Energetics of Formation of Nanocrystalline Structures in Finemet, Nanoperm and Hitperm Alloys

Processes controlling transformation in three rapidly quenched nanocrystal-forming systems, Finemet, Nanoperm and Hitperm, were analyzed using a novel approach which provides the distribution of true activation energies of nanocrystallization and their temperature dependencies. This approach yields new information with respect to the original local ordering of atoms in the amorphous phase and its influence on the formation of nanostructures. Additional information is extracted which allows to compare processes in the early stages of nanocrystallization with those at the end of the phase transformation.     

First energy and angle differential measurements of e+e−-pairs emitted by internal pair conversion of excited heavy nuclei

We present the first energy and angle resolved measurements of e⁺e⁻-pairs emitted from heavy nuclei (Z≥ 40) at rest by internal pair conversion (IPC) of transitions with energies of less than 2 MeV as well as recent theoretical results using the DWBA method, which takes full account of relativistic effects, magnetic substates and finite size of the nucleus. The 1.76 MeV E0 transition in ⁹⁰Zr (⁹⁰Sr source) and the 1.77 MeV M1 transition in ²⁰⁷Pb (²⁰⁷Bi source) have been investigated experimentally using the essentially improved setup at the double-ORANGE β-spectrometer of GSI. The measurements prove the capability of the setup to cleanly identify the IPC pairs in the presence of five orders of magnitude higher β⁻ and γ background from the same source and to yield essentially background-free sum spectra despite the large background. Using the ability of the ORANGE setup to directly determine the opening angle of the e⁺e⁻–pairs (Θ_e+e−), the angular correlation of the emitted pairs was measured within the range covered experimentally (40°≤Θ_e+e−≤ 180°). In the ⁹⁰Zr case the correlation could be deduced for a wide range of energy differences E _Δ of the pairs (−530 keV ≤E _Δ≤ 530 keV). The ⁹⁰Zr results are in good agreement with recent theory. The angular correlation deduced for the M1 transition in ²⁰⁷Pb is in strong disagreement with theoretical predictions derived within the Born approximation and shows almost isotropic character. This is again in agreement with the new theoretical results. Received: 22 April 1997 / Revised version: 16 December 1997     

Discrete time analysis of MAP/PH/1 vacation queue with gated time‐limited service

We analyse a single‐server queue in which the server goes through alternating periods of vacation and work. In each work period, the server attends to the queue for no more than a fixed length of time, T. The system is a gated one in which the server, during any visit, does not attend to customers which were not in the system before its visit. As soon as all the customers within the gate have been served or the time limit has been reached (whichever occurs first) the server goes on a vacation. The server does not wait in the queue if the system is empty at its arrival for a visit. For this system the resulting Markov chain, of the queue length and some auxiliary variables, is level‐dependent. We use special techniques to carry out the steady state analysis of the system and show that when the information regarding the number of customers in the gate is not critical we are able to reduce this problem to a level‐independent Markov chain problem with large number of boundary states. For this modified system we use a hybrid method which combines matrix‐geometric method for the level‐independent part of the system with special solution method for the large complex boundary which is level‐dependent. This revised version was published online in June 2006 with corrections to the Cover Date.     

Charged particle density distributions in Au + Au collisions at relativistic heavy-ion collider energies

Charged particle pseudorapidity distributions have been measured in Au+ Au collisions using the BRAHMS detector at RHIC. The results are presented as a function of the collision centrality and the center of mass energy. They are compared to the predictions of different parton scattering models and the important role of hard scattering processes at RHIC energies is discussed. Keywords. Relativistic heavy-ion collisions; charged hadron production; pseudorapidity distributions; centrality dependence; hard scattering processes.     

Waiting Time Distributions Associated with Runs of Fixed Length in Two-State Markov Chains

In the present article a general technique is developed for the evaluation of the exact distribution in a wide class of waiting time problems. As an application the waiting time for the r-th appearance of success runs of specified length in a sequence of outcomes evolving from a first order two-state Markov chain is systematically investigated and asymptotic results are established. Several extensions and generalisations are also discussed.     

Statistical mechanics of choice: MaxEnt estimation of population heterogeneity

The paper studies heterogeneity of large populations of decision-makers in terms of their choice behavior. It is argued that heterogeneity measures may be deduced from the aggregate data by application of the Maximum Entropy (MaxEnt) formalism. The case of the aggregate data being comprised of value shares is studied in detail; it is shown that the estimate of heterogeneity belongs to the product-form family of probability distributions.     

Working group report: Quantum chromodynamics

This is the report of the QCD working sub-group at WHEPP-8 which was part of the QCD and QGP working group. Discussion and work on some aspects of resummation and parton distribution are reported.     

Iterated probability distributions and extremes with random sample size

In this paper the possible nondegenerated limit distributions for the n-fold mapping of a given probability distribution are considered. If the mapping used for the iteration procedure is a probability generating function of a positive integer-valued random variable then the results can be applied to the max-stability of distributions of random variables with random sample size.     

Economic Fluctuations and Statistical Physics: The Puzzle of Large Fluctuations

We present an overview of recent research applying ideas of statistical physics to try to better understand puzzles regarding economic fluctuations. One of these puzzles is how to describe outliers, phenomena that lie outside of patterns of statistical regularity. We review evidence consistent with the possibility that such outliers may not exist. This possibility is supported by recent analysis of a database containing the bid, ask, and sale price of each trade of every stock. Further, the data support the picture of economic fluctuations, due to Plerou et al., in which a financial market alternates between being in an “equilibrium phase” where market behavior is split roughly equally between buying and selling, and an “out-of-equilibrium phase” where the market is mainly either buying or selling.