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Lambiase G.,University of Salerno | Lambiase G.,National Institute of Nuclear Physics, Italy | Lambiase G.,International Institute for Advanced Scientific Studies | Sakellariadou M.,King's College London | And 2 more authors.
Journal of Cosmology and Astroparticle Physics | Year: 2013

Noncommutative spectral geometry offers a purely geometric explanation for the standard model of strong and electroweak interactions, including a geometric explanation for the origin of the Higgs field. Within this framework, the gravitational, the electroweak and the strong forces are all described as purely gravitational forces on a unified noncommutative space-time. In this study, we infer a constraint on one of the three free parameters of the model, namely the one characterising the coupling constants at unification, by linearising the field equations in the limit of weak gravitational fields generated by a rotating gravitational source, and by making use of recent experimental data. In particular, using data obtained by Gravity Probe B, we set a lower bound on the Weyl term appearing in the noncommutative spectral action, namely β10 -6m-1. This constraint becomes stronger once we use results from torsion balance experiments, leading to β104m -1. The latter is much stronger than any constraint imposed so far to curvature squared terms. © 2013 IOP Publishing Ltd and Sissa Medialab srl.


Bozza V.,University of Salerno | Bozza V.,National Institute of Nuclear Physics, Italy | Bozza V.,International Institute for Advanced Scientific Studies | Mancini L.,Max Planck Institute for Astronomy | Mancini L.,International Institute for Advanced Scientific Studies
Astrophysical Journal | Year: 2012

The massive black hole SgrA* at the Galactic center is surrounded by a cluster of stars orbiting around it. Light from these stars is bent by the gravitational field of the black hole, giving rise to several phenomena: astrometric displacement of the primary image, the creation of a secondary image that may shift the centroid of SgrA*, and magnification effects on both images. The soon-to-be second-generation Very Large Telescope Interferometer instrument GRAVITY will perform observations in the near-infrared of the Galactic center at unprecedented resolution, opening the possibility of observing such effects. Here we investigate the observability limits for GRAVITY of gravitational lensing effects on the S-stars in the parameter space 1[D LS, γ, K], where D LS is the distance between the lens and the source, γ is the alignment angle of the source, and K is the source's apparent magnitude in the K band. The easiest effect to observe in future years is the astrometric displacement of primary images. In particular, the shift of the star S17 from its Keplerian orbit will be detected as soon as GRAVITY becomes operative. For exceptional configurations, it will be possible to detect effects related to the spin of the black hole or post-Newtonian orders in the deflection. © 2012. The American Astronomical Society. All rights reserved.


Papini G.,University of Regina | Papini G.,International Institute for Advanced Scientific Studies
Modern Physics Letters A | Year: 2014

Any metric theory of gravity whose interaction with quantum particles is described by a covariant wave equation is equivalent to a vector theory that satisfies Maxwell-type equations identically. This result does not depend on any particular set of field equations for the metric tensor, but only on covariance. It is derived in the linear case, but can be extended to any order of approximation in the metric deviation. In this formulation of the interaction of gravity with matter, angular momentum and momentum are conserved locally. © 2014 World Scientific Publishing Company.


Papini G.,University of Regina | Papini G.,International Institute for Advanced Scientific Studies
Physics Letters, Section A: General, Atomic and Solid State Physics | Year: 2012

Berry phases mix states of positive and negative energy in the propagation of fermions and bosons in external gravitational and electromagnetic fields and generate Zitterbewegung oscillations. The results are valid in any reference frame and to any order of approximation in the metric deviation. © 2012 Elsevier B.V. All rights reserved.


Lambiase G.,University of Salerno | Lambiase G.,National Institute of Nuclear Physics, Italy | Lambiase G.,International Institute for Advanced Scientific Studies | Papini G.,International Institute for Advanced Scientific Studies | And 5 more authors.
Annals of Physics | Year: 2013

Recent experiments carried out at the storage ring of GSI in Darmstadt reveal an unexpected oscillation in the orbital electron capture and subsequent decay of hydrogen-like 140Pr58+, 142Pm60+ and 122I52+. The modulations have periods of 7.069(8) s, 7.10(22) s and 6.1 s respectively in the laboratory frame and are superimposed on the expected exponential decays.In this paper we propose a semiclassical model in which the observed modulations arise from the coupling of rotation to the spins of electron and nucleus. We show that the modulations are connected to quantum beats and to the effect of the Thomas precession on the spins of bound electron and nucleus, the magnetic moment precessions of electron and nucleus and their cyclotron frequencies. We also show that the spina-spin coupling of electron and nucleus, though dominant relative to the magnetic moment coupling of electron and nucleus with the storage ring magnetic field, does not contribute to the modulation because these terms average out during the time of flight of the ions, or cancel out. The model also predicts that the anomaly cannot be observed if the motion of the ions is rectilinear, or if the ions are stopped in a target (decay of neutral atoms in solid environments). It also supports the notion that no modulation occurs for the β+-decay branch. © 2013 Elsevier Inc.


Papini G.,University of Regina | Papini G.,International Institute for Advanced Scientific Studies
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2010

Kinematically forbidden processes may be allowed in the presence of external gravitational fields. These can be taken into account by introducing generalized particle momenta. The corresponding transition probabilities can then be calculated to all orders in the metric deviation from the field-free expressions by simply replacing the particle momenta with their generalized counterparts. The procedure applies to particles of any spin and to any gravitational fields. Transition probabilities, emission power, and spectra are, to leading order, linear in the metric deviation. It is also shown how a small dissipation term in the particle wave equations can trigger a strong backreaction that introduces resonances in the radiative process and deeply affects the resulting gravitational background. © 2010 The American Physical Society.


Lambiase G.,University of Salerno | Lambiase G.,National Institute of Nuclear Physics, Italy | Lambiase G.,International Institute for Advanced Scientific Studies | Papini G.,International Institute for Advanced Scientific Studies | And 5 more authors.
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2013

We propose a model in which a recently reported modulation in the decay of the hydrogenlike ions 140Pr58+, 142Pm60+ and 122I52+ arises from the coupling of rotation to the spin of electron and nucleus. The model shows that the spin-spin coupling of electron and nucleus does not contribute to the modulation and predicts that the anomaly cannot be observed if the motion of the ions is rectilinear, or if the ions are stopped in a target. It also supports the notion that the modulation frequency is proportional to the inverse of the atomic mass and that no modulation is expected for the β+-decay. The model predicts that for He-like ions the modulation is still present. © 2012 Elsevier B.V.


Papini G.,University of Regina | Papini G.,International Institute for Advanced Scientific Studies
Modern Physics Letters A | Year: 2013

Mixing of fermion and antifermion states occurs in gravitational interactions, leading to non-conservation of fermion number above temperatures determined by the particle masses. We study the evolution of a $(f, \bar{f})$-system and calculate the cross-sections for the reactions $f\rightleftharpoons\bar{f}$. Their values are identical in both directions. However, if $\bar{f}$ changes quickly into a lighter antiparticle, then the reaction symmetry is broken, resulting in an increased production of matter over antimatter. © 2013 World Scientific Publishing Company.


Lambiase G.,University of Salerno | Lambiase G.,National Institute of Nuclear Physics, Italy | Lambiase G.,International Institute for Advanced Scientific Studies | Papini G.,International Institute for Advanced Scientific Studies | And 2 more authors.
Physics Letters, Section A: General, Atomic and Solid State Physics | Year: 2013

We generalize spin-rotation coupling to compound spin systems. In the case of muons bound to nuclei in a storage ring the decay process acquires a modulation. Typical frequencies for Z/A∼1/2 are ∼3×106 Hz, a factor 10 higher than the modulation observed in g-2 experiments. © 2013 Elsevier B.V. All rights reserved.


Papini G.,University of Regina | Papini G.,International Institute for Advanced Scientific Studies
Physics Letters, Section A: General, Atomic and Solid State Physics | Year: 2013

The covariant Dirac equation and its solutions show that rotation and acceleration can be used to generate and control spin currents. © 2013 Elsevier B.V.

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