P-wave two-particle bound and scattering states in a finite volume including QED

The mass shifts for two-fermion bound and scattering P-wave states subject to the long-range interactions due to QED in the non-relativistic regime are derived. Introducing a short range force coupling the spinless fermions to one unit of angular momentum in the framework of pionless EFT, we first calculate both perturbatively and non-perturbatively the Coulomb corrections to fermion–fermion scattering in the continuum and infinite volume context. Motivated by the research on particle–antiparticle bound states, we extend the results to fermions of identical mass and opposite charge. Second, we transpose the system onto a cubic box with periodic boundary conditions and we calculate the finite volume corrections to the energy of the lowest bound and unbound $$T_1^{-}$$ T 1 - eigenstates. In particular, power law corrections proportional to the fine structure constant and resembling the recent results for S-wave states are found. Higher order contributions in $$\alpha $$ α are neglected, since the gapped nature of the momentum operator in the finite-volume environnement allows for a perturbative treatment of the QED interactions.

Peridynamic Model for the Numerical Simulation of Anchor Bolt Pullout in Concrete

Predictive simulation of anchor pullout from concrete structures is not only a serious problem in structural mechanics but also very important in structural design safety. In the finite element method (FEM), the crack paths or the points of crack initiation usually need to be assumed in advance. Otherwise, some special crack growth treatment or adaptive remeshing algorithm is normally used. In this paper, an extended peridynamic method was introduced to avoid the difficulties found in FEM, and its application on anchor bolt pullout in plain concrete is studied. In the analysis, the interaction between the anchor bolt and concrete is represented by a modified short-range force and an extended bond-level model for concrete is developed. Numerical analysis results indicate that the peak pullout load obtained and the crack branching of the anchoring system agreed well with the experimental investigations.

A Pipelined Parallelism Approach to Parallel Short-Range Molecular Dynamics Simulations on Multi-Core Platforms

We present a pipelined parallelism approach to implement the short-range force computations in molecular dynamic simulations on a multi-core machine. Our methodology is based on the OpenMP programming model. It uses multiple producer threads and a single consumer thread to adapt the application for pipeline parallelism, and utilizes the high inter-core communication bandwidth. Multiple producer threads compute the short-range force, and the consumer thread modifies the global force-array. Compared with some other methods applied in data parallelism that can parallelize reduction operations on a force-array, our method achieves high performance especially when the simulation system is characterized by irregular geometry or by inhomogeneous atom densities.