arXiv subjects
Publications and source records attributed to M. Ploszajczak.
The influence of shape of expanding and rotating source on various characteristics of the multifragmentation process is studied. The analysis is based on the extension of the statistical microcanonical multifragmentation model. The comparison with the data is done for central Xe+Sn collisions at 50 A MeV as measured by INDRA Collaboration.
We discuss the universal scaling laws of order parameter fluctuations in any system in which the second-order critical behavior can be identified. These scaling laws can be derived rigorously for equilibrium systems when combined with the finite-size scaling analysis. The relation between order parameter, criticality and scaling law of fluctuations has been established and the connexion between the scaling function and the critical exponents has been found.
Two standard models of sol-gel transition are revisited here from the point of view of their fluctutations in various moments of both the mass-distribution and the gel-mass. Bond-percolation model is an at-equilibrium system and undergoes a static second-order phase transition, while Monte-Carlo Smoluchowski model is an off-equilibrium one and shows a dynamical critical phenomenon. We show that the macroscopic quantities can be splitted into the three classes with different scaling properties of their fluctuations, depending on wheather they correspond to : (i) non-critical quantities, (ii) critical quantities or to (iii) an order parameter. All these three scaling properties correspond to a single form : $ ^δ P(M) = Φ((M- )/ ^δ)$, with the values of $δ$ respectively : =1/2 (regime (i)), \neq 1/2 and 1 (regime (ii)), and =1 (regime (iii)). These new scalings are very robust and, in particular, they do not depend on the precise form of an Hamiltonian.
Recently equations for the generating functional in the perturbative quantum chromodynamics (QCD) have been extended by including the non-perturbative dissipation in QCD jets. The resulting equations have been solved rigorously and new family of scaling solutions, the so-called delta - scaling, generalizing the well-known Kubo-Nielsen-Olesen scaling law for hadron multiplicity distributions have been found. The relevance of delta - scaling is discussed in the Landau - Ginzburg theory of phase transitions. Preliminary application of these ideas to the p{\bar p} data of the UA5 Collaboration is presented.
We present here the first application of realistic shell model (SM) including coupling between many-particle (quasi-)bound states and the continuum of one-particle scattering states to the spectroscopy of 8B and to the calculation of astrophysical factors in the reaction 7Be(p,gamma)8B.
Possibility of observing the Mott momentum in the distribution of the deuterons produced in the process $p + n \to d + γ$, in the first stage of a nuclear reaction is presented. The correlation of a hard photon with a deuteron allows to select those deuterons produced at the beginning of a reaction.
Scaling analysis of nuclear giant resonance transition probabilities with increasing level of complexity in the background states is performed. It is found that the background characteristics, typical for chaotic systems lead to nontrivial multifractal scaling properties.
We reconsider the Hung and Shuryak arguments in favour of searching for the deconfinement phase transition in heavy ion collisions {\em downward} from the nominal SPS energy, at $E_{lab} \approx 30 \ GeV/A$ where the fireball lifetime is the longest one. Using the recent lattice QCD data and the mixed phase model, we show that the deconfinement transition might occur at the bombarding energies as low as $E_{lab}=3 - 5 \ GeV/A$. Attention is drawn to the study of the mixed phase of nuclear matter in the collision energy range $E_{lab}= 2-10 \ GeV/A$.
Dynamics of classical scattering in the system of fermions is studied. The model is based on the coherent state representation and the equations of motion for fermions are derived from the time-dependent variational principle. It is found that the antisymmetrization due to the Pauli exclusion principle, may lead to hyperbolic chaotic scattering even in the absence of interaction between particles. At low bombarding energies, the same effect leads to the screening of the hard, short-ranged component in the two particle interaction and thus regularizes the dynamics.