arXiv subjects

Arjun Kumar

Publications and source records attributed to Arjun Kumar.

16 recordsLinked to original sources

arXiv2026

Pre-shipment optical characterization of the SCALES instrument

The Slicer Combined with an Array of Lenslets for Exoplanet Spectroscopy (SCALES) instrument is a 1-5 micron imager and 2-5 micron integral field spectrograph, currently being commissioned on the Keck II Telescope. SCALES is optimized for exoplanet high-contrast imaging and spectroscopic characterization, and will be sensitive to older, colder exoplanets than existing instrumentation. The 12.3" x 12.3" imaging channel is designed to replicate the capabilities of NIRC2, and the low (R~35-200, 2.2" x 2.2" FOV) and medium (R~2500-5000, 0.36" x 0.34" FOV) spectral resolution modes offer new capabilities compared to existing Keck instrumentation. We present preliminary optical performance results from laboratory testing and commissioning of SCALES.

astro-ph.IM↗

arXiv2026

Imprints of nuclear shell structure in exclusive vector meson production

We report for the first time that, within the saturation framework, exclusive vector meson production at small $x$ is sensitive to the shell structure of the target nucleus. Self-consistent nuclear densities from occupied single-particle orbitals in the quark-meson coupling (QMC) model modify the coherent $|t|$-differential cross section, enhancing secondary diffractive lobes in light nuclei and displacing the higher-order minima in intermediate-mass nuclei, whereas for heavy targets the shifts are weaker. Because the small $J/\psi$ dipole is insensitive to saturation, these features make coherent $J/\psi$ production a clean probe of nuclear shell structure, most favorably for intermediate-mass nuclei such as calcium isotopes. For the larger $\phi$ dipole, shell structure must be included in the nuclear initial state before saturation effects can be isolated in differential observables at the Electron Ion Collider. Our results establish exclusive vector meson production as a probe of the mean-field nuclear structure at small $x$ and provide a baseline for isolating residual many-body correlations.

hep-ph↗

arXiv2026

LEACL: LLM-Enhanced Automatic Curriculum Learning for Reinforcement Learning in Long-Horizon Manipulation Tasks

Long-horizon manipulation tasks pose significant challenges for reinforcement learning due to sparse reward signals and long horizons. Automatic curriculum learning (ACL) has been proposed to tackle these challenges by progressively training agents on a sequence of tasks, from easier to more difficult. However, the success of ACL depends heavily on task-dependent specifications-such as well-defined task parameter spaces and difficulty measures-which are often manually crafted and difficult to generalize across diverse tasks. Recent advances in large language models (LLMs) offer a promising alternative by enabling the decomposition of complex tasks into meaningful subtasks using the LLMs' web-scale common-sense knowledge. This decomposition can provide a natural curriculum structure for efficient learning of long-horizon tasks. However, existing LLM-based methods typically rely on hand-designed dense reward functions to learn each subtask, which can introduce bias and still requires significant human supervision. In this work, we propose LLM-enhanced automatic curriculum learning (LEACL), a framework that integrates LLMs and ACL to address these limitations. Specifically, LLMs are used to both decompose tasks into subtasks and to generate task-dependent specifications for each subtask. These specifications are then used by ACL algorithms to guide learning using only sparse reward signals, eliminating the need for dense reward design. We evaluate LEACL on five long-horizon manipulation tasks from the LIBERO benchmark. LEACL achieves better asymptotic performance in terms of the success rates compared to human-designed dense rewards.

cs.RO↗

arXiv2025

Opportunities for Imaging Light Nuclei with a Second Interaction Region at the Electron-Ion Collider

The upcoming Electron-Ion Collider (EIC) will address several outstanding puzzles in modern nuclear physics. Key questions-such as the partonic structure of nucleons and nuclei and the origin of their mass and spin-can be explored through high-energy electron-proton and electron-nucleus collisions. To maximize its scientific reach, the EIC community has advocated for the addition of a second interaction region equipped with a detector complementary to the EIC general purpose collider detector, ePIC. The pre-conceptual design of this interaction region aims to provide a different configuration from the first interaction region, which enhances forward acceptance at very small scattering angles ($\theta \sim 0$ mrad). This machine configuration would significantly benefit exclusive, tagging, and diffractive physics programs, complementing those of the ePIC experiment. In particular, accessing coherent diffractive processes on light nuclei by tagging of the full, intact nucleus is essential for mapping their spatial parton distributions. In this work, we present an exploratory study of the detection capabilities for light nuclei at a second EIC interaction region, with a detailed discussion of the accessible kinematic phase space and its implications for imaging.

nucl-ex↗

arXiv2025

mCardiacDx: Radar-Driven Contactless Monitoring and Diagnosis of Arrhythmia

Arrhythmia is a common cardiac condition that can precipitate severe complications without timely intervention. While continuous monitoring is essential for timely diagnosis, conventional approaches such as electrocardiogram and wearable devices are constrained by their reliance on specialized medical expertise and patient discomfort from their contact nature. Existing contactless monitoring, primarily designed for healthy subjects, face significant challenges when analyzing reflected signals from arrhythmia patients due to disrupted spatial stability and temporal consistency. In this paper, we introduce mCardiacDx, a radar-driven contactless system that accurately analyzes reflected signals and reconstructs heart pulse waveforms for arrhythmia monitoring and diagnosis. The key contributions of our work include a novel precise target localization (PTL) technique that locates reflected signals despite spatial disruptions, and an encoder-decoder model that transforms these signals into HPWs, addressing temporal inconsistencies. Our evaluation on a large dataset of healthy subjects and arrhythmia patients shows that both mCardiacDx and PTL outperform state-of-the-art approach in arrhythmia monitoring and diagnosis, also demonstrating improved performance in healthy subjects.

cs.HC↗

arXiv2024

Saturation and fluctuations in the proton wavefunction at large momentum transfers in exclusive diffraction at HERA

We present a model of proton geometry where the number and size of gluon density hotspots in the proton's thickness function evolves with the resolution scale of the event given by the Mandelstam $t$ variable in exclusive diffractive $ep$ collisions. We use the impact-parameter dependent saturation dipole model bSat/IPSat, as well as its linearised (non-saturated) version bNonSat. In the latter the proton thickness has a clear interpretation as a thickness and in the former it is directly related to the saturation scale. The resulting phenomenological model for the splitting of hotspots, making full use of earlier experimental and phenomenological studies, is able to describe the entire incoherent $t$-spectrum for $|t|>1.1~$GeV$^2$ with a single phenomenological parameter. We use the previously suggested hotspot model as an initial condition for our evolution. The resulting model is a resolution scale-evolution in the same vein as a parton shower.The incoherent cross section is directly proportional to geometrical fluctuations in the proton's inital state. The hotspot evolution give rise to several kinds of event-by-event fluctuations such as in the hotspot number, width and normalization, and saturation scale fluctuations is a direct effect of these. A natural consequence of our resolution based evolution is that the hotspots obtain an effective repulsion. We use our hotspot evolution model to investigate saturation scale effects in the $t$-spectrum, and found that HERA data is not sensitive to this physics.

hep-ph↗

arXiv2022

Geometric scaling in leading neutron events at HERA

This analysis provides new fits of the GBW model and the impact parameter-dependent saturation model (bSat or IP-Sat) to the leading neutron structure function HERA data in one pion exchange approximation. Both parametrizations of the dipole cross section provide good descriptions of the considered data. It is shown here for the first time that the experimental leading neutron production HERA data exhibits geometric scaling, which in this context means that the total $\gamma^* \pi^*$ cross section is a function of only one dimensionless variable $\tau = Q^2/Q_s^2(x)$. The geometric scaling region extends over a broad range of $Q^2$ and can be attributed to the presence of a saturation boundary which manifests at $Q^2\geq Q^2_s$. The scaling behaviour in leading neutron events is profoundly similar to what has been observed for the inclusive DIS events.

hep-ph↗

arXiv2022

Wireless Self-Powered Visual and NDE low-Cost Inspection System For Small Diameter Live Gas Distribution Mains

The arrangement of an in-pipe climbing robot that works using a sharp transmission part to explore complex relationship of lines. Standard wheeled/continued in-pipe climbing robots are leaned to slip and take while researching in pipe turns. The instrument helps in achieving the really unavoidable consequence of getting out slip and drag in the robot tracks during progression. The proposed transmission likes the useful uttermost scopes of the standard two-yield transmission, which is fostered the fundamental time for a transmission with three outcomes. The instrument decisively changes the track velocities of the robot considering the powers applied on each track inside the line relationship, by getting out the fundamental for any wonderful control. The entertainment of the robot crossing in the line network in different direction and in pipe-turns without slip shows the proposed course of action's ampleness.

cs.RO↗

arXiv2022

An In-Pipe Inspection Robot With Sensorless Underactuated Magnets and Omnidirectional Tracks: Design and Implementation

This paper presents the plan of an in-pipe climbing robot that works utilizing an astute transmission part to investigate complex relationship of lines. Standard wheeled/proceeded in-pipe climbing robots are inclined to slip and take while investigating in pipe turns. The instrument helps in accomplishing the main inevitable result of getting out slip and drag in the robot tracks during advancement. The proposed transmission appreciates the practical furthest reaches of the standard two-yield transmission, which is developed the basic time for a transmission with three results. The instrument conclusively changes the track speeds of the robot considering the powers applied on each track inside the line relationship, by getting out the essential for any remarkable control. The amusement of the robot crossing in the line network in various orientation and in pipe-turns without slip shows the proposed game plan's adequacy.

cs.RO↗

arXiv2022

Investigating saturation effects and the virtual pion in leading neutron events at HERA with the dipole model

We investigate events with very forward neutrons in $ep$ collisions at HERA using impact parameter dependent colour dipole models with and without saturation. This is the first study of the leading neutron process deploying these models. The model predictions are compared with the available HERA measurements for $6<Q^2<100$~GeV$^2$, $70<W<245$~GeV. Our analysis shows that the models exhibit Feynman scaling, independent of $Q^2$. Our results demonstrate that the $W$ and $Q^2$ dependence of the cross section is independent of the presence of a forward neutron as predicted by the limiting fragmentation hypothesis, which is a consequence of Feynman scaling itself. We infer that the HERA leading neutron production inclusive data is insensitive to saturation physics and these cross sections may not be able to distinguish gluon saturation effects in future $ep$ colliders. We provide a good description of the leading neutron structure function $F_2^{LN}$ at small $x$ using an assumption that the small-$x$ structure of protons and pions is universal up to a normalisation. We also show that the observables in the exclusive diffractive measurements with a vector meson in the final state are more sensitive to saturation physics at small $x$ than inclusive measurements. At last, we provide a prediction for the $\hat t$ spectrum in exclusive vector meson production in the dipole model using Yukawa theory to model the virtual pion's spatial wave function.

hep-ph↗

arXiv2022

Energy dependence of the proton geometry in exclusive vector meson production

The gluon radius of the proton is expected to increase at small gluon momentum fractions $x$, an effect which has hitherto not been considered in the dipole model framework. We investigate the energy dependence of exclusive $J/\psi$, $\phi$, and $\rho$ production by introducing three models for $x$ dependence of the gluon thickness function. We allow the transverse width of the proton to increase as $x$ decreases, using novel parametrisations in the spherical proton and the hotspot model. We compare these with a model where the number of hotspots increases as $x$ decreases and confront the models with HERA data. The models exhibit clear differences in the slope of the $t$-spectra and in the cross section ratios between coherent and incoherent events. Comparisons to $t$-slopes and $W_{\gamma p}$ measurements show a preference for models where the proton's size increases as $x$ decreases.

hep-ph↗

arXiv2022

In-Pipe Robot

This paper presents the arrangement of an in-pipe climbing robot that works using a clever differential part to explore complex associations of lines. Standard wheeled/continued in-pipe climbing robots are leaned to slip and take while exploring in pipe turns. The mechanism helps in achieving the first eventual outcome of clearing out slip and drag in the robot tracks during development. The proposed differential comprehends the down to earth limits of the standard two-yield differential, which is cultivated the underlying time for a differential with three outcomes. The mechanism definitively changes the track paces of the robot considering the powers applied on each track inside the line association, by clearing out the prerequisite for any unique control. The entertainment of the robot crossing in the line network in different bearings and in pipe-turns without slip shows the proposed arrangement's ampleness.

cs.RO↗

arXiv2022

Pipe Climbing Robot

This paper presents the plan of an in-pipe climbing robot that works utilizing a novel Three-Output Open Differential(3-OOD) component to navigate complex organizations of lines. Customary wheeled/followed in-pipe climbing robots are inclined to slip and haul while navigating in pipe twists. The 3-OOD component helps in accomplishing the original aftereffect of wiping out slip and drag in the robot tracks during movement. The proposed differential understands the practical capacities of the customary two-yield differential, which is accomplished the initial time for a differential with three results. The 3-OOD component precisely tweaks the track rates of the robot in light of the powers applied on each track inside the line organization, by wiping out the requirement for any dynamic control. The recreation of the robot crossing in the line network in various directions and in pipe-twists without slip shows the proposed plan's adequacy

cs.RO↗

arXiv2021

Probing gluon density fluctuations at large momentum transfer $|t|$ at HERA

The information on the gluonic structure and its fluctuations is captured by the differential $|t|$ spectrum in diffractive events. The incoherent cross-section is sensitive to the fluctuations in the target wavefunction in such events. We investigate the incoherent $ep$ cross-section in $J/\psi$ photoproduction using the impact-parameter dependent dipole model. The spatial gluonic structure is modelled as hotspots of gluon density having substructure where this substructure is modelled as hotspots within hotspots. We find that three levels of the substructure provide a good description of all the data, available up to $|t|=30~$GeV$^2$. We investigate these fluctuations in both the saturated and non-saturated dipole models and compare our predictions with the HERA Data.

hep-ph↗

arXiv2021

Investigating the structure of gluon fluctuations in the proton with incoherent diffraction at HERA

Impact parameter dependent dipole models are ideal tools for investigating the spatial structure of the proton. We investigate the incoherent $ep$ cross section in exclusive $J/\psi$ photoproduction as measured by HERA, and find that as $|t|$ increases, the models need several levels of the substructure of gluon density fluctuations in order to describe the measured data well. In lieu of a perturbative description, we add this substructure by hand. This substructure is modelled as hotspots within hotspots. This enables us to describe measurements for $|t|> 1$~GeV$^2$, which is necessary for describing any observable which integrates over the $t$-spectrum, such as the rapidity or $W_{\gamma p}$. We find that three levels of proton substructure are adequate for a good description of all available $ep$ data up to $|t|=30~$GeV$^2$. We note that the gluonic density fluctuation structure follows a scaling behaviour, such that the logarithms of the number of hotspots and their size fall on a line, effectively reducing the available parameter space of the model. Our findings systematically constrain and provide a benchmark for the development of a perturbative model of spatial gluon fluctuations in nucleons.

hep-ph↗

arXiv2020

Vacuum Stability in Inert Higgs Doublet Model with Right-handed Neutrinos

We analyze the vacuum stability in the inert Higgs doublet extension of the Standard Model (SM), augmented by right-handed neutrinos (RHNs) to explain neutrino masses at tree level by the seesaw mechanism. We make a comparative study of the high- and low-scale seesaw scenarios and the effect of the Dirac neutrino Yukawa couplings on the stability of the Higgs potential. Bounds on the scalar quartic couplings and Dirac Yukawa couplings are obtained from vacuum stability and perturbativity considerations. The regions corresponding to stability, metastability and instability of the electroweak vacuum are identified. These theoretical constraints give a very predictive parameter space for the couplings and masses of the new scalars and RHNs which can be tested at the LHC and future colliders. The lightest non-SM neutral CP-even/odd scalar can be a good dark matter candidate and the corresponding collider signatures are also predicted for the model.

hep-ph↗