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At least 1,009 records · Page 56Linked to original sources
arXiv2020

Maxwell's Demon and its Fallacies Demystified

A demonic being, introduced by Maxwell, to miraculously create thermal non-equilibrium and violate the Second law of thermodynamics, has been among the most intriguing and elusive wishful concepts for over 150 years. Maxwell and his followers focused on 'effortless gating' a molecule at a time, but overlooked simultaneous interference of other chaotic molecules, while the demon exorcists tried to justify impossible processes with misplaced 'compensations' by work of measurements and gate operation, and information storage and memory erasure with entropy generation. The illusive and persistent Maxwell's demon fallacies by its advocates, as well as its exorcists, are scrutinized and resolved here. Based on holistic, phenomenological reasoning, it is deduced here that a Maxwell's demon operation, against natural forces and without due work effort to suppress interference of competing thermal particles while one is selectively gated, is not possible at any scale, since it would be against the physics of the chaotic thermal motion, the latter without consistent molecular directional preference for selective timing to be possible. Maxwell's demon would have miraculous useful effects, but also some catastrophic consequences.

physics.hist-ph↗
arXiv2020

Joseph Polchinski: A Biographical Memoir

Joseph Polchinski (1954-2018), one of the the leading theoretical physicists of the past 50 years, was an exceptionally broad and deep thinker. He made fundamental contributions to quantum field theory, advancing the role of the renormalization group, and to cosmology, addressing the cosmological constant problem. Polchinski's work on D-branes revolutionized string theory and led to the discovery of a nonperturbative quantum theory of gravity. His recent, incisive reformulation of the black hole information paradox presents us with a profound challenge. Joe was deeply devoted to his family, a beloved colleague and advisor, an excellent writer, and an accomplished athlete.

physics.hist-ph↗
arXiv2020

Beyond Purity and Mixtures in Categorical Quantum Mechanics

In a recent paper [12], we discussed the serious inconsistency present within the operational and mathematical definition(s) of the notion of pure state. Continuing this analysis, in this work we attempt to address the role of 'purity' and 'mixtures' within two different categorical approaches to QM, namely, the topos approach originally presented by Chris Isham and Jeremy Butterfield [27, 28, 29] and the more recent logos categorical approach presented by the authors of this article [10, 11, 13]. While the first approach exposes the difficulties to produce a consistent understanding of pure states and mixtures, the latter approach presents a new scheme in which their reference is erased right from the start in favor of an intensive understanding of projection operators and quantum superpositions. This new account of the theory, grounded on an intensive interpretation of the Born rule, allows us not only to avoid the orthodox interpretation of projection operators --either as referring to definite valued properties or measurement outcomes-- but also to consider all matrices (of any rank) on equal footing. It is from this latter standpoint that we conclude that instead of distinguishing between pure and mixed states it would be recommendable --for a proper understanding of the theory of quanta-- to return to the original matrix formulation of quantum mechanics presented by Werner Heisenberg in 1925.

quant-ph↗
arXiv2022

On the relation of free bodies, inertial sets and arbitrariness

We present a fully relational definition of inertial systems based in the No Arbitrariness Principle, that eliminates the need for absolute inertial frames of reference or distinguished reference systems as the "fixed stars" in order to formulate Newtonian mechanics. The historical roots of this approach to mechanics are discussed as well. The work is based in part in the constructivist perspective of space advanced by Piaget. We argue that inertial systems admit approximations and that what is of practical use are precisely such approximations. We finally discuss a slightly larger class of systems that we call "relatively inertial" which are the fundamental systems in a relational view of mechanics.

physics.hist-ph↗
arXiv2020

Impact of JD Bernal Thoughts in the Science of Science upon China: Implications for Quantitative Studies of Science Today

John Desmond Bernal (1901-1970) was one of the most eminent scientists in molecular biology, and also regarded as the founding father of the Science of Science. His book The Social Function of Science laid the theoretical foundations for the discipline. In this article, we summarize four chief characteristics of his ideas in the Science of Science: the socio-historical perspective, theoretical models, qualitative and quantitative approaches, and studies of science planning and policy. China has constantly reformed its scientific and technological system based on research evidence of the Science of Science. Therefore, we analyze the impact of Bernal Science-of-Science thoughts on the development of Science of Science in China, and discuss how they might be usefully taken still further in quantitative studies of science.

physics.soc-ph↗
arXiv2020

Precision Theory of Electroweak Interactions

As a part of the celebration of 50 years of the Standard Model of particle physics, I present a brief history of the precision theory of electroweak interactions. I emphasize in particular the theoretical preparations for the LEP program and the prediction of m_t and m_h from the electroweak precision data. [to appear in the proceedings of the SM@50 Symposium, Case Western Reserve University, June 1-4, 2018]

hep-ph↗
arXiv2020

Is Chemistry Really Founded in Quantum Mechanics?

The relationship between the chemical picture of an isolated molecule and that arising from the eiegenfunctions of the Schrodinger Coulomb Hamiltonian ror the isolated molecule are examined and discussed.

physics.hist-ph↗
arXiv2020

The Gauss' Bayes Factor

In 'Theoria motus corporum coelestium in sectionibus conicis solem ambientum' Gauss presents, as a theorem and with emphasis, the rule to update the ratio of probabilities of complementary hypotheses, in the light of an observed event which could be due to either of them. Although he focused on a priori equally probable hypotheses, in order to solve the problem on which he was interested in, the theorem can be easily extended to the general case. But, curiously, I have not been able to find references to his result in the literature.

math.HO↗
arXiv2021

Mikhail Lomonosov. Panegyric to the Sovereign Emperor Peter the Great (1755). Panegyric to Empress Elizabeth (1749). English translations with footnotes and commentaries by V.Shiltsev

One of Russia most prominent Enlightenment figures, Mikhail Lomonosov (1711-1765) was a polymath, scientist and writer, who made important contributions to physics, chemistry, astronomy, literature and education. Among his discoveries were the atmosphere of Venus and the law of conservation of mass in chemical reactions. These Panegyrics to Peter the Great and to Empress Elisabeth, written and read in 1755 and 1749, correspodingly, continue the series of English translations of Mikhail Lomonosov seminal works which were included by himself in the convolute Lomonosow Opera Academica intended for distribution among European Academies.

physics.hist-ph↗
arXiv2020

Different minds in the jigsaw puzzle of H-bomb story

The Super-bomb issue contained two problems: feasibility of physical engineering and political need to get H-bomb ASAP. And there were two radically different assessments of these problems by outstanding physicists Hans Bethe and Edward Teller, connected by many years of personal friendship and engaged in the US nuclear project from the very beginning, as the head of the Theoretical Division at Los Alamos and the leading figure in thermonuclear research. This puzzle is solved by using the history of the Soviet H-bomb, in particular the declassified documents on the role of Klaus Fuchs.

physics.hist-ph↗
arXiv2020

Enrico Fermi in Argentina and his Lectures in Buenos Aires, Cordoba and La Plata

In 1934 Enrico Fermi accepted an invitation to deliver lectures in Argentina, Brazil and Uruguay. He arrived in Buenos Aires on July 30, lectured in Buenos Aires, Cordoba, La Plata and Montevideo, and then moved on August 18 to Sao Paulo via Santos and Rio de Janeiro; he traveled back from Rio to Naples on September 1st. His visit had a large resonance, and halls were crowded despite the fact that he lectured in Italian. The University of Buenos Aires recorded his five lectures and transcribed them in Spanish. They contain the first public presentations of the theory of beta decay and of the works on artificial radioactivity started by the via Panisperna group, but are not included in Fermi's Collected Works edited by the Accademia dei Lincei in Rome and by the University of Chicago, although listed in the Bibliography. In this paper we present the transcription of Fermi's five lectures in Buenos Aires, a summary of the lecture in La Plata and an extended summary of the lecture in Cordoba, translating them in English for the first time.

physics.hist-ph↗
arXiv2020

Evolution and Transformation of Scientific Knowledge over the Sphaera Corpus: A Network Study

We investigated the evolution and transformation of scientific knowledge in the early modern period, analyzing more than 350 different editions of textbooks used for teaching astronomy in European universities from the late fifteenth century to mid-seventeenth century. These historical sources constitute the Sphaera Corpus. By examining different semantic relations among individual parts of each edition on record, we built a multiplex network consisting of six layers, as well as the aggregated network built from the superposition of all the layers. The network analysis reveals the emergence of five different communities. The contribution of each layer in shaping the communities and the properties of each community are studied. The most influential books in the corpus are found by calculating the average age of all the out-going and in-coming links for each book. A small group of editions is identified as a transmitter of knowledge as they bridge past knowledge to the future through a long temporal interval. Our analysis, moreover, identifies the most disruptive books. These books introduce new knowledge that is then adopted by almost all the books published afterwards until the end of the whole period of study. The historical research on the content of the identified books, as an empirical test, finally corroborates the results of all our analyses.

physics.hist-ph↗
arXiv2020

The October 10, 1912 solar eclipse expeditions and the first attempt to measure light-bending by the Sun

In 1911 Einstein proposed that light-bending by the Sun's gravitational field could be measured during a total solar eclipse. The first opportunity in which this measurement would be tried, was during the total solar eclipse of October 10, 1912. We report about the expeditions sent to Brazil to observe this eclipse, including the one from the Córdoba Observatory, from Argentina, which aimed to measure this Einstein's effect.

physics.hist-ph↗
arXiv2020

The Solar Eclipses of the Pharaoh Akhenaten

We suggest an earlier date for the accession of the pharaoh Akhenaten of the New Kingdom in Egypt. His first year of reign would be placed in 1382 BCE. This conjecture is based on the possible witness of three annular eclipses of the sun during his lifetime: in 1399, 1389, and 1378 BCE. They would explain the motive for his worship of the sun that left its mark on later religious communities. Evidence from Akhenaten's era is scarce, though some lateral dependencies can be disentangled on implementing the historical course of the subsequent events.

physics.hist-ph↗
arXiv2020

From EPR, Schrödinger paradox to nonlocality based on perfect correlation

We give a conceptually simple proof of nonlocality using only the perfect correlations between results of measurements on distant systems discussed by Einstein, Podolsky and Rosen---correlations that EPR thought proved the incompleteness of quantum mechanics. Our argument relies on an extension of EPR by Schrödinger.

physics.hist-ph↗
arXiv2020

Relativistic Implications for Physical Copies of Conscious States

The possibility of algorithmic consciousness depends on the assumption that conscious states can be copied or repeated by sufficiently duplicating their underlying physical states, leading to a variety of paradoxes, including the problems of duplication, teleportation, simulation, self-location, the Boltzmann brain, and Wigner's Friend. In an effort to further elucidate the physical nature of consciousness, I challenge these assumptions by analyzing the implications of special relativity on evolutions of identical copies of a mental state, particularly the divergence of these evolutions due to quantum fluctuations. By assuming the supervenience of a conscious state on some sufficient underlying physical state, I show that the existence of two or more instances, whether spacelike or timelike, of the same conscious state leads to a logical contradiction, ultimately refuting the assumption that a conscious state can be physically reset to an earlier state or duplicated by any physical means. Several explanatory hypotheses and implications are addressed, particularly the relationships between consciousness, locality, physical irreversibility, and quantum no-cloning.

physics.hist-ph↗
arXiv2020

Noisy Machines

The abstract notion of a Universal Turing machine cannot exist as a physical subsystem without the introduction of noise from an external energy source. Like all other physical systems, physical Turing machines must convert energy sourced from an external environment into useful work, thus subjecting them to the laws of thermodynamics. Consequently, asymptotic mathematical theorems including those derived by Godel and Turing do not bear any consequence on physical world because they can never be truly realised in physical systems. Rather these theorems highlight the seemingly unbridgeable chasm between Platonic forms (mathematics) and objects (physics).

physics.hist-ph↗