Towards the demonstration of photon-photon collision with compact lasers

We report a proposal to observe the two-photon Breit-Wheeler process in plasma driven by compact lasers. A high charge electron bunch can be generated from laser plasma wakefield acceleration when a tightly focused laser pulse transports in a sub-critical density plasma. The electron bunch scatters with the laser pulse coming from the opposite direction and results the emitting of high brilliance X-ray pulses. In a three-dimensional particle-in-cell simulation with a laser pulse of $\sim$10 J, one could produce a X-ray pulse with photon number higher than $3\times10^{11}$ and brilliance above $1.6\times 10^{23}$ photons/s/mm$^2$/mrad$^2$/0.1$\%$BW at 1 MeV. The X-ray pulses collide in the plasma and create more than $1.1\times 10^5$ electron-positron pairs per shot. It is also found that the positrons can be accelerated transversely by a transverse electric field generated in the plasma, which enables the safe detection in the direction away from the laser pulses. This proposal which has solved key challenges in laser driven photon-photon collision could demonstrate the two-photon Breit-Wheeler process on a much more compact device in a single shot

How does digitalization alter the paradox of supply base concentration? The effects of digitalization intensity and breadth

Purpose – The highly uncertain and turbulent environments nowadays intensify the paradoxical effects of supply base concentration (SBC) on improving cost efficiency while increasing idiosyncratic risk (IR). Digitalization is regarded as a remedy for this paradox, yet digitization’s potentially curative effect has not been empirically tested. Leveraging the lenses of paradox theory and information processing theory (IPT), this study explores how two distinct dimensions of digitalization, i.e. digitalization intensity (DI) and digitalization breadth (DB), reconcile the paradoxical effects of SBC. Design/methodology/approach – Using a panel dataset of 1,238 Chinese manufacturing firms in the period of 2012–2020, this study utilizes fixed-effects regression models to test the proposed hypotheses. Findings – The authors discover that SBC enhances a firm’s cost efficiency but induces greater IR. More importantly, there is evidence that DI restrains the amplifying effect of SBC on IR. However, DB weakens the enhancing effect of SBC on cost efficiency and aggravates the SBC’s exacerbating effect on IR. Originality/value – This study advances the understanding of the paradoxical effects of SBC on cost efficiency and IR from a paradox theory perspective. More importantly, to the best of the authors’ knowledge, the authors’ study is the first to untangle the differential roles of DI and DB in reconciling the paradox of SBC. This study also provides practitioners with nuanced insights into how the practitioners should use appropriate tactics to deploy digital technologies effectively

Multi-Receiver Quantum Dense Coding with Non-Symmetric Quantum Channel

A two-receiver quantum dense coding scheme and an $N$-receiver quantum dense coding scheme, in the case of non-symmetric Hilbert spaces of the particles of the quantum channel, are investigated in this paper. A sender can send his messages to many receivers simultaneously. The scheme can be applied to quantum secret sharing and controlled quantum dense coding.Comment: To appear in Journal of the Korean Physical Societ

Modification of the Landau-Lifshitz Equation in the Presence of a Spin-Polarized Current in CMR and GMR Materials

We derive a continuum equation for the magnetization of a conducting ferromagnet in the presence of a spin-polarized current. Current effects enter in the form of a topological term in the Landau-Lifshitz equation . In the stationary situation the problem maps onto the motion of a classical charged particle in the field of a magnetic monopole. The spatial dependence of the magnetization is calculated for a one-dimensional geometry and suggestions for experimental observation are made. We also consider time-dependent solutions and predict a spin-wave instability for large currents.Comment: 4 two-column pages in RevTex, 3 ps-figure

Universal Fluctuation of the Hall Conductance in the Random Magnetic Field

We show that the RMS fluctuation of the antisymmetric part of the Hall conductance of a planar mesoscopic metal in a random magnetic field with zero average is universal, of the order of $e^2/h$, independent of the amplitude of the random magnetic field and the diffusion coefficient even in the weak field limit. This quantity is exactly zero in the case of ordinary scalar disorder. We propose an experiment to measure this surprising effect, and also discuss its implications on the localization physics of this system. Our result applies to some other systems with broken time-reversal ({\bf T}) symmetry.Comment: 4 pages, Revtex 3.0; added the paragraph regarding applicability to other systems with broken T-invariance, misc. minor change

Constitutive overexpression of soybean plasma membrane intrinsic protein GmPIP1;6 confers salt tolerance

BACKGROUND: Under saline conditions, plant growth is depressed via osmotic stress and salt can accumulate in leaves leading to further depression of growth due to reduced photosynthesis and gas exchange. Aquaporins are proposed to have a major role in growth of plants via their impact on root water uptake and leaf gas exchange. In this study, soybean plasma membrane intrinsic protein 1;6 (GmPIP1;6) was constitutively overexpressed to evaluate the function of GmPIP1;6 in growth regulation and salt tolerance in soybean. RESULTS: GmPIP1;6 is highly expressed in roots as well as reproductive tissues and the protein targeted to the plasma membrane in onion epidermis. Treatment with 100 mM NaCl resulted in reduced expression initially, then after 3 days the expression was increased in root and leaves. The effects of constitutive overexpression of GmPIP1;6 in soybean was examined under normal and salt stress conditions. Overexpression in 2 independent lines resulted in enhanced leaf gas exchange, but not growth under normal conditions compared to wild type (WT). With 100 mM NaCl, net assimilation was much higher in the GmPIP1;6-Oe and growth was enhanced relative to WT. GmPIP1;6-Oe plants did not have higher root hydraulic conductance (Lo) under normal conditions, but were able to maintain Lo under saline conditions compared to WT which decreased Lo. GmPIP1;6-Oe lines grown in the field had increased yield resulting mainly from increased seed size. CONCLUSIONS: The general impact of overexpression of GmPIP1;6 suggests that it may be a multifunctional aquaporin involved in root water transport, photosynthesis and seed loading. GmPIP1;6 is a valuable gene for genetic engineering to improve soybean yield and salt tolerance.Lian Zhou, Chuang Wang, Ruifang Liu, Qiang Han, Rebecca K Vandeleur, Juan Du, Steven Tyerman and Huixia Sho