arXiv subjects

Rahul Rana

Publications and source records attributed to Rahul Rana.

6 recordsLinked to original sources

arXiv2026

Far-infrared observations of dust in Ly$\alpha$ emitters at z=2-6

The bright Ly$\alpha$ line is regularly used to identify high-redshift star-forming galaxies known as Ly$\alpha$ emitters (LAEs). However, Ly$\alpha$ is affected by resonant scattering and dust absorption making interpretation of its brightness challenging without additional observations. We use SCUBA-2, PACS and SPIRE data to investigate the far-infrared emission, Ly$\alpha$ escape fraction ($f{esc}$(Ly$\alpha$)) and infrared excess (IRX=LIR/LUV) in $\sim$4000 LAEs at z=2.2-6 from SC4K. Five LAEs, all hosting AGN, are individually detected with fluxes $S_{850}$ = 3.7-5.5 mJy at 850$\mu\mathrm{m}$. Stacking is used to probe the average emission from all individually undetected LAEs, though the stacks are undetected at all wavelengths (e.g. $S_{850}$ < 0.09 mJy; 3$\sigma$). We group the sample into bins of redshift, stellar mass, Ly$\alpha$ luminosity and AGN status. Most subsets are undetected but LAEs containing AGN and that have high stellar masses ($M_{\star} = 10^{10} - 10^{12}\, M_{\odot}$; including and excluding AGN) are detected at most wavelengths, suggesting that stellar mass and AGN heating may be enhancing the dust visibility. Individually detected LAEs and detected stacks have $f{esc}$(Ly$\alpha$)=1-7%, while all undetected stacks $\geq$ 10%. All LAEs together average over > 21% and display significant scatter, suggesting a clumpy ISM dust distribution. Non-zero $f{esc}$(Ly$\alpha$) in massive and AGN-hosting LAEs suggests ionizing photons may escape even from dusty galaxies, challenging the idea that dusty galaxies are poor leakers. Examination of the IRX-$\beta_{UV}$ relation shows LAEs have higher IRX than typical star-forming galaxies at similar redshifts. However, our detections tend to favour more massive, AGN-hosting systems and deeper observations are therefore needed.

astro-ph.GA↗

arXiv2026

Airline Fleet Assignment Problems with Binary and Integer Programming models: Classical vs Quantum Annealing

This research highlights the potential of quantum annealing in tackling large-scale optimization problems within the airline industry,demonstrating its efficiency for certain problem sizes while also acknowledging its current limitations. The comparative analysis provides valuable insights into the performance of advanced computational techniques, paving the way for further advancements in optimizing fleet assignments in the aviation sector.

quant-ph↗

arXiv2025

Highly-ionized gas in lensed z = 6.027 Little Red Dot seen through [OIII] 88$\mu$m with ALMA

Determining the physical properties of galaxies during the first billion years after the big bang is key to understanding both early galaxy evolution and how galaxies contributed to the epoch of reionization. We present deep ALMA observations of the redshifted [OIII] 88um line for the gravitationally lensed ($\mu = 11.4\pm1.9$) galaxy A383-5.1 (z=6.027) that has previously been detected in [CII] 158um. Recent James Webb Space Telescope (JWST) imaging identified this sub-L* galaxy as a ''Little Red Dot'' (LRD). With a line luminosity of $L_{\rm [OIII]} = (1.29\pm0.24)\times10^8$ L$_\odot$ (corrected for lensing magnification) A383-5.1 is one of the faintest galaxies with combined [CII] and [OIII] detections. The ALMA data reveal no dust continuum emission, consistent with previous observations. The high line luminosity ratio of [OIII]/[CII] $\sim 14\pm5$ is consistent with A383-5.1 being low-metallicity and dust-poor. The non-detection of dust continuum in bands 6 and 8 is consistent with the high [OIII]/[CII] ratio and suggests a presence of a strong ultraviolet radiation field, which would be less affect by dust attenuation, implying that galaxies of this type could contribute significantly to the ionization of the intergalactic medium. The presence of strong ionizing field could provide an important piece of information for understanding the nature of LRDs and their role in cosmic reionization.

astro-ph.GA↗

arXiv2025

Grid-Partitioned MWIS Solving with Neutral Atom Quantum Computing for QUBO Problems

Quadratic Unconstrained Binary Optimization (QUBO) problems are prevalent in real-world applications, such as portfolio optimization, but pose significant computational challenges for large-scale instances. We propose a hybrid quantum-classical framework that leverages neutral atom quantum computing to address QUBO problems by mapping them to the Maximum Weighted Independent Set (MWIS) problem on unit disk graphs. Our approach employs spatial grid partitioning to decompose the problem into manageable subgraphs, solves each subgraph using Analog Hamiltonian Simulation (AHS), and merges solutions greedily to approximate the global optimum. We evaluate the framework on a 50-asset portfolio optimization problem using historical S&P 500 data, benchmarking against classical simulated annealing. Results demonstrate competitive performance, highlighting the scalability and practical potential of our method in the Noisy Intermediate-Scale Quantum (NISQ) era. As neutral atom quantum hardware advances, our framework offers a promising path toward solving large-scale optimization problems efficiently.

quant-ph↗

arXiv2025

Toward Quantum Enabled Solutions for Real-Time Currency Arbitrage in Financial Markets

Currency arbitrage leverages price discrepancies in currency exchange rates across different currency pairs to gain risk-free profits. It involves multiple trading, where short-lived price discrepancies require real-time, high-speed processing of vast solution space, posing challenges for classical computing. In this work, we formulate an enhanced mathematical model for the currency arbitrage problem by adding simple cycle preservation constraints, which guarantee trading cycle validity and eliminate redundant or infeasible substructures. To solve this model, we use and benchmark various solvers, including Quantum Annealing (QA), gate-based quantum approaches such as Variational Quantum Algorithm with Adaptive Cost Encoding (ACE), as well as classical solvers such as Gurobi and classical meta heuristics such as Tabu Search (TS). We propose a classical multi-bit swap post-processing to improve the solution generated by ACE. Using real-world currency exchange data, we compare these methods in terms of both arbitrage profit and execution time, the two key performance metrics. Our results give insight into the current capabilities and limitations of quantum methods for real-time financial use cases.

quant-ph↗

arXiv2019

Galaxy And Mass Assembly (GAMA): Properties and evolution of red spiral galaxies

We use multi-wavelength data from the Galaxy and Mass Assembly (GAMA) survey to explore the cause of red optical colours in nearby (0.002 = 47% of all spirals in our sample. Furthermore, for a small subsample of our spiral galaxies which are detected in HI, we find that the SFR of gas-rich red spiral galaxies is lower by ~1 dex than their blue counterparts.

astro-ph.GA↗