Narrow Results

We construct and study the stochastic force field generated by a Poisson distribution of sources at finite density, $x_1,x_2,\dots ,$ in ${ℝ}^3$ each of them yielding a long range potential $Q_i\mathrm{\Phi }(x-x_i)$ with possibly different charges $Q_i\in ℝ$. The potential $\mathrm{\Phi }$ is assumed to behave typically as $|x{|}^{-s}$ for large $\left|x\right|$, with $s>1/2$. We will denote the resulting random field as “generalized Holtsmark field”. We then consider the dynamics of one tagged particle in such random force fields, in several scaling limits where the mean free path is much larger than the average distance between the scatterers. We estimate the diffusive time scale and identify conditions for the vanishing of correlations. These results are used to obtain appropriate kinetic descriptions in terms of a linear Boltzmann or Landau evolution equation depending on the specific choices of the interaction potential.

Gliders in one-dimensional cellular automata are compact groups of non-quiescent and non-ether patterns (ether represents a periodic background) translating along automaton lattice. They are cellular automaton analogous of localizations or quasi-local collective excitations traveling in a spatially extended nonlinear medium. They can be considered as binary strings or symbols traveling along a one-dimensional ring, interacting with each other and changing their states, or symbolic values, as a result of interactions. We analyze what types of interaction occur between gliders traveling on a cellular automaton "cyclotron" and build a catalog of the most common reactions. We demonstrate that collisions between gliders emulate the basic types of interaction that occur between localizations in nonlinear media: fusion, elastic collision, and soliton-like collision. Computational outcomes of a swarm of gliders circling on a one-dimensional torus are analyzed via implementation of cyclic tag systems.

We describe an algorithm for the generation of relativistic kinematics for collision and decay processes with multiparticle final states. In the framework of this algorithm it is possible to generate different kinematics covering most of practically interesting cases. One gets a possibility to introduce different sets of integration variables. As a result different sets of kinematical singularities can be regularized. To smooth sharp peaks some regularization formulas and procedures are used covering most typical cases. The algorithm is realized in the package CompHEP created for automatic calculations of collision and decay processes.

A review is presented of recent results in QCD from the H1 and ZEUS experiments at HERA, emphasizing the use of higher order calculations to describe the data.

New technique is presented for modeling total cross-section of both pp and collisions from low to ultra high energy regions using an efficient artificial neural network (ANN). We have used the input (center-of-mass energy, , and type of particle P) and output (total cross-section σ_tot) data to build a prediction model by ANN. The neural network has been trained to produce a function that studies the dependence of σ_tot on and P. The trained ANN model shows a good performance in matching the trained distributions, predicts cross-sections that are not presented in the training set. The general trend of the predicted values shows a good agreement with the recent Large Hadron Collider (LHC) measurements, where the total cross-section at and 8 TeV are measured to be 98.6 mb and 101.7 mb, respectively. The predicted values of the total cross-section at and 14 TeV are found to be 105.8 mb and 111.7 mb, respectively. Those predictions are in good agreement with Block, Cudell and Nakamura.

This paper gives a survey of physical phenomena manifesting themselves in electron and photon collisions with atomic clusters. The emphasis is made on electron scattering, photoabsorption and photoionization of fullerenes and metal clusters, however some results are applicable to other types of clusters as well. It is demonstrated that the diffraction and interference phenomena play an important role in the processes of clusters interaction with photons and electrons. The essential role of the multipole surface and volume plasmon excitations is elucidated in the formation of electron energy loss spectra on clusters as well as in the total inelastic scattering cross sections and in multiphoton absorption regime. Attention is paid to the elucidation of the role of the polarization interaction in low energy electron-cluster collisions. This problem is considered for the electron attachment to metallic clusters and the plasmon enhanced photon emission. The mechanisms of electron excitation widths formation and the relaxation of electron excitations in metal clusters and fullerenes are discussed.

In Coulomb three-body problems, configurations of close proximity of the particles are classically unstable. In confined systems they might however exist as excited quantum states. By studying a maximally symmetric subspace of the three-body problem one obtains strong evidence for the existence of excited states for which the wavefunction is nonzero for triple collision configurations. Quantum control of such states by time-changing electromagnetic fields is discussed, with particular emphasis on the nature of the required controls.

Most network processors perform some kind of classification on the received packet stream, according to criteria set by the implemented networking application. Packet indexing is an integral part of the packet classification process. Indexing is considered as one of the most processor intensive part of network processing and is often supported by special hardware units. High performance Network processors usually rely upon Content Addressable Memories (CAMs) for the indexing of millions of packets per second into discrete "flow Identifiers" in ATM and IP networks. Most often, the indexing process examines packet data (tags) of significant size, necessitating the use of large CAM devices. This paper proposes an alternative method for searching lengthy tags, using RAM as storage medium instead of the expensive and complex CAMs. The technique applies the open-addressing hashing methodology to provide high speed lookups, close to CAM's performance. Our approach handles efficiently the limitations imposed by the hashing algorithms by appropriately selecting system parameters and resolving hashing collisions. The advantages of the proposed method are evaluated in detail.

We study a binary-cell-state eight-cell neighborhood two-dimensional cellular automaton model of a quasi-chemical system with a substrate and a reagent. Reactions are represented by semi-totalistic transitions rules: every cell switches from state 0 to state 1 depending on if the sum of neighbors in state 1 belongs to some specified interval, cell remains in state 1 if the sum of neighbors in state 1 belong to another specified interval. We investigate space-time dynamics of 1296 automata, establish morphology-bases classification of the rules, explore precipitating and excitatory cases and scrutinize collisions between mobile and stationary localizations (gliders, cycle life and still-life compact patterns). We explore reaction–diffusion like patterns produced as a result of collisions between localizations. Also, we propose a set of rules with complex behavior called Life 2c22.

Since their inception at Macy conferences in later 1940s, complex systems have remained the most controversial topic of interdisciplinary sciences. The term "complex system" is the most vague and liberally used scientific term. Using elementary cellular automata (ECA), and exploiting the CA classification, we demonstrate elusiveness of "complexity" by shifting space-time dynamics of the automata from simple to complex by enriching cells with memory. This way, we can transform any ECA class to another ECA class — without changing skeleton of cell-state transition function — and vice versa by just selecting a right kind of memory. A systematic analysis displays that memory helps "discover" hidden information and behavior on trivial — uniform, periodic, and nontrivial — chaotic, complex — dynamical systems.

In the case of one-dimensional cellular automaton (CA), a hybrid CA (HCA) is the member whose evolution of the cells is dependent on nonunique global functions. The HCAs exhibit a wide range of traveling and stationary localizations in their evolution. We focus on HCA with memory (HCAM) because they produce a host of gliders and complicated glider collisions by introducing the hybrid mechanism. In particular, we undertake an exhaustive search of gliders and describe their collisions using quantitative approach in HCAM$(43,74)$. By introducing the symbol vector space and exploiting the mathematical definition of HCAM, we present an analytical method of complex asymptotic dynamics of the gliders.

We describe the asymptotic states for the solutions of a nonlocal equation of evolutionary type, which have the physical meaning of the atom dislocation function in a periodic crystal. More precisely, we can describe accurately the “smoothing effect” on the dislocation function occurring slightly after a “particle collision” (roughly speaking, two opposite transitions layers average out) and, in this way, we can trap the atom dislocation function between a superposition of transition layers which, as time flows, approaches either a constant function or a single heteroclinic (depending on the algebraic properties of the orientations of the initial transition layers). The results are endowed with explicit and quantitative estimates and, as a byproduct, we show that the ODE systems of particles that govern the evolution of the transition layers does not admit stationary solutions (i.e. roughly speaking, transition layers always move).

We consider p–p collisions at very high energy. This becomes relevant in view of the LHC which has just resumed operation. Such collisions will take place in it and indeed already have taken place. Though recent results at the Tevatron in the U.S. seem to rule out the Higgs bosons, there are other results which are eagerly expected, some of these are surveyed here.

Pair collisions in atomic gases lead to decoherence and decay. Assuming that all the atoms in the gas are equally likely to collide one is led to consider Lindbladian of mean field type where the evolution in the limit of many atoms reduces to a single qudit Lindbladian with quadratic nonlinearity. We describe three smoking guns for nonlinear evolutions: power law decay and dephasing rates; dephasing rates that take a continuous range of values depending on the initial data and finally, anomalous flow of the Bloch ball towards a hemisphere.

Cosmic bubbles nucleated through the quantum tunneling process would expand and undergo collisions with each other. We focus on collisions of two equal-sized bubbles and compute gravitational waves emitted from the collisions. The mechanism of the collisions can be modeled by means of a real scalar field and its quartic potential. Out of this model we can compute gravitational waves from the collisions by integrating the energy-momentum tensors over the volume of the wave sources; in the quadrupole approximation. Our computational results show that the waveforms are characterized by (i) cusp-like bumps with frequency modulation during the initial-to-intermediate stage of strong collisions and (ii) smooth monochromatic oscillations during the final stage of weak collisions.

An overview is given of collisional energy transfer measurements made in uniform supersonic flows. The fundamentals of molecular collisions and electronic, vibrational, and rotational energy transfer are briefly described, followed by a summary of the collisional systems that have been studied to date. The measurement of total and state-to-state collisional rate constants and cross sections is described and illustrated by reference to case studies for rotational, vibrational, and electronic energy transfer. These experimental data are critical for radiative transfer modeling of astrophysical environments as well as for fundamental tests of theoretical calculations.

The history of correlation femtoscopy, recent results from femtoscopy of relativistic heavy ion collisions and their consequences are shortly reviewed.

We study possible collisions among the values of the DSA function f(s) = (g^srem p) rem t where g is order t modulo a prime p and n rem k denotes the remainder of n on division by k. In particular, in a certain range of p and t we guarantee the existence of collisions and also give a nontrivial algorithm for inverting this function.

We report the observation and interpretation of collision-induced perturbations in a ⁸⁸Sr lattice clock. Losses are observed in the collision channels ¹S₀+³P₀ and ³P₀+³P₀. Furthermore, we observe broadening and shift of the clock transition by collisions.

Cosmic bubbles nucleated through the quantum tunneling process would expand and undergo collisions with each other. We focus on collisions of two equal-sized bubbles and compute gravitational waves emitted from the collisions. The mechanism of the collisions can be modeled by means of a real scalar field and its quartic potential. Out of this model we can compute gravitational waves from the collisions by integrating the energy-momentum tensors over the volume of the wave sources; in the quadrupole approximation. Our computational results show that the waveforms are characterized by (i) cusp-like bumps with frequency modulation during the initial-to-intermediate stage of strong collisions and (ii) smooth monochromatic oscillations during the final stage of weak collisions.