This is the first Annual Conference organized by COST Action CA18108 (https://qg-mm.unizar.es/), an initiative funded by the COST Association (https://www.cost.eu/), aiming to enable researchers from different communities of quantum gravity theorists and phenomenologists and gamma-ray, neutrino, cosmic-ray and gravitational-wave experimentalists to learn about each other's work and cooperate on the goal of developing new strategies for testing candidate quantum gravity theories using multi-messenger high-energy astrophysical observations. The conference will cover a range of topics whose knowledge is required for properly interpreting astroparticle and gravitational-wave data, including cosmology, proposed quantum gravity frameworks, the physics of high-energy sources, hadronic interactions in air showers, and atmospheric monitoring for ground-based telescopes, and is open to both COST Action participants and outsiders.
Registration deadline: 24th February 2020
Deadline for submission of abstracts: 15th February 2020
Participation for COST Action participants from COST Member Countries and Near Neighbour countries can be funded by COST. A first round of COST invitations will be sent around mid-January
The meeting will be held at the Edificio Mecenas located in the Faculty of Science of the University of Granada (Campus Fuentenueva)
The registration desk will open on Tuesday March 10th, at the Amphitheater of Edificio Mecenas
On January 14, 2019, the MAGIC telescopes detected GRB 190114C at teraelectronvolt energies, recording the most energetic photons ever observed from a gamma-ray burst. Using this unique observation, we probe energy dependence of the speed of light in vacuo as predicted by several quantum-gravity models. Based on a set of well-justified assumptions on the possible intrinsic spectral and temporal evolution, we obtain competitive lower limits on the quadratic leading order modification of the speed of light. This is the first Lorentz invariance violation (LIV) test ever performed on a gamma-ray burst signal at TeV energies and will serve as a stepping stone to future studies. The results will be put into context of the most stringent bounds on LIV obtained using gamma rays.
The IceCube Neutrino Observatory at the South Pole is the world's largest neutrino telescope. It instruments a kilometer cube of ice with more than 5000 optical sensors that detect the Cherenkov light emitted by secondary particles produced in neutrino-nucleon interactions in the ice. Covering a wide range of neutrino energies, from a few of GeV to PeV, its physics program is extremely rich, spanning from high-energy astrophysics to dark matter searches, neutrino oscillations or tests of fundamental laws. In this talk we review recent IceCube results using the large statistics, high-energy atmospheric neutrino sample accumulated by IceCube to search for anomalous neutrino oscillation patterns as a signal of Lorentz invariance violation.
Noncommutative models offer a way to incorporate many of the expected features of quantum gravity in the language of Quantum Field Theory. Inspired by astrophysical and cosmological experimental data, we will try to build a noncommutative theory on de Sitter space. We will discuss the general problems that arise in building both the commutative and noncommutative versions, and discuss some of their features.
I will present a new method for extracting information from UHECR arrival directions, which could shed some new light on the physics of UHECR propagation and origin, as well as hopefully be applicable to using UHECRs as probes of Quantum Gravity effects.
Neutrino oscillation is a quantum phenomenon arising from the interference between mass eigenstates. These oscillations are observable over long distances of thousands of kilometres. It has been hypothesised that quantum gravity effects may act like a thermal bath leading to decoherence in quantum systems. Due to their long coherence lengths, neutrinos may be a powerful tool to probe these quantum gravity effects. In this talk, I will give a brief overview of searches for environmental decoherence in neutrino experiments.
Cosmic strings are one-dimensional topological defects, which arise naturally in field theories, as well as in scenarios of the early Universe based on superstring theory. One promising strategy to test their existence is to search for their gravitational wave (GW) emission. In particular, strong GW bursts are generated from non-smooth structures such as cusps and kinks, and overlapped GWs form a stochastic GW background. In my talk, I will discuss the possibilities of detecting cosmic string signatures by future gravitational wave experiments.
Gravitational lensing of very high energy photons has recently been observed in the JVAS B0218+357 strong lensing system. This observation opens the possibility of performing a test of gravity at high energy by comparing the difference in propagation time of high energy photons over different travel paths. The time delay is computed in the framework of a LIV (Lorentz Invariance Violation) extension of the equations of motion of photons in the field of a massive object. However, the method obtained can be transposed to other models of gravity at high energy. The potential for constraining high energy gravity with future observations of JVAS B0218+357 is discussed. The bounds on the LIV energy scale will not be competitive with other astrophysical bounds such as those coming from AGN and GRB flares. However, these bounds are free of any assumption on the emission process.
We consider the cosmological application of a (variant of) relatively newly proposed model \cite{1609.06915} unifying inflation, dark energy, dark matter, and the Higgs mechanism. The model was originally defined using additional non-Riemannian measures but it can be reformulated into effective quintessential model unifying inflation, dark energy and dark matter. Here we demonstrate numerically that it is capable of describing the entire Universe evolution in a seamless way, but this requires some revision of the model setup. The main reason is that there is a strong effective friction in the model, a feature which has been neglected in the pioneer work. This improves the model potential for proper description of the Universe evolution, because the friction ensures a finite time inflation with dynamically maintained low-value slow-roll parameters in the realistic scenarios. In addition, the model predicts the existence of a constant scalar field in late Universe.
We show how matter fields of arbitrary spin, when coupled to a broad class of metric-affine gravity theories (Ricci-Based Gravities), develop non-trivial effective interactions that can be treated perturbatively only below a characteristic high-energy scale Λ_Q, which characterizes when non-metricity-related effects ecome non-perturbative. We then set stringent constraints to Λ_Q by using data from particle-scattering experiments.
The Effective Field Theory (EFT) approach turned useful for the description of cosmological perturbations in modified gravity. A similar EFT approach for spherically symmetric, static black holes could provide a new insight into perturbations of beyond Horndeski scalar-tensor black holes. I will present an EFT action depending on a set of scalars cooked up from the metric and embedding variables of a novel 2+1+1 decomposition. The first order variation of the action generates four equations of motion, which for simplest General Relativistic case reproduce the Schwarzschild solution, and in more generic cases represent the equation of the background in unconventional variables. Second order variation leads to the evolution of perturbation both for the even and odd sectors. I will present a related unambiguous gauge fixing, which resembles most closely the Regge–Wheeler gauge of general relativity.
We disprove the widespread belief that higher order curvature theories of gravity in the metricaffine formalism are generally ghost-free. This is clarified by considering a sub-class of theories constructed only with the Ricci tensor and showing that the non-projectively invariant sector propagates ghost-like degrees of freedom. We also explain how these pathologies can be avoided either by imposing a projective symmetry or additional constraints in the gravity sector. Our results put forward that higher order curvature gravity theories generally remain pathological in the metricaffine (and hybrid) formalisms and highlight the key importance of the projective symmetry and/or additional constraints for their physical viability and, by extension, of general metric-affine theories.
In General Relativity (GR) the deflection of light modifies the number and position of images, generates Einstein rings and changes the magnification of images. I review how these weak lensing phenomena are affected by deviations from GR through a number of examples of spherically symmetric lenses in modified gravitational theories. In particular I emphasize that the magnification ratio (flux ratio, brightness ratio) of the images plotted as a function of the image separation yields different powerlaw relations in various theories. These might be the smoking gun for detecting the underlying black hole structure with precision observations, provided they are not blurred by environmental noise. In strong gravitational lensing the eventual detection of secondary images will place additional constraints on the parameters characterising the modifications from GR.
The κ-Poincaré model is a Hopf algebra-based deformation of special relativity featuring a modified dispersion relation, modified momentum conservation law, and relative locality effects. Such a model might emerge in a semi-classical limit of quantum gravity, the Plank mass acting as deformation parameter that characterizes the departure from special relativity and Poincare invariance. Until recently, the covariance of the κ-Poincare model was understood only partly. Here we present our result that the Hopf algebra structure can be used to lift all symmetry transformations to the multi-particle phase spaces in a non-trivial way, leading to a manifestly covariant theory that describes arbitrarily many interacting particles.
We present a way to derive a relativistic deformation of the kinematics of special relativity from the geometry of a maximally symmetric curved momentum space, and compare this construction, based on the algebra of isometries of the metric in momentum space, with previous attempts of connecting a deformed kinematics with a geometry in momentum space.
We calculate the transition radiation process ν→νγ at an interface of two media or at an edge of magnetic field. The neutrinos are taken to be with only standard-model couplings. The medium or magnetic field fulfills the dual purpose of inducing an effective neutrino-photon vertex and of modifying the photon dispersion relation. The neutrino mass is ignored due to its negligible contribution.
During the last decade, teleparallel theories of gravity have received growing interest as possible contender theories to resolve open questions in cosmology, as well as to provide a formulation of gravity theory which has more similarities with other field theories. An important question arising from these studies is the viability of such theories on smaller scales, such as the solar system, and the possibility to derive constraints from experiments. Such constraints are commonly obtained in a post-Newtonian limit. In my talk I show how to derive the post-Newtonian limit of a number of teleparallel theories which are relevant in cosmology, including the well-known f(T) and scalar-torsion models, and discuss their viability.
We discuss tests of Lorentz invariance, CPT symmetries and quantum gravity from LHAASO experiment in Sichuan province, China. LHAASO would provide new data on 50GeV-100PeV energy window in both gamma rays and charged cosmic rays. This offers a new exciting possibility for searching new physics in Very High Energy Cosmic Rays, from Chinese community.
Lorentz Invariance (LI) is nowadays at the root of our understanding of nature. Even if there is no definitive evidence to sustain departures from LI, there are consistent points indicating that Lorentz Invariance Violation (LIV) can be a consequence of quantum gravity. In this talk we will focus our attention on a new theoretical model HMSR (Homogeneously Modified Special Relativity), developed by the Milano research group (Eur.Phys.J. C79 (2019) no.9, 808), that attempts to reconcile these different approaches to LIV studies. The new model is characterized by its peculiar geometrical approach that allows the preservation of the isotropy with respect to rotations and boosts. This model indeed introduces a pseudo-Finsler geometric structure of momentum space via kinematical modifications in the dispersion relations. Every massive particle is supposed to generate its own personal space-time and has its own metric, with a personal maximum attainable velocity. All the physical quantities are therefore generalized, acquiring an explicit dependence on the momentum. Moreover every particle lives in a modified curved personal space-time, therefore it is necessary to introduce a new mathematical formalism to conduct computations between physical quantities related to different interacting particles. It is possible to construct a generalized tetrad that presents an explicit dependence on the particle momentum. The elements of the tetrad can be used as projectors from the local curved space to a common support Minkowski space-time. The possibility to construct a modified form of the Lorentz group is an original feature of this model and this means that HMSR preserves covariance even if in an amended formulation. Moreover the curved momentum space introduces a deformation of the composition rule of momenta, as in DSR theories. Finally HMSR introduces a Standard Model extension that preserves isotropy, is CPT even and presents possible interesting phenomenological applications. These applications range from ultra high energy cosmic rays propagation and GZK cut-off (JHEAp 18 (2018) 5-14) to neutrino oscillations (Eur.Phys.J. C78 (2018) no.8, 667).
This talk will review what we know (and we do not know)
about the sources and mechanisms that generate very high energy particles in the Galaxy and in the Universe. These sources can be studied with a multi-messenger (cosmic rays, gamma rays, neutrinos and gravitational waves) observations.
Recent studies have given very important information, but many fundamental question remain open.
Lorentz Invariance Violation introduced as a generic modification to particle dispersion relations is used to study high energy cosmic ray attenuation processes. A complete analysis of the effects of LIV on the propagation of cosmic rays, however, implies a more accurate knowledge of the sources. An other issue is the choice of the models of source distribution. All these topics involve a large number of parameters. For this reason we studied the effects of LIV on the extensive air showers. To this aim, the measurements on primary composition and number of muons in UHECRs published by the Pierre Auger Observatory have been used. After having modified the shower development in the atmosphere introducing LIV effects, we have simulated a shower library. Finally, the simulation products and therefore the shower observables in presence of LIV comparing them to the Pierre Auger results have been analyzed.
In this talk I address the possibility to measure CPT and Lorentz violation at the Deep Underground Neutrino Experiment. Models of quantum gravity which are non-local can induce Planck suppressed CPT violation, possibly detectable at neutrino experiments. In the first part of the talk I address generic CPT violation, assuming different oscillation patterns for neutrinos and antineutrinos at DUNE and discuss the DUNE potential to observe this effect. In the second part I discuss the DUNE potential to observe effects from Lorentz violating operators turning to one model specific case, namely operators from the so called Standard Model Extension.
Gravitational wave observations have given us a new observational window on the universe. We are now able to observe signals from highly relativistic collisions of black holes and neutron stars. These observations can be used to test Einstein’s theory of gravity and search for new physics, including possibly hints towards quantum gravity. In this overview talk I will discuss some of the observational tests that have been performed to date, explain about the assumptions that go into these tests and give an idea of what the future holds for this rapidly developing field.
We propose to deploy limits that arise from different tests of the Pauli Exclusion Principle in order: i) to provide theories of quantum gravity with an experimental guidance; ii) to distinguish among the plethora of possible models the ones that are already ruled out by current data; iii) to direct future attempts to be in accordance with experimental constraints. We firstly review experimental bounds on nuclear processes forbidden by the Pauli Exclusion Principle, which have been derived by several experimental collaborations making use of different detector materials. Distinct features of the experimental devices entail sensitivities on the constraints hitherto achieved that may differ one another by several orders of magnitude. We show that with choices of these limits, renown examples of flat noncommutative space-time instantiations of quantum gravity can be heavily constrained, and eventually ruled out. We devote particular attention to the analysis of the κ-Minkowski and θ-Minkowski noncommutative spacetimes. These are deeply connected to some scenarios in string theory, loop quantum gravity and noncommutative geometry. We emphasize that the severe constraints on these quantum spacetimes, although cannot rule out theories of top-down quantum gravity to whom are connected in various way, provide a powerful limitations of those models that it will make sense to focus on in the future.
Models of deformed Poincaré symmetries based on group valued momenta have long been studied as effective modifications of relativistic kinematics possibly capturing quantum gravity effects. In this contribution we show how they naturally lead to a generalized quantum time evolution of the type proposed to model fundamental decoherence for quantum systems in the presence of an evaporating black hole. The same structures which determine such generalized evolution also lead to a modification of the action of discrete symmetries and of the CPT operator. These features can in be used to put phenomenological constraints on these “effective” models of Planck scale physics.
In this talk I will describe ongoing efforts to shed light on still-unanswered questions in fundamental physics using cosmological observations. I will explain how we can use measurements of the Supernovae data, Baryon Acoustic Oscillations, Cosmic Microwave Background, Gamma Ray Burst and the large-scale structure of the universe to reconstruct the detailed physics of the dark universe. Also, I will address this inverse-problem reconstruction from a Bayesian and Machine Learning perspectives.
I will introduce the concept of Born geometry that underlies covariant relative locality and general quantum non-locality, consistent with causality. I will then discuss a realization of Born geometry in metastring theory, viewed as a theory of quantum gravity, and show how Born geometry is represented in the zero mode (metaparticle) sector. Finally, I will present a new picture of dark matter and dark energy in this formulation of quantum gravity. I will also discuss the phenomenology of the minimal length in this framework.
Various theoretical and phenomenological studies plan to test the validity of Lorentz invariance, one of the grounding symmetries of relativity, and to look for possible signals of Lorentz Invariance Violation (LIV). In this talk we will focus our attention on the LIV impact on high energy neutrino phenomenology, starting from the modifications of dispersion relations and the consequent modified flavor oscillation probabilities. We will refer in particular on a theoretical model, developed by the Milano research group (Eur.Phys.J. C79 (2019) no.9, 808), characterized by a geometrical approach that preserves a metric structure for the theory and enables to build a LIV extension of the Standard Model, preserving both CPT and full space-time isotropy. We will discuss the modifications of the oscillation probability, that we studied in Eur.Phys.J. C78 (2018) no.8, 667, and the possibile interesting phenomenological applications. These applications range from the study of high energy neutrinos with neutrino telescopes and the search of very high energy neutrinos emitted by cosmological sources, to the analyses of high energy atmospheric neutrinos at JUNO experiment and of artificial beams at LBL accelerator experiments.
The standard cosmological model has been established and its parameters are now measured with unprecedented precision. This model successfully describes observations from widely different epochs of the Universe, from primordial nucleosynthesis all the way to the present day. However, there is a big difference between modelling and understanding. The next decade will see the era of large surveys; a large coordinated effort of the scientific community in the field is on-going to map the cosmos producing an exponentially growing amount of data. In the past, whenever there was a major advance in observing the cosmos, cosmology has provided us with “surprises”, and some had profound implications for physics. I will discuss what the next “surprise” from cosmology may be and its possible implications.
We present the results of a new analysis of the data of the MiniBooNE experiment taking into account the additional background of photons from Δ+/0 decay. We show that the new background can explain part of the MiniBooNE low-energy excess and the statistical significance of the MiniBooNE indication in favor of short-baseline neutrino oscillation decreases from 5.1σ to 3.3σ.
After the detection of two new pulsars in the past year, the number of the total pulsars observed with the Cherenkov telescopes increased to four. Pulsars are one of the most popular targets both for the current Cherenkov telescopes and CTA. In addition to AGNs and GRBs, pulsars are another important source class for LIV tests because of their fast and periodical flux variabilities. The aim of this study is to have a general idea of the probable LIV results with focusing only on hypothetical light curves of different categories of pulsars.
We study the implications of a change of coordinatization of momentum space for theories with curved momentum space. We of course find that after a passive diffeomorphism the theory yields the same physical predictions, as one would expect considering that a simple reparametrization should not change physics. However, it appears that general momentum-space covariance (invariance under active diffeomorphisms of momentum space) cannot be enforced, and within a given set of prescriptions on how the theory should encode momentum-space metric and affine connection the physical predictions do depend on the momentum space background. These conclusions find support in some general arguments and in our quantitative analysis of a much-studied toy model with maximally-symmetric (curved) momentum space.
We investigated neutrino oscillations with altered dispersion re-lations in the presence of sterile neutrinos. Modified dispersion relations represent an agnostic way to parameterize new physics. Models of this type have been suggested to explain global neutrino oscillation data, including deviations from the standard three-neutrino paradigm as observed by a few experiments. We show that, unfortunately, in this type of models new tensions arise turning them incompatible with global data.
We review various theoretical models and scenarios based on torsional modifications of gravity. Then we present the recent possibility of using multi-messenger astronomy, namely data from gravitational waves observations alongside their electromagnetic counterparts, in order to investigate torsional modified gravity and test general relativity.
I discuss briefly how Planck-scale effects can modify particle kinematics in Friedmann-Robertson-Walker spacetime, both in the LIV (Lorentz Invariance Violation) and in the DSR (Deformed Special Relativity) scenarios. This allows to derive, for some models, a phenomenological formula for in-vacuo dispersion that can be used to constrain the Quantum Gravity scale with astrophysical observations. In particular I review some recent analyses for ultra-high energetic neutrinos detected by the IceCube collaboration.
We consider processes crucial for propagation and detection of very-high-energy photons in Lorentz-violating QED: photon decay to an electron-positron pair, photon splitting to three photons, and modified Bethe-Heitler process (pair production in Coulomb field), which is crucial for atmosphere shower formation. Taking into account modified cross-sections for these processes, we show that very-high-energy part of observed photon flux from a source gets reduced. We use the observational data of the Crab Nebula photon spectrum in energy range beyond 100 TeV obtained by the collaborations Tibet and HAWC to set two-sided constraints on Quantum Gravity energy scale for photons.
Mirar a lo lejos hacia el espacio es como mirar hacia atrás en el tiempo. Gracias a este truco y a potentes telescopios, hemos capturado la luz y tomado fotos del universo contemporáneo y del universo joven… hasta el universo niño.
Así, hemos aprendido mucho sobre el cosmos que nos rodea, su origen y evolución, y sobre las leyes físicas que lo rigen.
El modelo cosmológico estándar ha sido establecido y sus parámetros se miden con una precisión sin precedentes. Sin embargo, hay una gran diferencia entre el modelado y la comprensión. Un gran esfuerzo coordinado de la comunidad científica para “fotografiar” el cosmos está produciendo una cantidad de datos creciente de manera exponencial, lo que nos proporcionará nuevos desafíos y nuevas oportunidades.
Understanding gravity in the framework of quantum mechanics is one of the great challenges in modern physics. Along this line, a prime question is to find whether gravity is a quantum entity subject to the rules of quantum mechanics. It is fair to say that there are no feasible ideas yet to test the quantum coherent behaviour of gravity directly in a laboratory experiment. Here, we introduce an idea for such a test based on the principle that two objects cannot be entangled without a quantum mediator. We show that despite the weakness of gravity, the phase evolution induced by the gravitational interaction of two micron size test masses in adjacent matter-wave interferometers can detectably entangle them even when they are placed far apart enough to keep Casimir-Polder forces at bay. We provide a prescription for witnessing this entanglement, which certifies gravity as a quantum coherent mediator, through simple correlation measurements between two spins: one embedded in each test mass. Fundamentally, the above entanglement is shown to certify the presence of non-zero off-diagonal terms in the coherent state basis of the gravitational field modes.
In scenarios with extra dimensions the gravitational interaction may become strong at TeV energies. This could modify the nu-N cross section and imply distinct signals at neutrino telescopes. In particular, cosmogenic neutrinos of E\approx 10^9 GeV could experience frequent interactions with matter where they lose a very small fraction of their energy. We define a consistent model of strong gravity at the TeV scale with just one extra dimension and a first Kaluza-Klein excitation of the graviton of mass around 1 GeV. We describe the collisions at transplanckian energies (multigraviton exchange, graviton emission and black hole formation) as well as the possible signature of these processes at km^3 telescopes and their impact in cosmogenic neutrino searches [arXiv:2001.05195]
Quantum groups can be used to construct noncommutative spacetimes with nonvanishing cosmological constant by using the latter as an explicit parameter, whose vanishing limit leads to the flat Poincaré/Minkowskian models. In particular, the kappa-deformation of the (Anti)-de Sitter group is reviewed, and its associated non commutative (A)dS spacetimes and curved momentum spaces are explicitly presented. The non-trivial interplay between the cosmological constant and the Planck scale parameter is analysed, and differences with respect to the kappa-Poincaré models are stressed (non commutativity of the space coordinates and curved momentum space with higher dimensionality).
The multi-messenger approach to the study of Active Galactic Nuclei (AGNs) is of primary importance in astrophysics for the interpretation of mechanisms and scenarios of the emission. Very recently the Astrophysics community gained a wider view of the Active Galactic Nuclei emission with the detection of other messengers such as neutrinos and gravitational waves. Now that, thanks to the advances in technology and sensibility of the detectors, the multi-messenger era of Astrophysics has begun, it is of primary importance to have models and phenomenological interpretations which can explain the observations. We present latest results from Multi-wavelength and multi-messenger studies and review the models widely used in the field.