Abstract We developed a model of a quantum Otto engine using two coupled two-level atoms. Based on the platform, we show that frequency detuning and the coupling strength induced by dipole-dipole interactions can lead to decoherence by disrupting coherent energy exchange. We focus on fundamental thermodynamic quantities, including heat absorption, release to heat baths, work done and efficiency. It is noteworthy that the interatomic coupling strength and frequency detuning do not merely affect the shape of the work and the efficiency but ultimately govern its quantitative magnitude. In the field of quantum thermodynamics, we have established an upper bound efficiency that is stricter than the Carnot limit. Moreover, our analysis confirms that quantum coherence enables the system to exceed the efficiency threshold of a classical Otto heat engine. The second law of thermodynamics holds all the while. Our results constitute a step forward in the design of conceptually new quantum thermodynamic devices which take advantage of uniquely quantum resources of quantum coherence.

Abstract Using a model-independent Gaussian process (GP) method to reconstruct the dimensionless luminosity distance D and its derivatives, we derive the evolution of the dimensionless Hubble parameter E, the deceleration parameter q, and the state parameter w of dark energy. We utilize the PantheonPlus, SH0ES, and Gamma Ray Burst (GRB) data to derive the dimensionless luminosity distance D. Additionally, we employ observational H(z) data (OHD) and baryon acoustic oscillations (BAO) from Dark Energy Spectroscopic Instrument (DESI) Data Release 2 (DR2) to obtain the first derivative of the dimensionless luminosity distance D'. To obtain the reconstructed D and D', we utilize the fiducial value from each dataset, with particular emphasis on the varying H_0. According to the reconstruction results obtained from PantheonPlus+SH0ES+GRB+OHD and PantheonPlus+SH0ES+GRB+OHD+DESI data, we find that E are consistent with the predictions of the \LambdaCDM model at a 2\sigma confidence level within the redshift range of z<2. However, the reconstruction results for q exhibit deviations from the \LambdaCDM model in the range of z<0.3. Furthermore, we observe that the mean value of w exhibits evolving behavior, transiting from w < -1 to w > -1 around z_wt=0.464^+0.235_-0.120. Combining data from DESI DR2 can slightly enhance the accuracy of our constraints.

Abstract A physics-informed neural network (PINN) is built to solve the nucleonic Dirac equation. The PINN employs the residual of the Dirac equation as the objective function instead of the variation of energy expectation value, thereby avoiding the variational collapse problem. Integrating the automatic differentiation techniques, the PINN also overcomes the Fermion doubling problem. A constraint term in the loss function of the PINN is designed to avoid trivial solutions and an orthogonality constraint term is used to search for the excited states. The performance of the unsupervised PINN is evaluated by solving the orbitals below the Fermi surface of 16 O and 208 Pb in the Dirac Woods-Saxon potential. Compared to the results obtained by the traditional shooting method, obtained energies have relative errors on the order of 10 -3 and the root-mean-square errors of the corresponding wave functions are also on the order of 10 -3 .

Abstract Leveraging an optimized transfer matrix strategy, we numerically investigated the effect of δ-doping on the transmission probability, conductance, and magnetoresistance ratio in a semiconductor 2DEG heterostructure modulated by two overlapping magnetic barriers. High-precision computations revealed the dependence of the peak magnetoresistance ratio and its Fermi energy position on the weight and position of the δ-doping. The results demonstrate that the performance of GMR devices can be effectively tuned by optimizing both the position and strength of δ-doping. Comparing our results with prior calculations and theoretical predictions, we find strong agreement with theoretical expectations, but also significant deviations from earlier studies due to critical numerical inaccuracies in their methodologies. By addressing these discrepancies, our optimized approach provides a fast and versatile framework for analyzing spin-dependent transport in complex magnetic-electric hybrid systems.

Abstract In this study, we propose that many different thermodynamic modeling approaches, including GENERIC, Onsager's variational principle, Energetic Variational Approach and Classical Irreversible Thermodynamics, all could be cast into the gradient-conservative structure (GCS). GCS enjoys many nice mathematical properties, has close connection with large deviations principle and gradient flows in Wasserstein space, and fulfills laws of thermodynamics. Our results demonstrate that the GCS may serve as a unified theoretical framework to model various non-equilibrium thermodynamic processes.

Abstract Under study in this paper is a nonlinear Schr\"{o}dinger equation with local and nonlocal nonlinearities, which originates from the parity-symmetric reduction of the Manakov system and has applications in some physical systems with the parity symmetry constraint between two fields/components. Via the Riemann-Hilbert method, the theory of inverse scattering transform with the presence of double poles is extended for this equation under nonzero boundary conditions (NZBCs). Also, the double-pole soliton solutions with NZBCs are derived in the reflectionless case. It is shown that the quasi-periodic beating solitons can be obtained when the double pole lies off the circle $\Gamma$ centered at the origin with radius $\sqrt{2} q_0$ (where $q_0$ is the modulus of NZBCs) on the spectrum plane. Moreover, by the improved asymptotic analysis method, the asymptotic solitons are found to be located in some logarithmic curves of the $xt$ plane.