arXiv subjects

R. Botet

Publications and source records attributed to R. Botet.

8 recordsLinked to original sources

arXiv2013

Pseudo-critical clusterization in nuclear multifragmentation

In this contribution we show that the biggest fragment charge distribution in central collisions of Xe+Sn leading to multifragmentation is an admixture of two asymptotic distributions observed for the lowest and highest bombarding energies. The evolution of the relative weights of the two components with bombarding energy is shown to be analogous to that observed as a function of time for the largest cluster produced in irreversible aggregation for a finite system. We infer that the size distribution of the largest fragment in nuclear multifragmentation is also characteristic of the time scale of the process, which is largely determined by the onset of radial expansion in this energy range.

nucl-ex↗

arXiv2012

Nuclear multifragmentation time-scale and fluctuations of largest fragment size

Distributions of the largest fragment charge, Zmax, in multifragmentation reactions around the Fermi energy can be decomposed into a sum of a Gaussian and a Gumbel distribution, whereas at much higher or lower energies one or the other distribution is asymptotically dominant. We demonstrate the same generic behavior for the largest cluster size in critical aggregation models for small systems, in or out of equilibrium, around the critical point. By analogy with the time-dependent irreversible aggregation model, we infer that Zmax distributions are characteristic of the multifragmentation time-scale, which is largely determined by the onset of radial expansion in this energy range.

nucl-ex↗

arXiv2001

Universal fluctuations in heavy-ion collisions in the Fermi energy domain

We discuss the scaling laws of both the charged fragments multiplicity fluctuations and the charge of the largest fragment fluctuations for Xe+Sn collisions in the range of bombarding energies between 25 MeV/A and 50 MeV/A. We show close to E_{lab}=32 MeV/A the transition in the fluctuation regime of the charge of the largest fragment which is compatible with the transition from the ordered to disordered phase of excited nuclear matter. The size (charge) of the largest fragment is closely related to the order parameter characterizing this process.

nucl-ex↗

arXiv2000

Universal features of the order-parameter fluctuations : reversible and irreversible aggregation

We discuss the universal scaling laws of order parameter fluctuations in any system in which the second-order critical behaviour 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. We give examples in out-of-equilibrium aggregation models such as the Smoluchowski kinetic equations, or of at-equilibrium Ising and percolation models.

cond-mat.stat-mech↗

arXiv1999

Unversal Features of the Order-Parameter Fluctuations

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.

nucl-th↗

arXiv1999

Moment scaling at the sol - gel transition

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.

cond-mat↗

arXiv1999

New Families of Scaling Multiparticle Distributions

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.

hep-ph↗

arXiv1996

Decay of Nuclear Giant Resonances: Quantum Self-similar Fragmentation

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.

chao-dyn↗