相关论文: Cosmological Probes of Light Relics

Light thermal relics of the hot big bang, often quantified by the parameter $N_\mathrm{eff}$, are one of the primary targets of cosmological measurements. At present, the energy density in such relics is constrained to be less than ten…

The hot dense environment of the early universe is known to have produced large numbers of baryons, photons, and neutrinos. These extreme conditions may have also produced other long-lived species, including new light particles (such as…

Many well-motivated extensions of the Standard Model predict the existence of new light species that may have been produced in the early universe. Prominent examples include axions, sterile neutrinos, gravitinos, dark photons, and more. The…

The existence of a cosmic neutrino background -- the analogue of the cosmic microwave background -- is a fundamental prediction of standard big bang cosmology. Up to now, the observational evidence for its existence is rather indirect and…

The existence of big bang relic neutrinos - exact analogues of the big bang relic photons comprising the cosmic microwave background radiation - is a basic prediction of standard cosmology. At present, the observational evidence for their…

Many scenarios of physics beyond the standard model predict new light, weakly coupled degrees of freedom, populated in the early universe and remaining as cosmic relics today. Due to their high abundances, these relics can significantly…

Cosmological measurements of the radiation density in the early universe can be used as a sensitive probe of physics beyond the standard model. Observations of primordial light element abundances have long been used to place non-trivial…

Cosmological observations allow to measure the abundance of light relics produced in the early Universe. Most studies focus on the thermal freeze-out scenario, yet light relics produced by freeze-in are generic for models in which new light…

According to the standard models of particle physics and cosmology, there should be a background of cosmic neutrinos in the present Universe, similar to the cosmic microwave photon background. The weakness of the weak interactions renders…

The standard Big Bang cosmology predicts the existence of an, as yet undetected, relic neutrino background, similar to the photons observed in the cosmic microwave background. If neutrinos have mass, then such relic neutrinos are a natural…

Detecting the extremely low-energy neutrinos that form the Cosmic Neutrino Background (CNB) presents many experimental challenges, but pursuing this elusive goal is still worthwhile because these weakly-interacting particles could provide a…

We discuss how a laboratory detection of a sterile neutrino not only would constitute a fundamental discovery of a new particle, but could also provide an indication of the evolution of the Universe before Big-Bang Nucleosynthesis (BBN), a…

The Cosmic Neutrino Background (CNB) is a definite prediction of the standard cosmological model and its direct discovery would represent a milestone in cosmology and neutrino physics. In this work, we consider the capture of relic…

In the standard Big Bang cosmology the canonical value for the ratio of relic neutrinos to CMB photons is 9/11. Within the framework of the Standard Model of particle physics there are small corrections, in sum about 1%, due to slight…

The intersection of the cosmic and neutrino frontiers is a rich field where much discovery space still remains. Neutrinos play a pivotal role in the hot big bang cosmology, influencing the dynamics of the universe over numerous decades in…

Future CMB experiments have the potential to probe the density of relativistic species at the sub-percent level. Sensitivity at this level allows light thermal relics to be detected up to arbitrarily high decoupling temperatures.…

A measurement of the big bang relic neutrinos would open a new window to the early universe. We review various possibilities to detect this cosmic neutrino background and substantiate the assertion that -- apart from the rather indirect…

The connection between cosmological observations and neutrino physics is discussed in detail. Neutrinos decouple from thermal contact in the early Universe at a temperature of order 1 MeV which coincides with the temperature where light…

Very different processes characterize the decoupling of neutrinos to form the cosmic neutrino background (C$\nu$B) and the much later decoupling of photons from thermal equilibrium to form the cosmic microwave background (CMB). The C$\nu$B…

Cosmological measurements over the next decade will enable us to shed light on the content and evolution of the Universe. Complementary measurements of the Cosmic Microwave Background (CMB) and Baryon Acoustic Oscillations are expected to…