero-point oscillations. It is shown that this assumption turns Casimir's argument to the exact opposite: The observed Casimir-force positively proves, that the electromagnetic field's zero-point energy does not exert forces onto metallic surfaces, if that assumption on reflectivity should be correct. We add reasons for the assertion, that Casimir's assumption on reflectivity is probably wrong, and that an improved assumption is still disproving Casimir's model. → Download the complete article ( pdf, 391 KB )
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