The study of ultra-high energy cosmic rays (UHECRs) has recently experienced a jump in statistics as well as improved instrumentation. This has allowed a better sensitivity in searching for anisotropies in the arrival directions of cosmic rays. In this written version of the presentation given by the inter-collaborative “Anisotropy Working Group” at the International Symposium on Future Directions in UHECR physics at CERN in February 2012, we report on the current status for anisotropy searches in the arrival directions of UHECRs.

Presentation (obstetrics)

10.1051/epjconf/20135301008

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Citations (8)

Quasilocalized gravity without asymptotic flatness

Physical review. D. Particles, fields, gravitation, and cosmology/Physical review. D, Particles, fields, gravitation, and cosmology (2004)

Mikhail Shaposhnikov P. Tinyakov K. Zuleta

We present a toy model of a generic five-dimensional warped geometry in which the 4D graviton is not fully localized on the brane. Studying the tensor sector of metric perturbation around this background, we find that its contribution to the effective gravitational potential is of 4D type ($1/r$) at the intermediate scales and that at the large scales it becomes $1/{r}^{1+\ensuremath{\alpha}}$, $0<\ensuremath{\alpha}\ensuremath{\le}1$ being a function of the parameters of the model ($\ensuremath{\alpha}=1$ corresponds to the asymptotically flat geometry). Large-distance behavior of the potential is therefore not necessarily five-dimensional. Our analysis applies also to the case of quasilocalized massless particles other than graviton.

Flatness (cosmology)

10.1103/physrevd.70.104019

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Occupy magnetogenesis

arXiv (Cornell University) (2013)

P. Tinyakov F. Urban

The occupation number of a field is a sound discriminator between classical and quantum regimes. In this pamphlet we give an overview of what we can learn about inflationary magnetogenesis just by looking at the occupation numbers of the classical magnetic fields observed today, and those of the quantum electromagnetic field during inflation. The sole occupation number behaviour dictates that for a pure Maxwell theory in de Sitter space it appears impossible to match the two epochs.

10.48550/arxiv.1309.2270

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Black Holes and the Dark Sector

Fábio Capela P. Tinyakov

This thesis is divided in two parts: the first part is dedicated to the study of black hole solutions in a theory of modified gravity, called massive gravity, that may be able to explain the actual stage of accelerated expansion of the Universe, while in the second part we focus on constraining primordial black holes as dark matter candidates.In particular, during the first part we study the thermodynamical properties of specific black hole solutions in massive gravity. We conclude that such black hole solutions do not follow the second and third of law of thermodynamics, which may signal a problem in the model. For instance, a naked singularity may be created as a result of the evolution of a singularity-free state.In the second part, we constrain primordial black holes as dark matter candidates. To do that, we consider the effect of primordial black holes when they interact with compact objects, such as neutron stars and white dwarfs. The idea is as follows: if a primordial black hole is captured by a compact object, then the accretion of the neutron star or white dwarf’s material into the hole is so fast that the black hole destroys the star in a very short time. Therefore, observations of long-lived compact objects impose constraints on the fraction of primordial black holes. Considering both direct capture and capture through star formation of primordial black holes by compact objects, we are able to rule out primordial black holes as the main component of dark matter under certain assumptions that are discussed.To better understand the relevance of these subjects in modern cosmology, we begin the thesis by introducing the standard model of cosmology and its problems. We give particular emphasis to modifications of gravity, such as massive gravity, and black holes in our discussion of the dark sector of the Universe./Cette these est divisee en deux parties : la premiere partie est consacree a l’etude de certaines solutions de trous noirs dans une theorie modifiee de la gravite, appelee la gravite massive, qui peut etre en mesure d’expliquer l’expansion acceleree de l’Univers; tandis que dans la seconde partie, nous nous concentrons sur des contraintes sur les trous noirs primordiaux comme candidats de matiere noire.En particulier, au cours de la premiere partie, nous etudions les proprietes thermodynamiques de solutions specifiques de trous noirs en gravite massive. Nous en concluons que ces solutions de trous noirs ne suivent ni la deuxieme, ni la troisieme loi de la thermodynamique, ce qui semble indiquer une inconsistance dans le modele. Par exemple, une singularite nue peut etre creee a la suite de l’evolution d’un etat sans aucune singularite.Dans la deuxieme partie, nous mettons des contraintes sur les trous noirs primordiaux en tant que candidats de matiere noire. Pour ce faire, nous considerons l’effet des trous noirs primordiaux lorsqu’ils interagissent avec des objets compacts, tels que les etoiles a neutrons et les naines blanches. L’idee est comme suit : si un trou noir primordial est capture par un objet compact, alors l’accretion du materiel constituant l’etoile a neutrons ou la naine blanche est si rapide que le trou noir detruit l’etoile en un temps tres court. Par consequent, les observations d’objets compacts imposent des contraintes sur la fraction de trous noirs primordiaux. Considerant a la fois la capture directe des trous noirs primordiaux par les objets compacts et la capture au travers de la formation stellaire, nous sommes en mesure d’exclure les trous noirs primordiaux comme la composante principale de matiere noire sous certaines hypotheses qui sont discutees.Pour mieux comprendre la pertinence de ces sujets dans la cosmologie moderne, nous commencons la these par l’introduction du modele standard de la cosmologie et de ses problemes. Nous donnons une importance particuliere aux modifications de la gravite, telles que la gravite massive, et aux trous noirs dans notre discussion sur le secteur sombre de l’Univers.

Primordial black hole

Black hole (networking)

Compact star

Black dwarf

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

arXiv (Cornell University) (2021)

Andrea Addazi J. Álvarez-Muñiz Rafael Alves Batista Giovanni Amelino-Camelia V. Antonelli

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 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.

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Search for a correlation between the UHECRs measured by the Pierre Auger Observatory and the Telescope Array and the neutrino candidate events from IceCube and ANTARES

EPJ Web of Conferences (2019)

J. Aublin A. Coleiro A. Kouchner I. Al Samarai Anastasia Maria Barbano

High-energy neutrinos are expected to be produced by the interaction of accelerated particles near the acceleration sites. For this reason, it is interesting to search for correlation in the arrival directions of ultra-high energy cosmic rays (UHECRs) and HE neutrinos. We present here the results of a search for correlations between UHECR events measured by the Pierre Auger Observatory and Telescope Array and high-energy neutrino candidate events from IceCube and ANTARES. We perform a cross-correlation analysis, where the angular separation between the arrival directions of UHECRs and neutrinos is scanned. When comparing the results with the expectations from a null hypothesis contemplating an isotropic distribution of neutrinos or of UHECR we obtain post-trial p-values of the order of $\sim 10^{-2}$.

Pierre Auger Observatory

10.1051/epjconf/201921003003

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Third Quantization of Gravity and the Cosmological Constant Problem

Springer eBooks (1991)

George Lavrelashvili V. A. Rubakov P. Tinyakov

Cosmological constant

Hawking

Constant (computer programming)

Cosmological constant problem

Quintessence

10.1007/978-1-4899-0620-5_9

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First High‐Speed Video Camera Observations of a Lightning Flash Associated With a Downward Terrestrial Gamma‐Ray Flash

Geophysical Research Letters (2023)

Rasha Abbasi Marcelo M. F. Saba John Belz P. R. Krehbiel W. Rison

Abstract In this paper, we present the first high‐speed video observation of a cloud‐to‐ground lightning flash and its associated downward‐directed Terrestrial Gamma‐ray Flash (TGF). The optical emission of the event was observed by a high‐speed video camera running at 40,000 frames per second in conjunction with the Telescope Array Surface Detector, Lightning Mapping Array, interferometer, electric‐field fast antenna, and the National Lightning Detection Network. The cloud‐to‐ground flash associated with the observed TGF was formed by a fast downward leader followed by a very intense return stroke peak current of −154 kA. The TGF occurred while the downward leader was below cloud base, and even when it was halfway in its propagation to ground. The suite of gamma‐ray and lightning instruments, timing resolution, and source proximity offer us detailed information and therefore a unique look at the TGF phenomena.

Lightning

Lightning detection

Upper-atmospheric lightning

10.1029/2023gl102958

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Citations (9)