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The peculiar motion of the observer, if not accurately accounted for, is bound to induce a well-defined clustering signal in the distribution of galaxies. This signal is related to the Kaiser rocket effect. Here we examine the amplitude and form of this effect, both analytically and numerically, and discuss possible implications for the analysis and interpretation of forthcoming cosmological surveys. For an idealistic cosmic variance dominated full-sky survey with a Gaussian selection function peaked at $z\sim 1.5$ it is a $> 5\sigma$ effect and it can in principle bias very significantly the inference of cosmological parameters, especially for primordial non-Gaussianity. For forthcoming surveys, with realistic masks and selection functions, the Kaiser rocket is not a significant concern for cosmological parameter inference. However, it is a systematic effect whose origin, nature and imprint on galaxy maps are well known and thus should be subtracted or mitigated. We present several approaches to do so., Comment: Version matches the one accepted by JCAP

Searches for the anisotropy of the total electron and positron fluxes in high-energy galactic cosmic rays are performed. Data collected by the PAMELA magnetic spectrometer from June 2006, when it was launched into Earth’s orbit, to 2016 were used for the respective analysis. The main event selection and a determination of particle arrival directions were accomplished by means of a position-sensitive microstrip calorimeter. A neutron detector was used to suppress additionally the background of protons and nuclei. An analysis of information obtained over a nearly ten-year period of measurements made it possible to set upper limits on the amplitude of the dipole anisotropy of the total electron and positron fluxes for two energy ranges, between 25 and 100 GeV and between 100 GeV and 1 TeV. These results supplement data from other satellite-borne experiments, AMS-02 and Fermi.

An observer stationary with respect to comoving coordinates of the expanding universe should find the redshift distribution to be isotropic. However, a peculiar motion of the observer would introduce a dipole anisotropy in the observed redshift distribution. Conversely, a dipole anisotropy in observed redshift distribution could be exploited to infer our peculiar motion, or rather of our solar system. We determine here our peculiar velocity by studying the dipole anisotropy in the redshift distribution of a large sample of quasars. The magnitude of the peculiar velocity thus determined turns out to be $2350\pm280$ km s$^{-1}$, not only much larger than 370 km s$^{-1}$ determined from the dipole anisotropy in the Cosmic Microwave Background Radiation (CMBR), but also nearly in an opposite direction. Such large values for peculiar velocity have been found in a couple of radio surveys too, but with a direction along the CMBR dipole. Large genuine differences in the inferred motion, whether in magnitude or direction, are rather disconcerting since a solar peculiar velocity should not depend upon the method of its determination. Such discordant dipoles imply perhaps an anisotropic universe, violating the cosmological principle, a cornerstone of the modern cosmology., Comment: 5 pages, 3 figures, 2 tables, accepted in MNRAS

We test the anisotropy in the Finslerian cosmological model with the X-ray and ultraviolet (UV) fluxes of 808 quasars. The dipole amplitude is $A_D=0.302_{ -0.124}^{ +0.185}$ and the dipole direction points towards $(l, b) = ( 288.92_{~ -28.80^{\circ}}^{^{\circ}+23.74^{\circ}}, 6.10_{~ -16.40^{\circ}}^{^{\circ} +16.55^{\circ}} )$. We find that the dipole direction from the X-ray and UV fluxes of quasars is very close to the dipole direction given by the "Joint Light-curve Analysis" (JLA) compilation in the Finslerian cosmological model and the angular difference between the two dipole directions is only $10.44^{\circ}$. We also find the angular difference between the dipole direction from the 808 quasars in the Finslerian cosmological model and ones from the supernovae of type Ia (SNe Ia) samples in the dipole-modulated $\Lambda$CDM model is around $30^{\circ}$. Six gravitationally lensed quasars are considered to investigate the Hubble constant $H_0$ in the Finslerian cosmological model. We get a slightly smaller $H_0$ than the result given by the six gravitationally lensed quasars. Finally, we forecast the future constraints on the dipole parameters with the X-ray and UV fluxes of quasars. As the number of simulations increases, the precisions of the parameters related to anisotropy in the Finslerian cosmological model improve significantly. The X-ray and UV fluxes of quasars have a promising future as a probe of anisotropy in Finsler spacetime., Comment: 7 pages, 7 figures

When cosmic-ray arrival directions are observed in celestial coordinates, they appear to have a small anisotropy whose origin is still largely unknown. In addition to this celestial anisotropy, the Earth's revolution around the Sun produces a faint Compton-Getting dipole anisotropy with an excess oriented towards the direction of motion in solar coordinates. The relative rotation of the celestial and solar reference frames over a calendar year causes interference between the two sources of anisotropy. It is possible to characterize the resulting yearly modulations by studying the side-bands to the diurnal and sidereal frequencies in anti- and extended-sidereal time frames. This work provides a numerical simulation of the interference between anisotropies in sidereal and solar reference frames to predict the distributions in anti-sidereal and extended-sidereal frames.

A measurement of the cosmic ray anisotropy on the arrival directions of protons and light primary nuclei (helium, carbon and oxygen) has been performed in galactic coordinates by the Alpha Magnetic Spectrometer onboard the International Space Station. The analysis is based on the sample of events collected in the first 9 years of data taking. The results for the different particle species are consistent with isotropy and upper limits on the dipole amplitude ($\delta$) have been computed. In particular, an upper limit of $\delta < 0.32\%$ at the $95\%$ C.I. is established for galactic protons above 200 GV. On the other hand, limits on the dipole anisotropy of galactic helium, carbon and oxygen above 200 GV are quoted: $\delta < 0.32\%$, $\delta < 1.62\%$ and $\delta

Many observations in recent times have shown evidence against the standard assumption of isotropy in the Big Bang model. Introducing a superhorizon scalar metric perturbation has been able to explain some of these anomalies. In this work, we probe the net velocity arising due to the perturbation. We find that this extra component does not contribute to the CMB dipole amplitude while it does contribute to the dipole in large scale structures. Thus, within this model's framework, our velocity with respect to the large scale structure is not the same as that extracted from the CMB dipole, assuming it to be of purely kinematic origin. Taking this extra velocity component into account, we study the superhorizon mode's implications for the excess dipole observed in the NRAO VLA Sky Survey (NVSS). We find that the mode can consistently explain both the CMB and NVSS observations. We also find that the model leads to small contributions to the local bulk flow and the dipole in Hubble parameter, which are consistent with observations. The model leads to several predictions which can be tested in future surveys. In particular, it implies that the observed dipole in large scale structure should be redshift dependent and should show an increase in amplitude with redshift. We also find that the Hubble parameter should show a dipole anisotropy whose amplitude must increase with redshift in the CMB frame. Similar anisotropic behaviour is expected for the observed redshift as a function of the luminosity distance., 21 pages, 6 figures, Accepted for publication in JCAP

According to the Cosmological Principle, the Universe should appear isotropic, without any preferred directions, to a comoving observer. However, a peculiar motion of the observer, or equivalently of the solar system, might introduce a dipole anisotropy in some of the observed properties of the Cosmos. The peculiar motion of the solar system, determined from the dipole anisotropy in the Cosmic Microwave Background Radiation (CMBR), gave a velocity 370 km/s along l = 264°, b = 48°. However, dipoles from number counts, sky brightness or redshift distributions in large samples of distant active galactic Nuclei (AGNs) have yielded values of the peculiar velocity many times larger than that from the CMBR, though in all cases the directions agreed with the CMBR dipole. Here we determine our peculiar motion from a sample of ~0.28 million AGNs, selected from the Mid Infra Red Active Galactic Nuclei (MIRAGN) sample comprising more than a million sources. We find a peculiar velocity more than four times the CMBR value, although the direction seems to be within ~2σ of the CMBR dipole. Since a real solar peculiar velocity should be the same whatever the data or the technique of observations may be, such discordant dipoles could imply that the explanation for the genesis of these dipoles, including that of the CMBR, might lie elsewhere. At the same time, a common direction for all these dipoles, determined from completely independent surveys by different groups, does indicate that these dipoles are not merely due to some systematics, and it might instead suggest a preferred direction in the Universe implying a genuine anisotropy, which would violate the Cosmological Principle, the core of modern cosmology.

Ultra-high-energy cosmic rays (UHECRs) are atomic nuclei from space with vastly higher energies than any other particles ever observed. Their origin and chemical composition remain a mystery. As we show here, the large- and intermediate-angular-scale anisotropies observed by the Pierre Auger Observatory are a powerful tool for understanding the origin of UHECRs. Without specifying any particular production mechanism, but only postulating that the source distribution follows the matter distribution of the local Universe, a good accounting of the magnitude, direction and energy dependence of the dipole anisotropy at energies above $8 \times 10^{18}$ eV is obtained, after taking into account the impact of energy losses during propagation (the "GZK horizon"), diffusion in extragalactic magnetic field and deflections in the Galactic magnetic field (GMF). This is a major step toward the long-standing hope of using UHECR anisotropies to constrain UHECR composition and magnetic fields. The observed dipole anisotropy is incompatible with a pure proton composition in this scenario. With a more accurate treatment of energy losses, it should be possible to further constrain the cosmic-ray composition and properties of the extragalactic magnetic field, self-consistently improve the GMF model, and potentially expose individual UHECR sources., Accepted by the Astrophysical Journal Letters

Recently the AMS-02 reported the precise measurements of the energy spectra of medium-mass compositions (Neon, Magnesium, Silicon) of primary cosmic rays, which reveal different properties from those of light compositions (Helium, Carbon, Oxygen). Here we propose a nearby source scenario, together with the background source contribution, to explain the newly measured spectra of cosmic ray Ne, Mg, Si, and particularly their differences from that of He, C, O. Their differences at high energies can be naturally accounted for by the element abundance of the nearby source. Specifically, the abundance ratio of the nearby source to the background of the Ne, Mg, Si elements is lower by a factor of $\sim1.7$ than that of the He, C, O elements. Such a difference could be due to the abundance difference of the stellar evolution of the progenitor star or the acceleration process/environment, of the nearby source. This scenario can simultaneously explain the high-energy spectral softening features of cosmic ray spectra revealed recently by CREAM/NUCLEON/DAMPE, as well as the energy-dependent behaviors of the large-scale anisotropies. It is predicted that the dipole anisotropy amplitudes below PeV energies of the Ne, Mg, Si group are smaller than that of the He, C, O group, which can be tested with future measurements., 6 pages, 3 figures; accepted for publication in Frontiers of Physics

The hardening and softening features in the DAMPE proton spectrum are very likely to be originated from a nearby supernova remnant (SNR). The proton spectrum from the nearby SNR is required to be very hard below $\approx10$ TeV. To reproduce this feature, we illustrate that anomalously slow-diffusion zone for cosmic rays (CRs) must be existed in the local interstellar medium (ISM) after also taking the dipole anisotropy of CRs into account. Assuming that the diffusion coefficient is homogeneous in the nearby ISM, we show that the diffusion coefficient is constrained to the magnitude of $10^{26}$ cm$^2$ s$^{-1}$ when normalized to 1 GeV, which is about 100 times smaller than the average value in the Galaxy. We further discuss the spatial distribution of the slow diffusion and find two distinct possibilities. In one case, the SNR is several hundred of parsecs away from the solar system, meanwhile both the SNR and the solar system are required to be included in a large slow-diffusion zone. The homogeneous diffusion belongs to this case. In the other case, the SNR is very close with a distance of $\sim50$ pc and the slow-diffusion zone is only limited around the SNR. The required diffusion coefficient is further smaller in the latter case. This work provides a new way of studying the CR diffusion in the local ISM., 8 pages, 5 figures, 1 table

Cosmic rays are the only sample of matter coming from outer space. They carry rich information about particle physics, high-energy astrophysics, composition and evolution of the Universe. The highest energy of cosmic rays detected so far is about 3×10 20 eV. "How are the cosmic rays accelerated?""What kind of astronomic sources do the cosmic rays originate from?""Are the fundamental physics laws still valid in such high-energy scales?" are all important scientific problems waiting to be addressed. To answer these questions, various space and ground experiments have been carried out to explore the nature of cosmic rays in a multi-messenger approach. The past few decades have witnessed great achievements in high-energy cosmic ray, gamma ray, neutrino observations, and detection of gravitational wave. (1) The cosmic ray spectra, composition, and anisotropy have been measured with unprecedented precision leading to better understanding of cosmic ray acceleration and transport and stricter constraints on properties of potential candidates of dark matter particles, and the dipole anisotropy of ultrahigh energy cosmic rays indicates that they have an extragalactic origin. (2) Space borne experiments have discovered more than 3000 sources in the GeV range, and the ground based experiments have uncovered more than 200 sources at TeV energies. Most of these sources are high-energy electron accelerators, and a few of them are identified as the accelerators of cosmic ray nuclei. Diffuse gamma-ray emission associated with galactic disks and jets and/or outbursts of Active Galactic Nuclei is also measured with better spatial and energy resolutions, which can be used to study cosmic ray transport in the interstellar/galactic/cluster medium. (3) With the IceCube experiment, about 100 high-energy neutrino events have been recorded and their isotropic distribution suggests an extragalactic origin. (4) The first gravitational wave event with simultaneous multi-wavelength observations has been detected opening the epoch of gravitational wave astronomy. Strong gravitational wave events represent the most catastrophic energy release in the Universe and can be important cosmic ray sources. These new results established the foundation to address the origin of cosmic rays and to develop theories of particle acceleration and transport. The study of cosmic ray transport has gone beyond the diffusion approximation to study the effect of magnetic field fluctuations on small scale anisotropy of cosmic rays and comprehensive numerical modelings of cosmic ray transport in the Galaxy are advanced with multi-wavelength observations. Diffusive particle acceleration by strong shocks of supernova remnants (SNRs) is also advanced based on multi-wavelength observations and cosmic ray measurements. The scenario of SNR origin of Galactic cosmic rays is being quantified with testable predictions. Although there are still uncertainties in amplification of magnetic field by cosmic rays and cosmic ray scattering by turbulent plasmas, sophisticated numerical codes are being developed to address these issues. Successful construction and operation of new generation cosmic ray and gamma-ray experiments will open a new chapter of the astro-particle physics study.

Results are presented from studying the anisotropy of the flux of very high-energy cosmic rays on the basis of muon bundles. Events were recorded in the period 2012–2018 by the DECOR coordinate-tracking detector, part of the unique research setup of the NEVOD experimental complex. The results from analyzing the anisotropy for two samples of events with muon bundles corresponding to different ranges of primary particle energy (E > 1015 eV and E > 1016 eV) are discussed, and estimates are made of dipole anisotropy parameters (amplitude and phase).

Type Ia supernovae (SNe Ia) provided the first strong evidence that the expansion of the universe is accelerating. With SN samples now more than ten times larger than those used for the original discovery and joined by other cosmological probes, this discovery is on even firmer ground. Two recent, related studies (Nielsen et al. 2016 and Colin et al. 2019, hereafter N16 and C19, respectively) have claimed to undermine the statistical significance of the SN Ia constraints. Rubin & Hayden (2016) (hereafter RH16) showed N16 made an incorrect assumption about the distributions of SN Ia light-curve parameters, while C19 also fails to remove the impact of the motion of the solar system from the SN redshifts, interpreting the resulting errors as evidence of a dipole in the deceleration parameter. Building on RH16, we outline the errors C19 makes in their treatment of the data and inference on cosmological parameters. Reproducing the C19 analysis with our proposed fixes, we find that the dipole parameters have little effect on the inferred cosmological parameters. We thus affirm the conclusion of RH16: the evidence for acceleration is secure., Accepted for publication in ApJ

We show that the observed anisotropy of extragalactic ultra-high energy cosmic rays (UHECRs above 8 EeV) is well-described by treating sources as a continuous distribution following the local large-scale structure of matter (LSS). We assume homogeneous, rigidity-dependent diffusion in the extragalactic magnetic field (EGMF), taking its strength and coherence length as free parameters. We use high-resolution particle tracking ($\sim 1.8 \times 10^9$ trajectories) to treat the impact of the Galactic magnetic field (GMF), for rigidities (E/Z) from $10^{17.4}$--$10^{20}$ EV. We adopt the Jansson and Farrar (2012) model for the GMF, and consider values of the coherence length of the random component from 30--100 pc. We describe the composition and spectrum of UHECRs using both direct fits from Auger (2017) and the physically-based Muzio, Unger, Farrar (2019) model, and assess the impact of UHECR spectrum and composition uncertainties on predicted arrival direction anisotropies. Our model accounts for the magnitude and direction of the dipole anisotropy in the $>8$ EeV bin, as well as its evolution (in both magnitude and direction) in the 8-16, 16-32 and $>32$ EeV bins (although the dipole is not significant above 32 EeV due to the lack of statistics). The quadrupole is also in agreement with data. Our best fit parameters are $B_{\rm EGMF}\sim0.6$ nG, $\lambda_{\rm EGMF}\sim0.2$ Mpc and $\lambda_{\rm GMF}\sim75$ pc. We show that this result is robust against different dipole reconstruction methods (Rayleigh/K-inverse) and different hadronic interaction models (EPOS-LHC/Sybill 2.3). We note that in an alternative scenario where the dipole would be due to a few local sources, the effect of cosmic variance would dominate over the magnetic deflection and horizon effects, and the direction and magnitude of the anisotropy could not be predicted. We also note that a pure proton composition would not explain simultaneously the strength and direction of the dipole in this model.

Pulsar-timing arrays (PTAs) are seeking gravitational waves from supermassive-black-hole binaries, and there are prospects to complement these searches with stellar-astrometry measurements. Theorists still disagree, however, as to whether the local gravitational-wave background will be statistically isotropic, as arises if it is the summed contributions from many SMBH binaries, or whether it exhibits the type of statistical anisotropy that arises if the local background is dominated by a handful (or even one) bright source. Here we derive, using bipolar spherical harmonics, the optimal PTA estimators for statistical anisotropy in the GW background and simple estimates of the detectability of this anisotropy. We provide results on the smallest detectable amplitude of a dipole anisotropy (and several other low-order multipole moments) and also the smallest detectable amplitude of a "beam'' of gravitational waves. Results are presented as a function of the signal-to-noise with which the GW signal is detected and as a function of the number of pulsars (assuming uniform distribution on the sky and equal sensitivity per pulsar). We provide results first for measurements with a single time-domain window function and then show how the results are augmented with the inclusion of time-domain information. The approach here is intended to be conceptually straightforward and to complement the results of more detailed (but correspondingly less intuitive) modeling of the actual measurements.

A measurement of the dipole anisotropy in the arrival directions of galactic cosmic positrons, electrons and protons has been performed with the Alpha Magnetic Spectrometer (AMS) onboard the International Space Station (ISS) using the first 6 years of data. Thanks to its wide field of view and to the inclination of the ISS orbit, AMS provides nearly full sky coverage in galactic coordinates, which allows to determine the three independent dipole components for each cosmic ray species. The results are consistent with isotropy for all three particle species and upper limits on the dipole amplitude have been derived. A 95% C.I. upper limit of $\delta

The high-energy electrons suffer severe energy loss during their propagation, owing to the Syn chrotron and Inverse-Compton processes. Thus, the electrons exceeding TeV are most likely originating from few local sources, such as dark matter particle and astrophysical sources. The dipole anisotropy of the electrons is also regard as an unique signature about the nearby sources. With the merit of large detecting area and strong background suppression, the LHAASO exper iment provides an opportunity on extending the detection of high-energy cosmic-ray electrons from 500 GeV to 100 TeV. In this paper, We explore the efficient rejection of hadronic back ground of LHAASO, in combination with KM2A and WCDA and make the expectation on the spectrum of cosmic-ray electrons and the sensitivity of dipole anisotropy with LHAASO. The influence on the research of electronic origin is also discussed.

The ISS-based Calorimetric Electron Telescope (CALET) is directly measuring the energy spectrum and direction distribution of electron+positron cosmic-rays up to 20 TeV. A main goal of CALET is to identify a signature of a nearby supernova remnant in electron+positron cosmic-rays, such as a spectral feature in the TeV region and/or a detectable anisotropy. The electron+positron events measured by CALET have been analyzed for a possible dipole anisotropy, as well as higher multipole moments. The methods for deriving limits on the anisotropy from the reconstructed events, as well as the procedures to compensate for the non-uniform exposure to the sky and inhomogeneous acceptance of the detector are explained. Preliminary results for the measured anisotropy and upper limits depending on threshold energy are presented, together with sensitivity estimations and a comparison to the expected anisotropy caused by the Vela supernova remnant.

Recently, the Pierre Auger Observatory observed a large scale anisotropy in the arrival direction of Ultra-High-Energy Cosmic Rays (UHECRs). As the Galactic magnetic field cannot produce such an anisotropy, the distribution of UHECRs hitting the Milky Way has to be anisotropic already. In this case, the Galactic magnetic field may change the observed energy spectrum with regard to the spectrum outside of the Milky Way as the UHECR intensity from certain directions can be enhanced and suppressed, respectively. We discuss the effect for the case of a dipole anisotropy and a commonly used magnetic field model, and demonstrate that the effect is negligible if the anisotropy outside the Milky Way is small, i.e. a dipole amplitude of about a few percentage.

We employ the hemisphere comparison (HC) method and the dipole fitting (DF) method to investigate the cosmic anisotropy in the recently released Pantheon sample of type Ia supernovae (SNe Ia) and five combinations among Pantheon. For the HC method, we find the maximum anisotropy level in the full Pantheon sample is $\mathrm{AL}_{max}=0.361\pm0.070$ and corresponding direction $(l,b)=({123.05^{\circ}}^{+11.25^{\circ}}_{-4.22^{\circ}}, {4.78^{\circ}}^{+1.80^{\circ}}_{-8.36^{\circ}})$. A robust check shows the statistical significance of maximum anisotropy level is about $2.1\sigma$. We also find that the Low-$z$ and SNLS subsamples have decisive impact on the overall anisotropy while other three subsamples have little impact. Moreover, the anisotropy level map significantly rely on the inhomogeneous distribution of SNe Ia in the sky. For the DF method, we find the dipole anisotropy in the Pantheon sample is very weak. The dipole magnitude is constrained to be less than $1.16\times10^{-3}$ at $95\%$ confidence level. However, the dipole direction is well inferred by MCMC method and it points towards $(l,b)=({306.00^{\circ}}^{+82.95^{\circ}}_{-125.01^{\circ}}, {-34.20^{\circ}}^{+16.82^{\circ}}_{-54.93^{\circ}})$. This direction is very close to the axial direction to the plane of SDSS subsample. It may imply that SDSS subsample is the decisive part to the dipole anisotropy in the full Pantheon sample. All these facts imply that the cosmic anisotropy found in Pantheon sample significantly rely on the inhomogeneous distribution of SNe Ia in the sky. More homogeneous distribution of SNe Ia is necessary to search for a more convincing cosmic anisotropy., Comment: 12 pages, 10 figures, 3 tables, MNRAS accepted

The dominant CMB dipole anisotropy is a Doppler effect due to a particular motion of the solar system with velocity of 370 km/s. Since this derives from peculiar motions and local inhomogeneities, one could meaningfully consider a fundamental frame of rest $\Sigma$ associated with the Universe as a whole. From the group properties of Lorentz transformations, two observers, individually moving within $\Sigma$, would still be connected by the relativistic composition rules. But ultimate implications could be substantial. Physical interpretation is thus traditionally demanded to correlating some dragging of light observed in laboratory with the direct CMB observations. Today the small residuals, from Michelson-Morley to present experiments with optical resonators, are just considered instrumental artifacts. However, if the velocity of light in the interferometers is not the same parameter "c" of Lorentz transformations, nothing would prevent a non-zero dragging. Furthermore, observable effects would be much smaller than classically expected and most likely of irregular nature. We review an alternative reading of experiments which leads to remarkable correlations with the CMB observations. Notably, we explain the irregular $10^{-15}$ fractional frequency shift presently measured with optical resonators operating in vacuum and solid dielectrics. For integration times of about 1 second, and typical Central-Europe latitude, we also predict daily variations of the Allan variance in the range $(5\div12) \cdot 10^{-16}$., Comment: 43 pages, 13 figures, 3 tables

We probe the anisotropy of the large-scale structure (LSS) with the WISE-2MASS catalogue. This analysis is performed by a directional comparison of the galaxy number counts through the entire celestial sphere once systematic effects, such as star-galaxy separation and foregrounds contamination, are properly taken into account. We find a maximal hemispherical asymmetry whose dipolar component is $A = 0.0507 \pm 0.0014$ toward the $(l,b) = (323^{\circ},-5^{\circ})$ direction, whose result is consistent with previous estimations of our proper motion in low and intermediate redshifts, as those carried out with Type Ia Supernovae and similar LSS catalogues. Furthermore, this dipole amplitude is statistically consistent ($p$-value = $0.061$) with mock catalogues simulated according to the expected $\Lambda$CDM matter density fluctuations, in addition to observational biases such as the incomplete celestial coverage and anisotropic sky exposure. Our results suggest, therefore, that there is no strong evidence for anomalous anisotropy in the LSS, given the limitations and systematics of current data, in the concordance model scenario., Comment: 8 pages, 4 figures, 1 table, accepted in MNRAS

A brief review of the results of identification of the cosmological distance scale based on the redshift in the spectra of extragalactic sources based on the data used for detecting the "acceleration of the expansion of the Universe" is given. The data deviation scattering parameter is about 13 ... 20% of the calculated distance value, which is an order of magnitude greater than the accuracy estimates accepted in a number of studies as the average quadratic deviations of arithmetic averages. In addition, there is a dipole anisotropy in this data. It is shown that among the reasons for the so-called "metrological and scientific deadlock" in cosmology may be the lack of error estimates of the inadequacy of the models used and violations of the logic of statistical inference when identifying them by supernovae of type SN Ia.

We investigate weak lensing effect on cosmic microwave background (CMB) in the presence of dipole anisotropy. The approach of flat-sky approximation is considered. We determine the functions $\sigma_0^2$ and $\sigma_2^2$ that appear in expressions of the lensed CMB power spectrum in the presence of a dipole anisotropy. We determine the correction to B-mode power spectrum which is found to be appreciable at low multipoles ($l$). However, the temperature and E-mode power spectrum are not altered significantly., Comment: 9 pages

Motivated by the ~7 % dipole anisotropy in the distribution of ultra-high energy cosmic-rays (UHECRs) above 8 EeV, we explore the anisotropy induced by the large scale structure, using constrained simulations of the local Universe and taking into account the effect of magnetic fields. The value of the intergalactic magnetic field (IGMF) is critical as it determines the UHECR cosmic horizon. We calculate the UHECR sky maps for different values of the IGMF variance and show the effect of the UHECR horizon on the observed anisotropy. The footprint of the local ($\lesssim350$ Mpc) Universe on the UHECR background, a small angular scale enhancement in the Northern Hemisphere, is seen. At 11.5 EeV (the median value of the energy bin at which the dipole has been reported), the LSS-induced dipole amplitude is $A_1\sim10\%$, for IGMF in the range [0.3-3] nG for protons, helium and nitrogen, compatible with the rms value derived from the cosmic power spectrum. However at these energies the UHECRs are also influenced by the Galactic Magnetic Field (GMF) and we discuss its effect on the LSS-induced anisotropy., Comment: 7 pages, 6 figures, submitted to MNRAS (revised version)

The data on the inclusive flux of cosmic positrons and electrons ($e^++e^{-}$) have been recently collected from GeV to tens of TeV energies by several experiments with unprecedented precision. In addition, the Fermi-LAT Collaboration has provided a new energy spectrum for the upper bounds on the $e^++e^{-}$ dipole anisotropy. This observable can bring information on the emission from local Galactic sources, notably measured with high precision at radio frequencies. We develop a framework in which $e^-$ and $e^+$ measured at Earth from GeV up to tens of TeV energies have a composite origin. A dedicated analysis is deserved to Vela YZ and Cygnus Loop Supernova Remnants (SNRs), for which we consider two different models for the injection of $e^-$. We investigate the consistency of these models using the three physical observables: the radio flux from Vela YZ and Cygnus Loop at all the available frequencies, the $e^++e^-$ flux from five experiments from the GeV to tens of TeV energy, the $e^++e^-$ dipole anisotropy upper limits from 50 GeV to about 1 TeV. We find that the radio flux for these nearby SNRs strongly constraints the properties of the injection electron spectrum, partially compatible with the looser constraints derived from the $e^+ + e^-$ flux data. We also perform a multi-wavelength multi-messenger analysis by fitting simultaneously the radio flux on Vela YZ and Cygnus Loop and the $e^+ + e^-$ flux, and checking the outputs against the $e^+ + e^-$ dipole anisotropy data. Remarkably, we find a model which is compatible with all the $e^++e^-$ flux data, the radio data for Vela YZ and Cygnus Loop, and with the anisotropy upper bounds. We show the severe constraints imposed by the most recent data on the $e^+ + e^-$ dipole anisotropy., Comment: 20 pages, 9 figures. Accepted for publication in the JCAP. Changes in v3: discussion and results extended to include an evolutionary model for the injection of cosmic-ray electrons in SNRs

Conventional cosmic-ray propagation models usually assume an isotropic diffusion coefficient to account for the random deflection of cosmic rays by the turbulent interstellar magnetic field. Such a picture is very successful in explaining many observational phenomena related to the propagation of Galactic cosmic rays, such as broken power-law energy spectra, secondary-to-primary ratios, etc. However, the isotropic diffusion presupposition is facing severe challenges from recent observations. In particular, such observations on the large-scale anisotropy of TeV cosmic rays show that the dipole direction differs from the prediction of the conventional model. One possible reason is that the large-scale regular magnetic field, which leads to an anisotropic diffusion of cosmic rays, has not been included in the model provided by the public numerical packages. In this work, we propose two numerical schemes to solve the $3$-dimensional anisotropic transport equation: the pseudo source method and Hundsdorfer-Verwer scheme. Both methods are verified by reproducing the measured B/C and proton spectrum and the radial variation of spectral index expected by former 2D simulation. As a demonstration of the prediction capability, dipole anisotropy is also calculated by a toy simulation with a rough magnetic field., Comment: 11 pages, 5 figures

The arrival directions of Galactic cosmic rays exhibit anisotropies up to the level of one per-mille over various angular scales. Recent observations of TeV-PeV cosmic rays show that the dipole anisotropy has a strong energy dependence with a phase-flip around 100 TeV. We argue that this behavior can be well understood by the combination of various effects: the anisotropic diffusion of cosmic rays, the presence of nearby sources, the Compton-Getting effect from our relative motion and the reconstruction bias of ground-based observatories., 10 pages, 4 figures, Proceedings of the 26th Extended European Cosmic Ray Symposium 2018

The Pierre Auger Observatory is the world's largest operating detection system for the observation of ultra high energy cosmic rays (UHECRs). The detector allows detailed measurements of their energy spectrum, mass composition and arrival directions of primary cosmic rays in the energy range above $10^{17}$ eV. The data collected at the Observatory over the last decade show the suppression of the cosmic ray flux at energies above $4\times10^{19}$ eV. However, it is still unclear if this suppression is caused by the propagation of cosmic rays or rather by energy limitation of their sources. The other puzzle is the origin of UHECRs. Some clues can be drawn from studying the distribution of their arrival directions. The recently observed dipole anisotropy has an orientation which indicates an extragalactic origin of UHECRs. The Auger surface detector array is also sensitive to showers due to ultra high energy neutrinos of all flavours and photons, and recent neutrino and photon limits provided by the Observatory can constrain models of the cosmogenic neutrino production and exotic scenarios of the UHECRs origin, such as the decays of super heavy particles. In this paper the recent results on measurements of the energy spectrum, mass composition and arrival directions of cosmic rays, and future prospects are presented., This article belongs to the Special Issue Selected Papers from the 7th International Conference on New Frontiers in Physics (ICNFP 2018)

The Pierre Auger Observatory has recently reported the detection of a dipole anisotropy in the arrival directions of cosmic rays above 8 EeV with a post-trial significance of more than 5.2$\sigma$. This observation has profound consequences for the distribution and composition of candidate sources of cosmic rays above the ankle (3-5 EeV). In this paper we search for the presence of anisotropies on all angular scales in public Auger data. The analysis follows a likelihood-based reconstruction method that automatically accounts for variations in the observatory's angular acceptance and background rate. Our best-fit dipole anisotropy in the equatorial plane has an amplitude of 5.3 $\pm$ 1.3 percent and right ascension angle of 103 $\pm$ 15 degrees, consistent with the results of the Pierre Auger Collaboration. We do not find evidence for the presence of medium- or small-scale anisotropies. The method outlined in this paper is well-suited for the future analyses of cosmic ray anisotropies below the ankle, where cosmic ray detection in surface arrays is not fully efficient and dominated by systematic uncertainties., Comment: version published in Astrophys.J. 863 (2018) no.2, 146

According to the Cosmological Principle, the matter distribution on very large scales should have a kinematic dipole that is aligned with that of the CMB. We determine the dipole anisotropy in the number counts of two all-sky surveys of radio galaxies. For the first time, this analysis is presented for the TGSS survey, allowing us to check consistency of the radio dipole at low and high frequencies by comparing the results with the well-known NVSS survey. We match the flux thresholds of the catalogues, with flux limits chosen to minimise systematics, and adopt a strict masking scheme. We find dipole directions that are in good agreement with each other and with the CMB dipole. In order to compare the amplitude of the dipoles with theoretical predictions, we produce sets of lognormal realisations. Our realisations include the theoretical kinematic dipole, galaxy clustering, Poisson noise, simulated redshift distributions which fit the NVSS and TGSS source counts, and errors in flux calibration. The measured dipole for NVSS is $\sim\!2$ times larger than predicted by the mock data. For TGSS, the dipole is almost $\sim\! 5$ times larger than predicted, even after checking for completeness and taking account of errors in source fluxes and in flux calibration. Further work is required to understand the nature of the systematics that are the likely cause of the anomalously large TGSS dipole amplitude., 13 pages, 8 figures, 2 tables; Significant improvements. Version accepted by JCAP

Current hypotheses for the origin of structure in the Universe lead to predictions of the amplitudes of anisotropies in the cosmic microwave background radiation. The dipole anisotropy is related to density fluctuations on large scales and to other determinations of our motion relative to distant galaxies. Observation and theory are coming tantalizingly close to measuring the elusive anisotropy, or to revealing that our ideas about the origin of galaxies and large-scale structures are in need of substantial revision.

Arrival directions of 40 neutrino events with energies >~100 TeV, observed by the IceCube experiment, are studied. Their distribution in the Galactic latitude and in the angular distance to the Galactic Center allow to search for the Milky-Way disk and halo-related components, respectively. No statistically significant evidence for the disk component is found, though even 100% disk origin of the flux is allowed at the 90% confidence level. Contrary, the Galactic Center-Anticenter dipole anisotropy, specific for dark-matter decays (annihilation) or for interactions of cosmic rays with the extended halo of circumgalactic gas, is clearly favoured over the isotropic distribution (the probability of a fluctuation of the isotropic signal is ~2%)., V2: references added, matches the published version. 4 pages, 5 figures, jetpl.sty

Observations of the cosmic ray (CR) anisotropy are widely advertised as a means of finding nearby sources. This idea has recently gained currency after the discovery of a rise in the positron fraction and is the goal of current experimental efforts, e.g., with AMS-02 on the International Space Station. Yet, even the anisotropy observed for hadronic CRs is not understood, in the sense that isotropic diffusion models overpredict the dipole anisotropy in the TeV–PeV range by almost two orders of magnitude. Here, we consider two additional effects normally not considered in isotropic diffusion models: anisotropic diffusion due to the presence of a background magnetic field and intermittency effects of the turbulent magnetic fields. We numerically explore these effect by tracking test-particles through individual realisations of the turbulent field. We conclude that a large misalignment between the CR gradient and the background field can explain the observed low level of anisotropy.

While the importance of detecting the Global spectral signatures of the red-shifted 21-cm line of atomic hydrogen from the very early epochs cannot be overstated, the associated challenges primarily include isolating the weak signal of interest from the orders of magnitude brighter foregrounds, and extend equally to reliably establishing the origin of the {\it apparent} global signal to the very early epochs. This letter proposes a critical dipole test that the measurements of the monopole component of the spectrum of interest should necessarily pass. Our criterion is based on a unique correspondence between the intrinsic monopole spectrum and the differential spectrum as an imprint of dipole anisotropy resulting from motion of observer with respect to the rest frame of our source (such as that of our Solar system, interpreted from the dipole anisotropy in CMBR). More importantly, the spectral manifestation of the dipole anisotropy gets {\it amplified} by a significant factor, depending on the monopole spectral slopes, rendering it feasible to measure. We describe details of such a test, and illustrate its application with the help of simulations. The letter also alludes to a novel model-independent path toward isolating the foreground contribution, using the diurnal pattern readily apparent in drift-scan observations. Such dipole qualifier for the monopole spectrum, when combined with reliable foreground estimation, is expected to pave way for in situ validation of spectral signatures from early epochs, important to presently reported and future detections of EoR signal., Comment: 8 pages, 3 figures, Accepted in ApJL

The dipole anisotropy seen in the {cosmic microwave background radiation} is interpreted as due to our peculiar motion. The Cosmological Principle implies that this cosmic dipole signal should also be present, with the same direction, in the large-scale distribution of matter. Measurement of the cosmic matter dipole constitutes a key test of the standard cosmological model. Current measurements of this dipole are barely above the expected noise and unable to provide a robust test. Upcoming radio continuum surveys with the SKA should be able to detect the dipole at high signal to noise. We simulate number count maps for SKA survey specifications in Phases 1 and 2, including all relevant effects. Nonlinear effects from local large-scale structure contaminate the {cosmic (kinematic)} dipole signal, and we find that removal of radio sources at low redshift ($z\lesssim 0.5$) leads to significantly improved constraints. We forecast that the SKA could determine the kinematic dipole direction in Galactic coordinates with an error of $(\Delta l,\Delta b)\sim(9^\circ,5^\circ)$ to $(8^\circ, 4^\circ)$, depending on the sensitivity. The predicted errors on the relative speed are $\sim 10\%$. These measurements would significantly reduce the present uncertainty on the direction of the radio dipole, and thus enable the first critical test of consistency between the matter and CMB dipoles., Comment: 9 pages, 6 figures, 4 tables. Version accepted by MNRAS

We discuss the effects on the CMB, CIB, and thermal SZ effect due to the peculiar motion of an observer with respect to the CMB rest frame, which induces boosting effects. We investigate the scientific perspectives opened by future CMB space missions, focussing on the CORE proposal. The improvements in sensitivity offered by a mission like CORE, together with its high resolution over a wide frequency range, will provide a more accurate estimate of the CMB dipole. The extension of boosting effects to polarization and cross-correlations will enable a more robust determination of purely velocity-driven effects that are not degenerate with the intrinsic CMB dipole, allowing us to achieve a S/N ratio of 13; this improves on the Planck detection and essentially equals that of an ideal cosmic-variance-limited experiment up to a multipole l of 2000. Precise inter-frequency calibration will offer the opportunity to constrain or even detect CMB spectral distortions, particularly from the cosmological reionization, because of the frequency dependence of the dipole spectrum, without resorting to precise absolute calibration. The expected improvement with respect to COBE-FIRAS in the recovery of distortion parameters (in principle, a factor of several hundred for an ideal experiment with the CORE configuration) ranges from a factor of several up to about 50, depending on the quality of foreground removal and relative calibration. Even for 1% accuracy in both foreground removal and relative calibration at an angular scale of 1 deg, we find that dipole analyses for a mission like CORE will be able to improve the recovery of the CIB spectrum amplitude by a factor of 17 in comparison with current results based on FIRAS. In addition to the scientific potential of a mission like CORE for these analyses, synergies with other planned and ongoing projects are also discussed., 61+5 pages, 17 figures, 25 tables, 8 sections, 5 appendices. In press on JCAP - Version 3 - Minor changes, affiliations fixed, references updated - version in line with corrected proofs

We probe the isotropy of the Universe with the largest all-sky photometric redshift dataset currently available, namely WISE~$\times$~SuperCOSMOS. We search for dipole anisotropy of galaxy number counts in multiple redshift shells within the $0.10 < z < 0.35$ range, for two subsamples drawn from the same parent catalogue. Our results show that the dipole directions are in good agreement with most of the previous analyses in the literature, and in most redshift bins the dipole amplitudes are well consistent with $��$CDM-based mocks in the cleanest sample of this catalogue. In the $z, 5 pages, 4 figures, 2 tables. Published in MNRAS

Based on the limiting continuation of Lorentz-Poincaré invariance, we propose an alternative formulation of the generalized Planck distribution for inertial and noninertial frames. The Lorentz invariant Planck distribution law leads to a new physical interpretation of the dipole anisotropy of the Cosmic Microwave Background. The Big Jets model predicts a distant ‘antimatter blackbody,’ whose radiations could make 50% of the sky very slightly warmer than the isotropic CMB temperature TCMB with a cosine function. The other 50% of the sky has the same isotropic temperature TCMB. Thus, we could have a pseudo-dipole anisotropy because the microwaves emitted from the antimatter blackbody are totally absorbed by our matter blackbody. We suggest that accurate data of satellite experiments might be used to search for the pseudo-dipole anisotropy and the missing half of the antimatter universe.

We study the dipole anisotropy in integrated linearly polarization flux density in NRAO VLA Sky Survey (NVSS). We extract the anisotropy parameters in the number counts, number counts weighted by polarization observables, i.e. degree of polarization (p) and polarization flux (P). We also determine the anisotropy in the degree of polarization per source and polarization flux per source. We consider data with several different cuts on the flux density, S>10,20,30,40,50 mJy. For studies with degree of polarization we impose the additional cut 0.0120 mJy to S>50 mJy. The corresponding direction parameters are found to be stable with the cut on flux density. The significance is even higher for the case of p weighted number counts. The observed anisotropy is found to be much larger in comparison to the CMBR expectations. We find that polarization observables show a much higher level of anisotropy in comparison to pure number counts or flux weighted number counts., Comment: 13 pages, 7 figures, submitted to MNRAS

The existence of the cosmic ray Halo in our Galaxy has been discussed for more than half a century. If it is real it could help to explain some puzzling features of the cosmic ray flux: its small radial gradient, nearly perfect isotropy and the low level of the fine structure in the energy spectra of the various particles. All these features could be understood if: (a) the Halo has a big size (b) cosmic rays in the Halo have a unform spatial distribution and (c) the cosmic ray density in the Halo is comparable or even higher than that in the Galactic Disk. The main topic of the paper concerns the present status of the anisotropy and a model for its formation. In our model the extremely small amplitude of the dipole anisotropy is due to the dilution of the anisotropy in the Disk by the dominating isotropic cosmic rays from the Halo. Some minor deviations from complete isotropy in the sub-PeV and PeV energy regions point out to the possible contribution of the Single Source with the phase of its first harmonic opposite to the phase produced by the Disk., Comment: 11 pages, 2 figures, accepted by Astroparticle Physics

In this contribution an interpretation of the most recent data on cosmic-ray electron and positron (CRE) fluxes (from Fermi-LAT, HESS, CALET and AMS-02), with a special focus on the electron contribution from supernova remnants (SNRs), is presented. For the first time, the constraints coming from CRE flux up to 20 TeV, as well as Fermi-LAT dipole upper limits and radio measurements of individual nearby SNRs are consider together. It is discussed how CRE data up to 20 TeV can constrain the energy cutoff of the electron emission from a smooth distribution of SNRs in the Galaxy. Also, the consequences of the recent Fermi-LAT measurement of the dipole anisotropy are explored, studying in particular the total emission energy in electrons and spectral index of Vela YZ and the Cygnus Loop SNRs. Finally, the full radio spectrum of nearby SNRs is used to constrain their electron injection spectrum. Results show how the combination of constraints from different observables shed light on the interpretation of present CRE data.