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Maximum-likelihood methods are applied to the problem of absorption tomography. The reconstruction is done with the help of an iterative algorithm. We show how the statistics of the illuminating beam can be incorporated into the…

Data Analysis, Statistics and Probability · Physics 2009-11-07 J. Rehacek , Z. Hradil , M. Zawisky , W. Treimer , M. Strobl

The two main advantages of space-based observation of extreme energy ($\gtrsim5\times10^{19}$ eV) cosmic rays (EECRs) over ground based observatories are the increased field of view and the full-sky coverage with nearly uniform systematics…

High Energy Astrophysical Phenomena · Physics 2015-07-20 Peter B. Denton , Thomas J. Weiler

Measurements of anisotropies in the arrival directions of ultra-high-energy cosmic rays are crucial to pinpoint their sources, which are yet to be discovered. A dipolar anisotropy in right ascension above 8~EeV has been detected by the…

High Energy Astrophysical Phenomena · Physics 2025-07-28 Marta Bianciotto

We present an iterative method to reconstruct the linear-theory initial conditions from the late-time cosmological matter density field, with the intent of improving the recovery of the cosmic distance scale from the baryon acoustic…

Cosmology and Nongalactic Astrophysics · Physics 2018-11-05 Ryuichiro Hada , Daniel J. Eisenstein

Anisotropy in the arrival direction distribution of ultrahigh-energy cosmic rays (UHECRs) produced by powerful sources is numerically evaluated. We show that, taking account of the Galactic magnetic field, nondetection of significant…

High Energy Astrophysical Phenomena · Physics 2016-01-22 Hajime Takami , Kohta Murase , Charles D. Dermer

The relative sidereal variation in the arrival direction of primary cosmic ray nuclei of median energy 10 TeV was measured using downward, through-going muons detected with the Super-Kamiokande-I detector. The projection of the anisotropy…

Astrophysics · Physics 2019-08-14 Gene Guillian

We briefly review current theoretical and experimental status of Ultra-High Energy Cosmic Rays. We show that ``top-down'' mechanisms of UHE CR which involve heavy relic particle-like objects predict Galactic anisotropy of highest energy…

High Energy Physics - Phenomenology · Physics 2007-05-23 S. L. Dubovsky , P. G. Tinyakov

In our previous work, we have investigated Galactic cosmic ray (GCR) spectra and anisotropy from 100 GeV to PeV, under anisotropic propagation model with axisymmetric distributed galactic sources. Numerous observational evidence have…

High Energy Astrophysical Phenomena · Physics 2024-12-24 Aifeng Li , Zhaodong Lv , Wei Liu , Yiqing Guo , Fangheng Zhang

In this study, we investigated the anisotropy of diffusive Ultra-High Energy Cosmic Rays (UHECRs) by employing three cosmological models: two models from the $f(R, T)$ gravity theory and the other is the standard $\Lambda$CDM model. The…

High Energy Astrophysical Phenomena · Physics 2025-09-03 Swaraj Pratim Sarmah , Umananda Dev Goswami

We extend our maximum likelihood method for reconstructing the cluster-mass cross-correlation from cosmic microwave background (CMB) temperature anisotropies and develop new estimators that utilize six different quadratic combinations of…

Cosmology and Nongalactic Astrophysics · Physics 2014-11-21 Jaiyul Yoo , Matias Zaldarriaga , Lars Hernquist

A novel computational, non-iterative and noise-robust reconstruction method is introduced for the planar anisotropic inverse conductivity problem. The method is based on bypassing the unstable step of the reconstruction of the values of the…

Analysis of PDEs · Mathematics 2015-06-25 Sarah Jane Hamilton , Matti Lassas , Samuli Siltanen

Recently different experiments mention to have observed a large scale cosmic-ray anisotropy at TeV energies, e.g. Milagro, Tibet and Super-Kamiokande. For these energies the cosmic-rays are expected to be nearly isotropic. Any measurements…

Instrumentation and Methods for Astrophysics · Physics 2019-08-13 Salvatore Mangano

There is a growing set of observational data demonstrating that cosmic rays exhibit small-scale anisotropies (5-30 deg) with amplitude deviations lying between 0.01-0.1 percent that of the average cosmic ray flux. A broad range of models…

High Energy Astrophysical Phenomena · Physics 2021-01-20 Margot Fitz Axen , Julia Speicher , Aimee Hungerford , Chris L. Fryer

In the last decade, a number of experiments dealt with the problem of measuring the arrival direction distribution of cosmic rays, looking for information on the propagation mechanisms and the identification of their sources. Any deviation…

Instrumentation and Methods for Astrophysics · Physics 2015-06-12 Roberto Iuppa , Giuseppe Di Sciascio

Recent studies suggest that the anisotropy in cosmic-ray arrival directions can provide insight into local acceleration sites and propagation conditions. We developed a unified framework to interpret both the observed energy spectra and the…

High Energy Astrophysical Phenomena · Physics 2025-11-25 Bing-qiang Qiao , Wei Liu , Huirong Yan , Yi-qing Guo

Cosmography is a widely applied method to infer kinematics of the Universe at small cosmological scales while remaining agnostic about the theory of gravity at play. Usually cosmologists invoke the Friedmann-Lemaitre-Robertson-Walker (FLRW)…

Cosmology and Nongalactic Astrophysics · Physics 2025-11-25 Hayley J. Macpherson , Asta Heinesen

The COBE time ordered data (TOD) was reanalysed for anisotropies in the cosmic microwave background with a novel technique that is much simpler and more robust than used in the official analysis of the COBE TOD. The technique extends the…

Astrophysics · Physics 2007-07-18 Keith S Cover

The search of a clustering signal in the arrival directions of ultra-high-energy cosmic rays (UHECRs) is a standard method to assess the level of anisotropy of the data sets under investigation. Here, we first show how to quantify the…

High Energy Astrophysical Phenomena · Physics 2015-06-03 Guillaume Decerprit , Nicolas G. Busca , Etienne Parizot

We obtain the dipolar anisotropies in the arrival directions of ultra-high energy cosmic rays diffusing from nearby extragalactic sources. We discuss both the energy regime of spatial diffusion and the quasi-rectilinear one leading to just…

High Energy Astrophysical Phenomena · Physics 2014-06-11 Diego Harari , Silvia Mollerach , Esteban Roulet

Although the existence of cosmic rays with energies extending well above $10^{19}$ eV has been confirmed, their origin remains one of the most important questions in astro-particle physics today. Several source models have been proposed for…

Astrophysics · Physics 2011-04-19 B. T. Stokes , C. C. H. Jui , J. N. Matthews