The Physics of Maxwell's demon and information

Maxwell's demon was born in 1867 and still thrives in modern physics. He plays important roles in clarifying the connections between two theories: thermodynamics and information. Here, we present the history of the demon and a variety of interesting consequences of the second law of thermodynamics, mainly in quantum mechanics, but also in the theory of gravity. We also highlight some of the recent work that explores the role of information, illuminated by Maxwell's demon, in the arena of quantum information theory.Comment: 24 pages, 13 figures. v2: some refs added, figs improve

Dissipative, Entropy-Production Systems across Condensed Matter and Interdisciplinary Classical VS. Quantum Physics

The thematic range of this book is wide and can loosely be described as polydispersive. Figuratively, it resembles a polynuclear path of yielding (poly)crystals. Such path can be taken when looking at it from the first side. However, a closer inspection of the book’s contents gives rise to a much more monodispersive/single-crystal and compacted (than crudely expected) picture of the book’s contents presented to a potential reader. Namely, all contributions collected can be united under the common denominator of maximum-entropy and entropy production principles experienced by both classical and quantum systems in (non)equilibrium conditions. The proposed order of presenting the material commences with properly subordinated classical systems (seven contributions) and ends up with three remaining quantum systems, presented by the chapters’ authors. The overarching editorial makes the presentation of the wide-range material self-contained and compact, irrespective of whether comprehending it from classical or quantum physical viewpoints

Landauer Defended: Reply to Norton

Ladyman et al (2007) proposed a model of the implementation of logical operations by physical processes in order to clarify the exact statement of Landauer's Principle, and then ordered a new proof of the latter based on the construction of a thermodynamic cycle, arguing that if Landauer's Principle were false it would be possible to harness a machine that violated it to produce a violation of the second law of thermodynamics. In a recent paper in this journal, John Norton (2011) directly challenges the consistency of that proof. In the present paper we defend the proof given by Ladyman et al against his critique. In particular, contrary to what Norton claims, we argue that the pro- cesses used in the proof cannot be used to construct a cycle that enacts erasure in a thermodynamically reversible way, and that he does not show that the processes used in the proof violate the Second Law of Thermodynamics

Landauer Defended: Reply to Norton

Ladyman et al (2007) proposed a model of the implementation of logical operations by physical processes in order to clarify the exact statement of Landauer's Principle, and then ordered a new proof of the latter based on the construction of a thermodynamic cycle, arguing that if Landauer's Principle were false it would be possible to harness a machine that violated it to produce a violation of the second law of thermodynamics. In a recent paper in this journal, John Norton (2011) directly challenges the consistency of that proof. In the present paper we defend the proof given by Ladyman et al against his critique. In particular, contrary to what Norton claims, we argue that the pro- cesses used in the proof cannot be used to construct a cycle that enacts erasure in a thermodynamically reversible way, and that he does not show that the processes used in the proof violate the Second Law of Thermodynamics

Assessment of the state of health by the measurement of a set of biophysiological signals

The dissertation studies the estimation of the degree of self-similarity and entropy of Shannon of several real electrocardiography (ECG) signals for healthy and non-healthy humans. The goal of the dissertation is to create a starting point algorithm which allows distinguishing between healthy and non-healthy subjects and can be used as a basis for further study of a diagnosis algorithm, necessarily more complex. We used a novel Hurst parameter estimation algorithm based on the Embedded Branching Process, termed modified Embedded Branching Process algorithm. The algorithm for estimation of entropy was based on Shannon‟s entropy. Both algorithms were applied on the spatial distribution of ECG signals in a windowed manner. The studied signals were retrieved from the Physionet website, where they are diagnosed as normal or as having certain pathologies. The results presented for the Hurst parameter estimation allow us to confirm the results already published on the temporal self-similarity of ECG signals, this time for its spatial distribution. We also conclude that the non-self similar signals belong to non-healthy subjects. The results obtained for entropy estimation on the spatial distribution of ECG signals also allowed a comparison between healthy and non-healthy systems. We obtained high entropy estimates both for healthy and non-healthy subjects; nevertheless, non-healthy subjects show higher variability of Shannon‟s entropy than healthy ones.A dissertação estuda a estimativa do grau de auto-semelhança e da entropia de Shannon de vários sinais reais de electrocardiograma (ECG) obtidos em humanos saudáveis e não saudáveis. O objectivo da dissertação é criar um algoritmo inicial que permita distinguir entre indivíduos saudáveis e não saudáveis e que possa ser usado como base para o estudo de um posterior algoritmo de diagnóstico, necessariamente mais complexo. Utilizamos um algoritmo novo para estimativa do parâmetro de Hurst baseado no Embedded Branching Process, denominado algoritmo modified Embedded Branching Process. A entropia foi estimada através da entropia de Shannon. Ambos algoritmos foram aplicados sob a distribuição espacial dos sinais ECG numa forma de janela. Os sinais estudados foram retirados do website Physionet, onde estão diagnosticados como normais ou possuindo uma determinada patologia. Os resultados apresentados para a estimativa do parâmetro de Hurst permitem confirmar resultados já publicados sobre a auto-semelhança temporal dos sinais ECG, desta vez para a sua distribuição espacial. Também se concluí que os sinais não auto-semelhantes correspondem a indivíduos não saudáveis. Os resultados obtidos na estimativa da entropia para a distribuição espacial dos sinais de ECG também permitiram uma comparação entre sistemas saudáveis e não saudáveis. Obtiveram-se estimativas de entropia elevadas quer para indivíduos saudáveis quer para indivíduos não saudáveis; no entanto, os indivíduos não saudáveis mostram uma maior variabilidade da entropia de Shannon em relação aos saudáveis