Photon Mass Bound Destroyed by Vortices

The Particle Data Group gives an upper bound on the photon mass $m < 2 \times 10^{-16}$eV from a laboratory experiment and lists, but does not adopt, an astronomical bound $m < 3 \times 10^{-27}$eV, both of which are based on the plausible assumption of large galactic vector-potential. We argue that the interpretations of these experiments should be changed, which alters significantly the bounds on $m$. If $m$ arises from a Higgs effect, both limits are invalid because the Proca vector-potential of the galactic magnetic field may be neutralized by vortices giving a large-scale magnetic field that is effectively Maxwellian. In this regime, experiments sensitive to the Proca potential do not yield a useful bound on $m$. As a by-product, the non-zero photon mass from Higgs effect predicts generation of a primordial magnetic field in the early universe. If, on the other hand, the galactic magnetic field is in the Proca regime, the very existence of the observed large-scale magnetic field gives $m^{-1}\gtrsim 1$kpc, or $m\lesssim 10^{-26}$eV.Comment: 9 pages, discussion of primordial magnetic field adde

The quality analysis of multi-step forming the higher D/t cylinder

In order to solve the problem of large springback in higher D/t cylinder stamping, the method of hydroforming following drawing is adopted in this paper. It can reduce the residual stress of the cylinder after heat treatment. The effects of the stretching height, hydraulic pressure and blank holder force on the cylinder quality are investigated using the finite element software dynaform, and the optimal process parameters are obtained. In case that the stretching height, blank holder force and hydraulic pressure are relatively 55 mm, 12,5 MPa and 20 KN, the rate of wall thickness variation and springback are obviously reduced. The research results lay a theoretical foundation for improving the plastic deformation of thin-walled cylinder

Effect of aluminum alloy wheel forging and spinning process parameters on forming force

In order to study the influence of process parameters on the forming force during the forging and spinning process of the wheel hub, five parameters were selected: die preheating temperature, blank temperature, upper die down speed, friction coefficient and feed rate.Use Deform and Simufact software to simulate and obtain the influence law of each process parameter on forming force. The results provide a certain reference for reasonable selection of process parameters in the forming process

Estimation of Spin-Spin Interaction by Weak Measurement Scheme

Precisely knowing an interaction Hamiltonian is crucial to realize quantum information tasks, especially to experimentally demonstrate a quantum computer and a quantum memory. We propose a scheme to experimentally evaluate the spin-spin interaction for a two-qubit system by the weak measurement technique initiated by Yakir Aharonov and his colleagues. Furthermore, we numerically confirm our proposed scheme in a specific system of a nitrogen vacancy center in diamond. This means that the weak measurement can also be taken as a concrete example of the quantum process tomography.Comment: 4 pages, 1 table, 2 figures, to appear in Europhysics Letter

Effect of 6061 aluminum alloy wheel forging and spinning process parameters on forming quality

This paper mainly studies the influence of process parameters on the forming quality during the spinning process of 6061 aluminum alloy wheel forging blanks. The four parameters of spinning temperature, spindle speed, wheel feed and wall thickness reduction rate are selected for research, and the quality of the surface of the hub and the influence on the size of the hub are judged. Simufact software is used to simulate the influence of various process parameters on the forming quality of the hub. The results provide a certain reference for the reasonable selection of process parameters during the spinning forming process of 6061 aluminum alloy hub

The influence law of process parammeters on end concavity of hexahedral blank cross wedge rolling (CWR)

In order to expand the range of the cross wedge rolling (CWR) product, realize CWR of hexahedral blank. In this paper, the three-dimensional Finite element model (FEM) of hexahedral blank CWR is established by DEFORM finite element software. The influence of forming angle, spreading angle and section shrinkage on the length of concavity is analyzed, compared with the round billet rolling results under the same parameters, the concavity length of the hexahedral blank is slightly larger than that of round billet, and the influence of process parameters on the concavity is basically the same. The research results provide theoretical guidance for the rational determination of process parameters for CWR of hexahedral blank