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Cosmology

About: Cosmology is a research topic. Over the lifetime, 18004 publications have been published within this topic receiving 631028 citations. The topic is also known as: physical cosmology & cosmologies.


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Journal ArticleDOI
TL;DR: In this article, the authors study how the oscillations of the neutrinos affect their thermalization process during the reheating period with temperature $O(1)$ MeV in the early universe.
Abstract: We study how the oscillations of the neutrinos affect their thermalization process during the reheating period with temperature $O(1)$ MeV in the early universe. We follow the evolution of the neutrino density matrices and investigate how the predictions of big bang nucleosynthesis vary with the reheating temperature. For the reheating temperature of several MeV, we find that including the oscillations makes different predictions, especially for $^{4}\mathrm{He}$ abundance. Also, the effects on the lower bound of the reheating temperature from cosmological observations are discussed.

202 citations

Book
01 Jan 2000
TL;DR: In this article, the authors used time reversal and elementary logic to conclude that the universe must originally have been so compact that we can talk of a beginning, which they called the primeval atom.
Abstract: Modern cosmology began with the solutions to Einstein's theory of gravity discovered by Aleksandr Friedmann and Georges Lemaitre in the 1920s. When combined with the Hubble redshift‐distance relation, these solutions could be interpreted as showing that we live in an expanding universe. By 1930, the scientific establishment and much of the lay public believed in this expanding cosmos. It then requires only time reversal and elementary logic to conclude that the universe must originally have been so compact that we can talk of a beginning. Lemaitre tried to describe this state as the “primeval atom.”

202 citations

Journal ArticleDOI
05 Aug 1982-Nature
TL;DR: In this article, a mechanism for the spontaneous creation of density perturbations during the transition in the early Universe from unconfined quark matter to hadronic matter is presented.
Abstract: A long-standing problem in cosmology has been to understand the origins of density inhomogeneities in the Universe. Calculations involving inhomogeneities have for the most part required the assumption of some initial spectrum of perturbations, which is inserted ‘by hand’. We present here a mechanism for the spontaneous creation of density perturbations during the transition in the early Universe from unconfined quark matter to hadronic matter. The subsequent evolution of these perturbations remains a problem for further study.

201 citations

Journal ArticleDOI
TL;DR: Einstein Telescope (ET) is a 3rd generation gravitational-wave (GW) detector that is currently undergoing a design study and can detect millions of compact binary mergers up to redshifts 2-8 as discussed by the authors.
Abstract: Einstein Telescope (ET) is a 3rd generation gravitational-wave (GW) detector that is currently undergoing a design study. ET can detect millions of compact binary mergers up to redshifts 2-8. A small fraction of mergers might be observed in coincidence as gamma-ray bursts, helping to measure both the luminosity distance and red-shift to the source. By fitting these measured values to a cosmological model, it should be possible to accurately infer the dark energy equation-of-state, dark matter and dark energy density parameters. ET could, therefore, herald a new era in cosmology.

201 citations

Posted Content
TL;DR: Cosmic Origins Explorer (Cosmic Explorer) as mentioned in this paper is a full-sky, microwave-band satellite with an angular resolution ranging from 23 arcmin (45 GHz) and 1.3 arcmin(795 GHz).
Abstract: COrE (Cosmic Origins Explorer) is a fourth-generation full-sky, microwave-band satellite recently proposed to ESA within Cosmic Vision 2015-2025. COrE will provide maps of the microwave sky in polarization and temperature in 15 frequency bands, ranging from 45 GHz to 795 GHz, with an angular resolution ranging from 23 arcmin (45 GHz) and 1.3 arcmin (795 GHz) and sensitivities roughly 10 to 30 times better than PLANCK (depending on the frequency channel). The COrE mission will lead to breakthrough science in a wide range of areas, ranging from primordial cosmology to galactic and extragalactic science. COrE is designed to detect the primordial gravitational waves generated during the epoch of cosmic inflation at more than $3\sigma $ for $r=(T/S)>=10^{-3}$. It will also measure the CMB gravitational lensing deflection power spectrum to the cosmic variance limit on all linear scales, allowing us to probe absolute neutrino masses better than laboratory experiments and down to plausible values suggested by the neutrino oscillation data. COrE will also search for primordial non-Gaussianity with significant improvements over Planck in its ability to constrain the shape (and amplitude) of non-Gaussianity. In the areas of galactic and extragalactic science, in its highest frequency channels COrE will provide maps of the galactic polarized dust emission allowing us to map the galactic magnetic field in areas of diffuse emission not otherwise accessible to probe the initial conditions for star formation. COrE will also map the galactic synchrotron emission thirty times better than PLANCK. This White Paper reviews the COrE science program, our simulations on foreground subtraction, and the proposed instrumental configuration.

200 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20241
2023768
20221,518
2021737
2020784
2019782