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200 papers

A higher value of Hubble constant has been obtained from measurements with nearby Type Ia supernovae, than that obtained at much higher redshift. With the peculiar motions of their hosts, we find that the matter content at such low redshift…

Cosmology and Nongalactic Astrophysics · Physics 2013-07-25 Shuang-Nan Zhang , Yin-Zhe Ma

The Standard Model of particle physics assumes that the so-called fundamental constants are universal and unchanging. Absorption lines arising in molecular clouds along quasar sightlines offer a precise test for variations in the…

Astrophysics · Physics 2009-08-18 Michael T. Murphy , Victor V. Flambaum , Sebastien Muller , Christian Henkel

We present cosmological parameters measurements from the full combination of DESI DR1 galaxy clustering data described with large-scale structure effective field theory. By incorporating additional datasets (photometric galaxies and CMB…

Cosmology and Nongalactic Astrophysics · Physics 2026-01-23 Mikhail M. Ivanov , James M. Sullivan , Shi-Fan Chen , Anton Chudaykin , Mark Maus , Oliver H. E. Philcox

We explore observational constraints on a cosmological brane-world scenario in which the bulk is not empty. Rather, exchange of mass-energy between the bulk and the bane is allowed. The evolution of matter fields to an observer on the brane…

Astrophysics · Physics 2009-11-13 K. Umezu , K. Ichiki , T. Kajino , G. J. Mathews , R. Nakamura , M. Yahiro

A new U(1) gauge symmetry is the simplest extension of the Standard Model and has various theoretical and phenomenological motivations. In this paper, we study the cosmological constraint on the MeV scale dark photon. After the neutrino…

High Energy Physics - Phenomenology · Physics 2020-09-30 Masahiro Ibe , Shin Kobayashi , Yuhei Nakayama , Satoshi Shirai

We revisit the observational constraints on spatial curvature following recent claims that the Planck data favour a closed Universe. We use a new and statistically powerful Planck likelihood to show that the Planck temperature and…

Cosmology and Nongalactic Astrophysics · Physics 2020-06-03 George Efstathiou , Steven Gratton

We derive analytic lower bounds on the cosmic baryon density by requiring that the high-redshift IGM contain enough neutral hydrogen to produce the observed \lya absorption in quasar spectra. The key theoretical assumption is that absorbing…

Astrophysics · Physics 2009-10-30 David H. Weinberg , Jordi Miralda-Escude , Lars Hernquist , Neal Katz

The unexpectedly strong 21cm absorption signal detected by the EDGES experiment suggests that the baryonic gas was colder at redshift $z\sim 17$ than predicted in the standard scenario. We discuss a mechanism to lower the baryon temperature…

High Energy Physics - Phenomenology · Physics 2018-04-03 Adam Falkowski , Kalliopi Petraki

The $\Lambda$ cold dark matter ($\Lambda\textrm{CDM}$) model is currently known as the simplest cosmology model that best describes observations with minimal number of parameters. Here we introduce a cosmology model that is preferred over…

Cosmology and Nongalactic Astrophysics · Physics 2015-03-05 Chan-Gyung Park

The determination of the mean density of the Universe is a long standing problem of modern cosmology. The number density evolution of x-ray clusters at a fixed temperature is a powerful cosmological test, new in nature (Oukbir and…

Astrophysics · Physics 2009-10-30 Alain Blanchard , James G. Bartlett , Rachida Sadat

The tired-light cosmology is considered in the framework of Kaluza-Klein theory in 5D. The solution of the five-dimensional semi-classical Einstein equations with nonzero five-dimensional energy-momentum tensor gives density of matter in…

General Relativity and Quantum Cosmology · Physics 2007-05-23 W. B. Belayev

In the past years 'quintessence' models have been considered which can produce the accelerated expansion in the universe suggested by recent astronomical observations. One of the key differences between quintessence and a cosmological…

Astrophysics · Physics 2014-10-13 Rachel Bean , Steen H. Hansen , Alessandro Melchiorri

We present updated cosmological constraints from measurements of the gas mass fractions ($f_{gas}$) of massive, dynamically relaxed galaxy clusters. Our new data set has greater leverage on models of dark energy, thanks to the addition of…

It is extraordinary that a number of observations indicate that we live in a spatially flat, low matter density Universe, which is currently undergoing a period of accelerating expansion. The effort to explain this current state has focused…

Astrophysics · Physics 2010-02-18 R. R. Caldwell

We have shown earlier that, contrary to popular belief, Einstein--de Sitter (E--deS) models can still fit the {\sl WMAP} data on the cosmic microwave background provided one adopts a low Hubble constant and relaxes the usual assumption that…

Astrophysics · Physics 2008-11-26 Alain Blanchard , Marian Douspis , Michael Rowan-Robinson , Subir Sarkar

The cosmological constant, which was introduced by Einstein a century ago to allow for a static universe, experienced a revival two decades ago under the label dark energy as a parameter to model the observed accelerated expansion of the…

General Physics · Physics 2019-01-08 Jan O. Stenflo

We have analyzed the properties of a sample of 33 groups and clusters of galaxies and examine the baryon content to check for trends over a decade in temperature down to 1 keV. We examine the relative contribution of galaxies and ICM to…

Astrophysics · Physics 2007-05-23 H. Roussel , R. Sadat , A. Blanchard

The Cosmological General Relativity (CGR) of Carmeli, a 5-dimensional (5-D) theory of time, space and velocity, predicts the existence of an acceleration a_0 = c / tau due to the expansion of the universe, where c is the speed of light in…

General Physics · Physics 2015-06-04 Firmin J. Oliveira

We discuss the entropy and the size/homogeneity/horizon problems in power-law expanding universes with one scale initial conditions. We set the minimal scale $\Lambda = 10^{25}$ GeV at which a non-inflationary solution is possible and show…

High Energy Physics - Phenomenology · Physics 2009-01-07 Natalia Shuhmaher

A large lepton number asymmetry of $\mathcal{O}(0.1-1)$ at present universe might not only be allowed but also necessary for consistency among cosmological data. We show that, if a sizeable lepton number asymmetry were produced before the…

High Energy Physics - Phenomenology · Physics 2017-05-10 Gabriela Barenboim , Wan-Il Park