Wide-angle X-ray scattering experiments for supercritical CO2 near the higher-order phase transition line on the isotherm at T = 308 K were carried out. Radial distribution functions were compared with that of the high-pressure liquid CO2. The results show that the higher-order phase transition line divides supercritical state into two phases, i.e., liquidlike and gaslike regions, from the viewpoint of the structure. Radial distribution functions, however, indicate that this phase transition is remarkably gentle even near the critical point.

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The sfar operations and reality conditions for the complex quantum algebra U q ( d ( 4 C ) ) providing real quantum algebras U,,(0(6k . k ) ) k = 0, I. 2.3 and Uq(su(3. 1)) are classified. S W x d and non-standud sex operations me considered. It appears that only four choices of real forms (one with 141 = 1, h e with q real) provide real Hopf algebra Uq(su(2, 2)) = Uq(0(4, 2)) describing D = 4 conformal quanNm alpbras. We show that only the antipod-extended Cartan-Weyi basis of Uq(sl(4; C)) permits to define real q-defomd D = 4 wnformal algebra generators. In order to obtain the real D = 4 Weyi algebra as Hopf subalgebra of Uq(sw(2. 2)) only the non-standard real forms can be employed.

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