An easy and practical system of feeble fluctuation of liquid electrical conductivity is described. The system, which increases a precision on the three orders magnitude as compared with that of the recent domestic con...An easy and practical system of feeble fluctuation of liquid electrical conductivity is described. The system, which increases a precision on the three orders magnitude as compared with that of the recent domestic conductivity meter, is used to measure the feeble fluctuation of the conductivity by means of compensation and comparison, so that it solves the problem of measuring the feeble fluctuation.展开更多
The first measurement of the temperature of the hydrogen 21-cm signal reported by EDGES strongly fa-vors the Coulomb-like interaction between freeze-in dark matter and baryon fluid.We investigate such dark matter in b...The first measurement of the temperature of the hydrogen 21-cm signal reported by EDGES strongly fa-vors the Coulomb-like interaction between freeze-in dark matter and baryon fluid.We investigate such dark matter in both the one-and two-component context with the light force carrier(s)essential for the Coulomb-like interaction being other than photons.Using a conversion of cross sections used by relevant experiments and Boltzmann equations to encode the effects of the dark matter-baryon interaction,we show that both cases are robustly excluded by the stringent stellar cooling bounds in the sub-GeV dark matter mass range.The exclusion of the one-component case applies to simplified freeze-in dark matter with the light force carrier as dark photons,gauged B-L,Le-Lμ,Le-Lτ,or axion-like particles,whereas the exclusion of the two-component case applies to simplified freeze-in dark matter with the two light force carriers as two axion-like particles coupled to standard model quarks and leptons.展开更多
文摘An easy and practical system of feeble fluctuation of liquid electrical conductivity is described. The system, which increases a precision on the three orders magnitude as compared with that of the recent domestic conductivity meter, is used to measure the feeble fluctuation of the conductivity by means of compensation and comparison, so that it solves the problem of measuring the feeble fluctuation.
基金Supported in part by the National Natural Science Foundation of China(11775039)the High-level Talents Research and Startup Foundation Projects for Doctors of Zhoukou Normal University(ZKNUC2021006)the Natural Science Foundation of Henan Province,China(232300421358)。
文摘The first measurement of the temperature of the hydrogen 21-cm signal reported by EDGES strongly fa-vors the Coulomb-like interaction between freeze-in dark matter and baryon fluid.We investigate such dark matter in both the one-and two-component context with the light force carrier(s)essential for the Coulomb-like interaction being other than photons.Using a conversion of cross sections used by relevant experiments and Boltzmann equations to encode the effects of the dark matter-baryon interaction,we show that both cases are robustly excluded by the stringent stellar cooling bounds in the sub-GeV dark matter mass range.The exclusion of the one-component case applies to simplified freeze-in dark matter with the light force carrier as dark photons,gauged B-L,Le-Lμ,Le-Lτ,or axion-like particles,whereas the exclusion of the two-component case applies to simplified freeze-in dark matter with the two light force carriers as two axion-like particles coupled to standard model quarks and leptons.
