Weak interactions universality

E. D. Commins and P. H. Bucksbaum, Weak Interactions oJEeptons and Quarks, Cambridge University Press, Cambridge, U.K., 1983, p. 389. 

Another interesting version of the MM model considers a variable excluded-volume interaction between same species particles [92]. In the absence of interactions the system is mapped on the standard MM model which has a first-order IPT between A- and B-saturated phases. On increasing the strength of the interaction the first-order transition line, observed for weak interactions, terminates at a tricritical point where two second-order transitions meet. These transitions, which separate the A-saturated, reactive, and B-saturated phases, belong to the same universality class as directed percolation, as follows from the value of critical exponents calculated by means of time-dependent Monte Carlo simulations and series expansions [92]. 

There are many different extensions of the standard model of particle physics which result in modifications of the early universe expansion rate (the time -temperature relation). For example, additional particles will increase the energy density (at fixed temperature), resulting in a faster expansion. In such situations it is convenient to relate the extra energy density to that which would have been contributed by an additional neutrino with the ordinary weak interactions [19]. Just prior to e annihilation, this may be written as... 

The search for weakly interacting particle, which may constitute the dark matter in the universe. The elucidation of the nature of this dark matter is one of the most pressing problems in astrophysics and in cosmology. 

G.A. Ozin, University of Toronto In our Cr/CO matrix cocondensation experiments (Angew. Chem., Int. Ed. Eng. 1975, 14, 292), we reported evidence for the facile formation of a binuclear chromium carbonyl complex Cr2(CO)i0 or Cr2 (CCOi x which could be described as square pyramidal Cr(CO)5 weakly interacting with either a Cr(CO)5 or Cr(CO)6 moiety in the vacant (sixth) site. As a result, the infrared spectrum of this "weakly-coupled" binuclear species closely resembled that of the mononuclear fragment Cr(CO)5. I would like to ask you, whether or not you have any evidence for the existence of such a binuclear species in your Cr(CO)6 /Xe cryogenic solutions following various photolysis treatments. 

In a superconducting system, when one increases the temperature at a given chemical potential, thermal motion will eventually break up the quark Cooper pairs. In the weakly interacting Bardeen-Copper-Schrieffer (BCS) theory, the transition between the superconducting and normal phases is usually of second order. The ratio of the critical temperature TcBCS to the zero temperature value of the gap AbGS is a universal value [18]... 

This chain of events involved the so-called weak interaction, a puny and slow force compared with the strong and electromagnetic interactions. The weak interaction governs the conversion of protons into neutrons and vice versa, with creation of a neutrino (antineutrino). It thus determines the lifetime of free neutrons, which naturally decay into protons. In fact, neutrons have a life expectancy of around 10 minutes. However, before they disappear, they may have the opportunity to combine with protons, one which they readily accept. In that case, nuclear physics makes its appearance in the Universe. 

As the weak interaction is the slowest of all, it was the first to find itself unable to keep up with the rapid expansion of the Universe. The neutrinos it produces, which serve as an indicator of the weak interaction, were the first to experience decoupling, the particle equivalent of social exclusion. By the first second, expansion-cooled neutrinos ceased to interact with other matter in the form of protons and neutrons. This left the latter free to organise themselves into nuclei. Indeed, fertile reactions soon got under way between protons and neutrons. However, the instability of species with atomic masses between 5 and 8 quickly put paid to this first attempt at nuclear architecture. The two species of nucleon, protons and neutrons, were distributed over a narrow range of nuclei from hydrogen to lithium-7, but in a quite unequal way. 

In the mid-fifties the violation of parity was discovered, and a universal theory of weak interactions—the (F-A)-theory—was created. Construction of composite hadron models was begun. The first non-abelian gauge theory was developed. 

Weak Interactions were treated by Pais who, starting from Fermi s original theory, discussed the discovery by Lee and Yang,74 almost 5 years before, of the parity violation by weak interactions, its experimental confirmation,75 the muon-electron universality,76 the idea of an intermediate boson as a mediator of weak interaction, and the two-neutrinos question. 77... 

The preceding construction indicates that the electromagnetic and weak interactions may be dual-field theories. If the preceding construction is experimentally verified, then this would be the first empirical indication that the universe is... 

Another important classification of particle dark matter rests upon its production mechanism. Particles that were in thermal equilibrium in the early Universe, like neutrinos, neutralinos, and most other WIMPs (weakly interacting massive particles), are called thermal relics. Particles which were produced by a non-thermal mechanism and that never had the chance of reaching thermal equilibrium in the early Universe are called non-thermal relics. There are several examples of non-thermal relics axions emitted by cosmic strings, solitons produced in phase transitions, WIMPZILLAs produced gravitationally at the end of inflation, etc. 

At temperatures above a few MeV, when the universe is tens of milliseconds old, interactions among photons, neutrinos, electrons, and positrons establish and maintain equilibrium (T7 = TV = Te). When the temperature drops below a few MeV the weakly interacting neutrinos decouple, continuing to cool and dilute along with the expansion of the universe (T oc a-1, nv oc 7j), and pv oc 7))). 

Up to now we haven t considered the baryon (nucleon) content of the universe. At these early times there are neutrons and protons present whose relative abundance is determined by the usual weak interactions. 

In contrast to the other light nuclides, the primordial abundance of 4He (mass fraction Y) is relatively insensitive to the baryon density, but since virtually all neutrons available at BBN are incorporated in 4He, it does depend on the competition between the weak interaction rate (largely fixed by the accurately measured neutron lifetime) and the universal expansion rate (which depends on geff)- The higher the nucleon density, the earlier can the D-bottleneck be breached. At early times there are more neutrons and, therefore, more 4He will be synthesized. This latter effect is responsible for the very slow (logarithmic) increase in Y with rj. Given the standard model relation between time and temperature and the nuclear and weak cross sections and decay rates measured in the laboratory, the evolution of the light nuclide abundances may be calculated and the frozen-out relic abundances predicted as a function of the one free parameter, the nucleon density or rj. These are shown in Fig. 1. 

When the temperature in the universe was T = 1012K, only weak interactions causing conversions between protons and neutrons occurred, namely ... 

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