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This paper introduces three cosmic expansion models with constant, decelerating and accelerating speed of expansion respectively. Then characters of these cosmic expansion models are compared. Based on these cosmic expansion models, the thresholds of observable universe are calculated via simulations, where the earliest observable cosmic radius R(tearliest) is always 0.368R (R is cosmic radius at current universe time) for any cosmic expansion models.

Using the model based on the Regge-like laws, new analytical formulas are obtained for the moment of inertia, the rotation frequency, and the radius of astronomical non-exotic objects (planets, stars, galaxies, and clusters of galaxies). The rotation frequency and moment of inertia of a neutron star and the observable Universe are estimated. The estimates of the average numbers of stars and galaxies in the observable Universe are given. The Darwin instability effect in the binary systems (di-planets, di-stars, and di-galaxies) is also analyzed.

Autorzy: Abe K., Adrich P., Aihara H., Akutsu, R., Alekseev I., Ali A. , Ameli F., Anghel I., Anthony L. H. V., Antonova M. , Araya A., Asaoka Y., Ashida Y., Aushev V., Ballester F., Bandac I., Barbi M., Barker G. J., Barr G., Batkiewicz-Kwasniak M., Bellato M., Berardi V., Bergevin M., Bernard L., Bernardini E., Berns L., Bhadra S., Bian J., Blanchet A., Blaszczyk F. d. M., Blonde A., Boiano A., Bolognesi S., Bonavera L., Booth N., Borjabad S., Boschi, T., Bose D., Boyd S . B., Bozza C., Bravar A., Bravo-Berguño D., Bronner C., Brown L., Bubak Arkadiusz, Buchowicz A., Buizza Avanzini M., Cafagna F. S., Calabria N. F., Calvo-Mozota J. M., Cao S., Cartwright S.L., Carroll A., Catanesi M. G., Cebriàn, S., Chabera M., Chakraborty, S., Checchia C., Choi J.H., Choubey S., Cicerchia M., Coleman J., Collazuol G., Cook L., Cowan G., Cuen-Rochin, S., Danilov M., Díaz López G., De la Fuente E., de Perio P., De Rosa G., Dealtry T., Densham C. J., Dergacheva A., Deshmukh N., Devi M. M., Di Lodovico F., Di Meo, P., Di Palma I., Doyle T. A., Drakopoulou E., Drapier O., Dumarchez J., Dunne P., Dziewiecki M., Eklund L., El Hedri S., Ellis J., Emery S., Esmaili A., Esteve R., Evangelisti A., Feely M., Fedotov S., Feng J., Fernandez P., Fernández-Martinez E., Ferrario P., Ferrazzi,B., Feusels T., Finch A., Finley C., Fiorentini A., Fiorillo G., Fitton M., Frankiewicz K., Friend M., Fujii Y., Fukuda Y., Galinski G., Gao J., Garde C., Garfagnini A., Garode S., Gialanella L., Giganti C., Gomez-Cadenas J.J., Gonin M., González-Nuevo J., Gorin A., Gornea R., Gousy-Leblanc V. Gramegna F. Grassi M. Grella G. Guigue M. Gumplinger P. Hadley D.R. Harada M., Hartfiel B., Hartz M., Hassani S., Hastings N.C., Hayato Y., Hernando-Morata J.A., Herrero V., Hill J., Hiraide K., Hirota S., Holin A., Horiuchi S., Hoshina K., Hultqvist K., Iacob F., Ichikawa A.K., Idrissi Ibnsalih W., Iijima T., Ikeda M., Inomoto M., Inoue K., Insler J., Ioannisian A., Ishida T., Ishidoshiro K., Ishino H., Ishitsuka M., Ito H., Ito S., Itow Y., Iwamoto K., Izmaylov A., Izumi N., Izumiyama S., Jakkapu M., Jamieson B., Jang H.I., Jang J.S., Jenkins S.J., Jeon S.H., Jiang M., Jo H.S., Jonsson P., Joo K.K., Kajita T., Kakuno H., Kameda J., Kano Y., Kalaczynski P., Karlen D., Kasperek J., Kataoka Y., Kato A., Katori T., Kazarian N., Kearns E., Khabibullin M., Khotjantsev A., Kikawa T., Kekic M., Kim J.H., Kim J.Y., Kim S.B., Kim S.Y., King S., Kinoshita T., Kisiel Jan, Klekotko A., Kobayashi T., Koch L., Koga M., Koerich L., Kolev N., Konaka A., Kormos L.L., Koshio Y., Korzenev A., Kotsar Y., Kouzakov K.A., Kowalik K.L., Kravchuk L., Kryukov A.P., Kudenko Y., Kumita T., Kurjata R., Kutter T., Kuze M., Kwak K., La Commara M., Labarga L., Lagoda J., Lamers James J., Lamoureux M., Laveder M., Lavitola L., Lawe M., Learned J.G., Lee J., Leitner R., Lezaun V., Lim I.T., Lindner T., Litchfield R.P., Long K.R., Longhin A., Loverre P., Lu X., Ludovici L., Maekawa Y., Magaletti L., Magar K., Mahn K., Makida Y., Malek M., Malinský M., Marchi T., Maret L., Mariani C., Marinelli A., Martens K., Marti L., Martin J.F. Martin D., Marzec J., Matsubara T., Matsumoto R., Matsuno S., Matusiak M., Mazzucato E., McCarthy M., McCauley N., McElwee J., McGrew C., Mefodiev A., Medhi A., Mehta P., Mellet L., Menjo H., Mermod P., Metelko C., Mezzetto M., Migenda J., Migliozzi P., Mijakowski P., Miki S., Miller E.W., Minakata H., Minamino A., Mine S., Mineev O., Mitra A., Miura M., Moharana R., Mollo C.M., Mondal T., Mongelli M., Monrabal F., Moon D.H., Moon C.S., Mora F.J., Moriyama S., Mueller Th.A., Munteanu L., Murase K., Nagao Y., Nakadaira T., Nakagiri K., Nakahata M., Nakai S., Nakajima Y., Nakamura K., Nakamura KI., Nakamura H., Nakano Y., Nakaya T., Nakayama S., Nakayoshi K., Nascimento Machado L., Naseby C.E.R., Navarro-Garcia B., Needham M., Nicholls T., Niewczas K., Nishimura Y., Noah E., Nova F., Nugent J.C., Nunokawa H., Obrebski W., Ochoa-Ricoux J.P., O’Connor E., Ogawa N., Ogitsu T., Ohta K., Okamoto K., O’Keeffe H.M., Okumura K., Onishchuk Y., Orozco-Luna F., Oshlianskyi A., Ospina N., Ostrowski M., O’Sullivan E., O’Sullivan L., Ovsiannikova T., Oyama Y., Ozaki H., Pac M.Y., Paganini P., Palladino V., Paolone V., Pari M., Parsa S., Pasternak J., Pastore C., Pastuszak G., Patel D.A., Pavin M., Payne D., Peña-Garay C., Pidcott C., Pinzon Guerra E., Playfer S., Pointon B.W., Popov A., Popov B., Porwit Kamil, Posiadala-Zezula M., Poutissou J.M., Pozimski J., Pronost G., Prouse N.W., Przewlocki P., Quilain B., Quiroga A.A., Radicioni E., Radics B., Rajda P.J., Renner J., Rescigno M., Retiere F., Ricciardi G., Riccio C., Richards B., Rondio E., Rose H.J., Roskovec B., Roth S., Rott C., Rountree S.D., Rubbia A., Ruggeri A.C., Ruggles C., Russo S., Rychter A., Ryu D., Sakashita K., Samani S., Sánchez F., Sánchez M.L., Sanchez M.C., Sano S., Santos J.D., Santucci G., Sarmah P., Sashima I., Sato K., Scott M., Seiya Y., Sekiguchi T., Sekiya H., Seo J.W., Seo S.H., Sgalaberna D., Shaikhiev A., Shan Z., Shaykina A., Shimizu I., Shin C.D., Shinoki M., Shiozawa M., Sinnis G., Skrobova N., Skwarczynski K., Smy M.B., Sobczyk J., Sobel H.W., Soler F. J. P., Sonoda Y., Spina R., Spisso B., Spradlin B., Stankevich K.L., Stawarz L., Stellacci S.M., Stopa K., Studenikin A.I., Suárez Gómez S.L., Suganuma T., Suvorov S., Suwa Y., Suzuki A.T., Suzuki S.Y., Suzuki Y., Svirida D., Svoboda R., Taani M., Tada M., Takeda A., Takemoto Y., Takenaka A., Taketa A., Takeuchi Y., Takhistov V., Tanaka H., Tanaka H.A., Tanaka H.I., Tanaka M., Tashiro T., Thiesse M., Thompson L.F., Toledo J., Tomatani-Sánchez A.K., Tortone G., Tsui K.M., Tsukamoto T., Tzanov M., Uchida Y., Vagins M.R., Valder S., Valentino V., Vasseur G., Vijayvargi A., Vilela C., Vinning W. G. S., Vivolo D., Vladisavljevic T., Vogelaar R.B., Vyalkov M.M., Wachala T., Walker J., Wark D., Wascko M.O., Wendell R.A., Wilkes R.J., Wilking M.J., Wilson M.R., Wronka S., Xia J., Xie Z., Xin T., Yamaguchi Y., Yamamoto K., Yanagisawa C., Yano T., Yen S., Yershov N., Yeum D.N., Yokoyama M., Yonenaga M., Yoo J., Yu I., Yu M., Zakrzewski T., Zaldivar B., Zalipska J., Zaremba K., Zarnecki G., Ziembicki M., Zietara K., Zito M., Zsoldos S., Core-collapse supernovae are among the most magnificent events in the observable universe. They produce many of the chemical elements necessary for life to exist and their remnants-neutron stars and black holes-are interesting astrophysical objects in their own right. However, despite millennia of observations and almost a century of astrophysical study, the explosion mechanism of core-collapse supernovae is not yet well understood. Hyper-Kamiokande is a next-generation neutrino detector that will be able to observe the neutrino flux from the next galactic core-collapse supernova in unprecedented detail. We focus on the first 500 ms of the neutrino burst, corresponding to the accretion phase, and use a newly-developed, high-precision supernova event generator to simulate Hyper-Kamiokandeʼs response to five different supernova models. We show that Hyper-Kamiokande will be able to distinguish between these models with high accuracy for a supernova at a distance of up to 100 kpc. Once the next galactic supernova happens, this ability will be a powerful tool for guiding simulations toward a precise reproduction of the explosion mechanism observed in nature.

This paper introduces a cosmic expansion model with constant speed of cosmic spatial expansion via derivation and simulations, where the speed of cosmic spatial expansion equals the speed of light c. Simulation results show that the earliest observable universe time is t = 5.084 Gyrs where the current universe time T = 13.82 Gyrs, and the furthest observable distance at the earliest observable universe time t is S = 0.632R, where R is the cosmic radius at current universe time T. The above constant cosmic expansion model does not consider the inflation period in the early universe according to the Big Bang model, nor does it considered the cosmic acceleration in recent universe time. However, this simplified cosmic expansion model could be a benchmark that will be helpful to understand the cosmic expansion and the observable universe. Based on the derivation and simulation of the constant cosmic expansion model, the threshold of observable universe for the accelerated cosmic expansion model can also be calculated similarly, as far as the speed of cosmic spatial expansion at any universe time t can be provided.

SPIDERS (The SPectroscopic IDentification of eROSITA Sources) is a large spectroscopic programme for X-ray selected galaxy clusters as part of the Sloan Digital Sky Survey-IV (SDSS-IV). We describe the final dataset in the context of SDSS Data Release 16 (DR16): the survey overall characteristics, final targeting strategies, achieved completeness and spectral quality, with special emphasis on its use as a galaxy cluster sample for cosmology applications. SPIDERS now consists of about 27,000 new optical spectra of galaxies selected within 4,000 photometric red sequences, each associated with an X-ray source. The excellent spectrograph efficiency and a robust analysis pipeline yield a spectroscopic redshift measurement success rate exceeding 98%, with a median velocity accuracy of 20 km s$^{-1}$ (at $z=0.2$). Using the catalogue of 2,740 X-ray galaxy clusters confirmed with DR16 spectroscopy, we reveal the three-dimensional map of the galaxy cluster distribution in the observable Universe up to $z\sim0.6$. We highlight the homogeneity of the member galaxy spectra among distinct regions of the galaxy cluster phase space. Aided by accurate spectroscopic redshifts and by a model of the sample selection effects, we compute the galaxy cluster X-ray luminosity function and we present its lack of evolution up to $z=0.6$. Finally we discuss the prospects of forthcoming large multiplexed spectroscopic programmes dedicated to follow up the next generation of all-sky X-ray source catalogues., 19 pages, 21 figures. Accepted for publication in MNRAS

We hypothesize that the quantum realm and the cosmos are linked by a scaling relation where the gravitational coupling constant αG is the scale factor and decreases with cosmic time. We propose a simple cosmological model where cosmic inflation, dark energy and dark matter could be redundant concepts. We show that cosmological parameters such as the Hubble constant, the age, density and mass of the observable Universe could be derived simply from quantum parameters. Finally, we propose a fundamental MOND formula with no interpolating function and an acceleration parameter simply derived from the Hubble constant.

In theories with extra dimensions, the cosmological hierarchy problem can be thought of as the unnaturally large radius of the observable universe in Kaluza-Klein units. We sketch a dynamical mechanism that relaxes this. In the early universe scenario we propose, three large spatial dimensions arise through tunneling from a 'cosmic egg', an effectively one-dimensional configuration with all spatial dimensions compact and of comparable, small size. If the string landscape is dominated by low-dimensional compactifications, cosmic eggs would be natural initial conditions for cosmology. A quantum cosmological treatment of a toy model egg predicts that, in a variant of the Hartle-Hawking state, cosmic eggs break to form higher dimensional universes with a small, but positive cosmological constant or quintessence energy. Hence cosmic egg cosmology yields a scenario in which the seemingly unnaturally small observed value of the vacuum energy can arise from natural initial conditions., 11 pages, 4 figures, 1 appendix

Indirect searches for signatures of corpuscular dark matter have been performed using all cosmic messengers: gamma rays, cosmic rays, and neutrinos. The search for dark matter with neutrinos is important since they are the only courier that can reach detectors from dark matter processes in dense environments, such as the core of the Sun or Earth, or the edge of the observable Universe. One thing essential to experiments is the prediction of the neutrino signature in the detector. I will introduce χaroν, a software that bridges the dark sector and Standard Model by predicting neutrino fluxes from different celestial dark matter agglomerations in diverse scenarios. This package includes an updated computation of neutrino production and propagation to the detector.

In this work we propose the quantization of a cosmological model describing the primordial universe filled with five barotropic fluids, namely: radiation, dust, vacuum, cosmic strings and domain walls. We intend to identify which fluid is best suited to provide phenomenologically the temporal variable in accordance with the observable universe. Through the Galerkin spectral method and the finite difference method in the Crank-Nicolson scheme (vacuum case), the quantum cosmological solutions are obtained and compared. We, also, compare the quantum cosmological solutions with the corresponding classical ones. The vacuum case is especially interesting because it provides a tunneling transition mechanism from the quantum to the classical phase and the possibility of calculating quantum tunneling probabilities., Comment: 26 pages, 25 figures, 2 tables

Blanchard, A., et al., Today, thanks in particular to the results of the ESA Planck mission, the concordance cosmological model appears to be the most robust to describe the evolution and content of the Universe from its early to late times. It summarizes the evolution of matter, made mainly of dark matter, from the primordial fluctuations generated by inflation around 10 second after the Big Bang to galaxies and clusters of galaxies, 13.8 billion years later, and the evolution of the expansion of space, with a relative slowdown in the matter-dominated era and, since a few billion years, an acceleration powered by dark energy. But we are far from knowing the pillars of this model which are inflation, dark matter and dark energy. Comprehending these fundamental questions requires a detailed mapping of our observable Universe over the whole of cosmic time. The relic radiation provides the starting point and galaxies draw the cosmic web. JAXA’s LiteBIRD mission will map the beginning of our Universe with a crucial test for inflation (its primordial gravity waves), and the ESA Euclid mission will map the most recent half part, crucial for dark energy. The mission concept GAUSS, described in this White Paper, aims at being a mission to fully map the cosmic web up to the reionization era, linking early and late evolution, to tackle and disentangle the crucial degeneracies persisting after the Euclid era between dark matter and inflation properties, dark energy, structure growth and gravitation at large scale.

We investigate the balance of power between stars and AGN across cosmic history, based on the comparison between the infrared (IR) galaxy luminosity function (LF) and the IR AGN LF. The former corresponds to emission from dust heated by stars and AGN, whereas the latter includes emission from AGN-heated dust only. We find that at all redshifts (at least up to z~2.5), the high luminosity tails of the two LFs converge, indicating that the most infrared-luminous galaxies are AGN-powered. Our results shed light to the decades-old conundrum regarding the flatter high-luminosity slope seen in the IR galaxy LF compared to that in the UV and optical. We attribute this difference to the increasing fraction of AGN-dominated galaxies with increasing total infrared luminosity (L_IR). We partition the L_IR-z parameter space into a star-formation and an AGN-dominated region, finding that the most luminous galaxies at all epochs lie in the AGN-dominated region. This sets a potential `limit' to attainable star formation rates, casting doubt on the abundance of `extreme starbursts': if AGN did not exist, L_IR>10^13 Lsun galaxies would be significantly rarer than they currently are in our observable Universe. We also find that AGN affect the average dust temperatures (T_dust) of galaxies and hence the shape of the well-known L_IR-T_dust relation. We propose that the reason why local ULIRGs are hotter than their high redshift counterparts is because of a higher fraction of AGN-dominated galaxies amongst the former group., 18 pages; 15 figures; accepted for publication in MNRAS

The [CII] deficit, which describes the observed decrease in the ratio of [CII] 158 micron emission to continuum infrared emission in galaxies with high star formation surface densities, places a significant challenge to the interpretation of [CII] detections from across the observable universe. In an attempt to further decode the cause of the [CII] deficit, the [CII] and dust continuum emission from 18 Local Volume galaxies has been split based on conditions within the interstellar medium where it originated. This is completed using the Key Insights in Nearby Galaxies: a Far-Infrared Survey with Herschel (KINGFISH) and Beyond the Peak (BtP) surveys and the wide-range of wavelength information, from UV to far-infrared emission lines, available for a selection of star-forming regions within these samples. By comparing these subdivided [CII] emissions to isolated infrared emission and other properties, we find that the thermalization (collisional de-excitation) of the [CII] line in HII regions plays a significant role in the deficit observed in our sample., To be published in MNRAS, 8 pages, 6 figures

Cosmological phase transitions are thought to have taken place at the early Universe imprinting their properties on the observable Universe. There is strong evidence that, through the dynamics of a scalar field that lead a second order phase transition, inflation shaped the Universe accounting for the most conspicuous features of the observed Universe. It is argued that inflation has also striking implications for the vacuum energy. Considerations for subsequent second order phase transitions are also discussed., Comment: 9 pages. Version to match to one to be published in General Relativity and Gravitation

One of the greatest challenges of science is to understand the current accelerated expansion of the Universe. In this work, we show that by considering the quantum nature of the gravitational field, its wavelength can be associated with an effective Compton mass. We propose that this mass can be interpreted as dark energy, with a Compton wavelength given by the size of the observable Universe, implying that the dark energy varies depending on this size. If we do so, we find that: 1.- Even without any free constant for dark energy, the evolution of the Hubble parameter is exactly the same as for the LCDM model, so we expect this model to have the same predictions as LCDM. 2.- The density rate of the dark energy is $\Omega_{\Lambda}= 0.69$ which is a very similar value as the one found by the Planck satellite $\Omega_{\Lambda}= 0.684$. 3.- The dark energy has this value because it corresponds to the actual size of the radius of the Universe, thus the coincidence problem has a very natural explanation. 4.-It is possible to find also a natural explanation to why observations inferred from the local distance ladder find the value $H_0= 73$ km/s/Mpc for the Hubble constant. We show that if we take the variability of the dark energy into account, they should measure $H_0= 67.3$ km/s/Mpc as well. 5.-In this model the inflationary period contains a natural successful graceful exit., Comment: Work based on a presentation at the congress IWARA2020

We propose the development of X-ray interferometry (XRI), to reveal the universe at high energies with ultra-high spatial resolution. With baselines which can be accommodated on a single spacecraft, XRI can reach 100 $\mu$as resolution at 10 \AA (1.2 keV) and 20 $\mu$as at 2 \AA (6 keV), enabling imaging and imaging-spectroscopy of (for example) X-ray coronae of nearby accreting supermassive black holes (SMBH) and the SMBH `shadow'; SMBH accretion flows and outflows; X-ray binary winds and orbits; stellar coronae within ~100 pc and many exoplanets which transit across them. For sufficiently luminous sources XRI will resolve sub-pc scales across the entire observable universe, revealing accreting binary SMBHs and enabling trigonometric measurements of the Hubble constant with X-ray light echoes from quasars or explosive transients. A multi-spacecraft `constellation' interferometer would resolve well below 1 $\mu$as, enabling SMBH event horizons to be resolved in many active galaxies and the detailed study of the effects of strong field gravity on the dynamics and emission from accreting gas close to the black hole., Comment: White Paper submitted in response to ESA's Voyage 2050 call

We explore the possibility of using a gigaparsec-scale local void to reconcile the Hubble tension. Such a gigaparsec-scale void can be produced by multi-stream inflation where different parts of the observable universe follow different inflationary trajectories. The impact of such a void for cosmological observations is studied, especially those involving supernovae, Baryon Acoustic Oscillations (BAO) and the kinetic Sunyaev-Zel'dovich (kSZ) effect. As a benchmark model, a 1.7Gpc scale with boundary width 0.7Gpc and density contrast -0.14 may ease the Hubble tension., 11 pages, 8 figures

We study the details of eternal inflation in the presence of a spectator Higgs field within the framework of the minimal Standard Model. We have recently shown that in the presence of scalar field(s) which allow inflation only within a finite domain of field values, the universe reaches a steady state where the normalized distribution for the field(s) converges to a steady state distribution [1]. In this paper, we analyze this eternal inflation scenario with the renormalized Standard Model Higgs potential, since it also allows inflation in a finite domain, but turns over at high scales due to the running of the self-coupling, marking an exit from inflation. We compute the full steady state distribution for the Higgs using an integral evolution technique that we formulated in [1] and the fractal dimension of the universe. We then obtain a bound on the inflationary Hubble scale in order to have a large observable universe contained within the instability scale of $H\lesssim\mathcal{O}(10^9)$GeV depending on the top mass. Upon reheating of the universe, thermal fluctuations in the Higgs field could potentially pose another problem; however, we compute the rate of thermal bubble production and find that the probability of tunneling in the post-inflationary era is negligibly small even for very high reheat temperatures., Comment: 15 pages in double column format, 10 figures. V2: Further clarifications. Updated towards version published in Phys. Rev. D

The Black hole cosmology is a cosmological model in which the observable universe is the interior of a black hole. When this cosmology was proposed, it was unknown that the expansion of the universe is accelerated and therefore the cosmological model should have a contribution of the dark energy. In this work we revisited Black hole cosmology in relation to the currently accepted model of the universe. However this model up to now has insurmountable problems and the unique main contribution of the Black hole cosmology is the cosmological horizon whose existence guarantees the existence of an entropic force that gives the correct accelerated expansion of the universe. The justification about the existence of this cosmological horizon is still open although recent works within the so-called entropic cosmology provide models that fit strongly with observation and that reinforce the idea of the existence of the cosmological horizon.

The origin of power asymmetry and other measures of statistical anisotropy on the largest scales of the universe, as manifested in cosmic microwave background (CMB) and large-scale structure data, is a long-standing open question in cosmology. In this paper, we analyse the Planck Legacy temperature anisotropy data and find strong evidence for a violation of the Cosmological principle of isotropy, with a probability of being a statistical fluctuation of the order of ∼10-9. The detected anisotropy is related to large-scale directional ΛCDM cosmological parameter variations across the CMB sky, which are sourced by three distinct patches in the maps with circularly averaged sizes between 40° and 70° in radius. We discuss the robustness of our findings to different foreground separation methods and analysis choices, and find consistent results from WMAP data when limiting the analysis to the same scales. We argue that these well-defined regions within the cosmological parameter maps may reflect finite and casually disjoint horizons across the observable universe. In particular, we show that the observed relation between horizon size and mean dark energy density within a given horizon is in good agreement with expectations from a recently proposed model of the universe that explains cosmic acceleration and cosmological parameter tensions between the high- and low-redshift universe from the existence of casual horizons within our universe., This work is dedicated to the memory of my father, Marcelo. PF is specially grateful to K. Benabed and O. Doré for useful comments on the draft, I. Tutusaus for advice with iMinuit⁠, and J. Guerrero for help with the Hidra computing cluster at ICE. Hidra is funded by CSIC project EQC2019-005664-P, with European FEDER funds. The development of this project required 800 000+ CPU hours at Hidra. Some of the results in this paper have been derived using the HEALPY (Zonca et al. 2019), HEALPIX (Górski et al. 2005), and CAMB (Lewis, Challinor & Lasenby 2000) packages. We acknowledge support from MINECO through grants ESP2017-89838-C3-1-R and PGC2019-102021-B-100, the H2020 European Union grants LACEGAL 734374 and EWC 776247 with ERDF funds, and Generalitat de Catalunya through CERCA to grant 2017-SGR-885 and funding to IEEC.

Anti-de Sitter (AdS) vacua, being theoretically important, might have an unexpected impact on the observable universe. We find that in early dark energy (EDE) scenarios the existence of AdS vacua around recombination can effectively lift the CMB-inferred $H_0$ value. As an example, we study a phenomenological EDE model with an AdS phase starting at the redshift $z\sim2000$ and ending shortly after recombination (hereafter the universe will settle down in a $\Lambda>0$ phase until now), and obtain a best-fit $H_0=72.74$ km/s/Mpc without degrading the CMB fit compared with the standard $\Lambda$CDM model., Comment: 7 pages, 5 figures, matched published version in PRD

Assuming a closed universe with slight positive curvature, cosmic expansion is modeled as a heat engine where the '"system'" is defined collectively as those regions of space within the observable universe which will later evolve into voids or empty space, and the '"surroundings'" are identified collectively as those pockets of space which will eventually develop into matter filled galaxies, clusters, super-clusters and filament walls. Using this model, we show that the energy needed for cosmic expansion can be found using basic thermodynamic principles, and that cosmic expansion had as its origin, a finite initial energy density, pressure, volume, and temperature. Inflation in the traditional sense, with the inflaton field, may also not be required as it can be argued that homogeneities and in-homogeneities in the WMAP temperature profile can be attributed to quantum mechanical fluctuations about a fixed background temperature in the initial isothermal expansion phase. Fluctuations in temperature can cause certain regions of space to lose heat to other pockets producing voids forcing, i.e., fueling expansion of the latter and creating slightly cooler temperatures in the former, where matter will later congregate. Upon freeze-out, this could produce the observed WMAP signature with its associated CBR fluctuation in magnitude. Finally, we estimate that the freeze-out temperature and time for WMAP in-homogeneities occurred at roughly 3.02 * 1027 K and 2.54 * 10-35 s, respectively, after first initiation of volume expansion, in line with current estimates for the end of the inflationary epoch. The heat absorbed in the inflationary phase is estimated to be Q = 1.81 * 1094 J, and the system volume increases by a factor of only 5.65. The bubble voids in the observable universe increase, collectively, in volume from about .046 m3 to .262 m3 within this time., 19 pages

The cosmic microwave background (CMB) is the approximately 2.728K microwave field that pervades the observable universe and is a key part of the evidence for the big bang.What is remarkable about t...

Just 5 years ago, physicists opened a new window on the universe when they first detected gravitational waves, ripples in space itself set off when massive black holes or neutron stars spiral together. Even as discoveries pour in, researchers are already planning bigger, more sensitive detectors. And a Ford versus Ferrari kind of rivalry has emerged, with scientists in the United States simply proposing detectors 10 times bigger than the ones they have now, and researchers in Europe pursuing a more radical design that would combine six detectors in a single underground observatory. Researchers say detectors 10 times more sensitive than the ones they have now could detect all black hole mergers within the observable universe and spot hundreds of mergers of neutron stars, laying bare the nature of the ultradense matter in neutron stars. But, it9s early days for the U.S. project, which is called the Cosmic Explorer, and the European project, which is known as the Einstein Telescope.

To span the great distance from our solar system to the farthest clusters of galaxies in our universe, astronomers break down the distance indicators into steps. The nearest ones are measured geometrically, with what is known as parallax. Among the objects whose distances are thus directly measured are a rare type of star known as a Cepheid variable. Henrietta Leavitt about a hundred years ago discovered, by looking at a number of such stars in the Small Magellanic Cloud, that the brighter the star, the longer its period. This secondary indicator can be used in nearby galaxies to calibrate as a standard candle a specific type of supernova (Type Ia, from explosions of white-dwarf stars), whose peak intensities are so bright that they can be seen throughout the observable universe.

International audience; Since the baryonic matter of the observable Universe consists mainly of protons and neutrons, then the numerical value of its mass can be represented and calculated on the basis of an additive-multiplicative golden algebraic fractal, based on golden algebraic fractals of the masse of proton, neutron, and muon. Based on an analytical estimate of the mass of the observable Universe, using the law “Planck’s Universal Proportions”, an analytical estimate of the Hubble constant and the main spatial-energy characteristics of the observed Universe is obtained. An analytical estimate of the Hubble constant is consistent with the experimental data of Planck’s mission, SDSS-III Baryon Oscillation Spectroscopic Survey, DES Collaboration. The objectivity of the experimental estimation of the Hubble constant from the H0LiCOW, Riess et al, Hubble Space Telescope collaborations does not raise any doubts. This means that the Hubble constant describes two similar, but different physical processes and has at least two values. The value of the Hubble constant from the collaborations Planck’s mission, SDSS-III Baryon Oscillation Spectroscopic Survey, DES Collaboration describes the process of rotation of the space of the observed Universe, and the value of the Hubble constant from the collaborations H0LiCOW, Riess et al, Hubble Space Telescope describes the process of rotation of substance in the space of the observed Universe. New estimates of the values of Dirac's large energy numbers are presented. It is confirmed that all coefficients in Planck’s proportions, which are calculated on the basis of Planck’s constants — length, mass, time, are equal to similar coefficients, which are calculated on the basis of the main characteristics of the observed Universe. Estimation of the numerical values of the Schwarzschild and Hubble radii for the observable Universe suggests that the Hubble sphere is inside the Schwarzschild sphere, therefore the observable Universe is a black hole. The presence of a redshift from distant objects of the observable Universe suggests that this is a rotating black hole. It has been shown that the vacuum pressure cannot be a source of dark energy. It is shown that the force of imaginary dark energy is equal in magnitude to the force of gravitational compression of the observed Universe and is equal to the Planck force. It is shown that after the Big Bang, the space of the observable Universe made one incomplete revolution of at 345 degrees, and the substance in it made one complete revolution of approximately 379 degrees. Estimates are given for the energy of dark matter, as the kinetic energy of rotation of the space of the observable Universe, as well as the equivalent mass of dark matter. New estimates are given: of the gravitational constant, of the Planck energy, of the Planck acceleration, of the Planck force, of the gravity factor of the observable Universe, of the Planck temperature, of the angular velocity of rotation of the space of the observable Universe. Estimates of temperature and wavelength of thermal radiation of the observable Universe, as the Hubble sphere, are given.

Recent multi-telescope observations of the repeating Fast Radio Burst FRB 121102 reveal a Gaussian-like spectral profile and associate the event with a dwarf metal-poor galaxy at a cosmological redshift of 0.19. Assuming that this event represents the entire FRB population, we make predictions for the expected number counts of FRBs observable by future radio telescopes between 50 MHz and 3.5 GHz. We vary our model assumptions to bracket the expected rate of FRBs, and find that it exceeds one FRB per second per sky when accounting for faint sources. We show that future low-frequency radio telescopes, such as the Square Kilometer Array, could detect more than one FRB per minute over the entire sky originating from the epoch of reionization., Comment: Accepted for publication in ApJ Letters, 6 pages, 2 figures

Since the 1990s, a wealth of astrophysical measurements have demonstrated that we live in a universe dominated by dark energy and dark matter. The data, which range over several orders of magnitude in length scale and originate from across the observable universe, are well-fit by a model parametrization called ΛCDM, which describes a universe of cold dark matter and a cos- mological constant. However, while cosmological data sets agree broadly with ΛCDM, the model provides no insight about the fundamental nature of either dark energy or dark matter. During the 2020s, a raft of new astronomical surveys will produce cosmological measurements of unprece- dented precision and provide sensitive new probes of dark energy and gravitation. The new data will also yield information about the microphysics of dark matter, and allow tests of cosmological models beyond ΛCDM. In this contribution, we describe the cosmological measurements made possible with the next generation of large galaxy redshift surveys, and focus in particular on the upcoming Dark Energy Spectroscopic Instrument (DESI).

The astrophysical and cosmological evidence of dark matter and dark energy provides some of the most compelling clues to the nature of physics beyond the Standard Model. If it interacts weakly with the Standard Model, dark matter can be produced directly at the LHC. Dark energy may exist in the form of light scalar particles that could contribute to the accelerating expansion of the observable universe. The following shows the results of the search for dark matter and the first collider search for dark energy, using events with large missing transverse momentum produced in association with jets using 36.1 fb$^{-1}$ of $\sqrt{s} = 13$ TeV $pp$ collision ATLAS data. This search sets the most stringent constraints on the suppression scale of disformal couplings of dark energy to Standard Model matter in the context of an effective field theory of dark energy following the Horndeski theory framework.

The little sibling of the big rip is a cosmological abrupt event predicted by some phantom cosmological models that could describe our Universe. When this event is approached the observable Universe and its expansion rate grow infinitely, but its cosmic derivative remains finite. In this work we have obtained the group of metric $f(R)$ theories of gravity that reproduce this classical cosmological background evolution. Furthermore, we have considered the quantization of some of the resulting models in the framework of quantum geometrodynamics, showing that the DeWitt criterion can be satisfied. Therefore, as it also happens in general relativity, this event may be avoided in $f(R)$ quantum cosmology.

The neutral hydrogen 21cm line is potentially a very powerful probe of the observable universe, and a number of on-going experiments are trying to detect it at cosmological distances. However, the presence of strong foreground radiations such as the galactic synchrotron radiation, galactic free-free emission and extragalactic radio sources make it a very challenging task. For the design of 21cm experiments and analysis of their data, simulation is an essential tool, and good sky foreground model is needed. With existing data the whole sky maps are available only in low angular resolutions or for limited patches of sky, which is inadequate in the simulation of these new 21cm experiments. In this paper, we present the method of constructing a high resolution self-consistent sky model at low frequencies, which incorporates both diffuse foreground and point sources. Our diffuse map is constructed by generating physical foreground components including the galactic synchrotron emission and galactic free-free emission. The point source sample is generated using the actual data from the NRAO VLA Sky Survey (NVSS) and the Sydney University Molonglo Sky Survey (SUMSS) where they are available and complete in flux limit, and mock point sources according to statistical distributions. The entire model is made self-consistent by removing the integrated flux of the point sources from the diffuse map so that this part of radiation is not double counted. We show that with the point sources added, a significant angular power is introduced in the mock sky map, which may be important for foreground subtraction simulations. Our sky maps and point source catalogues are available to download., 14 pages, 9 figures, Science China Physics, Mechanics & Astronomy accepted

The observable universe contains density perturbations on scales larger than any finite volume survey. Perturbations on scales larger than a survey can measure degrade its power to constrain cosmological parameters. The dependence of survey observables such as the weak lensing power spectrum on these long-wavelength modes results in super-sample covariance. Accurately forecasting parameter constraints for future surveys requires accurately accounting for the super-sample effects. If super-sample covariance is in fact a major component of the survey error budget, it may be necessary to investigate mitigation strategies that constrain the specific realization of the long-wavelength modes. We present a Fisher matrix based formalism for approximating the magnitude of super-sample covariance and the effectiveness of mitigation strategies for realistic survey geometries. We implement our formalism in the public code SuperSCRAM: Super-Sample Covariance Reduction and Mitigation. We illustrate SuperSCRAM with an example application, where the modes contributing to super-sample covariance in the WFIRST weak lensing survey are constrained by the low-redshift galaxy number counts in the wider LSST footprint. We find that super-sample covariance increases the volume of the error ellipsoid in 7D cosmological parameter space by a factor of 4.5 relative to Gaussian statistical errors only, but our simple mitigation strategy more than halves the contamination, to a factor of 2.0., Comment: 32 pages, 7 figures, 1 table, comments/suggestions welcome!

In this paper we investigate an observable universe in Bianchi type V space-time by taking into account the cosmological constant as the source of energy. We have performed a $\chi^{2}$ test to obtain the best fit values of the model parameters of the universe in the derived model. We have used two types of data sets, viz: i) 31 values of the Hubble parameter and ii) the 1048 Phanteon data set of various supernovae distance moduli and apparent magnitudes. From both the data sets, we have estimated the current values of the Hubble constant, density parameters $(\Omega_{m})_{0}$ and $(\Omega_{\Lambda})_{0}$. The present value of deceleration parameter of the universe in derived model is obtained as $q_{0} = 0.59^{+0.04}_{-0.03}$ and $0.59^{+0.02}_{-0.03}$ in accordance with $H(z)$ and Pantheon data respectively. Also we observe that there is a signature flipping in the sign of deceleration parameter from positive to negative and transition red-shift exists. Thus, the universe in derived model represents a transitioning universe which is in accelerated phase of expansion at present epoch. We have estimated the current age of the universe $(t_{0})$ and present value of jerk parameter $(j_{0})$. Our obtained values of $t_{0}$ and $j_{0}$ are in good agreement with its values estimated by Plank collaborations and WMAP observations., Comment: 7 pages, 4 figure panels

Indirect searches for signatures of corpuscular dark matter have been performed using all cosmic messengers: gamma rays, cosmic rays, and neutrinos. The search for dark matter from neutrinos is of particular importance since they are the only courier that can reach detectors from dark matter processes in dense environments, such as the core of the Sun or Earth, or from the edge of the observable Universe. In this work, we introduce $\chi$aro$\nu$, a software package that, in the spirit of its mythological Greek namesake $\chi \acute\alpha \rho \omega \nu $, bridges the dark sector and Standard Model by predicting neutrino fluxes from different celestial dark matter agglomerations. The flux at the point of production is either computed internally by $\chi$aro$\nu$ or is taken from user supplied tables. $\chi$aro$\nu$ then propagates this flux through vacuum or dense media and returns the expected neutrino yield at an observer's location. In developing $\chi$aro$\nu$, we have revisited and updated the production of neutrinos in dense media, updated the propagation of high-energy neutrinos, and studied the sources of uncertainty in neutrino transport. This package is coupled to a new calculation that includes electroweak corrections resulting in the most up-to-date and complete repository of neutrino fluxes from dark matter decay and annihilation over the energy range of 1 GeV to 10 PeV coming from the Earth, the Sun, and the Galactic halo., Comment: 29 pages, 12 figures, code available at: https://github.com/IceCubeOpenSource/charon - comments received are addressed

Relations for the relativistic energy and metric are analyzed inside and outside the body in the framework of the covariant theory of gravitation. The methods of optimal energy gauging and equations for the metric are chosen. It is shown that for the matter inside the body a procedure is required to average the physical quantities, including the cosmological constant and the scalar curvature. For the case of the relativistic uniform system, the cosmological constant and the scalar curvature are explicitly calculated, which turn out to be constant values inside the body and are assumed to be equal to zero outside the body. Comparison of the cosmological constants inside a proton, a neutron star and in the observable Universe allows us to explain the cosmological constant problem arising in the Lambda-CDM model.

12 pags., 5 figs., 2 apps., We analyze a quantized toy model of a universe undergoing eternal inflation using a quantum-field-theoretical formulation of the Wheeler–DeWitt equation. This so-called third quantization method leads to the picture that the eternally inflating universe is converted to a multiverse in which sub-universes are created and exhibit a distinctive phase in their evolution before reaching an asymptotic de Sitter phase. From the perspective of one of these sub-universes, we can thus analyze the pre-inflationary phase that arises naturally. Assuming that our observable universe is represented by one of those sub-universes, we calculate how this pre-inflationary phase influences the power spectrum of the cosmic microwave background (CMB) anisotropies and analyze whether it can explain the observed discrepancy of the power spectrum on large scales, i.e. the quadrupole issue in the CMB. While the answer to this question is negative in the specific model analyzed here, we point out a possible resolution of this issue., This article is based upon work from COST Action CA15117 “Cosmology and Astrophysics Network for Theoretical Advances and Training Actions (CANTATA)”, supported by COST (European Cooperation in Science and Technology). The research of M. B.-L. is supported by the Basque Foundation of Science Ikerbasque. She and J. M. also would like to acknowledge the partial support from the Basque government Grant No. IT956-16 (Spain) and the project FIS2017-85076-P (MINECO/AEI/FEDER, UE). The research of M. K. was financed by the Polish National Science Center Grant DEC2012/06/A/ST2/00395 as well as by a Grant for the Short Term Scientific Mission (STSM) “Multiverse impact onto the cosmic microwave background and its relation to modified gravity” (COST-STSM-CA15117- 36137) awarded by the above-mentioned COST Action. For their kind hospitality while part of this work was done, M. K. and J. M. would like to thank the Centro de Matemática e Aplicações of the Universidade da Beira Interior in Covilhã, Portugal and M. K. also thanks the Department of Theoretical Physics and History of Science of the University of the Basque Country (UPV/EHU).

This paper intends to design a payload for a Nanosat to record and analyze the Cosmic Microwave Background Radiation (CMBR). Since its discovery in 1965, CMBR has become a much-discussed topic with the speculation that it might hold the key to the birth of our Universe. The big bang theory not only scattered the matter which condensed into galaxies, but also a massive amount of radiation which can be detected by using appropriate instruments, albeit as microwaves due to massive redshift (Redshift is shifting of the wavelength of light or some other form of electromagnetic radiation to the red end of the spectrum. It occurs when a light source moves away from the observer) of our ever-expanding universe. The space missions for detection of CMBR have not been cost efficient, and the Earth-based laboratories deal with too much interference from the surrounding sources. The radiation that was first discovered was of the wavelength 10cm at a reported temperature of 3.5 ± 1 K. The data received about the cosmic microwave background radiation can provide us much information about the anisotropic nature of the observable universe, the cosmic inflation era as well as the recombination era. In the present scenario, CMBR can be detected at a wavelength of about 2 mm. The challenge lies in using a Nanosat in the low earth orbit (LEO) to study CMBR because, being a form of radiation in itself, it is very susceptible to noise from the surrounding sources. The radiation from the sun, the earth as well as the satellite itself will contribute to the noise which needs to be calibrated off since the radiation due to the Cosmic Microwave Background is faint. The interference due to the ambient plasma will also be added to the noise. The antennas are designed with reflectors and calibrated to deal away with all of the aforementioned noises. The use of appropriate rectifiers and amplifiers for selection and amplification of the desired data has also been employed. The whole setup is cooled externally and the orbit selected to minimise the interfering radiation. The spinning of the satellite is controlled to gather desired amount data from a particular region of space. A detailed analysis for noise mitigation and selection of appropriate equipment has been discussed in this paper.

We present a systematic investigation of the cosmological constant effects in compact stars interiors in the framework of Einstein's gravity. Consideration of a cosmological constant $\Lambda$ in compact stars is motivated by the mechanism of acceleration of the observable universe, where $\Lambda$ is usually related to the dark energy. In particular, we consider compact star mass twins, hybrid neutron stars that populate both the second and third branch of the mass-radius diagram. For those models, the need of consideration of excluded volume effects in the equation of state, resulting from the finite size volume of nucleons, leads to a stiffening of matter causing compact stars to acquire higher mass and radius values. We demonstrate that certain values of the cosmological constant can also modify the compact star properties but in an opposite way. In addition, we find that the inclusion of $\Lambda$ can have a similar effect to the existence of pasta phases at the hadron-quark interface., Comment: 5 pages, 1 figure, Proceedings of The XXII International Scientific Conference of Young Scientists and Specialists (AYSS-2018), Dubna, April 23-27, 2018; references added, typos corrected

There are many inflationary models that allow the formation of the large-scale structure of the observable universe. The non-gaussianity parameter $f_{NL}$ is a useful tool to discriminate among these cosmological models when comparing the theoretical predictions with the satellite survey results like those from WMAP and Planck. The goal of this proceeding contribution is to review the moment transport equations methodology and the subsequent calculation of the $f_{NL}$ parameter., LaTeX file in elsarticle style, 7 pages, 1 figure. To be published in Nuclear and Particle Physics Proceedings as the proceedings of the Tenth Latin American Symposium on High Energy Physics (Medellin - Colombia, 24th-28th November, 2014). v2: no changes in the file. Just to mention that this work is entirely based on Ref. [4] and is the result of Carlos A. Sierra's MSc thesis

One of the major challenges of modern physics is to decipher the nature of dark matter. Astrophysical observations provide ample evidence for the existence of an invisible and dominant mass component in the observable universe, from the scales of galaxies up to the largest cosmological scales. The dark matter could be made of new, yet undiscovered elementary particles, with allowed masses and interaction strengths with normal matter spanning an enormous range. Axions, produced non-thermally in the early universe, and weakly interacting massive particles (WIMPs), which froze out of thermal equilibrium with a relic density matching the observations, represent two well-motivated, generic classes of dark matter candidates. Dark matter axions could be detected by exploiting their predicted coupling to two photons, where the highest sensitivity is reached by experiments using a microwave cavity permeated by a strong magnetic field. WIMPs could be directly observed via scatters off atomic nuclei in underground, ultra low-background detectors, or indirectly, via secondary radiation produced when they pair annihilate. They could also be generated at particle colliders such as the LHC, where associated particles produced in the same process are to be detected. After a brief motivation and an introduction to the phenomenology of particle dark matter detection, I will discuss the most promising experimental techniques to search for axions and WIMPs, addressing their current and future science reach, as well as their complementarity.

We present a new model of cosmology which appears to show great promise. Our flat space cosmology model, using only four basic and reasonable assumptions, derives highly accurate Hubble parameter H0, Hubble radius R0 and total mass M0 values for our observable universe. Our model derives a current Hubble parameter of , in excellent agreement with the newly reported (lower limit) results of the 2015 Planck Survey. Remarkably, all of these derivations can be made with only these basic assumptions and the current CMB radiation temperature . The thermodynamic equations we have generated follow Hawking’s black hole temperature formula. We have also derived a variety of other useful cosmological formulae. These include angular velocity and other rotational formulae. A particularly useful hyperbolic equation, , has been derived, which appears to be an excellent fit for the Planck scale as well as the current observable universe scale. Using the flat space Minkowski relativistic formula for Doppler effect, and a formula for staging our cosmological model according to its average mass-energy density at every Hubble time (universal age) in its expansion, a persuasive argument can be made that the observable phenomena attributed to dark energy are actually manifestations of Doppler and gravitational redshift. Finally, a theory of cosmic inflation becomes completely unnecessary because our flat space cosmology model is always at critical density.

Dark energy and dark matter constitute 95% of the observable Universe. Yet the physical nature of these two phenomena remains a mystery. Einstein suggested a long-forgotten solution: gravitationally repulsive negative masses, which drive cosmic expansion and cannot coalesce into light-emitting structures. However, contemporary cosmological results are derived upon the reasonable assumption that the Universe only contains positive masses. By reconsidering this assumption, I have constructed a toy model which suggests that both dark phenomena can be unified into a single negative mass fluid. The model is a modified $\Lambda$CDM cosmology, and indicates that continuously-created negative masses can resemble the cosmological constant and can flatten the rotation curves of galaxies. The model leads to a cyclic universe with a time-variable Hubble parameter, potentially providing compatibility with the current tension that is emerging in cosmological measurements. In the first three-dimensional N-body simulations of negative mass matter in the scientific literature, this exotic material naturally forms haloes around galaxies that extend to several galactic radii. These haloes are not cuspy. The proposed cosmological model is therefore able to predict the observed distribution of dark matter in galaxies from first principles. The model makes several testable predictions and seems to have the potential to be consistent with observational evidence from distant supernovae, the cosmic microwave background, and galaxy clusters. These findings may imply that negative masses are a real and physical aspect of our Universe, or alternatively may imply the existence of a superseding theory that in some limit can be modelled by effective negative masses. Both cases lead to the surprising conclusion that the compelling puzzle of the dark Universe may have been due to a simple sign error., Comment: Accepted for publication in Astronomy and Astrophysics (A&A). Videos of the simulations are available online at: https://goo.gl/rZN1Ps

Galaxy clusters are the largest virialized structures in the observable Universe. The knowledge of their properties provides many useful astrophysical and cosmological information. Our aim is to derive the luminosity and stellar mass profiles of the nearby galaxy clusters of the Omega-WINGS survey and to study the main scaling relations valid for such systems. We have merged the data of the WINGS and Omega-WINGS databases, sorted the sources according to the distance from the brightest cluster galaxy (BCG) and calculated the integrated luminosity profiles in the $B$ and $V$ bands, taking into account extinction, photometric and spatial completeness, K-correction and background contribution. Then, by exploiting the spectroscopic sample we derived the stellar mass profiles of the clusters. We got the luminosity profiles of 46 galaxy clusters, reaching $r_{200}$ in 30 cases, and the stellar mass profiles of 42 of our objects. We successfully fitted all the integrated luminosity growth profiles with one or two embedded S\'ersic components, deriving the main clusters parameters. Finally, we checked the main scaling relation among the clusters parameters in comparison with those obtained for a selected sample of early-type galaxies (ETGs) of the same clusters. We found that the nearby galaxy clusters are non-homologous structures like ETGs and exhibit a color-magnitude (CM) red-sequence relation very similar to that observed for galaxies in clusters. These properties are not expected in the current cluster formation scenarios. In particular the existence of a CM relation for clusters, shown here for the first time, suggests that the baryonic structures grow and evolve in a similar way at all scales., Comment: 45 pages, 41 figures

It is shown here that a model for inertial mass, called quantised inertia, or MiHsC (Modified inertia by a Hubble-scale Casimir effect) predicts the rotational acceleration of the 153 good quality galaxies in the SPARC dataset (2016 AJ 152 157), with a large range of scales and mass, from just their visible baryonic matter, the speed of light and the co-moving diameter of the observable universe. No dark matter is needed. The performance of quantised inertia is comparable to that of MoND, yet it needs no adjustable parameter. As a further critical test, quantised inertia uniquely predicts a specific increase in the galaxy rotation anomaly at higher redshifts. This test is now becoming possible and new data shows that galaxy rotational accelerations do increase with redshift in the predicted manner, at least up to Z=2.2., Comment: 9 pages, 2 figures. Published in Astrophys Space Sci

Cosmic strings are topological defects possibly formed in the early Universe, which may be observable due to their gravitational effects on the cosmic microwave background radiation or gravitational wave experiments. To this effect it is important to quantitatively ascertain the network properties, including their density, velocity or the number of strings present, at the various epochs in the observable Universe. Attempts to estimate these numbers often rely on simplistic approximations for the string parameters, such as assuming that the network is scaling. However, in cosmological models containing realistic amounts of radiation, matter and dark energy a string network is never exactly scaling. Here we use the velocity-dependent one-scale model for the evolution of a string network to better quantify how these networks evolve. In particular we obtain new approximate analytic solutions for the behavior of the network during the radiation-to-matter and matter-to-acceleration transitions (assuming, in the latter case, the canonical $\Lambda$ cold dark matter model), and numerically calculate the relevant quantities for a range of possible dark energy models., Comment: 10 pages, 5 figures

The most energetic gamma-ray bursts (GRBs) are remarkable sources releasing huge amounts of energy on short timescales. Their prompt emission, which usually lasts few seconds, is so bright that it is visible across the whole observable universe. Studying these extreme events may provide clues on the nature of GRB progenitors and on the physical processes at work in relativistic jets. In this paper, we study the bright end of the isotropic energy distribution of long GRBs. We use two samples of long GRBs with redshift detected by Fermi/GBM or Konus-Wind, two instruments which measure the spectral shape and the energetics of the prompt emission accurately. We focus on GRBs within a range of redshifts z = 1 -- 5, a volume that contains a large number of energetic GRBs, and we propose a simple method to reconstruct the bright end of the GRB energy distribution from the observed one. We find that the GRB energy distribution cannot be described by a simple power law but requires a strong cutoff above $1-3 \times 10^{54}$ erg. We attribute this feature to an intrinsic limit on the energy per unit of solid angle radiated by gamma-ray bursts., Revised version after correcting an error in the computation of the horizon of Konus GRBs (Table 3). Changes in the text are marked in bold. The main result is not affected

Observations by the Wilkinson Microwave Anisotropy Probe and the Planck mission suggest a hemispherical power amplitude asymmetry in the cosmic microwave background, with a correlation length on the order of the size of the observable Universe. We find that this anomaly can be naturally explained by an axion-like particle (ALP) cosmic string formed near our visible Universe. The field variation associated to this cosmic string creates particle density fluctuations after inflation, which consequently decay into radiation before the Big Bang Nucleosynthesis (BBN) era and resulted in the observed power asymmetry. We find in this scenario that the hemispherical power amplitude asymmetry is strongly scale dependent: $A(k)\propto {\rm exp}(-kl)/k$. Admittedly, typical inflation models predict a relic number density of topological defects of order one per observable Universe and so in our model the cosmic string must be tuned to have an impact factor of order $1/H_0$. Interestingly, the constraints based on purely cosmological considerations also give rise to a Peccei-Quinn scale $F_a$ of order $10^3$ larger then the Hubble scale of inflation $H_I$. Assuming $H_I\sim 10^{13}$GeV, we then have an ALP with $F_a\sim 10^{16}$GeV, which coincides with the presumed scale of grand unification. As we require ALP decays occur before the BBN era, which implies a relatively heavy mass or strong self-coupling, and considering that the associated potential should break the shift symmetry softly in order to protect the system from radiative corrections, we also conclude that the required ALP potential should be monodromic in nature., Comment: 16 pages, 2 figures, references and comments added, published version

The article examines why there are so few galaxies in the observable universe. According to the author, astronomers wonder why only a small fraction of matter resides in galaxies. He cites a hypothesis by astronomers that states the bulk of matter in the universe is trapped in giant gaseous filaments, called warm-hot intergalactic medium (WHIM), which is difficult to detect directly. Topics include what a galaxy is, the process in galaxy formation, called feedback, and the idea that galaxies and their contents are not fixed structures, but the bright components of a wider sea of gas. INSETS: Betrayed by Its Shadow;Spitting It Back Out.

In a flat Friedmann-Lema\^itre-Robertson-Walker background, a scheme of dark matter-dark energy interaction is studied considering a holographic Ricci-like model for the dark energy. Without giving a priori some specific model for the interaction function, we show that this function can experience a change of sign during the cosmic evolution. The parameters involved in the holographic model are adjusted with Supernova data and we obtained results compatible with the observable universe., Comment: 16 pages, 6 figures, references and comments added, to appear in Astrophys. Space Sci

The visible mass of the observable universe agrees with that needed for a flat cosmos, and the reason for this is not known. It is shown that this can be explained by modelling the Hubble volume as a black hole that emits Hawking radiation inwards, disallowing wavelengths that do not fit exactly into the Hubble diameter, since partial waves would allow an inference of what lies outside the horizon. This model of “horizon wave censorship” is equivalent to a Hubble-scale Casimir effect. This incomplete toy model is presented to stimulate discussion. It predicts a minimum mass and acceleration for the observable universe which are in agreement with the observed mass and acceleration, and predicts that the observable universe gains mass as it expands and was hotter in the past. It also predicts a suppression of variation on the largest cosmic scales that agrees with the low-l cosmic microwave background anomaly seen by the Planck satellite.

High-resolution, low-noise observations of the cosmic microwave background (CMB) planned for the near-future will enable new cosmological probes based on re-scattered CMB photons -- the secondary CMB. At the same time, enormous galaxy surveys will map out huge volumes of the observable Universe. Using the technique of kinetic Sunyaev Zel'dovich (kSZ) tomography these new probes can be combined to reconstruct the remote dipole field, the CMB dipole as observed from different vantage points in our Universe. The volume accessible to future galaxy surveys is large enough that general relativistic corrections to the observed distribution of galaxies must be taken into account. These corrections are interesting probes of gravity in their own right, but can also obscure potential signatures of primordial non-Gaussianity. In this paper, we demonstrate that correlations between the reconstructed remote dipole field and the observed galaxy number counts can in principle be used to detect general relativistic corrections. We show that neglecting general relativistic corrections leads to an $\mathcal{O}(1)$ bias on the inferred amplitude of primordial non-Gaussianity, $f_{\rm NL}$. In addition, we demonstrate that the reconstructed remote dipole field can provide useful constraining power on various bias parameters appearing in the galaxy number counts, and can significantly mitigate the effects of alignment bias., Comment: 13 pages, 3 figures