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The Weak Interaction in the Framework of Grand Unification Theories
Published in K Grotz, H V Klapdor, S S Wilson, The Weak Interaction in Nuclear, Particle and Astrophysics, 2020
K Grotz, H V Klapdor, S S Wilson
As far as is known today, the SU(3)c symmetry is realised unbroken in nature. An argument for this is given by the quark confinement (see below). As a result, the gauge bosons, the gluons, are massless. On the other hand the other interactions (weak, electromagnetic) should not be affected by the quark colour charges, they are so-to-speak ‘colour-blind’. This means that the SU(3)c transformations must commute with the SU(2)L ⨂ U(1) transformations. Accordingly, the members of an SU(3)c multiplet must differ only in their colour charge, and not in any other quantum number. Otherwise members would be distinguishable by their properties under the electroweak interaction, and by their masses, and the SU(3)c symmetry would be broken. The fundamental SU(3)ctriplets are: () (urugub)(drdgdb)(crcgcb)(srsgsb)(trtgtb)(brbgbb)
Non-adiabatic dynamics of ring opening in cyclohexa-1,3-diene described by an ensemble density-functional theory method
Published in Molecular Physics, 2019
Michael Filatov, Seung Kyu Min, Kwang S. Kim
The commonly accepted mechanism of the gas phase photochemical ring opening of the cyclohexa-1,3-diene [66-72,75,90], which leads to the formation of the s-cis,Z,s-cis-1,3,5-hexatriene (cZc-HT) is shown in Scheme 1. After photoexcitation of CHD at the equilibrium geometry (1A under the C symmetry) to the optically bright state an ultrafast transformation of the state's character from 1B to 2A (C symmetry) [70] occurs on a timescale of ca. 50–70 fs [66,68,69] and is followed by 2A ( ) → 1A () decay on a timescale of ca. 80 fs [66,68,69]. At the / conical intersection (CI), bifurcation of the reaction path occurs with the major fraction (ca. 0.7) of the nuclear wavepacket falling back to the CHD conformation and a minor fraction (ca. 0.3) continuing to cZc-HT [69]. The latter undergoes fast thermal transformation to more stable trans conformers and a back photoreaction, e.g. tZt-HT → CHD is not observed.