LFV couplings of the extra gauge boson Z' and leptonic decay and production of pseudoscalar mesons

Considering the constraints of the lepton flavor violating (LFV) processes $\mu \rightarrow 3e$ and $\tau\rightarrow3\mu$ on the LFV couplings $Z'\ell_{i}\ell_{j}$, in the contexts of the $E_{6}$ models, the left-right (LR) models, the "alternative" left-right (ALR) models and the 331 models, we investigate the contributions of the extra gauge boson $Z'$ to the decay rates of the processes $\ell_{i}\rightarrow\ell_{j}\nu_{\ell}\nu_{\ell}$, $\tau\rightarrow\mu P$ and $P\rightarrow \mu e$ with $P=\pi^{0},\eta$ and $\eta '$. Our numerical results show that the maximal values of the branching ratios for these processes are not dependent on the $Z'$ mass $M_{Z'}$ at leader order. The extra gauge boson $Z'_{X}$ predicted by the $E_{6}$ models can make the maximum value of the branching ratio $Br(\tau\rightarrow\mu\nu_{\ell}\nu_{\ell})$ reach $1.1\times10^{-7}$. All $Z'$ models considered in this paper can produce significant contributions to the process $\tau\rightarrow\mu P$. However, the value of $Br(P\rightarrow\mu e)$ is far below its corresponding experimental upper bound.Comment: 14 pages, 2 figures; matches published versio

Pseudo-Model-Free Hedging for Variable Annuities via Deep Reinforcement Learning

This paper applies a deep reinforcement learning approach to revisit the hedging problem of variable annuities. Instead of assuming actuarial and financial dual-market model a priori, the reinforcement learning agent learns how to hedge by collecting anchor-hedging reward signals through interactions with the market. By the recently advanced proximal policy optimization, the pseudo-model-free reinforcement learning agent performs equally well as the correct Delta, while outperforms the misspecified Deltas. The reinforcement learning agent is also integrated with online learning to demonstrate its full adaptive capability to the market

Ground-state phase diagram of the three-band Hubbard model from density matrix embedding theory

We determine the ground-state phase diagram of the three-band Hubbard model across a range of model parameters using density matrix embedding theory. We study the atomic-scale nature of the antiferromagnetic (AFM) and superconducting (SC) orders, explicitly including the oxygen degrees of freedom. All parametrizations of the model display AFM and SC phases, but the decay of AFM order with doping is too slow compared to the experimental phase diagram, and further, coexistence of AFM and SC orders occurs in all parameter sets. The local magnetic moment localizes entirely at the copper sites. The magnetic phase diagram is particularly sensitive to Δ_(pd) and t_(pp), and existing estimates of the charge transfer gap Δ_(pd) appear too large in so-called minimal model parametrizations. The electron-doped side of the phase diagram is qualitatively distinct from the hole-doped side and we find an unusual two-peak structure in the SC in the full model parametrization. Examining the SC order at the atomic scale, within the larger scale d_(x²−y²)-wave SC pairing order between Cu-Cu and O-O, we also observe a local p_(x(y)) [or d_(xz(yz))] symmetry modulation of the pair density on the Cu-O bonds. Our work highlights some of the features that arise in a three-band versus one-band picture, the role of the oxygen degrees of freedom in new kinds of atomic-scale SC orders, and the necessity of re-evaluating current parametrizations of the three-band Hubbard model

Research on the radiation characteristics of aerodynamic noises in the connection position of high-speed trains

To study unsteady aerodynamic noise characteristics in the connection position of high-speed trains, this paper established a computational model for aerodynamic noises in the connection position of high-speed trains based on computational fluid dynamics theories. This model included 2 middle trains and 1 connection structure. The detached eddy simulation (DES) was adopted to conduct a numerical simulation for the flow field around high-speed trains which were running in the open air without crosswind. The acoustic model of Ffowcs Williams-Hawkings (FW-H) was used to conduct an unsteady computation for far field aerodynamic noises in the connection position of high-speed trains. In the meanwhile, the boundary element method (BEM) was also applied to conduct an unsteady computation for the radiation of near field aerodynamic noises in the connection position. When the running speed was 250 km/h, time-domain characteristics, frequency-domain characteristics and sound propagation characteristics of aerodynamic noises in the connection position and the unsteady flow field around the connection position were obtained. Studied results showed that: vortex shedding and fluid separations in the connection position were main reasons for aerodynamic noises. In addition, main aerodynamic noise sources were at the recess and rear (the second train) in the connection position, and the first train was not an aerodynamic noise source. Peak frequencies of aerodynamic noises in the far field were 34 Hz, 79 Hz, 124 Hz and 170 Hz. When observation points were 7.5 m away from the center line of track, the maximum sound pressure level was 83.6 dB. When observation points were 25 m away from the center line of track, the maximum sound pressure level was 75.9 dB