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 Pair of Muons

Russian Physics Journal -     

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

Russian Physics Journal -     

Transformation of an Electron-Positron Pair into a Pair of Massive Fermions

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     

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.     

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 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.     

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.     

Pair numbers and two-nucleon transfer

Counting numbers of different kinds of nucleon pairs is considered within the context of the isovector-pairing SO(5) model. Connection of the pair numbers with the two-nucleon-transfer-reaction strength is discussed. Presented at Workshop on calculation of double-beta-decay matrix elements (MEDEX’97), Prague, May 27–31, 1997. This work has been supported by the Grant Agency of the Academy of Sciences of the Czech Republic under grant No. A1048504.     

Pair production and heavy electron

Production of electron positron pairs is analysed with the hypothesis of the heavy electrone ^*. A rough agreement between theory and experiment is found if the coupling constant is suitably chosen as a function of the massm ^* of thee ^*. Comparison with upper limits for this coupling constant taken from inelastic electron proton scattering indicates that a heavy electron withm ^* between 120 MeV and 1 GeV cannot explain observed deviations from pure quantum electrodynamics.     

Pair Events in Superluminal Optics

When an object moves faster than emissions it creates, it may appear at two positions simultaneously. The appearance or disappearance of this bifurcation is referred to as a pair event. Inherently convolved with superluminal motion, pair events have no subluminal counterparts. Common examples of superluminal motions that exhibit pair events include Cherenkov radiation, sonic booms, illumination fronts from variable light sources, and rotating beams. The minimally simple case of pair events from a single massive object is explored here: uniform linear motion. A pair event is perceived when the radial component of the object's speed toward the observer drops from superluminal to subluminal. Emission from the pair creation event will reach the observer before emission from either of the two images created. Potentially observable image pair events are described for sonic booms and Cherenkov light. To date, no detection of discrete images following a projectile pair event have ever been reported, and so the pair event nature of sonic booms and Cherenkov radiation, for example, remains unconfirmed. Recent advances in modern technology have made such pair event tracking feasible. If measured, pair events could provide important information about object distance and history.     

Pair Tunneling through Single Molecules

By a polaronic energy shift, the effective charging energy of molecules can become negative, favoring ground states with even numbers of electrons. Here we show that charge transport through such molecules near ground-state degeneracies is dominated by tunneling of electron pairs which coexists with (featureless) single-electron cotunneling. Because of the restricted phase space for pair tunneling, the current-voltage characteristics exhibit striking differences from the conventional Coulomb blockade. In asymmetric junctions, pair tunneling can be used for gate-controlled current rectification and switching.     

Pair Excitations in Even-Even Nuclei

A charge exchange term is added to the n-p effective interaction in treating eveneven nuclei with shape coexistence. The energy spectra and some of the E2 transition rates are calculated for ^112,114Cd, ^114,116Sn and ^118,120Te nuclei. The inclusion of this new term helps to improve an agreement with experimental data.