Giorgio Papini

E-mail: papini(at)uregina.ca or papini@(at)a.infn.it

General interests lie in quantum mechanics and relativistic theories of gravity.

THE INTERACTION OF GRAVITY WITH QUANTUM SYSTEMS. Fully covariant wave equations predict the existence of a class of inertial-gravitational effects that can be tested experimentally. In these equations inertia and gravity appear as external classical fields, but, by conforming to general relativity, provide  information on how Einstein's views carry through in the world of the quantum. Experiments already confirm that inertia and Newtonian gravity affect quantum particles in ways that are fully consistent with general relativity down to distances of 10^{-4}cm for superconducting electrons and of 10^{-8}cm for neutrons. Other aspects of the interaction of gravity with quantum systems are just beginning to be investigated. Gravitational-inertial fields affect particle wave functions in a variety of ways. They induce quantum phases (Berry's phase) that afford a unified treatment of interferometry and gyroscopy. They interact with particle spins giving rise to a number of significant effects. Two of the predicted effects, spin-gravity interaction for photons (2003) and neutrons (2015), have been observed. Rapid experimental advances in particle interferometry require that quantum phases be derived with precision. This has been done for Schroedinger, Klein-Gordon, Maxwell, Dirac and spin-2 equations. Large, sensitive interferometers hold great promise in many of these investigations. They can play a role in testing general relativity. On the other hand, spin-inertia and spin-gravity interactions are particularly important in precise tests of fundamental theories and in certain types of neutrino oscillations. Particle accelerators may be also called to play a role in these investigations.

MAXIMAL ACCELERATION. Other aspects of the interplay of gravitation with quantum systems regard a geometrical model of quantum mechanics proposed by E.R. Caianiello. The model interprets quantization as curvature of the relativistic eight--dimensional space--time tangent bundle TM, satisfies the Born reciprocity principle and incorporates the notion that the proper accelerations of massive particles along their worldlines are normalized to an upper limit referred to as maximal acceleration (MA). The value of MA can be derived from quantum mechanical considerations. Classical and quantum arguments supporting the existence of a MA have been frequently advanced in the literature. MA also appears in the context of Weyl space and of a geometrical analogue of Vigier'stochastic theory and plays a role in numerous issues. It is invoked as a tool to rid black hole entropy of ultraviolet divergences and of inconsistencies stemming from the application of the point-like concept to relativistic particles. MA may be also regarded as a regularization procedure, alternative to those in which space--time is quantized by means of a fundamental length. The advantage of Caianiello's proposal lies in the preservation of the continuum structure of space-time. An upper limit to the acceleration also exists in string theory where Jeans--like instabilities occur when the acceleration induced by the background gravitational field is large enough to render the string extremities causally disconnected. Applications of Caianiello's model include cosmology, where the initial singularity can be avoided while preserving inflation, the dynamics of accelerated strings, the energy spectrum of a uniformly accelerated particle and neutrino oscillations. The model also makes the metric observer--dependent, as conjectured by Gibbons and Hawking. We have worked out the consequences of the model for photons in a cavity,  the classical electrodynamics of a particle, the mass of the Higgs boson and the Lamb shift in hydrogenic atoms. In the last instance the agreement between experimental data and MA corrections is very good for H and D. For He^+ the agreement between theory and experiment is improved by 50% when MA corrections are included. MA affects the helicity and chirality of particles and muonic atoms, the fall of massive particles in the gravitational field of a spherically symmetric collapsing object. In this problem MA manifests itself through a spherical shell external to the Schwarzschild horizon and impenetrable to classical particles. Massive, spinless bosons do not fare better. Nor is the shell a sheer product of the coordinate system. It does survive, for instance, in isotropic coordinates. It is also present in the Reissner-Nordstrom and Kerr cases and the usual process of formation of a black hole does not therefore appear viable in the model. Hints of a MA have also been found in one-loop quantum gravity (2015).

Recent works:

• Condensation phenomena in gravity, Modern Physics Letters A,2020.
• Gravitational qubits, Universe, 5, 123 (2019).
• Long range order in gravity, International Journal of Modern Physics D 28, 1950099 (2019).
• Structured objects in quantum gravity. The external field approximation, International Journal of Modern
  Physics D, 27, 1850104 (2018).
• Spin and maximal acceleration, Galaxies, 5, 103 (2017).
• Classical and quantum aspects of particle propagation in external gravitational fields, International
  Journal od Modern Physics D, 26, 1750137 (2017).
• Maximal acceleration and radiative processes, Modern Physics Letters A, 30, 1550166 (2015).
• Perspectives on gravity-induced radiative processes in astrophysics, Galaxies, 3, 72 (2015).
• Covariance and gauge invariance in relativistic theories of gravity, Modern Physics Letters A, 29, 1450075 (2014).
• Fermion antifermion mixing in gravitational fields, Modern Physics Letters A, 28, 1350071 (2013).
• Spin-rotation coupling in compound spin objects (with G. Lambiase), Physics Letters A, 377, 1021 (2013).
• Spin currents in non-inertial frames, Physics Letters A, 377, 960 (2013).
• The role of spin-rotation coupling in the non-exponential decay of hydrogen-like heavy ions (with G. Lambiase e G. Scarpetta), Annals of Physics, 332, 143 (2013).
• GSI Anomaly and Spin-Rotation Coupling (with G. Lambiase and G. Scarpetta), Physics Letters B, 718, 998 (2013).

List of Publications: (from the SLAC-SPIRES database)