A theoretical scheme which relates multiparticle states generated in ultrarelativistic nuclear collisions to a QCD phase transition is considered in the framework of the universality class provided by the 3-D Ising model. Two different evolution scenarios for the QGP system are examined. The statistical mechanics of the critical state is accounted for in terms of (critical) cluster formation consistent with suitably cast effective action functionals, one for each considered type of expansion. Fractal properties associated with these clusters, characterizing the density fluctuations near the QCD critical point, are determined. Monte-Carlo simulations are employed to generate events, pertaining to the total system, which correspond to signals associated with unconventional sources of pion production

The three complex form factors entering the ⌬˜N␥* vertex are calculated to O( 3 ) in the framework of a chiral effective theory with explicit ⌬(1232) degrees of freedom included. It is shown that the low q 2 behavior of the form factors is governed by N, ⌬ loop effects. Predictions are given for the q 2 dependence of the three transition multipoles M 1(q 2 ), E2(q 2 ), C2(q 2 ). Furthermore, the role of the presently unknown low energy constants that affect the values of the multipole ratios EMR(q 2 ) and CMR(q 2 ) is elucidated.

The Statistical Bootstrap Model (SBM) is extended to describe hadronic systems which carry the quantum number of strangeness. The study is conducted in the threedimensional space (T, µ q , µ s ) of temperature, up-down and strange chemical potentials, respectively, wherein the existence of a "critical" surface is established, which sets the limits of the hadronic phase of matter. A second surface, defined by the null expectation value of strangeness number (< S >= 0) is also determined. The approach of the latter surface to the critical one becomes the focal point of the present considerations. Two different versions of the extended SBM are examined, corresponding to the values 2 and 4 for the exponent α, which determines the asymptotic fall-off of the mass spectrum ρ(m). It is found that the α = 4 version has decisive physical advantages. This model is subsequently adopted to discuss (strange) particle ratios pertaining to multiparticle production processes, for which a thermal equilibrium mode of description applies.