Science China Physics, Mechanics & Astronomy最新文献

Accurate theoretical prediction for halo mass function across a broad cosmological space is crucial for the forthcoming Chinese Space Station Survey Telescope (CSST) observations, which will capture cosmological information from multiple probes, e.g., cluster abundance, and weak lensing. In this work, we quantify the percent-level impact of different mass binning schemes when measuring the differential halo mass function from simulations, and demonstrate that the cumulative form of the halo mass function is independent of the binning scheme. Through the recently finished Kun simulation suite, we propose a generalized framework to construct multiple accurate halo mass function emulators for different halo mass definitions, including M_200m, M_vir, and M_200c. This extends our CSST Emulator to provide fast and accurate halo mass function predictions for halo mass M ⩾ 10¹²h⁻¹M_⊙ up to z = 3.0. For redshifts z ⩽ 1.0, the accuracy is within 2% for M ⩽ 10¹³h⁻¹M_⊙, 5% for M ⩽ 10¹⁴h⁻¹M_⊙, and 10% for M ⩽ 10¹⁵h⁻¹M_⊙, which is comparable with the statistical errors of training simulations. This tool is integrated in CSST Emulator and publicly available at https://github.com/czymh/csstemu, providing a fast and accurate theoretical tool to obtain unbiased cosmological constraints of the upcoming CSST survey.

Most problems in uncertainty quantification, despite their ubiquitousness in scientific computing, applied mathematics and data science, remain formidable on a classical computer. For uncertainties that arise in partial differential equations (PDEs), large numbers M ≫ 1 of samples are required to obtain accurate ensemble averages. This usually involves solving the PDE M times. In addition, to characterise the stochasticity in a PDE, the dimension L of the random input variables is high in most cases, and classical algorithms suffer from the curse-of-dimensionality. We propose new quantum algorithms for PDEs with uncertain coefficients that are more efficient in M and L in various important regimes, compared to their classical counterparts. We introduce transformations that convert the original d-dimensional equation (with uncertain coefficients) into d + L (for dissipative equations) or d + 2L (for wave type equations) dimensional equations (with certain coefficients) in which the uncertainties appear only in the initial data. These transformations also allow one to superimpose the M different initial data, so the computational cost for the quantum algorithm to obtain the ensemble average from M different samples is independent of M, while also showing potential advantage in d, L and precision ϵ in computing ensemble averaged solutions or physical observables.

We study the quasinormal modes of Boulware-Deser-Wheeler black hole in Einstein-Gauss-Bonnet gravity theory within the hyperboloidal framework. The effective potentials for the test Klein-Gordon field and gravitational perturbations of scalar, vector, and tensor types are thoroughly investigated and put into several typical classes. The effective potentials for the gravitational perturbations have more diverse behaviors than those in general relativity, such as double peaks, the existence of a negative region adjacent to or far away from the event horizon. These lead to the existence of unstable modes (Imω < 0), and the presence of gravitational wave echoes. These rich phenomena are inherent in Einstein-Gauss-Bonnet theory, rather than artificially introduced by hand. What’s more, the (in)stability of quasinormal modes is studied in the frequency domain and time domain, respectively. For the frequency domain, the pseudospectrum is used to account for the instability of the spectrum. For the time domain, we add a small bump to the effective potential, and find that the new waveform does not differ significantly from the original one, where the comparison is characterized by the so-called mismatch functions. This means that quasinormal modes are stable in the time domain regardless of the shapes of the original effective potentials. In this way, our study reveals the non-equivalence of the stability of quasinormal modes in the frequency domain and the time domain. Besides, we also numerically investigate Price’s law at both finite distances and infinity with the assistance of the hyperboloidal approach.

Magnon, the quanta of spin wave, low energy excitation from magnetic ground state, not only carries spin angular momentum which is of crucial importance in new generation of information technology, but also serves as powerful probes for investigating the corresponding ground-state properties. Here, we investigate magnetic order transitions in the antiferromagnetic van der Waals insulator NiPS₃ using non-local magnon transport. We observe a dimensional cross-over behavior with a critical thickness of approximately 12–14 nm. Below the threshold, the thermally activated magnon carries angular momentum that is opposite to the conventional case, corresponding to the vestigial order with higher symmetry. While above this critical thickness, where NiPS₃ exhibits in-plane zigzag antiferromagnetic order with lower symmetry, the thermally activated magnon signals show anomalous high-magnetic-field responses. After the spin-flop transition, the Néel vector becomes strongly pinned near the a-axis, resulting in a flattening of the detected signals that can only be switched when the magnetic field is oriented perpendicular to the Néel vector. These findings demonstrate that magnon spin currents provide an effective means to investigate exotic orders and phase transitions in van der Waals magnetic insulators, offering new insights for both fundamental research and potential applications in spin-based technologies.

Recently, a 3σ-4σ preference for dynamical dark energy has been reported by the Dark Energy Spectroscopic Instrument (DESI) collaboration, which has inspired hot debates on new physics or systematics. In this paper, we reveal that this preference is significantly biased by an external low-redshift supernova (low-z SN) sample, which was combined with the Dark Energy Survey SN program (DES-SN) in their Year-Five data release (DESY5). Using the intercept in the SN magnitude-distance relation as a diagnostic for systematics, we find not only large dispersions but also a large discrepancy in the low-z SN sample when compared with the high-z DES-SN sample within the single DESY5 compilation, in contrast to the uniform behavior found in the PantheonPlus data. Correcting for this low-z systematics with or without including the cosmic microwave background data can largely reduce the preference for dynamical DE to be less than 2σ. Therefore, the DESI preference for dynamical DE is biased by some unknown systematics in the low-z SN sample.

In this paper, a quantum-enhanced framework is proposed to optimize observation point selection in environmental data assimilation. The method transforms the task into a QUBO problem, balancing uncertainty reduction and spatial diversity. By leveraging a quantum-inspired optical Ising machine, it avoids the exponential complexity of classical optimization. Tests on the Lorenz-1996 model demonstrate its superiority over traditional methods, enhancing computational efficiency without loss of accuracy. The findings underscore the potential of quantum-inspired optimization for scalable, real-time assimilation in high-resolution weather prediction, reducing dimensionality and computational cost.

In the framework of open quantum systems, we study the dynamics of an accelerated quantum battery (QB), modeled as an Unruh-DeWitt detector interacting with a real massless scalar quantum field. The QB is driven by an external classical force acting as a charger. A major challenge in this setup is the environment-induced decoherence, which leads to energy dissipation of the QB. Accelerated motion exacerbates this dissipation, manifesting effects analogous to those experienced by a static QB in a thermal bath in free space, consistent with the Unruh effect. To overcome these challenges, we introduce a reflecting boundary in a space, which modifies the vacuum fluctuations of the field and leads to a position-dependent suppression of dissipation for the Unruh-DeWitt QB. Our analysis reveals that as the QB approaches the boundary, the relevant dissipation is significantly reduced. In particular, when the QB is placed extremely close to the boundary, the dissipation is nearly eliminated, as if the QB were a closed system. Furthermore, we identify a characteristic length scale associated with the acceleration of QB. When the distance between the QB and the boundary is much smaller than this scale, the boundary effectively suppresses dissipation, and this suppression effect becomes identical for both an accelerated QB and a static QB in a thermal bath. Conversely, when the distance is beyond this scale, the suppression effect weakens and manifests a significant difference between these two cases. Our findings demonstrate the potential of boundary-induced modifications in vacuum fluctuations to effectively suppress dissipation, offering valuable insights for optimizing QB performance. This work paves the way for the development of high-efficiency quantum energy storage systems in the relativistic framework.

The investigation of physical processes across various temporal scales is essential for comprehending and forecasting the behavior of intricate systems over extended periods. Relaxation processes, which span 16 orders of magnitude, are a prime example of multiscale physical processes. However, the description of the relaxation process across multiple time spans is not yet clear. This study employs advanced flash differential scanning calorimetry to probe multiscale relaxation dynamics across various glass systems. We discovered that the relaxation behavior exhibits self-similar scaling across multiple time scales, arising from the accumulation of temporally fractal activation events. Due to the heterogeneous distribution of energy in the system, not every activation event contributes to global energy reduction. Microscopic mechanisms underlying the temporal fractal of activation events are proposed based on both experimental and simulation results. The temporal fractal serves as a critical link connecting microscopic activation events with macroscopic relaxation processes in disordered materials. This fractal framework provides a powerful approach for probing multiscale dynamics in complex systems.