Quantum gravity phenomenology at the dawn of the multi-messenger era -- A review

Abstract

The exploration of the universe has recently entered a new era thanks to the multi-messenger paradigm, characterized by a continuous increase in the quantity and quality of experimental data that is obtained by the detection of the various cosmic messengers (photons, neutrinos, cosmic rays and gravitational waves) from numerous origins. They give us information about their sources in the universe and the properties of the intergalactic medium. Moreover, multi-messenger astronomy opens up the possibility to search for phenomenological signatures of quantum gravity. On the one hand, the most energetic events allow us to test our physical theories at energy regimes which are not directly accessible in accelerators; on the other hand, tiny effects in the propagation of very high energy particles could be amplified by cosmological distances. After decades of merely theoretical investigations, the possibility of obtaining phenomenological indications of Planck-scale effects is a revolutionary step in the quest for a quantum theory of gravity, but it requires cooperation between different communities of physicists (both theoretical and experimental). This review, prepared within the COST Action CA18108 "Quantum gravity phenomenology in the multi-messenger approach", is aimed at promoting this cooperation by giving a state-of-the art account of the interdisciplinary expertise that is needed in the effective search of quantum gravity footprints in the production, propagation and detection of cosmic messengers.

Diffeomorphisms in momentum space: physical implications of different choices of momentum coordinates in the Galilean Snyder model

“…For example, if one considers an atomic-size oscillator with mω ∼ 10 21 kg/sec, they are of order 10 −14 . However, one cannot exclude that the parameter β has a much greater value [36,37] (see also discussion in [38] and references therein).…”

“…The Hilbert space of these operators is that of square integrable functions ψ(p, E) of p and E. With the choice (38) of operator ordering, the measure in this Hilbert space is…”

Noncommutativity, Sáez–Ballester Theory and Kinetic Inflation

“…Another category of alternative theories has arisen due to the incapability of the GR in predicting the effects of some phenomena at the Planck regime [19,20]. Among such theories, one can refer to some approaches to noncommutative (NC) gravity (see, [21][22][23][24][25], and references therein), which has roots in noncommutative geometry and noncommutative quantum field theories. As these frameworks are highly nonlinear, therefore, for investigating effects of noncommutativity on different aspects of the universe, noncommutative cosmology has been proposed, see, for instance [26][27][28].…”

Scalarized Black Holes in Teleparallel Gravity

“…with some specific potentials and coupling functions [19][20][21][22][23]. Other attempts to construct scalarised black hole solutions consider a scalar field coupled to modifications and extensions of GR, motivated by the search for dark matter, dark energy and quantum gravity (see [24][25][26][27][28][29] for reviews). These new theories of gravity contain additional terms to the Ricci scalar (or its reformulations in terms of torsion or non-metricity) in the gravitational action.…”