A quantum theory of the photon is developed in a natural manner. Newton-Wigner and Wightman demonstrated that the photon could not be strictly localized according to natural criteria. These investigations involved the identification of an elementary system with a uirrep of the Poincare group. We identify a particle with the localized measurement of the states satisfying the uirrep. In the case of zero mass and unit spin, the photon is identified with those components of the state that can be localized. (...) A c-number four-vector potential and Lorentz condition are derived from the relativistic wave equation. The Wightman localization is demonstrated for the three independent space components of the vector potential, and the photon is identified with these components. A position operator and probability density follow immediately from the localization. A consequence of the subjective definition of a photon is that the transformations of the vector potential are unitary, and hence the unitary scalar product can be obtained for the four-vector potential. A Hilbert space is defined for the three space components of the vector potential. A position operator and probability density are derived from the scalar product, which compare directly with those obtained from the localization and the non-relativistic theory. As the longitudinal and scalar polarizations do not contribute to the measured transition probability, they are considered virtual. Lastly, a conserved four-vector current is derived from the scalar product. The possibility of observing a strict localization of the photon in the laboratory is suggested. (shrink)

Many of the "counterintuitive" features of relativistic quantum field theory have their formal root in the Reeh-Schlieder theorem, which in particular entails that local operations applied to the vacuum state can produce any state of the entire field. It is of great interest then that I.E. Segal and, more recently, G. Fleming (in a paper entitled "Reeh-Schlieder meets Newton-Wigner") have proposed an alternative "Newton-Wigner" localization scheme that avoids the Reeh-Schlieder theorem. In this paper, I reconstruct the Newton-Wigner localization (...) scheme and clarify the <em>limited</em> extent to which it avoids the counterintuitive consequences of the Reeh-Schlieder theorem. I also argue that there is no coherent interpretation of the Newton-Wigner localization scheme that renders it free from act-outcome correlations at spacelike separation. (shrink)

The Reeh-Schlieder theorem asserts the vacuum and certain other states to be spacelike superentangled relative to local fields. This motivates an inquiry into the physical status of various concepts of localization. It is argued that a covariant generalization of Newton-Wigner localization is a physically illuminating concept. When analyzed in terms of nonlocally covariant quantum fields, creating and annihilating quanta in Newton-Wigner localized states, the vacuum is seen to not possess the spacelike superentanglement that the Reeh-Schlieder theorem displays relative (...) to local fields, and to be locally empty as well as globally empty. Newton-Wigner localization is then shown to be physically interpretable in terms of a covariant generalization of the center of energy, the two localizations being identical if the system has no internal angular momentum. Finally, some of the counterintuitive features of Newton-Wigner localization are shown to have close analogues in classical special relativity. (shrink)

The Reeh-Schlieder theorem asserts the vacuum and certain other states to be spacelike superentangled relative to local quantum fields. This motivates an inquiry into the physical status of various concepts of localization. It is argued that a covariant generalization of Newton-Wigner localization is a physically illuminating concept. When analyzed in terms of nonlocally covariant quantum fields, creating and annihilating quanta in Newton-Wigner localized states, the vacuum is seen to not possess the spacelike superentanglement that the Reeh-Schlieder theorem displays (...) relative to local fields, and to be locally empty as well as globally empty. Newton-Wigner localization is then shown to be physically interpretable in terms of a covariant generalization of the center of energy, the two localizations being identical if the system has no internal angular momentum. Finally, some of the counterintuitive features of Newton-Wigner localization are shown to have close analogues in classical special relativity. (shrink)

The crossing property is perhaps the most subtle aspect of the particle-field relation. Although it is not difficult to state its content in terms of certain analytic properties relating different matrixelements of the S-matrix or formfactors, its relation to the localization- and positive energy spectral principles requires a level of insight into the inner workings of QFT which goes beyond anything which can be found in typical textbooks on QFT. This paper presents a recent account based on new ideas (...) derived from “modular localization” including a mathematic appendix on this subject. Its main achievement is the proof of the crossing property from a two-algebra generalization of the KMS condition.The main content is an in-depth criticism of the dual model and its string theoretic extension. The conceptual flaws of these models are closely related to misunderstandings of crossing. The correct interpretation of string theory is that of a dynamic infinite component one particle space where “dynamic” means that, unlike a mere collection of independent free fields, the formalism contains also operators which communicate between the different irreducible Poincaré representations and set the mass/spin spectrum. Whereas in pre-string times there were unsuccessful attempts to achieve this in analogy to the O(4,2) hydrogen spectrum by the use of higher noncompact groups, the superstring in d=9+1, which uses instead (bosonic/fermionic) oscillators obtained from multicomponent chiral currents, is the only known solution of the dynamical infinite component pointlike field (or pointlike generated wave function) project. (shrink)

David Hume is the greatest figure in the empiricist tradition in philosophy and was a particular source of inspiration for the logical positivists (see logical positivism). Hume was born in 1711 and entered Edinburgh University at the age of 12. After graduating, he had a varied career in commerce, diplomacy, as a librarian, and as a writer of history. Twice he was secretary to General St Clair and on one occasion set off with him on an expedition to drive the (...) French out of Canada. Forced back by the wind, it was decided instead to make a brief incursion on the coast of Brittany. This failed, for the expedition had maps of Canada, but none of Brittany. During a three‐year stay in France he wrote his major philosophical work Treatise of Human Nature. It appeared in 1739 and, in his own words, “fell dead‐born from the Press.” His Inquiry Concerning Human Understanding, which was intended to be a more popular version of book I of his Treatise, was published in 1748 but was only a little more favorably received. His six‐volume History of England, on the other hand, was a great success. He died in 1776, never having succeeded in his ambition to be appointed to a professorship of philosophy in Scotland, due to his religious skepticism. (shrink)

It is not too early to suggest that the attempts to place medical care in private hands (through group insurance arrangements) has not fulfilled its promise—or better, the promises that were made for it. Yet history has not been kind to plans to make government the single payer, and the laudable progress in medical technology has placed high-technology medical care beyond the reach of most privatebudgets. In this paper I suggest that the major problem of the U.S. health care system (...) as presently conceived is a failure of legitimacy,and I put forward a proposal that purports to solve that problem. The proposal is to localize health care, on the model of a public school system, on the argument that such localization will answer most of the questions of legitimacy at the core of the private insurance imbroglio, provide a brake for medical costs, while preserving our ability to take advantage of the most advanced medical interventions. I present some initial arguments for the proposal, but await its proof in the dialogue emerging as the present insurance system collapses. (shrink)

The significance of the de Broglie/Bohm hidden-particle position in the relativistic regime is addressed, seeking connection to the single-particle Newton–Wigner position. The effect of non-positive excursions of the ensemble density for extreme cases of positive-energy waves is easily computed using an integral of the equations of motion developed here for free spin-0 particles in 1 + 1 dimensions and is interpreted in terms of virtual-like pair creation and annihilation beneath the Compton wavelength. A Bohm-theoretic description of the acausal explosion of (...) a specific Newton–Wigner-localized state is presented in detail. The presence of virtual pairs found is interpreted as the Bohm picture of the spatial extension beyond single point particles proposed in the 1960s as to why space-like hyperplane dependence of the Newton–Wigner wavefunctions may be needed to achieve Lorentz covariance. For spin-1/2 particles the convective current is speculatively utilized for achieving parity with the spin-0 theory. The spin-0 improper quantum potential is generalized to an improper stress tensor for spin-1/2 particles. (shrink)

The current status of localization and related concepts, especially localized statevectors and position operators, within Lorentz-invariant Quantum Theory (LIQT) is ambiguous and controversial.1 Ever since the early work of Newton & Wigner (1949), and the subsequent extensions of their work, particularly by Hegerfeldt (1974, 1985), it has seemed impossible to identify localized statevectors or position operators in LIQT that were not counterintuitive—strange—in one way or another; the most striking strange property being the superluminal propagation of the localized states. The (...) ambiguous and controversial status of these concepts arises from the varied reactions that workers have to the strange properties. Some regard them, particularly the superluminal propagation, as utterly unacceptable, and conclude that no precise concepts of localized statevectors and position operators exist in LIQT (Wigner 1973, p. 325-327; 1983, pp. 310-313; Malament 1996). Others downplay the whole issue, on the grounds that current theoretical and experimental practice has no need of sharply formulated concepts of localization, localized states etc. (Birrell & Davies 1984, pp. 48-59; Haag 1992, p. 34). Still others, including ourselves, believe that the superluminal propagation does not lead to causal contradictions, and is not in conflict with available empirical data: so that it should not be ruled out. We also believe that the other strange properties are merely unfamiliar novelties of LIQT which we must simply learn to accept. (Like the superluminal propagation, they do not lead to causal contradictions, nor conflict with available data.) So in this paper, we aim to help remove the ambiguous and controversial status of localization concepts in LIQT. Overall, our strategy will be to assess a number of localization concepts, and thereby clarify the often complex relationships among them. (shrink)

Newton's Philosophiae Naturalis Principia Mathematica provides a coherent and deductive presentation of his discovery of the universal law of gravitation. It is very much more than a demonstration that 'to us it is enough that gravity really does exist and act according to the laws which we have explained and abundantly serves to account for all the motions of the celestial bodies and the sea'. It is important to us as a model of all mathematical physics.Representing a decade's work from (...) a distinguished physicist, this is the first comprehensive analysis of Newton's Principia without recourse to secondary sources. Professor Chandrasekhar analyses some 150 propositions which form a direct chain leading to Newton's formulation of his universal law of gravitation. In each case, Newton's proofs are arranged in a linear sequence of equations and arguments, avoiding the need to unravel the necessarily convoluted style of Newton's connected prose. In almost every case, a modern version of the proofs is given to bring into sharp focus the beauty, clarity, and breath-taking economy of Newton's methods.Subrahmanyan Chandrasekhar is one of the most reknowned scientists of the twentieth century, whose career spanned over 60 years. Born in India, educated at the University of Cambridge in England, he served as Emeritus Morton D. Hull Distinguished Service Professor of Theoretical Astrophysics at the University of Chicago, where he has was based from 1937 until his death in 1996. His early research into the evolution of stars is now a cornerstone of modern astrophysics, and earned him the Nobel Prize for Physics in 1983. Later work into gravitational interactions between stars, the properties of fluids, magnetic fields, equilibrium ellipsoids, and black holes has earned him awards throughout the world, including the Gold Medal from the Royal Astronomical Society in London, the National Medal of Science in the United States, and the Copley Medal from the Royal Society. His many publications include Radiative transfer, Hydrodynamic and hydromagnetic stability, and The mathematical theory of black holes, each being praised for its breadth and clarity. Newton's Principia for the common reader is the result of Professor Chandrasekhar's profound admiration for a scientist whose work he believed is unsurpassed, and unsurpassable. (shrink)

Isaac Newton was born on 25 December 1642 in the hamlet of Colsterworth, Lincolnshire, about six miles south of Grantham. The posthumous and only son of Isaac Newton, père, he found himself deposited with grandparents at the age of three when his mother married a second time; he remained with the grandparents for eight years until the death of his stepfather. After successfully resisting his mother's intention that he manage the considerable estate she had inherited from the two husbands, Newton (...) graduated from the grammar school in Grantham and enrolled in Trinity College, Cambridge, in June 1661. Trinity was Newton's home for the following 35 years. He received his B.A. in 1665 and his M.A. three years later. Meanwhile he had been elected to a fellowship in the college, and in 1669, upon the resignation of Isaac Barrow, he was appointed Lucasian Professor of Mathematics. Newton did not strain himself with teaching. During his nearly 30 years as a fellow of Trinity he tutored only three students, all of them wealthy fellow commoners; he formed no perceptible bond with any of them. As Lucasian Professor, he lectured once a week during one term each year, at least early in his tenure. There is testimony that frequently no one attended the lectures, and even later, when he was famous and a connection with him was potentially valuable, only two men claimed to have heard them. He ceased to lecture altogether after 1687, and may have stopped before that. (shrink)

In French mechanical treatises of the nineteenth century, Newton’s second law of motion was frequently derived from a relativity principle. The origin of this trend is found in ingenious arguments by Huygens and Laplace, with intermediate contributions by Euler and d’Alembert. The derivations initially relied on Galilean relativity and impulsive forces. After Bélanger’s Cours de mécanique of 1847, they employed continuous forces and a stronger relativity with respect to any commonly impressed motion. The name “principle of relative motions” and the (...) very idea of using this principle as a constructive tool were born in this context. The consequences of Poincaré’s and Einstein’s awareness of this approach are analyzed. Lastly, the legitimacy and significance of a relativity-based derivation of Newton’s second law are briefly discussed in a more philosophical vein. (shrink)

William (Bill) Newton-Smith was a renowned Canadian philosopher of science who spent his career largely in Oxford and then at the Central European University in Hungary.Newton-Smith was born in Ori...

Gottfried Wilhelm Leibniz, who was born in 1646 just before the end of the Thirty Years War and who died 1716, is surely one of the most bizarre and interesting of the early modern philosophers. He was an astonishing polymath, and responsible for some of the most advanced work in the sciences of his day—he was, for instance, the co-inventor along with Newton, of differential calculus, and is generally recognized as the greatest logician of the early modern period, responsible for (...) advances in logic not rivaled until the mid-nineteenth century. But this progressive aspect of Leibniz’s thought is paired by one that was more backward looking, deeply engaged with premodern forms of thinking that referred back through Medieval culture to the philosophy of ancient times. And alongside of his scientific advances, he is known for having created one of the most baroque and puzzling metaphysical systems in the history of philosophy—the so-called “Monadology”. For much of his life he was also absorbed in theological disputes that have now been long been forgotten, and generally thought of as alien to modern scientific modes of thought. (shrink)

The rigorous equivalence of the Schrödinger and Heisenberg pictures requires that one uses Born–Jordan quantization in place of Weyl quantization. We confirm this by showing that the much discussed “ angular momentum dilemma” disappears if one uses Born–Jordan quantization. We argue that the latter is the only physically correct quantization procedure. We also briefly discuss a possible redefinition of phase space quantum mechanics, where the usual Wigner distribution has to be replaced with a new quasi-distribution associated with Born–Jordan quantization, and (...) which has proven to be successful in time-frequency analysis. (shrink)

The present discussion arose from the desire to explain, to an audience of non-physicists, the epistemology to which one is forced if one pursues the quantum mechanical theory of observation to its ultimate consequences. However, the conclusions will not be derived from the aforementioned theory but obtained on the basis of a rather general analysis of what we mean by real. Quantum theory will form the background but not the basis for the analysis. The concept of the real to be (...) arrived at shows considerable similarity to that of the idealist. As the title indicates, it is formulated as a dualism. It is quite possible that it will soon be rejected not only by the community of the philosophers but also by that of the scientists. If this should be the case, the attempt to derive an epistemology from physics will prove to have been premature. Naturally, the author hopes that this will not be the case because, quite apart from the quantum theoretical background, the concepts to be presented appear natural also as an outgrowth of common sense considerations. They have been arrived at by many who did not accept the epistemology of quantum mechanics. (shrink)

Versuch über die ursprünglichen Grundlagen des menschlichen Denkens - und die davon abhängigen Schranken unserer Erkenntniss ist ein unveränderter, hochwertiger Nachdruck der Originalausgabe aus dem Jahr 1791. Hansebooks ist Herausgeber von Literatur zu unterschiedlichen Themengebieten wie Forschung und Wissenschaft, Reisen und Expeditionen, Kochen und Ernährung, Medizin und weiteren Genres. Der Schwerpunkt des Verlages liegt auf dem Erhalt historischer Literatur. Viele Werke historischer Schriftsteller und Wissenschaftler sind heute nur noch als Antiquitäten erhältlich. Hansebooks verlegt diese Bücher neu und trägt damit zum (...) Erhalt selten gewordener Literatur und historischem Wissen auch für die Zukunft bei. (shrink)

It is proposed to consider present-day physics as dealing with a special situation, the situation in which the phenomena of life and consciousness play no role. It is pointed out that physical theory has often dealt, in the past, with similarly special situations. Planetary theory neglects all but gravitational forces, macroscopic physics neglects fluctuations due to the atomic structure of matter, nuclear physics disregards weak and gravitational interactions. In some of these cases, physicists were well aware of dealing with special (...) situations, or limiting cases as they are called in the article; in other cases, they were not. It is pointed out that, even if it were true that present-day physics accurately describes the motion of the physical constituents of living bodies, it would not give the whole story. Arguments are adduced, however, to show that the laws of physics, applicable for inanimate matter, will have to be modified when dealing with the more general situation in which life and consciousness play significant roles. (shrink)

Introduction -- What is proportionality? -- Proportionality : a multiplicity of meanings -- Proportionality in the just war tradition -- Proportionality in international humanitarian law -- Proportionality in human rights law and morality -- The uniqueness of jus in bello proportionality -- Countermeasures and counterinsurgency -- Human shields and risk -- Targeted killings and proportionality in law : two models -- The nature of war and the idea of "cyberwar" -- Thresholds of jus in bello proportionality.

The book should be a gem for all those interested in the history and philosophy of science.

Can business be a moral enterprise? -- Employee rights and responsibilities : the internal constituencies of business -- Customers, community, and world : the external constituencies of business.

A shrewd and compelling examination of how political figures throughout history have used scientific findings to achieve their objectives--just as scientists have often put political forces to work to achieve their own goals.

Dieses Buch ist bis heute eine der populärsten Darstellungen der Relativitätstheorie geblieben. In der vorliegenden Version haben J. Ehlers und M. Pössel vom Max-Planck-Institut für Gravitationsphysik (Albert-Einstein-Institut) in Golm/Potsdam den Bornschen Text kommentiert und einen den anschaulichen, aber präzisen Stil Borns wahrendes, umfangreiches Ergänzungskapitel hinzugefügt, das die stürmische Entwicklung der Relativiatätstheorie bis hin zu unseren Tagen nachzeichnet. Eingegangen wird auf Gravitationswellen und Schwarze Löcher, auf neuere Entwicklungen der Kosmologie, auf Ansätze zu einer Theorie der Quantengravitation und auf die zahlreichen raffinierten (...) Experimente, welche die Gültigkeit der Einsteinschen Theorie mit immer größerer Genauigkeit bestätigt haben. Damit bleibt dieses Buch nach wie vor einer der unmittelbarsten Zugänge zur Relativitätstheorie für alle die sich für eine über das rein populärwissenschaftliche hinausgehende Einführung interessieren. (shrink)

Le christianisme est, au-delà de la philosophie, une religion philosophique où l'homme tout entier se retrouve. Écartelés entre l'idée du Dieu vivant, qui est constitutive de la pensée et l'agonie de Dieu qui se laisse déchiffrer dans ce mélange de sens et de non-sens qu'on appelle l'expérience, se trouvent cette passion et ce devoir dont nous avons assez dit qu'ils étaient l'homme même. Lorsque la philosophie tente de résoudre le problème du mal en acceptant le risque de l'échec absolu, elle (...) ne trouve pas de solution mais elle rencontre l'homme, l'homme nu au-delà du mythe, l'homme seul en deçà de Dieu, l'homme naturellement prométhéen et chrétien, à qui il n'est pas interdit de trouver dans l'espérance le sens de son existence, c'est-à-dire de sa passion. (shrink)