In relativistic classical and quantum mechanics with Poincaré-invariant parameter, particle worldlines are traced out by the evolution of spacetime events. The formulation of a covariant canonical framework for the evolving events leads to a dynamical theory in which mass conservation is demoted from a priori constraint to the status of conserved Noether current for a certain class of interactions. In pre-Maxwell electrodynamics—the local gauge theory associated with this framework —events induce five local off-shell fields, which mediate interactions between instantaneous (...) events, not between the worldlines which represent entire particle histories. The fifth field, required to compensate for dependence of gauge transformations on the evolution parameter, enables the exchange of mass between particles and fields. In the equilibrium limit, these pre-Maxwell fields are pushed onto the zero-mass shell, but during interactions there is no mechanism regulating the mass that photons may acquire, even when event trajectories evolve far into the spacelike region. This feature of the off-shell formalism requires the application of some ad hoc mechanism for controlling the photon mass in two opposite physical domains: the low energy motion of a charged event in classical Coulomb scattering, and the renormalization of off-shell quantum electrodynamics. In this paper, we discuss a nonlocal, higher derivative correction to the photon kinetic term, which provides regulation of the photon mass in a manner which preserves the gauge invariance and Poincaré covariance of the original theory. We demonstrate that the inclusion of this term is equivalent to an earlier solution to the classical Coulomb problem, and that the resulting quantum field theory is renormalized. (shrink)

Reasons for taking1/2h/c 2 in cgs units as an equivalent in grams for the photon “rest mass” are given. Its numerical value of3.68×10 −48 g corresponds to the minimum mass equivalent energy for one half-cycle of an electromagnetic dipole field distribution, which is discontinuous. For the fluid models that are discussed, this field distribution corresponds somewhat to a hydrodynamic toroidal vortex which is stationary—if we use toroidal coordinates and assume that the ring origin has the radial velocity (...) c, that the gauge is defined by the ring origin diameter, and that free space is represented by a two-fluid model (the fluids oppositely charged). There are mappings which can transform such toroidal entities (photons) into spherical ones. The toroidal entities are possible candidates for the role of “hidden variables.”. (shrink)

We present a mini review of the Stueckelberg mechanism, which was proposed to make the abelian gauge theories massive as an alternative to Higgs mechanism, within the framework of Minkowski as well as curved spacetimes. The higher the scale the tighter the bounds on the photon mass, which might be gained via the Stueckelberg mechanism, may be signalling that even an extremely small mass of the photon which cannot be measured directly could have far reaching effects (...) in cosmology. We present a cosmological model where Stueckelberg fields, which consist of both scalar and vector fields, are non-minimally coupled to gravity and the universe could go through a decelerating expansion phase sandwiched by two different accelerated expansion phases. We discuss also the possible anisotropic extensions of the model. (shrink)

The idea that the mass m of an elementary particle is explained in the semi-classical approximation by quantum-mechanical zero-point vacuum fluctuations has been applied previously to spin-1/2 fermions to yield a real and positive constant value for m, expressed through the spinorial connection Γ i in the curved-space Dirac equation for the wave function ψ due to Fock. This conjecture is extended here to bosonic particles of spin 0 and spin 1, starting from the basic assumption that all fundamental (...) fields must be conformally invariant. As a result, in curved space-time there is an effective scalar mass-squared term $m_{0}^{2}=-R/6=2\varLambda_{\mathrm{b}}/3$ , where R is the Ricci scalar and Λ b is the cosmological constant, corresponding to the bosonic zero-point energy-density, which is positive, implying a real and positive constant value for m 0, through the positive-energy theorem. The Maxwell Lagrangian density $\mathcal{L} =- \sqrt{-g}F_{ij}F^{ij}/4$ for the Abelian vector field F ij ≡A j,i −A i,j is conformally invariant without modification, however, and the equation of motion for the four-vector potential A i contains no mass-like term in curved space. Therefore, according to our hypothesis, the free photon field A i must be massless, in agreement with both terrestrial experiment and the notion of gauge invariance. (shrink)

The photon box thought experiment can be considered a forerunner of the EPR-experiment: by performing suitable measurements on the box it is possible to ``prepare'' the photon, long after it has escaped, in either of two complementary states. Consistency requires that the corresponding box measurements be complementary as well. At first sight it seems, however, that these measurements can be jointly performed with arbitrary precision: they pertain to different systems (the center of mass of the box and (...) an internal clock, respectively). But this is deceptive. As we show by explicit calculation, although the relevant quantities are simultaneously measurable, they develop non-vanishing commutators when calculated back to the time of escape of the photon. This justifies Bohr's qualitative arguments in a precise way; and it illustrates how the details of the dynamics conspire to guarantee the requirements of complementarity. In addition, our calculations exhibit a ``fine structure'' in the distribution of the uncertainties over the complementary quantities: depending on when the box measurement is performed, the resulting quantum description of the photon differs. This brings us close to the argumentation of the later EPR thought experiment. (shrink)

This paper proves that it is possible to build a Lagrangian for quantum electrodynamics which makes it explicit that the photon mass is eventually set to zero in the physical part on observational ground. Gauge independence is achieved upon considering the joint effect of gauge-averaging term and ghost fields. It remains possible to obtain a counterterm Lagrangian where the only non-gauge-invariant term is proportional to the squared divergence of the potential, while the photon propagator in momentum space (...) falls off like k −2 at large k which indeed agrees with perturbative renormalizability. The resulting radiative corrections to the Coulomb potential in QED are also shown to be gauge-independent. The experience acquired with quantum electrodynamics is used to investigate properties and problems of the extension of such ideas to non-Abelian gauge theories. (shrink)

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)

‘From now on, I'll describe the cities to you’, the Khan had said, ‘in your journeys you will see if they exist.’ But the cities visited by Marco Polo were always different from those thought of by...

No paradox exists in the fact that, in the Special Relativity, for the mass of a material body, considered in motion at constant speed, whose measure is u, the formula: m = m0/√ can be written, while for a photon the same formula holds, when between its source and the observer a state of relative motion at constant speed, whose measure is u, exists and it is observed along the direction perpendicular to the direction of his speed.

It is shown that no concrete particle can have zero rest mass. A separate photon is proven to be a concrete particle. The nonexistence of the electromagnetic field as an independent physical reality is demonstrated. The existence of a subatomic electromagnetic particle of a very small rest mass, theemon, instead of the electromagnetic field, is stated. The compatibility of the notion of the emon with the special relativity theory is elucidated. Some corollaries of the existence of the (...) emon as well as the possibilities of determining its rest mass are discussed. The explanations of the relativity aberration and Doppler effect in terms of the emon are given. The importance of the principle of concreteness of experiments is emphasized and illustrated. Some related problems are noticed. (shrink)

Une tentative de rapprochement entre un certain nombre d'interrogations esthétiques et le contexte historique dans lequel elles s'inscrivent. Sortir les propositions artistiques contemporaines de leur histoire spécifique et les articuler sur les questions que posent certaines mutations récentes de nos sociétés.

Recently, there has been renewed interest in the search for low-mass magnetic monopoles. At the University of Oklahoma we are performing an experiment (Fermilab E882) using material from the old D0 and CDF detectors to set limits on the existence of Dirac monopoles of masses of the order of 500 GeV. To set such limits, estimates must be made of the production rate of such monopoles at the Tevatron collider, and of the binding strength of any such produced monopoles (...) to matter. Here we sketch the still primitive theory of such interactions, and indicate why we believe a credible limit may still be obtained. On the other hand, there have been proposals that the classic Euler–Heisenberg Lagrangian together with duality could be employed to set limits on magnetic monopoles having masses less than 1 TeV, based on virtual, rather than real processes. The D0 collaboration at Fermilab has used such a proposal to set mass limits based on the nonobservation of pairs of photons each with high transverse momentum. We critique the underlying theory, by showing that the cross section violates unitarity at the quoted limits and is unstable with respect to radiative corrections. We therefore believe that no significant limit can be obtained from the current experiments, based on virtual monopole processes. (shrink)

A funny, touching look at the life of a social media influencer who starts to question the #goals life she has created for herself. Every day, Élie motivates her hundreds of thousands of followers to become the best versions of themselves by posting videos of exercise routines and high-protein breakfast recipes. Far from the shy teenager that she was, she is now in a very public relationship with singer Samuel Vanasse, and together they have become one of the most popular (...) influencer couples in the country. She has succeeded. She shines. And yet, Élie worries that her life is not as flawless as she makes it seem on YouTube and Instagram. Between her obsession with the "ideal weight," her growing attraction to another man, her family's disdain for her career as a content creator and a collaboration with another influencer who Élie can't stand, a thought haunts her. What if, by trying to become everything she wanted to be, she's lost herself along the way? Suck it In and Smile is an intimate exploration of our obsession with appearances and the hypocrisies that appear when you must craft the perfect online life. (shrink)

"Die Logik der Erfahrung" stellt eine Systematisierung der wissenschaftsphilosophischen Gedanken der klassischen Pragmatisten (Charles S. Peirce, William James, John Dewey) dar. Die pragmatistische Erfahrungstheorie sowie die Bestimmung des Verhältnisses von Theorie und Praxis bilden die Grundlage einer holistischen Wissenschaftsphilosophie, deren Aktualität durch die exemplarische Anwendung auf klassische wissenschaftstheoretische Fragestellungen gezeigt wird. Die AutorinTina Massing ist Akademische Rätin am Institut für Philosophie der Universität Koblenz. In ihrer Forschung beschäftigt sie sich insbesondere mit wissenschaftsphilosophischen Themen und dem Klassischen Pragmatismus.

The text confronts the elements of which Luhmann theorizes the educative system, from a critical form to center the suitable approach to know the multiplicity of elements from the educative system. Luhmann’s foundations are criticized and other levels are proposed, from a critical vision of social..

This article deals with a set of images which were probably the first in history to be reproduced on four continents: the Jesuit Jerome Nadal's Evangelicae Historiae Imagines, first published in Antwerp in 1593. It begins with a brief discussion of what we know about Nadal's life and the production history of his book, as well as its relationship to his Adnotationes et Meditationes in Evangelia quae in sacrosanto missae sacrificio toto anno leguntur, which acts as a commentary to the (...) Imagines. Then follows a description of the structure of the two books, and how they narrate and expound the significance of the Gospels. The remaining sections discuss the adaptations of Nadal's imagery. While his work has received much attention from scholars around the world in recent decades, the aim of the present article is to bring together research on the use and re-use of these images in Europe, the Americas, India, China, Japan, Iran and Ethiopia, and to make clear their global impact in a way that has not been attempted before. (shrink)

Qu'entend-on par enchantement et désenchantement du monde? Quelles seraient les voies à suivre pour susciter un réenchantement du monde qui sera le fait de l’humain lui-même? La raison et la rationalité sont-elles les causes des maux de nos errements ou des outils pour les contrer? Suffira-t-il d’avoir « foi en la raison » pour surmonter les défis que l’humanité s’est elle-même imposés par négligence et irresponsabilité.

The dualism of knowledge and values as well as of the objective and the subjective views has accompanied the social work profession from its inception and presents a particular dilemma for the link between academia and practice. It is either that academia is split off from the practice of social work, or that these two fields of professional activity merge into each other. Either of these solutions impoverishes the profession. The key for the understanding of this dilemma as well as (...) its resolution rests with the particular ontological definitions adhered to by the profession. It is proposed that by fostering the moral ontology the dualism inherent in the nature of the profession may enrich it and a fruitful link between academia and the practice of social work will evolve. The arguments presented as well as the resolution proposed are illustrated by theoretical explanations, empirical studies and clinical practice in the area of the parent-infant relationship. (shrink)

Hallucinations do not originate in a single region of the brain, the thalamus, and cannot be traced back to a single pathological mechanism. They emerge from the complex interaction of several brain regions, and are not necessarily the result of sensory impairment or the effect of a defective filter. In the case of schizophrenia, hallucinations are accessory symptoms, in Bleuler's sense, and are thus not central to this disorder.