Joudaki, S., Doré, O., Ferramacho, L., Kaplinghat, M. The bispectrum of redshifted 21 centimeter fluctuations from the dark ages. The future of primordial features with 21 cm tomography. Possible interaction between baryons and dark-matter particles revealed by the first stars. Heating of baryons due to scattering with dark matter during the dark ages. Effects of dark matter-baryon scattering on redshifted 21 cm signals. New light on 21 cm intensity fluctuations from the dark ages. 21cm angular-power spectrum from the dark ages. Growth of linear perturbations before the era of the first galaxies. A method for separating the physics from the astrophysics of high-redshift 21 centimeter fluctuations. The cosmic microwave background radiation fluctuations from HI perturbations prior to reionization. Probing the epoch of early baryonic infall through 21-cm fluctuations. Measuring the small-scale power spectrum of cosmic density fluctuations through 21cm tomography prior to the epoch of structure formation. 21 centimeter tomography of the intergalactic medium at high redshift. The 21-cm line at high redshift: a diagnostic for the origin of large scale structure. Spectral appearance of non-uniform gas at high z. Formation of clusters of galaxies protocluster fragmentation and intergalactic gas heating. Our analysis sets a baseline for upcoming lunar and space-based dark-ages experiments. Enhancing the collecting area or integration time by an order of magnitude would yield a 0.5% parameter combination, a helium measurement five times better than Planck and a constraint on the neutrino mass as good as Planck. Precision cosmology with 21 cm fluctuations requires a collecting area of 10 km 2 (corresponding to 400,000 stations), which, with a 1,000 h integration, would exceed the same global case by a factor of ~2. A 10,000 h integration would improve this measurement to 3.2% and constrain the cosmic helium fraction to 9.9%. A measurement of the global (sky-averaged) 21 cm signal to the precision of thermal noise from a 1,000 h integration would yield a measurement within 10% of a combination of cosmological parameters. While exotic physics could be discovered, here we quantify the expected benefits within the standard cosmology. In 2019, the meter has been re-defined based on the changes made to the definition of a second.The 21 cm signal from the dark ages provides a potential new probe of fundamental cosmology. Prior to this definition, the meter was based on the length of a prototype meter bar. The relationship between the meter and the millimeter is constant however. The definition of the meter has changed over time, the current definition being based on the distance traveled by the speed of light in a given amount of time. It indicates one thousandth of the base unit, in this case the meter. History/origin: The milli- prefix is one of many metric prefixes. It is defined in terms of the meter, as 1/1000 of a meter, or the distance traveled by light in 1/299 792 458 000 of a second. Millimeterĭefinition: A millimeter (symbol: mm) is a unit of length in the International System of Units (SI). Unlike the United States, the UK has adopted the metric system while the metric system is widely used in government, commerce, and industry, remnants of the imperial system can still be seen in the UK's use of miles in its road systems. However, there still remain a number of countries that primarily use the mile instead of the kilometer including the United States and the United Kingdom (UK). This definition is subject to change, but the relationship between the meter and the kilometer will remain constant.Ĭurrent use: It is currently the official unit of measurement for expressing distances between geographical places on land in most of the world. The origin of the kilometer is linked to that of the meter, and its current definition as the distance traveled by light in 1/299 792 458 second. One kilometer is therefore one thousand meters. History/origin: The prefix kilo- is a metric prefix indicating one thousand. One kilometer is equivalent to 0.6214 miles. Definition: A kilometer (symbol: km) is a unit of length in the International System of Units (SI).
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