Topical seminars


December 2nd, 2011

Sapienza Universita' di Roma, Dipartimento di Fisica

Aula Conversi


14:30 N. Mavromatos (King's College, London) Quantum gravity and entangled particle states [slides pdf, ppt]
Quantum Gravitational (QG) Fluctuations at microscopic (Planckian scales) may induce, depending on the model, interesting properties of the ``vacuum'', entailing non trivial optical properties (refractive index, possible birefringence etc), as a consequence of violation or modification of Lorentz symmetry, as well as decoherence of low energy matter in the QG background, leading in turn to modifications of the quantum mechanical (Einstein-Podolsky-Rosen) correlations of entangled particle states. The latter phenomenon is associated with an intrinsic breakdown of the generator of CPT symmetry (C=Charge, P=Parity, T=Time reversal) as a well-defined quantum mechanical operator, due to a theorem by R. Wald (strong form of CPT non invariance). The modifications of EPR correlators (termed omega-effect) are strongest in neutral Kaon systems, as opposed to B-systems, as a result of the existence of a specific CP violating decay channel in the former system. The talk will review such phenomena and the associated theoretical estimates, based on concrete models of QG foam (inspired from string theory, but not necessarily restricted to it), and discuss prospects for falsification in current and future facilities, such as upgrades of the DaPhiNE collider. The omega-effect, if realized in nature, is a ``smoking gun'' signature of this type of CPT Violation. However, as will be discussed in the talk, not all models of QG are characterised by such an effect.
15:20 coffee break
15:35 F. De Martini (Accademia Nazionale dei Lincei, Roma), E. Santamato (Universita' Federico II, Napoli) Quantum dynamics and Weyl’s conformal geometry: the Dirac’s equation and the mystery of "Quantum Nonlocality" [slides pdf, ppt]
A rigorous ab initio derivation of the 4-spinor Dirac’s equation for a single spinning particle is presented on the basis of a novel approach, the "Affine Quantum Mechanics" (AQM), which assumes that quantum phenomena originate from the interplay between the motion of a relativistic top and the non trivial Weyl’s background geometry acting on its configuration space. The theory, based on the Hamilton-Jacobi formulation is intrinsically nonlinear but is found to be linearized by an "anzatz" solution that can be straightforwardly interpreted as the ΄quantum wavefunction‘. In turn, this one can be interpreted as a gauge field of a conformal space. By the extension of the AQM theory to the case of two spins, the so far ΄mysterious‘ process of ΄quantum nonlocality‘ which is at the basis of the EPR Paradox, the Einstein’s "Spooky action - at - a - distance", and is implied by the violation of the Bell’s inequalities, appears to be finally understood.
16:25 G. Amelino-Camelia (Sapienza, Roma) Quantum space-time, relative locality and entanglement  [slides pdf]
Several partial results that have been reported in the quantum-gravity literature over the last decade have been recently interpreted by Freidel, Kowalski, Smolin and myself in terms of properties of the geometry of momentum space. This establishes several valuable connections between otherwise only vaguely related notions, such as the ones of Planck-scale modifications of the on-shell relation, Planck-scale modifications of the laws of conservation of momentum, and Planck-scale relativity of spacetime locality. Some aspects of "quantum-gravity phenomenology" may now be viewed as attempts to establish experimentally the geometry of momentum space, and this new geometric perspective is proving to be rather powerful for seeking new phenomenological avenues, including some preliminary indications relevant for entangled states
17:15 Discussion Cocktail

    INFN Sezione di Roma - Piano Formativo 2011