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Search Results: 1 - 10 of 208419 matches for " L. Phair "
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Reduciblity, Arrhenius plots and the Uroboros Dragon, a reply to the preprint "Correlations in Nuclear Arrhenius-Type Plots" by M.B. Tsang and P. Danielewicz
L. G. Moretto,L. Beaulieu,L. Phair,G. J. Wozniak
Physics , 1997,
Abstract: In a recent preprint by Tsang and Danielewicz, the authors attempt to give alternative or trivial explanations for the reducible and "thermal" nature of the intermediate mass fragment excitation functions reported previously (Phys. Rev. Lett. 74, 1530 (1995), Phys. Lett B 361, 25 (1995), Phys. Rep. 287, 249 (1997)). We demonstrate that their proposed "self-correlation" explanation for linear Arrhenius plots is based upon a flawed autocorrelation analysis involving circular reasoning.
Statistical Exploration of Fragmentation Phase Space Source Sizes in Nuclear Multifragmentation
L. G. Moretto,L. Beaulieu,L. Phair,G. J. Wozniak
Physics , 1998, DOI: 10.1016/S0370-2693(00)00683-3
Abstract: The multiplicity distributions for individual fragment Z values in nuclear multifragmentation are binomial. The extracted maximum value of the multiplicity is found to depend on Z according to m=Z_0/Z, where Z_0 is the source size. This is shown to be a strong indication of statistical coverage of fragmentation phase space. The inferred source sizes coincide with those extracted from the analysis of fixed multiplicity charge distributions.
Z-dependent Barriers in Multifragmentation from Poissonian Reducibility and Thermal Scaling
L. Beaulieu,L. Phair,L. G. Moretto,G. J. Wozniak
Physics , 1998, DOI: 10.1103/PhysRevLett.81.770
Abstract: We explore the natural limit of binomial reducibility in nuclear multifragmentation by constructing excitation functions for intermediate mass fragments (IMF) of a given element Z. The resulting multiplicity distributions for each window of transverse energy are Poissonian. Thermal scaling is observed in the linear Arrhenius plots made from the average multiplicity of each element. ``Emission barriers'' are extracted from the slopes of the Arrhenius plots and their possible origin is discussed.
Multifragmentation at Intermediate Energy: Dynamics or Statistics?
L. Beaulieu,L. Phair,L. G. Moretto,G. J. Wozniak
Physics , 1998,
Abstract: To make a statement about the nature and mechanism of fragmentation, it is necessary to probe directly any competition, or lack thereof, between the emission of various particle species as a function of excitation energy. The task is then to find a global observable that best follows the increase in excitation energy or dissipated energy. In the following, we will consider two contradictory claims that have been advanced recently: 1) the claim for a predominantly dynamical fragment production mechanism; and 2) the claim for a dominant statistical and thermal process. We will present a new analysis in terms of Poissonian reducibility and thermal scaling, which addresses some of the criticisms of the binomial analysis.
Uniqueness of Fisher plots and their inferred (nuclear) liquid-vapor phase diagrams
J. B. Elliott,L. G. Moretto,L. Phair
Physics , 2004,
Abstract: A detailed study of the lattice gas (Ising) model shows that the correct definition of cluster concentration in the vapor at coexistence with the liquid leads to Fisher plots that are unique, independent of fixed particle number density $\rho_{\text{fixed}}$, and completely reliable for the characterization of the liquid-vapor phase diagram of any van der Waals systems including nuclear matter.
Compound nuclear decay and the liquid to vapor phase transition: a physical picture
L. G. Moretto,J. B. Elliott,L. Phair
Physics , 2005, DOI: 10.1103/PhysRevC.72.064605
Abstract: Analyses of multifragmentation in terms of the Fisher droplet model (FDM) and the associated construction of a nuclear phase diagram bring forth the problem of the actual existence of the nuclear vapor phase and the meaning of its associated pressure. We present here a physical picture of fragment production from excited nuclei that solves this problem and establishes the relationship between the FDM and the standard compound nucleus decay rate for rare particles emitted in first-chance decay. The compound thermal emission picture is formally equivalent to a FDM-like equilibrium description and avoids the problem of the vapor while also explaining the observation of Boltzmann-like distribution of emission times. In this picture a simple Fermi gas thermometric relation is naturally justified and verified in the fragment yields and time scales. Low energy compound nucleus fragment yields scale according to the FDM and lead to an estimate of the infinite symmetric nuclear matter critical temperature between 18 and 27 MeV depending on the choice of the surface energy coefficient of nuclear matter.
Comment on "Circumstantial Evidence for Critical Behavior in Peripheral Au+Au Collisions at 35 MeV/nucleon"
L. Phair,Th. Rubehn,L. G. Moretto,G. J. Wozniak
Physics , 1996, DOI: 10.1103/PhysRevLett.79.3538
Abstract: Mastinu et al. recently reported the observation of several positive signals possibly indicating critical behavior in peripheral collisions of Au+Au at $E/A$=35 MeV. In our comment, we examine the choice of variables used to determine the presence (or absence) of critical behavior. We do this by repeating the analysis the work of Mastinu et al. on "data" from a simulation with no critical behavior.
Do phase transitions survive binomial reducibility and thermal scaling?
L. G. Moretto,L. Phair,G. J. Wozniak
Physics , 1996,
Abstract: First order phase transitions are described in terms of the microcanonical and canonical ensemble, with special attention to finite size effects. Difficulties in interpreting a "caloric curve" are discussed. A robust parameter indicating phase coexistence (univariance) or single phase (bivariance) is extracted for charge distributions.
The resistible effects of Coulomb interaction on nucleus-vapor phase coexistence
L. G. Moretto,J. B. Elliott,L. Phair
Physics , 2003, DOI: 10.1103/PhysRevC.68.061602
Abstract: We explore the effects of Coulomb interaction upon the nuclear liquid vapor phase transition. Because large nuclei (A>60) are metastable objects, phases, phase coexistence, and phase transitions cannot be defined with any generality and the analogy to liquid vapor is ill-posed for these heavy systems. However, it is possible to account for the Coulomb interaction in the decay rates and obtain the coexistence phase diagram for the corresponding uncharged system.
Comment on ``Entry Distribution, Fission Barrier, and Formation Mechanism of 254No''
L. G. Moretto,L. Phair,G. J. Wozniak
Physics , 2002,
Abstract: A recent paper has reported the observation of the rotational band of 254No for spins up to I=20, showing that the compound nucleus was formed and survived fission decay at angular momenta I >= 20. We show that this survival is consistent with the leading effects of angular momentum on the barrier height.
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