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Heuristic Approach for Solving the Dual Dominating Set Problem With Conflicts

Thu, 01 Jan 2026 00:00:00 GMT

Title: Heuristic Approach for Solving the Dual Dominating Set Problem With Conflicts Authors: Jovanovic, Raka; Aličić, Denis; Sezer, Nurettin; Marić, Miroslav Abstract: This paper introduces a novel combinatorial optimization problem, the Dual Dominating Set Problem with Conflicts (DDSP-C), which extends the classical Dominating Set Problem by requiring the identification of two disjoint dominating sets under pairwise conflict constraints. Such constraints prohibit specific node pairs from appearing in different dominating sets, reflecting practical considerations in facility location and resource allocation. We present an Integer Linear Programming (ILP) formulation to model the problem precisely and propose a metaheuristic solution approach based on the Greedy Randomized Adaptive Search Procedure (GRASP). The GRASP algorithm combines a randomized greedy construction with a local search phase, aiming to efficiently generate high-quality solutions. Experiments on random instances show the approach’s effectiveness and reveal insights into problem complexity across different graph densities and conflict levels.

AGN STORM 2. XII. Ground-based Optical Photometry and Lag Measurements of Mrk 817

Mon, 01 Jun 2026 00:00:00 GMT

Title: AGN STORM 2. XII. Ground-based Optical Photometry and Lag Measurements of Mrk 817 Authors: Montano, John W.; Barth, Aaron J.; Horne, Keith; Cackett, Edward M.; De Rosa, Gisella; Homayouni, Y.; Kara, Erin A.; Kriss, Gerard A.; Landt, Hermine; Apolonio, Gilvan G.; Arav, Nahum; Boizelle, Benjamin D.; Dalla Bontà, Elena; Chelouche, Doron; Dehghanian, Maryam; Edelson, Rick; Ferland, Gary J.; Fian, Carina; Sobrino Figaredo, Catalina; Goad, Michael R.; Gonzalez-Buitrago, Diego H.; Guo, Wei Jian; Hu, Chen; Ilić, Dragana; Joner, Michael D.; Kaspi, Shai; Kochanek, Christopher S.; Kovačević, Anđelka; Lewin, Collin; Li, Sha Sha; Li, Yan Rong; Liu, Jun Rong; Miller, Jake A.; Neustadt, Jack M.M.; Netzer, Hagai; Ochner, Paolo; Partington, Ethan R.; Pizzella, Alessandro; Plesha, Rachel; Popović, Luka; Sanmartim, David; Hernández Santisteban, Juan V.; Vestergaard, Marianne; Wooley, Jack H.F.; Yang, Sen; Yao, Zhu Heng; Zaidouni, Fatima Abstract: We present the ground-based imaging campaign and light curves of Markarian 817 as part of the multiwavelength monitoring program AGN STORM 2. Observations were carried out over 1.4 yr in the uBgVriz filters, with a median cadence of 0.4 day in the g band. Reverberation lags are measured using three methods (interpolated cross-correlation function (ICCF), Just Another Vehicle for Estimating Lags In Nuclei, and PyROA) with the Swift UVW2 band (1928 Å) as the reference light curve. The ICCF centroid lags range from 3.0 ± 0.8 days for the u band up to 7.9 ± 1.5 days for z, and are consistent with a τ ∝ λ^4/3 dependence, the relation expected for lamppost reprocessing by a Shakura–Sunyaev disk. Lags measured with the other methods are systematically shorter, and deviate from a λ^4/3 power-law spectrum at long wavelengths. The lags exceed thin-disk reprocessing predictions by factors of ∼3–6, similar to the “disk size discrepancy” seen in other Seyfert galaxies. We divide the campaign into three epochs with different levels of mean luminosity and X-ray obscuring column density and find that the lags vary by as much as a factor of 2 between epochs. The intrinsic spectral energy distribution is bluer and brighter during the first third of the campaign, and the longest continuum reverberation lags are obtained during that period. These results suggest that changes in ionizing luminosity can produce large variations in continuum lags on short timescales by altering the diffuse continuum luminosity emitted by the broad-line region (BLR) and/or obscuring outflow, although changes in obscuration between the central engine and BLR may also contribute to the lag variations.

Twenty Years of Personality Computing: Threats, Challenges and Future Directions

Mon, 27 Apr 2026 00:00:00 GMT

Title: Twenty Years of Personality Computing: Threats, Challenges and Future Directions Authors: Celli, Fabio; Kartelj, Aleksandar; Đorđević, Miljan; Suhartono, Derwin; Filipović, Vladimir; Milutinović, Veljko; Spathoulas, Georgios; Vinciarelli, Alessandro; Kosinski, Michal; Lepri, Bruno Abstract: Personality Computing is a field at the intersection of Personality Psychology and Computer Science. Started in 2005, research in the field utilizes computational methods to understand and predict human personality traits. The expansion of the field has been very rapid and, by analyzing digital footprints (text, images, social media, etc.), it helped to develop systems that recognize and even replicate human personality. While offering promising applications in talent recruiting, marketing and healthcare, the ethical implications of Personality Computing are significant. Concerns include data privacy, algorithmic bias, and the potential for manipulation by personality-aware Artificial Intelligence. This article provides an overview of the field, explores key methodologies, discusses the challenges and threats, and outlines potential future directions for responsible development and deployment of Personality Computing technologies.

Continuum reverberation in bright quasars using NASA/ATLAS

Mon, 01 Jun 2026 00:00:00 GMT

Title: Continuum reverberation in bright quasars using NASA/ATLAS Authors: Steyn, Zachary; Wolf, Christian; Onken, Christopher; Smith, Ken; Tang, Ji Jia; Kovačević, Anđelka; Tonry, John; Clocchiatti, Alejandro Abstract: Variable continuum emission from active galactic nuclei (AGNs) can be used to probe the structure of their accretion discs via reverberation mapping. Assuming a variable, hot inner light source irradiates the surrounding accretion disc, time delays between different continuum band light curves reveal light-travel times between their respective emission regions. Inter-band delays measured in several low-luminosity AGNs are ubiquitously (Formula presented) times longer than expected from standard disc theory, with evidence that this size discrepancy may decrease in more luminous AGNs. We have analysed high-cadence light curves of 9498 of the brightest quasars between redshift 0.3–2.5 in the largest continuum reverberation study to date. Given the large sample size, we construct bins and fit delays jointly to combine inference across the parameter space and improve lag detections. We find that the size discrepancy persists in our high-luminosity sample, and that the previously seen anticorrelation with luminosity is likely driven by wavelength effects. The complex, non-monotonic wavelength dependence of delay amplitudes strongly suggests that contamination of inter-band delays by variable diffuse emission is widespread in the AGN population. We test delay behaviour against a variety of quasar properties finding longer lags in quasars with: higher Eddington ratios, redder colours, larger optical Fe ii EWs, higher iron ratios (both UV Fe ii/Mg ii and optical Fe ii/H(Formula presented) ), C iv broad absorption troughs, and lower C iv blueshift.