arXiv subjects

Yixuan Dang

Publications and source records attributed to Yixuan Dang.

7 recordsLinked to original sources

arXiv2026

One Year and One Night to 1% in $\mathbf{H_0}$: Efficient Spectroscopic Strategy for Dark Siren Cosmology

Gravitational-wave events from compact binary coalescences (CBCs) can be used as standard sirens: they encode the luminosity distance to their sources, which yields a measurement of the Hubble constant ($H_0$) if the source's redshift is known. In the absence of an electromagnetic counterpart, $H_0$ can still be inferred statistically from the cataloged galaxies within the event's sky localization volume via the dark siren, or galaxy catalog method. In this work we examine how the depth of a volume-limited galaxy catalog affects this inference and identify the most efficient spectroscopic strategy for an unbiased measurement of $H_0$ at a median precision of $0.98\%$. The strategy is to carry out spectroscopic surveys to a depth of $r \sim 19$ for the ten best-localized events observed in one year by the LIGO Hanford, LIGO Livingston, and LIGO-India network at A$^\#$ sensitivity. Such a campaign requires a minimum of one night of electromagnetic follow-up observations, or five nights under the most conservative assumptions. For the Hanford, Livingston, and Virgo network at A$+$ sensitivity, the same ten-event strategy yields a median precision of $2.63\%$.

astro-ph.CO↗

arXiv2025

Golden and Silver Dark Sirens for precise H0 measurement with HETDEX

Gravitational waves (GWs) from compact binary coalescences are standard sirens that provide a direct measure of the source's luminosity distance, enabling an independent measurement of the Hubble constant (H0). While a bright siren -- a GW event with an identified electromagnetic (EM) counterpart -- provided the first such constraint, most detections, currently dominated by black hole mergers, lack EM signatures. A measurement of H0 is still possible with these dark sirens by statistically associating GW events with galaxies in existing catalogs based on the sky localization. In this work, we explore the potential of two subsets of sirens: rare golden dark sirens, for which a single galaxy dominates the H0 posterior, and silver dark sirens, which are far more common but have a larger set of plausible host galaxies. Using the fifth internal data release of the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX), we assess the suitability of the Visible Integral-field Replicable Unit Spectrograph (VIRUS) for spectroscopic follow-up of dark sirens. VIRUS exposures of the standard HETDEX depth provide precise redshifts and exquisite completeness within z = 0.2. After a single year of observations with the upgraded LIGO-A# network, the combined sample of golden and silver dark sirens with z < 0.2 and follow-up VIRUS observations can potentially yield a few-percent constraint on H0. Our predictions suggest that spectroscopic redshift surveys such as HETDEX can play a key role in realizing high-precision cosmology with dark sirens in the near future. Standard-siren distance measurements offer a critical, fully independent path to the local value of H0 to resolve the Hubble tension.

astro-ph.CO↗

arXiv2025

Direction Informed Trees (DIT*): Optimal Path Planning via Direction Filter and Direction Cost Heuristic

Optimal path planning requires finding a series of feasible states from the starting point to the goal to optimize objectives. Popular path planning algorithms, such as Effort Informed Trees (EIT*), employ effort heuristics to guide the search. Effective heuristics are accurate and computationally efficient, but achieving both can be challenging due to their conflicting nature. This paper proposes Direction Informed Trees (DIT*), a sampling-based planner that focuses on optimizing the search direction for each edge, resulting in goal bias during exploration. We define edges as generalized vectors and integrate similarity indexes to establish a directional filter that selects the nearest neighbors and estimates direction costs. The estimated direction cost heuristics are utilized in edge evaluation. This strategy allows the exploration to share directional information efficiently. DIT* convergence faster than existing single-query, sampling-based planners on tested problems in R^4 to R^16 and has been demonstrated in real-world environments with various planning tasks. A video showcasing our experimental results is available at: https://youtu.be/2SX6QT2NOek

cs.RO↗

arXiv2025

Whisker-based Active Tactile Perception for Contour Reconstruction

Perception using whisker-inspired tactile sensors currently faces a major challenge: the lack of active control in robots based on direct contact information from the whisker. To accurately reconstruct object contours, it is crucial for the whisker sensor to continuously follow and maintain an appropriate relative touch pose on the surface. This is especially important for localization based on tip contact, which has a low tolerance for sharp surfaces and must avoid slipping into tangential contact. In this paper, we first construct a magnetically transduced whisker sensor featuring a compact and robust suspension system composed of three flexible spiral arms. We develop a method that leverages a characterized whisker deflection profile to directly extract the tip contact position using gradient descent, with a Bayesian filter applied to reduce fluctuations. We then propose an active motion control policy to maintain the optimal relative pose of the whisker sensor against the object surface. A B-Spline curve is employed to predict the local surface curvature and determine the sensor orientation. Results demonstrate that our algorithm can effectively track objects and reconstruct contours with sub-millimeter accuracy. Finally, we validate the method in simulations and real-world experiments where a robot arm drives the whisker sensor to follow the surfaces of three different objects.

cs.RO↗

arXiv2024

On corrugation mode radial wavelengths of the vertical shear instability

The vertical shear instability (VSI) is a promising mechanism to drive turbulence in protoplanetary disks. Numerical simulations in the literature demonstrate that the VSI non-linear saturation is predominated by the linear corrugation modes. These modes possess vertical wavelengths crucially longer than radial wavelengths. This paper aims to investigate the natural radial wavelength of corrugation modes upon VSI saturation, by a series of numerical simulations conducted in Athena++ at different grid resolutions, disk aspect ratios, and viscosity parameterized by $ν$. We find a sign of convergence emerges at 64 cells per gas scale height for fiducial simulations, below which a continuous reduction of wavelengths with grid resolution is observed. Synthetic ALMA molecular line observations of $^{12}\rm CO(2-1)$ are performed to inspect the observability of the corrugation modes feature, which is significantly diminished with more than 32 cells per scale height. Flared and viscous disks, exhibiting longer saturation wavelengths, may mitigate the observational difficulty.

astro-ph.EP↗

arXiv2024

Impact of overlapping signals on parameterized post-Newtonian coefficients in tests of gravity

Gravitational waves have been instrumental in providing deep insights into the nature of gravity. Next-generation detectors, such as the Einstein Telescope, are predicted to have a higher detection rate given the increased sensitivity and lower cut-off frequency. However, this increased sensitivity raises challenges concerning parameter estimation due to the foreseeable overlap of signals from multiple sources. Overlapping signals (OSs), if not properly identified, may introduce biases in estimating post-Newtonian (PN) coefficients in parameterized tests of general relativity (GR). We investigate how OSs affect $-1$PN to 2PN terms in parameterized GR tests, examining their potential to falsely suggest GR deviations. We estimate the prevalence of such misleading signals in next-generation detectors, and their collective influence on GR tests. We compare the effects of OSs on coefficients at different PN orders, concluding that overall the 1PN coefficient suffers the most. Our findings also reveal that while a non-negligible portion of OSs exhibit biases in PN coefficients that might individually prefer to conclude deviations from GR, collectively, the direction to deviate is random and a statistical combination will still be in favor of GR.

astro-ph.IM↗

arXiv2022

Scene Graph Generation: A Comprehensive Survey

Deep learning techniques have led to remarkable breakthroughs in the field of generic object detection and have spawned a lot of scene-understanding tasks in recent years. Scene graph has been the focus of research because of its powerful semantic representation and applications to scene understanding. Scene Graph Generation (SGG) refers to the task of automatically mapping an image into a semantic structural scene graph, which requires the correct labeling of detected objects and their relationships. Although this is a challenging task, the community has proposed a lot of SGG approaches and achieved good results. In this paper, we provide a comprehensive survey of recent achievements in this field brought about by deep learning techniques. We review 138 representative works that cover different input modalities, and systematically summarize existing methods of image-based SGG from the perspective of feature extraction and fusion. We attempt to connect and systematize the existing visual relationship detection methods, to summarize, and interpret the mechanisms and the strategies of SGG in a comprehensive way. Finally, we finish this survey with deep discussions about current existing problems and future research directions. This survey will help readers to develop a better understanding of the current research status and ideas.

cs.CV↗