Fluctuations are a key property of both classical and quantum systems. While the fluctuations are well understood for many quantum systems at zero temperature, the case of an interacting quantum system at finite temperature still poses numerous challenges. Despite intense theoretical investigations of atom number fluctuations in Bose-Einstein condensates, their amplitude in experimentally relevant interacting systems is still not fully understood. Moreover, technical limitations have prevented their experimental investigation to date. Here we report the observation of these fluctuations. Our experiments are based on a stabilization technique, which allows for the preparation of ultracold thermal clouds at the shot noise level, thereby eliminating numerous technical noise sources. Furthermore, we make use of the correlations established by the evaporative cooling process to precisely determine the fluctuations and the sample temperature. This allows us to observe a telltale signature: the sudden increase in fluctuations of the condensate atom number close to the critical temperature. arXiv:1812.03064v2 [cond-mat.quant-gas]

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This paper argues for a theory of memory that I have coined “the theory of causal memory processes”. The central claim of the paper is that it is more empirically sound to construct theories of memory in accordance with the theory of causal processes rather than in accordance with causality as regulation. In order to put this claim forward I will, first, describe what kind of function causality serves in philosophical theories of memory. Secondly, I will show that regularity theories of causation is dominant in the causal theories of memory. Thirdly, I will account for the theory of causal processes. Lastly, I will sketch a definition of the theory of causal memory processes.

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