An unknown story: Majorana and the Pauli-Weisskopf scalar electrodynamics

An account is given of an interesting but unknown theory by Majorana regarding scalar quantum electrodynamics, elaborated several years before the known Pauli-Weisskopf theory. Theoretical calculations and their interpretation are given in detail, together with a general historical discussion of the main steps towards the building of a quantum field theory for electrodynamics. A possible peculiar application to nuclear constitution, as conceived around 1930, considered by Majorana is as well discussed.Comment: Latex, amsart, 20 pages, 2 figures; to be published in Annalen der Physi

Vector Currents of Massive Neutrinos of an Electroweak Nature

The mass of an electroweakly interacting neutrino consists of the electric and weak parts responsible for the existence of its charge, charge radius, and magnetic moment. Such connections explain the formation of paraneutrinos, for example, at the polarized neutrino electroweak scattering by spinless nuclei. We derive the structural equations that relate the self-components of mass to charge, charge radius, and magnetic moment of each neutrino as a consequence of unification of fermions of a definite flavor. They indicate the availability of neutrino universality and require following its logic in a constancy law dependence of the size implied from the multiplication of a weak mass of neutrino by its electric mass. According to this principle, all Dirac neutrinos of a vector nature, regardless of the difference in their masses, have the same charge, an identical charge radius, as well as an equal magnetic moment. Thereby, the possibility appears of establishing the laboratory limits of weak masses of the investigated types of neutrinos. Finding estimates show clearly that the earlier measured properties of these particles may testify in favor of the unified mass structure of their interaction with any of the corresponding types of gauge fields.Comment: 14 pages, LaTex, Published version in CJ

Local zeta regularization and the scalar Casimir effect IV. The case of a rectangular box

Applying the general framework for local zeta regularization proposed in Part I of this series of papers, we compute the renormalized vacuum expectation value of several observables (in particular, of the stress-energy tensor and of the total energy) for a massless scalar field confined within a rectangular box of arbitrary dimension.Comment: Some overlaps with our works arXiv:1104.4330, arXiv:1505.00711, arXiv:1505.01044, arXiv:1505.01651. These overlaps aim to make the present paper self-contained, and do not involve the main results. In comparison with version v3, reference [26] adde

A time machine for free fall into the past

Inspired by some recent works of Tippett-Tsang and Mallary-Khanna-Price, we present a new spacetime model containing closed timelike curves (CTCs). This model is obtained postulating an ad hoc Lorentzian metric on $\mathbb{R}^4$, which differs from the Minkowski metric only inside a spacetime region bounded by two concentric tori. The resulting spacetime is topologically trivial, free of curvature singularities and is both time and space orientable; besides, the inner region enclosed by the smaller torus is flat and displays geodesic CTCs. Our model shares some similarities with the time machine of Ori and Soen but it has the advantage of a higher symmetry in the metric, allowing for the explicit computation of a class of geodesics. The most remarkable feature emerging from this computation is the presence of future-oriented timelike geodesics starting from a point in the outer Minkowskian region, moving to the inner spacetime region with CTCs, and then returning to the initial spatial position at an earlier time; this means that time travel to the past can be performed by free fall across our time machine. The amount of time travelled into the past is determined quantitatively; this amount can be made arbitrarily large keeping non-large the proper duration of the travel. An important drawback of the model is the violation of the classical energy conditions, a common feature of many time machines. Other problems emerge from our computations of the required (negative) energy densities and of the tidal accelerations; these are small only if the time machine is gigantic.Comment: 40 pages, 10 figures; the final version accepted for publication. In comparison with version v2, some references added (see [4,21,35]) and commented on in the Introductio