The action of neutrino ponderomotive force on supernova dynamics

Collective interactions of a beam of neutrinos/antineutrinos traversing a dense magnetized plasma of electrons/positrons, protons and neutrons are studied with particular reference to the case of a Supernova. We find that the ponderomotive force exerted by neutrinos gives, contrary to expectations, a negligible contribution to the revival of the shock for a successful Supernova explosion, although new types of convection and plasma cooling processes induced by the ponderomotive force could be, in principle, relevant for the dynamics itself.Comment: latex, 14 pages; numerical error corrected, conclusions changed; to be published in Mod. Phys. Lett.

Majorana and the path-integral approach to Quantum Mechanics

We give, for the first time, the English translation of a manuscript by Ettore Majorana, which probably corresponds to the text for a seminar delivered at the University of Naples in 1938, where he lectured on Theoretical Physics. Some passages reveal a physical interpretation of the Quantum Mechanics which anticipates of several years the Feynman approach in terms of path integrals, independently of the underlying mathematical formulation.Comment: revtex, 9 pages, 2 figures; a contribution in the centenary of the birth of Ettore Majoran

Physical realization of Photonic Klein Tunneling

General physical conditions for the occurrence of photonic Klein tunneling are studied, where (controlled) spontaneous emission from the devices considered plays a key role. The specific example of a simple dielectric slab bounded by two dielectric half spaces with arbitrary refractive indices is worked out quite in detail, the measured reflection and transmission probabilities being calculated analytically. It is found that, in given cases, the measured reflection probability may be arbitrarily large (for large incident wavelengths) irrespective of the fact that the transmission probability is exponentially suppressed or not. Other interesting features of photonic Klein tunneling driven by (controlled) spontaneous emission are as well envisaged for practical applications.Comment: revtex4, 6 pages, 4 figure

A demonstration device for cosmic rays telescopes

We describe a hands-on accurate demonstrator for cosmic rays realized by six high school students, whose main aim is to show the relevance and the functioning of the principal parts of a cosmic rays telescope (muon detector), with the help of two large size wooden artifacts. The first one points out how cosmic rays can be tracked in a muon telescope, while the other one shows the key avalanche process of electronic ionization that effectively allows muon detection through a photomultiplier. Incoming cosmic rays are visualized in terms of laser beams, whose 3D trajectory is highlighted by the turning on of LEDs on two orthogonal matrices. Instead the avalanche ionization process is demonstrated through the avalanche falling of glass marbles on an inclined plane, finally turning on a LED. A pictured poster accompanying the demonstrator is as well effective in assisting cosmic rays demonstration and its detection. The success of the demonstrator has been fully proven by general public during a Science Festival, the corresponding project winning the Honorable Mention in a dedicated competition.Comment: Latex, 8 pages, 6 figures; to be published in Physics Educatio

A Personal Point of View about Scientific Discussions on Free Will

I briefly present a personal view about alleged scientific results on free will.Comment: latex, 3 pages, no figure

Four variations on Theoretical Physics by Ettore Majorana

An account is given of some topical unpublished work by Ettore Majorana, revealing his very deep intuitions and skilfulness in Theoretical Physics. The relevance of the quite unknown results obtained by him is pointed out as well.Comment: latex, 23 pages, 1 figure; review article to be published in the special issue of EJTP dedicated to the centenary of the birth of Ettore Majoran

Transition from Majorana to Weyl fermions and anapole moments

The apparent splitting of zero-bias conductance peaks, apparently observed in recent experiments concerning Majorana fermions in nanowires coupled to superconductors, can be interpreted as a manifestation of a transition in the structure from (massive) Majorana to (massless) Weyl fermions. A modification of the experiments in order to test such phenomenon is proposed by making recourse to the only possible electromagnetic interaction allowed to (massive) Majorana particles and mediated by their anapole moment. In suitably designed heterostructures with toroidal symmetry, the additional anapole interaction manifests itself in the lowering of the critical magnetic field required for the appearance of the zero-bias peak, a shift that can be directly measured and thus reveal the presence of Majorana (rather than Weyl) fermions. Anapole interactions, though not previously considered, may also be a powerful method to control the dynamics of Majorana fermions, and then to manipulate the qubit state in quantum computationComment: revtex, 6 pages, 2 figures; to be published in Europhysics Letter

Hole theory and Quantum Electrodynamics in an unknown French manuscript by Ettore Majorana

We give an accurate historical and scientific account of a previously unknown manuscript written by Ettore Majorana in French. The retrieved text deals with Quantum Electrodynamics by using the formalism of field quantization, and it is here reported, for the first time, in translation. It is likely related to an invited talk for a conference at Leningrad (or Kharkov) in 1933 (or 1934) which, however, Majorana never attended. Probably this manuscript refers to the last missing papers of the ``Senatore folder'', given by Majorana to one student of his at the University of Naples in 1938, just before his disappearance.Comment: 16 pages, latex, amsar