arXiv subjects

Wenrong Sun

Publications and source records attributed to Wenrong Sun.

5 recordsLinked to original sources

arXiv2026

Capture Driven Evolution of Asymmetric Dark Matter in Non-rotating Neutron Stars

We develop a self-consistent framework that connects dark matter capture to the long term accumulation and structural evolution of neutron stars, allowing us to quantify the impact of capture driven asymmetric dark matter on gravitational wave observables over astrophysical timescales. We model cold, non-rotating neutron stars using a three layer polytropic EoS coupled to a dark matter component through the two fluid Tolman Oppenheimer Volkoff equations, and reconstruct the long term evolution using a time dependent dark matter capture formalism. By exploring a wide range of astrophysical conditions, including extreme environments designed to maximize the capture efficiency, we derive conservative upper bounds on the effects of dark matter accumulation over a Hubble time. Even under these deliberately optimistic assumptions, the accumulated dark matter component remains subdominant and induces limited structural modifications. In particular, dark matter accumulation increases the stellar compactness while suppressing the Love number and tidal deformability. Significant evolution occurs only in extreme Galactic center like environments over Hubble time scales, whereas for realistic Galactic or cluster dark matter densities the corresponding deviations remain negligible. We therefore conclude that capture driven dark matter accumulation is unlikely to produce detectable signatures in current or near future gravitational wave observations of neutron stars.

astro-ph.HE↗

arXiv2026

Localized patterns and dispersive structures in two-dimensional Fermi-Pasta-Ulam lattices

In this paper, we study an analog of the scalar two-dimensional Fermi-Pasta-Ulam (FPU) lattice. In particular, a variety of dispersive wave structures and localized patterns are numerically identified in the numerical simulations of the FPU lattice, but, to the best of our knowledge, all of these particular wave structures do not admit analytical closed-form expressions. In order to resolve this issue, we perform a dimensional reduction and accordingly derive a modified KdV equation. Based on this reduction, we first take advantage of some of its exact localized solutions to model the associated wave patterns in the FPU lattice. In addition, we explore the two-dimensional generalization of the Riemann problems for the FPU lattice and the corresponding modified KdV reduction, whose evolution dynamics lead to the formation of multiple composite dispersive structures. Moreover, we propose and rigorously derive the KPII limit of the FPU lattice and investigate their associated wedge problems. Finally, all these relevant numerical dynamics are compared to examine the performance of these quasi-continuum long-wave asymptotic limits.

nlin.PS↗

arXiv2026

Information-Theoretic Adaptive Cooling for Deterministic MPPI via Entropy Feedback

This paper investigates deterministic optimal control using Model Predictive Path Integral (MPPI) control, a sampling-based and derivative-free framework well suited for systems with complex dynamics and nonsmooth objectives. In deterministic MPPI, the temperature must be driven to zero to recover the true optimum, yet the design of an effective cooling schedule remains a fundamental challenge. Existing methods typically rely on predefined open-loop schedules, which limit the efficiency and robustness of the algorithm. To overcome this limitation, we propose an Information-Theoretic Adaptive Cooling (ITAC) framework that uses the Shannon entropy of the importance weights as an online feedback signal to regulate the temperature. The proposed mechanism adapts the cooling rate to the current sampling state, enabling fast progress when the weights are diffuse and cautious cooling when they become concentrated. We prove asymptotic convergence of the resulting scheme to the deterministic optimum, and further derive a critical entropy threshold that leads to a smooth barrier against premature weight collapse. Experiments on nonsmooth signal temporal logic motion-planning tasks show that ITAC improves sampling efficiency and achieves substantially faster convergence than state-of-the-art baselines without sacrificing the derivative-free nature of MPPI.

eess.SY↗

arXiv2026

Symbiotic Magnetogenesis during Radiation Domination

We present a late-time magnetogenesis mechanism in which a coupled axion-dilaton system sources a dark $U(1)$ gauge field. The dilaton's exponential coupling drives tachyonic amplification by reshaping the instability band, while the axion controls the helicity structure of the field. Together, they amplify both gauge helicities and produce a moderately chiral dark magnetic field without fine-tuning in either scalar sector. The field is generated in the dark sector, thus the mechanism avoids plasma-conductivity suppression in the visible sector, while the model remains robust across a broad range of scalar-masses and couplings. Numerical evolution from $z=10^5$ to matter-radiation equality, combined with a parameter search over the axion mass, dilaton initial conditions, and dilaton coupling, shows that astrophysically relevant amplification persists across fuzzy-dark-matter and ultralight-axion regimes. A benchmark case yields $B\approx0.9 ~\mathrm{nG}$ on $λ_0\sim1 \mathrm{Mpc}$, with kinetic mixing transferring the field to the visible sector over a broad range of mixing parameters.

astro-ph.HE↗

arXiv2026

On the quasi-continuum approximation of some localized patterns in the FPUT lattice

In the present work, we present a number of localized wave patterns that are theoretically analyzed and numerically illustrated to be observable within the widely applicable paradigm of the FPUT lattice. In particular, we derive a modified KdV equation from the FPUT lattice, which admits a variety of localized waves including these exact rational solutions representing rogue-wave profiles, solitons and breathers on the top of not only homogeneous, but also periodic elliptic function traveling-wave background. We utilize these exact solutions of the modified KdV reduction to construct consistent initial conditions for the FPUT lattice and perform time stepping of the latter. Relevant comparisons between these numerical solutions of the FPUT lattice and their associated analytical counterparts have been conducted to demonstrate good performance of the derived modified KdV reduction in approximating distinct localized wave structures from the FPUT lattice. This approach paves the way for importing a number of quasi-continuum waveforms to the FPUT lattice and the potential associated physical experiments, including recent ones in mechanical metamaterials.

nlin.PS↗