arXiv subjects

Daisuke Sato

Publications and source records attributed to Daisuke Sato.

At least 19 recordsLinked to original sources

arXiv2026

Photonic Crystal Defect Nanocavities Based on Monocrystalline Yttrium Iron Garnet

Monocrystalline yttrium iron garnet (YIG) is a key material for magneto optics and quantum magnonics owing to its high optical transparency, large magneto-optical (MO) effects at room temperature, and exceptionally-long spin coherence. While rich MO phenomena have been demonstrated in the microwave regime, extending these concepts to technologically important telecommunication wavelengths remains challenging due to the difficulty of fabricating high-quality YIG nanostructures. Here, we demonstrate photonic crystal (PhC) defect nanocavities based on monocrystalline Bi-substitudted YIG by developing a YIG-on-insulator platform and high-precision YIG nanopatterning. The fabricated nanocavities exhibit cavity resonances around lambda = 1500 nm with Q factors up to 1,800 and a mode volume V of 1.1(lambda/n)^3, corresponding to Q/V reaching around 10^3. The measured Q factor is primarily governed by intentionally introduced lattice modulations for out-of-plane light coupling, suggesting that further optimization of the cavity geometry and measurement configuration could yield an order-of-magnitude improvement of the experimental Q factor. YIG-based PhC nanocavities provide a platform for strongly confined light-magnetism interactions in the optical regime, opening pathways toward downsized nonreciprocal photonic devices and enhanced photon-magnon coupling.

physics.optics↗

arXiv2026

ACME: A Multi-Cultural, Multi-Embodiment Social-Navigation Dataset

Understanding how robots and humans move in shared spaces is essential for designing effective social robot navigation policies and predicting human behavior. However, existing datasets often lack the diversity needed to capture differences in culture, geography, and human-robot interaction-factors that strongly shape appropriate social behavior. To address this gap, we introduce ACME: A Cross-cultural, Multi-Embodiment dataset for social navigation. A large-scale data collection effort across 8 sites in 5 countries, using 7 robot embodiments, ACME is a large and diverse multi-modal dataset aimed at advancing social navigation research, providing 29.35 hours of onboard robot data and 43.5 hours of overhead pedestrian tracking data. Unlike prior datasets, it focuses on capturing goal-driven social navigation behavior in complex social scenarios with explicit robot-crowd interaction through robot speech. To facilitate learning navigation policies and predicting pedestrian trajectories, ACME provides 3D and 2D scene features, odometry, interaction information, and human-annotated pedestrian trajectory labels. We make ACME easy to use by providing both human-readable data for each sensor modality as well as raw binary data. Our qualitative and quantitative analyses show that our dataset captures more challenging scenarios and a broader distribution of pedestrian behavior than previous datasets.

cs.RO↗

arXiv2026

Robot-Assisted Group Tours for Blind People

Group interactions are essential to social functioning, yet effective engagement relies on the ability to recognize and interpret visual cues, making such engagement a significant challenge for blind people. In this paper, we investigate how a mobile robot can support group interactions for blind people. We used the scenario of a guided tour with mixed-visual groups involving blind and sighted visitors. Based on insights from an interview study with blind people (n=5) and museum experts (n=5), we designed and prototyped a robotic system that supported blind visitors to join group tours. We conducted a field study in a science museum where each blind participant (n=8) joined a group tour with one guide and two sighted participants (n=8). Findings indicated users' sense of safety from the robot's navigational support, concerns in the group participation, and preferences for obtaining environmental information. We present design implications for future robotic systems to support blind people's mixed-visual group participation.

cs.HC↗

arXiv2026

An ultrafast diamond nonlinear photonic sensor

The integration of light and materials technology is key to the creation of innovative sensing technologies. Sensing of electric and magnetic fields, and temperature with high spatio-temporal resolution is a critical task for the development of the next-generation of nanometer-scale quantum devices. Color centers in diamonds are attractive for potential applications owing to their characteristic quantum states, although they require metallic contacts for the introduction of external microwaves. Here, we build an ultrafast diamond nonlinear photonic sensor to assess the surface electric field; an electro-optic sensor based on nitrogen-vacancy centers in a diamond nanotip breaks the spatial-limit of conventional pump-probe techniques. The 10-fs near-infrared optical pulse modulates the surface electric field of a 2D transition metal dichalcogenide and we monitor the dynamics of the local electric field at nanometer-femtosecond spatio-temporal resolutions. Our nanoscopic technique will provide new horizons to the sensing of advanced nano materials.

physics.optics↗

arXiv2025

More than One Step at a Time: Designing Procedural Feedback for Non-visual Makeup Routines

Makeup plays a vital role in self-expression, identity, and confidence - yet remains an underexplored domain for assistive technology, especially for people with vision impairments. While existing tools support isolated tasks such as color identification or product labeling, they rarely address the procedural complexity of makeup routines: coordinating step sequences, managing product placement, and assessing the final look with accessible feedback. To understand the real-world process, we conducted a contextual inquiry with 15 visually impaired makeup users, capturing real-time makeup application behaviors and their step-by-step information needs and assessment approaches. Our findings reveal embodied, tactile-first strategies; persistent challenges in blending, symmetry, and assessment; and a desire for honest, real-time, goal-aligned feedback. We also interviewed five professional makeup artists, who reviewed participant makeup videos and provided expert responses to participant-raised questions and assessment practices. We contribute a taxonomy of feedback needs in non-visual makeup, and outline design implications for future assistive systems - emphasizing hands-free, conversational interaction and context-aware, procedural support for expressive and independent beauty practices.

cs.HC↗

arXiv2024

Memory-Maze: Scenario Driven Visual Language Navigation Benchmark for Guiding Blind People

Visual Language Navigation (VLN) powered robots have the potential to guide blind people by understanding route instructions provided by sighted passersby. This capability allows robots to operate in environments often unknown a prior. Existing VLN models are insufficient for the scenario of navigation guidance for blind people, as they need to understand routes described from human memory, which frequently contains stutters, errors, and omissions of details, as opposed to those obtained by thinking out loud, such as in the R2R dataset. However, existing benchmarks do not contain instructions obtained from human memory in natural environments. To this end, we present our benchmark, Memory-Maze, which simulates the scenario of seeking route instructions for guiding blind people. Our benchmark contains a maze-like structured virtual environment and novel route instruction data from human memory. Our analysis demonstrates that instruction data collected from memory was longer and contained more varied wording. We further demonstrate that addressing errors and ambiguities from memory-based instructions is challenging, by evaluating state-of-the-art models alongside our baseline model with modularized perception and controls.

cs.RO↗

arXiv2023

TBD Pedestrian Data Collection: Towards Rich, Portable, and Large-Scale Natural Pedestrian Data

Social navigation and pedestrian behavior research has shifted towards machine learning-based methods and converged on the topic of modeling inter-pedestrian interactions and pedestrian-robot interactions. For this, large-scale datasets that contain rich information are needed. We describe a portable data collection system, coupled with a semi-autonomous labeling pipeline. As part of the pipeline, we designed a label correction web app that facilitates human verification of automated pedestrian tracking outcomes. Our system enables large-scale data collection in diverse environments and fast trajectory label production. Compared with existing pedestrian data collection methods, our system contains three components: a combination of top-down and ego-centric views, natural human behavior in the presence of a socially appropriate "robot", and human-verified labels grounded in the metric space. To the best of our knowledge, no prior data collection system has a combination of all three components. We further introduce our ever-expanding dataset from the ongoing data collection effort -- the TBD Pedestrian Dataset and show that our collected data is larger in scale, contains richer information when compared to prior datasets with human-verified labels, and supports new research opportunities.

cs.CV↗

arXiv2021

Accessing Passersby Proxemic Signals through a Head-Worn Camera: Opportunities and Limitations for the Blind

The spatial behavior of passersby can be critical to blind individuals to initiate interactions, preserve personal space, or practice social distancing during a pandemic. Among other use cases, wearable cameras employing computer vision can be used to extract proxemic signals of others and thus increase access to the spatial behavior of passersby for blind people. Analyzing data collected in a study with blind (N=10) and sighted (N=40) participants, we explore: (i) visual information on approaching passersby captured by a head-worn camera; (ii) pedestrian detection algorithms for extracting proxemic signals such as passerby presence, relative position, distance, and head pose; and (iii) opportunities and limitations of using wearable cameras for helping blind people access proxemics related to nearby people. Our observations and findings provide insights into dyadic behaviors for assistive pedestrian detection and lead to implications for the design of future head-worn cameras and interactions.

cs.HC↗

arXiv2021

A shape optimisation with the isogeometric boundary element method and adjoint variable method for the three-dimensional Helmholtz equation

This paper presents a shape optimisation system to design the shape of an acoustically-hard object in the three-dimensional open space. Boundary element method (BEM) is suitable to analyse such an exterior field. However, the conventional BEM, which is based on piecewise polynomial shape and interpolation functions, can require many design variables because they are usually chosen as a part of the nodes of the underlying boundary element mesh. In addition, it is not easy for the conventional method to compute the gradient of the sound pressure on the surface, which is necessary to compute the shape derivative of our interest, of a given object. To overcome these issues, we employ the isogeometric boundary element method (IGBEM), which was developed in our previous work. With using the IGBEM, we can design the shape of surfaces through control points of the NURBS surfaces of the target object. We integrate the IGBEM with the nonlinear programming software through the adjoint variable method (AVM), where the resulting adjoint boundary value problem can be also solved by the IGBEM with a slight modification. The numerical verification and demonstration validate our shape optimisation framework.

math.NA↗

arXiv2020

Pedestrian Detection with Wearable Cameras for the Blind: A Two-way Perspective

Blind people have limited access to information about their surroundings, which is important for ensuring one's safety, managing social interactions, and identifying approaching pedestrians. With advances in computer vision, wearable cameras can provide equitable access to such information. However, the always-on nature of these assistive technologies poses privacy concerns for parties that may get recorded. We explore this tension from both perspectives, those of sighted passersby and blind users, taking into account camera visibility, in-person versus remote experience, and extracted visual information. We conduct two studies: an online survey with MTurkers (N=206) and an in-person experience study between pairs of blind (N=10) and sighted (N=40) participants, where blind participants wear a working prototype for pedestrian detection and pass by sighted participants. Our results suggest that both of the perspectives of users and bystanders and the several factors mentioned above need to be carefully considered to mitigate potential social tensions.

cs.HC↗

arXiv2019

Singularity Free Direct Calculation of Spontaneous Mass Generation

We propose a new iterative method to directly calculate the spontaneous mass generation. It is regarded as a new regularization method resembling the finite volume calculation which assures non-negative fluctuation property at every stage. We work with the Nambu--Jona-Lasinio model and the strong coupling gauge theory where the dynamical chiral symmetry breaking occurs. We are able to conclude the physical mass definitely without encountering any singularity nor recourse to any additional consideration like the free energy comparison. However in special case of the 1st order phase transition, we find that the iterative method has a chance to go wrong.

hep-th↗

arXiv2017

Anomalous Quasiparticle Reflection from the Surface of a $^3$He-$^4$He Dilute Solution

A free surface of a dilute $^3$He-$^4$He liquid mixture is a unique system where two Fermi liquids with distinct dimensions coexist: a three-dimensional (3D) $^3$He Fermi liquid in bulk and a two-dimensional (2D) $^3$He Fermi liquid at the surface. To investigate a novel effect generated by the interaction between the two Fermi liquids, mobility of a Wigner crystal of electrons formed on the free surface of the mixture is studied. An anomalous enhancement of the mobility, compared with the case where the 3D and 2D systems do not interact with each other, is observed. The enhancement is explained by non-trivial reflection of 3D quasiparticles from the surface covered with the 2D $^3$He system.

cond-mat.other↗

arXiv2016

Dynamical chiral symmetry breaking and weak nonperturbative renormalization group equation in gauge theory

We analyze the dynamical chiral symmetry breaking in gauge theory with the nonperturbative renormalization group equation (NPRGE), which is a first order nonlinear partial differential equation (PDE). In case that the spontaneous chiral symmetry breaking occurs, the NPRGE encounters some non-analytic singularities at the finite critical scale even though the initial function is continuous and smooth. Therefore there is no usual solution of the PDE beyond the critical scale. In this paper, we newly introduce the notion of a weak solution which is the global solution of the weak NPRGE. We show how to evaluate the physical quantities with the weak solution.

physics.gen-ph↗

arXiv2014

Analysis of the Dynamical Chiral Symmetry Breaking in QCD at Finite Temperature and Density using the Non-Perturbative Renormalization Group

We analyze the Nambu--Jona-Lasinio model which is a chiral effective model of QCD by using the non-perturbative renormalization group at finite temperature and finite density. We discuss the chiral phase diagram in the model. We include the large-$N$ non-leading contribution in the beta function and discuss its effects for the phase boundary.

hep-ph↗

arXiv2014

Weak solution of the non-perturbative renormalization group equation to describe the dynamical chiral symmetry breaking

We analyze the dynamical chiral symmetry breaking (D$χ$SB) in the Nambu-Jona-Lasinio (NJL) model by using the non-perturbative renormalization group (NPRG) equation. The equation takes a form of two-dimensional partial differential equation for the multi-fermion effective interactions $V(x,t)$ where $x$ is $\barψψ$ operator and $t$ is the logarithm of the renormalization scale. The D$χ$SB occurs due to the quantum corrections, which means it emerges at some finite $t_{\rm c}$ in the mid of integrating the equation with respect to $t$. At $t_{\rm c}$ some singularities suddenly appear in $V$ which is compulsory in the spontaneous symmetry breakdown. Therefore there is no solution of the equation beyond $t_{\rm c}$. We newly introduce the notion of weak solution to get the global solution including the infrared limit $t\rightarrow \infty$ and investigate its properties. The obtained weak solution is global and unique, and it perfectly describes the physically correct vacuum even in case of the first order phase transition appearing in finite density medium. The key logic of deduction is that the weak solution we defined automatically convexifies the effective potential when treating the singularities.

hep-th↗

arXiv2013

Replication of proto-RNAs sustained by ligase-helicase cycle in oligomer world

A mechanism of the replication of proto-RNAs in oligomer world is proposed. The replication is carried out by a minimum cycle which is sustained by a ligase and a helicase. We expect that such a cycle actually worked in the primordial soup and can be constructed in vitro. By computer simulation the products of the replication acquires diversity and complexity. Such diversity and complexity are the bases of the evolution.

q-bio.BM↗

arXiv2013

Weak solution method of the non-perturbative renormalization group equation to describe dynamical chiral symmetry breaking and its application to beyond the ladder analysis in QCD

The method of non-perturbative renormalization group (NPRG) is applied to the analysis of dynamical chiral symmetry breaking (DCSB) in QCD. We show that the DCSB solution of the NPRG flow equation can be obtained without the bosonization. The solution, having the singular point, can be authorized as the weak solution of partial differential equation, and can be easily evaluated using the method of the characteristic curve. Also we show that our non-ladder extended approximation improves almost perfectly the gauge dependence of the chiral condensates.

hep-th↗

arXiv2013

Uniqueness and Significance of Weak Solution of Non-perturbative Renormalization Group Equation to Analyze Dynamical Chiral Symmetry Breaking

We propose quite a new method of analyzing the dynamical chiral symmetry breaking in gauge theories. Starting with the non-perturbative renormalization group equation for the Wilsonian fermion potential, we define the weak solution of it in order to mathematically authorize solutions with singularity. The weak solution is obtained uniquely and it successfully predicts the physically correct vacuum, chiral condensates, dynamical mass, through its auto-convexizing power for the effective potential. Thus it works perfectly even for the first order phase transition in the finite density QCD.

hep-th↗