Transformation of an Electron-Positron Pair into a Pair of Muons

Russian Physics Journal -     

适用于配对近似计算的集体对凝聚组态变分方法

集体对凝聚组态(collective-pair condensate)的能量变分可用于判断在原子核低激发态中哪些集体对是重要的,并且可以同时给出这些重要集体对的具体结构。这在一定程度上缓解了此前原子核配对近似(Nucleon Pair Approximation, NPA)计算一直深受困扰的集体对不确定性问题。针对过渡区原子核132Ba的试探性计算体现了这种方法的优越性。它可以给出132Ba的三轴形变参数,它也定量地说明了这一原子核$I\!=\!10$基带回弯效应的主导集体对种类。更为重要的是,中子负宇称对凝聚状态的变分计算解释了为什么负宇称集体对这种回弯效应可以呈现出巨大影响。     

Transformation of an Electron-Positron Pair into a Massive Scalar Boson Pair

Russian Physics Journal -     

Existence of Pair Potential Corresponding to Specified Density and Pair Correlation

Given a potential of pair interaction and a value of activity, one can consider the Gibbs distribution in a finite domain . It is well known that for small values of activity there exist the infinite volume limiting Gibbs distribution and the infinite volume correlation functions. In this paper we consider the converse problem – we show that given ₁ and ₂(x), where ₁ is a constant and ₂(x) is a function on , which are sufficiently small, there exist a pair potential and a value of activity, for which ₁ is the density and ₂(x) is the pair correlation function.Partially supported by NSF Research Grant     

Pair production of squarks inep-collisions

The production of squarks atep colliders is studied by comparing the Weizsäcker-Williams approximation and an exact tree level calculation. We consider the processep→eqqX→eqqγγX. For this calculation, on the amplitude level, the Feynman diagrams can be split into sub-diagrams. This splitting has great advantages for numerical calculations. Using these techniques the dependence of the cross section on the mass of the squark is computed. We also present various kinematical distributions. An elegant method for calculating tree amplitudes with external fermions of arbitrary mass and spin is given for completeness.     

On Adiabatic Pair Creation

We give here a rigorous proof of the well known prediction of pair creation as it arises from the Dirac equation with an external time dependent potential. Pair creation happens with probability one if the potential changes adiabatically in time and becomes overcritical, which means that an eigenvalue curve (as a function of time) bridges the gap between the negative and positive spectral continuum. The potential can be thought of as being zero at large negative and large positive times. The rigorous treatment of this effect has been lacking since the pioneering work of Beck, Steinwedel and Sü?mann [1] in 1963 and Gershtein and Zeldovich [8] in 1970.     

Supersymmetric Pair Coherent States

Based on the permu table property between the two-mode boson-fermion annihilator for a supersymmetric harmonic oscillator, which is described by H = b^↑b + f^↑f, and the "charge" operators b^↑b - f^↑f we construct the supersymmetric pair coherent state. The super-lie algebra associated with the supersymmetric pair coherent state is analyzed.     

SD对壳模型：对结构对原子核集体性质的影响

在SD对壳模型的理论框架下, 利用变分法及TDA近似确定SD对结构. 结果发现利用上述方法确定SD对比以往通过对角化表面δ相互作用来确定SD对结构的方法可以更好地再现原子核低激发谱的集体性质.     

Quartet Pair and Radical Quartet Pair Mechanisms of Electron Spin Polarization Developed within Nonbonded Dimers

Novel mechanisms of the electron spin polarization were reported. Effect of spin-selective interactions within the photo-excited preexisting molecular dimers was utilized. Processes occurring within dimers and upon escape from the dimer cage were considered.     

Supersymmetric Pair of q-Deformed Nonlocal Operators

A simple version of the q-deformed calculus is used to generate a pair ofq-nonlocal, second-order difference operators by means of deformed counterpartsof Darboux intertwining operators for the Schrödinger—Hermite oscillators atzero factorization energy. These deformed nonlocal operators may be consideredas supersymmetric partners and their structure contains contributions originatingin both the Hermite operator and the quantum harmonic oscillator operator. Thereare also extra ±x contributions. The undeformed limit, in which allq-nonlocalities wash out, corresponds to the usual supersymmetric pair of quantum mechanicalharmonic oscillator Hamiltonians. The more general case of negative factorizationenergy is briefly discussed as well.     

Pair production of doubly heavy diquarks

The differential and total cross sections for the pair production of doubly heavy diquarks are calculated analytically within the diquark model. The cases of electron-positron and quark-antiquark annihilation are considered. The ratios of the total cross sections to the corresponding cross sections for annihilation into two heavy quarks are estimated numerically.     

Exploration of Entropy Pair Functional Theory

Evaluation of the entropy from molecular dynamics (MD) simulation remains an outstanding challenge. The standard approach requires thermodynamic integration across a series of simulations. Recent work Nicholson et al. demonstrated the ability to construct a functional that returns excess entropy, based on the pair correlation function (PCF); it was capable of providing, with acceptable accuracy, the absolute excess entropy of iron simulated with a pair potential in both fluid and crystalline states. In this work, the general applicability of the Entropy Pair Functional Theory (EPFT) approach is explored by applying it to three many-body interaction potentials. These potentials are state of the art for large scale models for the three materials in this study: Fe modelled with a modified embedded atom method (MEAM) potential, Cu modelled with an MEAM and Si modelled with a Tersoff potential. We demonstrate the robust nature of EPFT in determining excess entropy for diverse systems with many-body interactions. These are steps toward a universal Entropy Pair Functional, EPF, that can be applied with confidence to determine the entropy associated with sophisticated optimized potentials and first principles simulations of liquids, crystals, engineered structures, and defects.     

Pair creation by internal conversion

In this report we describe the general theory of internal electron-positron pair conversion. Within the point nucleus approximation we derive analytical formulae for the differential pair conversion coefficient using Coulomb wave functions for the electron. Numerical calculations of the pair conversion coefficient for pointlike and extended nuclei for various multipolarities, transition energies and nuclear charges are presented and compared with Born approximation results and experimental data.     

Pair production and optical lasers

Electron-positron pair creation in a standing wave is explored using a parameter-free quantum kinetic equation. Field strengths and frequencies corresponding to modern optical lasers induce a material polarization of the QED vacuum, which may be characterized as a plasma of e+e- quasiparticle pairs with a density of approximately 10(20) cm-3. The plasma vanishes almost completely when the laser field is zero, leaving a very small residual pair density n(r) which is the true manifestation of vacuum decay. The average pair density per period is proportional to the laser intensity but independent of the frequency nu. The density of residual pairs also grows with laser intensity but n(r) proportional to nu(2). With optical lasers at the forefront of the current generation, these dynamical QED vacuum effects can plausibly generate 5-10 observable two-photon annihilation events per laser pulse.     

Pair condensates produced in bosenovae

The fraction of residual particles N^′ in ⁸⁵Rb bosenovae is observed to satisfy N/2?N^′<N, where N/2 appears to be a strict lower bound. Here, we point out that Bose-Einstein condensates of particles of integer spin possess an ambiguity to a constituency of pairs. We explain the lower bound N/2 by the formation of pairs produced in collapse. Pair formation reduced the critical temperature by a factor of about three, sufficient for an instability to produce a prompt explosion. We propose a recount following forced pair dissociation upon exposure to an X-ray flash.