Leonardo Barcaroli

IceCube and GRB neutrinos propagating in quantum spacetime

Abstract Two recent publications have reported intriguing analyses, tentatively suggesting that some aspects of IceCube data might be manifestations of quantum-gravity-modified laws of propagation for neutrinos. We here propose a strategy of data analysis which has the advantage of being applicable to several alternative possibilities for the laws of propagation of neutrinos in a quantum spacetime. In all scenarios here of interest one should find a correlation between the energy of an observed neutrino and the difference between the time of observation of that neutrino and the trigger time of a GRB. We select accordingly some GRB-neutrino candidates among IceCube events, and our data analysis finds a rather strong such correlation. This sort of study naturally lends itself to the introduction of a “false alarm probability”, which for our analysis we estimate conservatively to be of 1 % . We therefore argue that our findings should motivate a vigorous program of investigation following the strategy here advocated.

Modeling Transverse Relative Locality

We investigate some aspects of relativistic classical theories with “relative locality”, in which pairs of events established to be coincident by nearby observers may be described as non-coincident by distant observers. While previous studies focused mainly on the case of longitudinal relative locality, where the effect occurs along the direction connecting the distant observer to the events, we here focus on transverse relative locality, in which instead the effect is found in a direction orthogonal to the one connecting the distant observer to the events. Our findings suggest that, at least for theories of free particles, transverse relative locality is as significant as longitudinal relative locality both conceptually and quantitatively. And we observe that “dual gravity lensing” can be viewed as one of two components of transverse relative locality. We also speculate about a type of spacetime noncommutativity for which transverse relative locality could be particularly significant.

Planck-scale-modified dispersion relations in homogeneous and isotropic spacetimes

The covariant understanding of dispersion relations as level sets of Hamilton functions on phase space enables us to derive the most general dispersion relation compatible with homogeneous and isotropic spacetimes. We use this concept to present a Planck-scale deformation of the Hamiltonian of a particle in Friedman-Lemaitre-Robertson-Walker (FLRW) geometry that is locally identical to the κ-Poincare dispersion relation, in the same way as the dispersion relation of point particles in general relativity is locally identical to the one valid in special relativity. Studying the motion of particles subject to such a Hamiltonian, we derive the redshift and lateshift as observable consequences of the Planck-scale deformed FLRW universe.

Planck-Scale Dual-Curvature Lensing and Spacetime Noncommutativity

It was recently realized that Planck-scale momentum-space curvature, which is expected in some approaches to the quantum-gravity problem, can produce dual-curvature lensing, a feature which mainly affects the direction of observation of particles emitted by very distant sources. Several gray areas remain in our understanding of dual-curvature lensing, including the possibility that it might be just a coordinate artifact and the possibility that it might be in some sense a by-product of the better studied dual-curvature redshift. We stress that data reported by the IceCube neutrino telescope should motivate a more vigorous effort of investigation of dual-curvature lensing, and we observe that studies of the recently proposed “ -Minkowski noncommutative spacetime” could be valuable from this perspective. Through a dedicated -Minkowski analysis, we show that dual-curvature lensing is not merely a coordinate artifact and that it can be present even in theories without dual-curvature redshift.

Longitudinal and transverse relativity of spacetime locality in Planck-scale-deformed phase spaces

We summarize some of the results we obtained in arXiv:1006.2126 (Physical Review Letters 106, 071301), arXiv:1102.4637 (Physics Letters B 700, 150-156) and in arXiv:1107.3334, giving complementary characterizations of the relativity of spacetime locality that affects certain Planck-scale-deformed phase-space constructions.

Quantum gravity phenomenology and metric formalism

In this proceedings for the MG14 conference, we discuss the construction of a phenomenology of Planck-scale effects in curved spacetimes, underline a few open issues and describe some perspectives for the future of this research line.

Hamilton geometry: Phase space geometry from modified dispersion relations

Leonardo Barcaroli,1, ∗ Lukas K. Brunkhorst,2, † Giulia Gubitosi,3, ‡ Niccoló Loret,1, § and Christian Pfeifer4, 2, ¶ Dipartimento di Fisica, Università ”La Sapienza” and Sez. Roma1 INFN, P.le A. Moro 2, 00185 Roma, Italy Center of Applied Space Technology and Microgravity (ZARM), University of Bremen, Am Fallturm, 28359 Bremen, Germany Theoretical Physics, Blackett Laboratory, Imperial College, London SW7 2AZ, United Kingdom. Institute for Theoretical Physics, Universität Hannover, Appelstrasse 2, 30167 Hannover, Germany

RAINBOW METRIC FORMALISM AND RELATIVE LOCALITY

This proceeding is based on a talk prepared for the XIII Marcell Grossmann meeting. We summarise some results of work in progress in collaboration with Giovanni Amelino-Camelia about momentum dependent (Rainbow) metrics in a Relative Locality framework and we show that this formalism is equivalent to the Hamiltonian formalization of Relative Locality obtained in arXiv:1102.4637.