Results for "D. Skowron"

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OGLE-ing the Magellanic System: Cepheids in the BridgeApr 17 2019We present a detailed analysis of Magellanic Bridge Cepheid sample constructed using the OGLE Collection of Variable Stars. Our updated Bridge sample contains 10 classical and 13 anomalous Cepheids. We calculate their individual distances using optical ... More
Fully Proportional Representation as Resource Allocation: Approximability ResultsAug 08 2012Jan 27 2013We model Monroe's and Chamberlin and Courant's multiwinner voting systems as a certain resource allocation problem. We show that for many restricted variants of this problem, under standard complexity-theoretic assumptions, there are no constant-factor ... More
Multiwinner Analogues of Plurality Rule: Axiomatic and Algorithmic PerspectivesFeb 28 2016We characterize the class of committee scoring rules that satisfy the fixed-majority criterion. In some sense, the committee scoring rules in this class are multiwinner analogues of the single-winner Plurality rule, which is uniquely characterized as ... More
FPT Approximation Schemes for Maximizing Submodular FunctionsOct 01 2015We investigate the existence of approximation algorithms for maximization of submodular functions, that run in fixed parameter tractable (FPT) time. Given a non-decreasing submodular set function $v: 2^X \to \mathbb{R}$ the goal is to select a subset ... More
What Do We Elect Committees For? A Voting Committee Model for Multi-Winner RulesNov 21 2016We present a new model that describes the process of electing a group of representatives (e.g., a parliament) for a group of voters. In this model, called the voting committee model, the elected group of representatives runs a number of ballots to make ... More
Proportionality Degree of Multiwinner RulesOct 20 2018We study multiwinner elections with approval-based preferences. An instance of a multiwinner election consists of a set of alternatives, a population of voters---each voter approves a subset of alternatives, and the desired committee size $k$; the goal ... More
The Complexity of Fully Proportional Representation for Single-Crossing ElectoratesJul 04 2013We study the complexity of winner determination in single-crossing elections under two classic fully proportional representation rules---Chamberlin--Courant's rule and Monroe's rule. Winner determination for these rules is known to be NP-hard for unrestricted ... More
OGLE-LMC-ECL-09937: The Most Massive Algol-Type Binary System With A Mass Measurement Accurate to 2%Jan 17 2018This paper presents a detailed analysis of the light and radial velocity curves of the semi-detached eclipsing binary system OGLE-LMC-ECL-09937. The system is composed of a hot, massive and luminous primary star of a late-O spectral type, and a more evolved, ... More
Period-Luminosity Relations for Ellipsoidal Binary Stars in the OGLE-III Fields of the Large Magellanic CloudDec 08 2014We report the discovery of two distinct types of ellipsoidal binary systems occupying, so called, sequence E on the period-luminosity (P-L) diagram. We propose that steeper P-L relation is composed of giant-dwarf binaries, while the other consists of ... More
The awakening of a classical nova from hibernationAug 16 2016Cataclysmic variable stars (CVs) are close binary systems consisting of a white dwarf (primary) that is accreting matter from a low-mass companion star (secondary). From time to time such systems undergo large-amplitude brightenings. The most spectacular ... More
Blazhko-type modulation in the double-mode RR Lyrae stars of the OGLE Galactic bulge collectionNov 10 2014Dec 16 2014We present the analysis of Blazhko-type modulation in double-mode RR Lyrae (RRd) stars found in the OGLE photometry of the Galactic bulge. Modulation is detected in 15 stars. Most of them have non-typical period ratio of the radial modes. In the Petersen ... More
Over 38000 RR Lyrae Stars in the OGLE Galactic Bulge FieldsOct 06 2014We present the most comprehensive picture ever obtained of the central parts of the Milky Way probed with RR Lyrae variable stars. This is a collection of 38257 RR Lyr stars detected over 182 square degrees monitored photometrically by the Optical Gravitational ... More
Multi-Mode and Non-Standard Classical Cepheids in the Magellanic SystemJan 08 2016Jan 19 2016We present a sample of the most interesting classical Cepheids selected from the OGLE collection of classical Cepheids in the Magellanic System. The main selection criterion for this sample was the presence of non-standard, unique pulsational properties. ... More
Eclipsing Binaries with Classical Cepheid Component in the Magellanic SystemJan 07 2016We present a census of eclipsing binary systems with classical Cepheid as a component. All such systems known were found in the OGLE collection of classical Cepheids in the Magellanic System. We extend the list of potential candidates adding four new ... More
OGLE Collection of Galactic CepheidsOct 22 2018We present here a new major part of the OGLE Collection of Variable Stars - OGLE Collection of Galactic Cepheids. The new dataset was extracted from the Galaxy Variability Survey images - a dedicated large-scale survey of the Galactic disk and outer bulge ... More
Three-Dimensional Distributions of Type II Cepheids and Anomalous Cepheids in the Magellanic Clouds. Do these Stars Belong to the Old, Young or Intermediate-Age Population?Sep 05 2018Oct 24 2018The nature of type II Cepheids and anomalous Cepheids is still not well known and their evolutionary channels leave many unanswered questions. We use complete collection of classical pulsating stars in the Magellanic Clouds discovered by the OGLE project, ... More
A Venus-Mass Planet Orbiting a Brown Dwarf: Missing Link between Planets and MoonsJul 09 2015Jul 13 2015The co-planarity of solar-system planets led Kant to suggest that they formed from an accretion disk, and the discovery of hundreds of such disks around young stars as well as hundreds of co-planar planetary systems by the Kepler satellite demonstrate ... More
Gaia and Variable StarsNov 24 2016We present a comparison of the Gaia DR1 samples of pulsating variable stars - Cepheids and RR Lyrae type - with the OGLE Collection of Variable Stars aiming at the characterization of the Gaia mission performance in the stellar variability domain. Out ... More
OGLE-ing the Magellanic System: Photometric Metallicity from Fundamental Mode RR Lyrae StarsJul 29 2016Nov 08 2016In an era of extensive photometric observations, the catalogs of RR Lyr type variable stars number tens of thousands of objects. The relation between the iron abundance [Fe/H] and the Fourier parameters of the stars light curve allows us to investigate ... More
OGLE-ing the Magellanic System: Photometric Metallicity from Fundamental Mode RR Lyrae StarsJul 29 2016In an era of extensive photometric observations, the catalogs of RR Lyrae type variable stars number tens of thousands of objects. The relation between the iron abundance [Fe/H] and the Fourier parameters of the stars light curve allows us to investigate ... More
The OGLE Collection of Variable Stars. Classical Cepheids in the Magellanic SystemJan 06 2016Jan 19 2016We present here a nearly complete census of classical Cepheids in the Magellanic System. The sample extends the set of Cepheids published in the past by the Optical Gravitational Lensing Experiment (OGLE) to the outer regions of the Large (LMC) and Small ... More
Deciphering the 3D structure of the old Galactic bulge from the OGLE RR Lyrae starsDec 12 2014Sep 16 2015We have analyzed a sample of 27,258 fundamental-mode RR Lyrae variable stars (type RRab) detected recently toward the Galactic bulge by the Optical Gravitational Lensing Experiment (OGLE) survey. The data support our earlier claim that these metal-poor ... More
The OGLE Collection of Variable Stars. Over 45 000 RR Lyrae Stars in the Magellanic SystemJun 08 2016Jul 14 2016We present the largest collection of RR Lyrae stars in the Magellanic System and in its foreground. The sample consists of 45 451 RR Lyr stars, of which 39 082 were detected toward the Large Magellanic Cloud and 6369 toward the Small Magellanic Cloud. ... More
The OGLE Collection of Variable Stars. Anomalous Cepheids in the Magellanic CloudsAug 04 2015We present a collection of 250 anomalous Cepheids (ACs) discovered in the OGLE-IV fields toward the Large (LMC) and Small Magellanic Cloud (SMC). The LMC sample is an extension of the OGLE-III Catalog of ACs published in 2008, while the SMC sample contains ... More
A New 3-D Picture of the Milky Way with Classical CepheidsJun 27 2018Aug 16 2018The global view of the Milky Way as a barred spiral galaxy was inferred from various tracers, e.g., star counts or radio maps of Galactic gas, as well as from our extrapolation of structures seen in other galaxies. However, distances to these tracers ... More
SDWFS-MT-1: A Self-Obscured Luminous Supernova at z~0.2Jun 21 2010Sep 05 2010We report the discovery of a six-month-long mid-infrared transient, SDWFS-MT-1 (aka SN 2007va), in the Spitzer Deep, Wide-Field Survey of the NOAO Deep Wide-Field Survey Bootes field. The transient, located in a z=0.19 low luminosity (M_[4.5]~-18.6 mag, ... More
Exploring heterogeneity of unreliable machines for p2p backupDec 03 2012Apr 20 2013P2P architecture is a viable option for enterprise backup. In contrast to dedicated backup servers, nowadays a standard solution, making backups directly on organization's workstations should be cheaper (as existing hardware is used), more efficient (as ... More
Network delay-aware load balancing in selfish and cooperative distributed systemsDec 03 2012We consider a request processing system composed of organizations and their servers connected by the Internet. The latency a user observes is a sum of communication delays and the time needed to handle the request on a server. The handling time depends ... More
We Are Impatient: Algorithms for Geographically Distributed Load Balancing with (Almost) Arbitrary Load FunctionsFeb 10 2014In geographically-distributed systems, communication latencies are non-negligible. The perceived processing time of a request is thus composed of the time needed to route the request to the server and the true processing time. Once a request reaches a ... More
Non-monetary fair scheduling---a cooperative game theory approachFeb 05 2013Apr 22 2014We consider a multi-organizational system in which each organization contributes processors to the global pool but also jobs to be processed on the common resources. The fairness of the scheduling algorithm is essential for the stability and even for ... More
The influence of weak lensing on measurements of the Hubble constant with quad-image gravitational lensesJul 21 2016We investigate the influence of matter along the line of sight and in the strong lens vicinity on the properties of quad image configurations and on the measurements of the Hubble constant (H0). We use simulations of light propagation in a nonuniform ... More
Consistent Approval-Based Multi-Winner RulesApr 08 2017May 12 2018This paper is an axiomatic study of consistent approval-based multi-winner rules, i.e., voting rules that select a fixed-size group of candidates based on approval ballots. We introduce the class of counting rules, provide an axiomatic characterization ... More
Multi-Attribute Proportional RepresentationSep 11 2015We consider the following problem in which a given number of items has to be chosen from a predefined set. Each item is described by a vector of attributes and for each attribute there is a desired distribution that the selected set should have. We look ... More
A Super-Jupiter Microlens Planet Characterized by High-Cadence KMTNet Microlensing Survey Observations of OGLE-2015-BLG-0954Feb 29 2016Jun 23 2016We report the characterization of a massive (m_p=3.9 +- 1.4 M_jup) microlensing planet (OGLE-2015-BLG-0954Lb) orbiting an M dwarf host (M=0.33 +- 0.12 M_sun) at a distance toward the Galactic bulge of 0.6 (+0.4,-0.2) kpc, which is extremely nearby by ... More
Approximating the MaxCover Problem with Bounded Frequencies in FPT TimeSep 17 2013We study approximation algorithms for several variants of the MaxCover problem, with the focus on algorithms that run in FPT time. In the MaxCover problem we are given a set N of elements, a family S of subsets of N, and an integer K. The goal is to find ... More
Approval-Based Elections and Distortion of Voting RulesJan 20 2019We consider elections where both voters and candidates can be associated with points in a metric space and voters prefer candidates that are closer to those that are farther away. It is often assumed that the optimal candidate is the one that minimizes ... More
Comparing Election Methods Where Each Voter Ranks Only Few CandidatesJan 30 2019Election rules are formal processes that aggregate voters preferences, typically to select a single candidate, called the winner. Most of the election rules studied in the literature require the voters to rank the candidates from the most to the least ... More
Anomalous Double-Mode RR Lyrae Stars in the Magellanic CloudsAug 01 2016We report the discovery of a new subclass of double-mode RR Lyrae stars in the Large and Small Magellanic Clouds. The sample of 22 pulsating stars have been extracted from the latest edition of the OGLE collection of RR Lyrae variables in the Magellanic ... More
OGLE-BLG182.1.162852: An Eclipsing Binary with a Circumstellar DiskOct 09 2014We present the discovery of a plausible disk-eclipse system OGLE-BLG182.1.162852. The OGLE light curve for OGLE-BLG182.1.162852 shows three episodes of dimming by $I \simeq 2 - 3$ magnitudes, separated by 1277 days. The shape of the light curve during ... More
Intriguing triple-mode RR Lyrae star with period doublingNov 11 2014Dec 22 2014We report the discovery of an intriguing triple-mode RR Lyrae star found in the OGLE Galactic bulge collection, OGLE-BLG-RRLYR-24137. In the OGLE catalog the star was identified as RRd star - double-mode pulsator, pulsating simultaneously in the fundamental ... More
OGLE-ing the Magellanic System: Three-Dimensional Structure of the Clouds and the Bridge Using RR Lyrae StarsNov 08 2016We present a three-dimensional analysis of a sample of 22 859 type $ab$ RR Lyrae stars in the Magellanic System from the OGLE-IV Collection of RR Lyrae stars. The distance to each object was calculated based on its photometric metallicity and a theoretical ... More
OGLE Collection of Star Clusters. New Objects in the Outskirts of the Large Magellanic CloudSep 26 2016The Magellanic System (MS), consisting of the Large Magellanic Cloud (LMC), the Small Magellanic Cloud (SMC) and the Magellanic Bridge (MBR), contains diverse sample of star clusters. Their spatial distribution, ages and chemical abundances may provide ... More
General Complex Polynomial Root Solver and Its Further Optimization for Binary MicrolensesMar 05 2012We present a new algorithm to solve polynomial equations, and publish its code, which is 1.6-3 times faster than the ZROOTS subroutine that is commercially available from Numerical Recipes, depending on application. The largest improvement, when compared ... More
A Quantitative Analysis of Multi-Winner RulesJan 04 2018May 12 2018To choose a suitable multi-winner rule, i.e., a voting rule for selecting a subset of $k$ alternatives based on a collection of preferences, is a hard and ambiguous task. Depending on the context, it varies widely what constitutes the choice of an "optimal" ... More
OGLE-ing the Magellanic System: Three-Dimensional Structure of the Clouds and the Bridge Using RR Lyrae StarsNov 08 2016Jul 10 2017We present a three-dimensional analysis of a sample of 22 859 type $ab$ RR Lyrae stars in the Magellanic System from the OGLE-IV Collection of RR Lyrae stars. The distance to each object was calculated based on its photometric metallicity and a theoretical ... More
$12\;660$ spotted stars toward the OGLE Galactic bulge fieldsMar 13 2019We present the discovery and statistical analysis of $12\;660$ spotted variable stars toward and inside the Galactic bulge from over two-decade-long Optical Gravitational Lensing Experiment (OGLE) data. We devise a new method of dereddening of individual ... More
OGLE Collection of Star Clusters. New Objects in the Magellanic Bridge and the Outskirts of the Small Magellanic CloudJan 17 2018The Magellanic System (MS) encompasses the nearest neighbors of the Milky Way, the Large (LMC) and Small (SMC) Magellanic Clouds, and the Magellanic Bridge (MBR). This system contains a diverse sample of star clusters. Their parameters, such as the spatial ... More
OGLE-ing the Magellanic System: Stellar populations in the Magellanic BridgeMay 28 2014Sep 30 2014We report the discovery of a young stellar bridge, that forms a continuous connection between the Magellanic Clouds. This finding is based on number density maps for stellar populations found in data gathered by OGLE-IV, that fully cover over 270 deg^2 ... More
OGLE-ing the Magellanic System: RR Lyrae Stars in the BridgeApr 16 2019We use the extended and updated OGLE Collection of Variable Stars to thoroughly analyze distribution of RR Lyrae stars in the Magellanic Bridge. We use photometric metallicities to derive absolute Wesenheit magnitude and then individual distance of each ... More
OGLE-ing the Magellanic System: Three-Dimensional Structure of the Clouds and the Bridge Using Classical CepheidsFeb 29 2016Jul 12 2016We analyzed a sample of 9418 fundamental-mode and first-overtone Classical Cepheids from the OGLE-IV Collection of Classical Cepheids. The distance to each Cepheid was calculated using the period-luminosity relation for the Wesenheit magnitude, fitted ... More
OGLE-2016-BLG-0613LABb: A Microlensing Planet in a Binary SystemOct 02 2017We present the analysis of OGLE-2016-BLG-0613, for which the lensing light curve appears to be that of a typical binary-lens event with two caustic spikes but with a discontinuous feature on the trough between the spikes. We find that the discontinuous ... More
OGLE-2017-BLG-1130: The First Binary Gravitational Microlens Detected From Spitzer OnlyFeb 25 2018Feb 27 2018We analyze the binary gravitational microlensing event OGLE-2017-BLG-1130 (mass ratio q~0.45), the first published case in which the binary anomaly was only detected by the Spitzer Space Telescope. This event provides strong evidence that some binary ... More
Metal-Rich RRc stars in the Carnegie RR Lyrae SurveyDec 01 2017We describe and employ a stacking procedure to investigate abundances derived from the low S/N spectra obtained in the Carnegie RR Lyrae Survey (CARRS; Kollmeier et al. 2013). We find iron metallicities that extend from [Fe/H] ~ -2.5 to values at least ... More
OGLE-2018-BLG-0532Lb: Cold Neptune With Possible Jovian SiblingMay 15 2019We report the discovery of the planet OGLE-2018-BLG-0532Lb, with very obvious signatures in the light curve that lead to an estimate of the planet-host mass ratio $q=M_{\rm planet}/M_{\rm host}\simeq 1\times10^{-4}$. Although there are no obvious systematic ... More
A Terrestrial Planet in a ~1 AU Orbit Around One Member of a ~15 AU BinaryJul 04 2014We detect a cold, terrestrial planet in a binary-star system using gravitational microlensing. The planet has low mass (2 Earth masses) and lies projected at $a_{\perp,ph}$ ~ 0.8 astronomical units (AU) from its host star, similar to the Earth-Sun distance. ... More
Eclipsing Binary Stars in the OGLE-III Fields of the Small Magellanic CloudOct 11 2013We present a large sample of eclipsing binary stars detected in the Small Magellanic Cloud fields covering about 14 square degrees that have been monitored for eight years during the third phase of the OGLE survey. This is the largest set of such variables ... More
Discovery of two quasars at $z=5$ from the OGLE SurveyOct 19 2018We have used deep Optical Gravitational Lensing Experiment (OGLE-IV) images ($V \lesssim 23$ mag, $I \lesssim 23$ mag at $3\sigma$) of the Magellanic System, encompassing an area of $\sim$670 deg$^2$, to perform a search for high-$z$ quasar candidates. ... More
Achieving Fully Proportional Representation is Easy in PracticeJan 27 2013We provide experimental evaluation of a number of known and new algorithms for approximate computation of Monroe's and Chamberlin-Courant's rules. Our experiments, conducted both on real-life preference-aggregation data and on synthetic data, show that ... More
Stable Marriage with Multi-Modal PreferencesJan 08 2018We introduce a generalized version of the famous Stable Marriage problem, now based on multi-modal preference lists. The central twist herein is to allow each agent to rank its potentially matching counterparts based on more than one "evaluation mode" ... More
Finding a Collective Set of Items: From Proportional Multirepresentation to Group RecommendationFeb 13 2014Jan 08 2016We consider the following problem: There is a set of items (e.g., movies) and a group of agents (e.g., passengers on a plane); each agent has some intrinsic utility for each of the items. Our goal is to pick a set of $K$ items that maximize the total ... More
Matchings under Preferences: Strength of Stability and Trade-offsFeb 15 2019We propose two solution concepts for matchings under preferences: robustness and near stability. The former strengthens while the latter relaxes the classic definition of stability by Gale and Shapley (1962). Informally speaking, robustness requires that ... More
Axiomatic Characterization of Committee Scoring RulesApr 06 2016We provide an axiomatic characterization of committee scoring rules, analogues of the scoring rules for the multiwinner elections. We show that committee scoring rules are characterized by the set of four standard axioms, anonymity, neutrality, consistency ... More
Cooperation and Competition when Bidding for Complex Projects: Centralized and Decentralized PerspectivesFeb 12 2014Sep 15 2016To successfully complete a complex project, be it a construction of an airport or of a backbone IT system, agents (companies or individuals) must form a team having required competences and resources. A team can be formed either by the project issuer ... More
Structure and stability of online chat networks built on emotion-carrying linksSep 21 2012High-resolution data of online chats are studied as a physical system in laboratory in order to quantify collective behavior of users. Our analysis reveals strong regularities characteristic to natural systems with additional features. In particular, ... More
Axiomatic Characterization of Committee Scoring RulesApr 06 2016Nov 02 2016Committee scoring rules form a rich class of aggregators of voters' preferences for the purpose of selecting subsets of objects with desired properties, e.g., a shortlist of candidates for an interview, a representative collective body such as a parliament, ... More
Proportional Approval Voting, Harmonic k-median, and Negative AssociationApr 07 2017Mar 12 2018We study a generic framework that provides a unified view on two important classes of problems: (i) extensions of the k-median problem where clients are interested in having multiple facilities in their vicinity (e.g., due to the fact that, with some ... More
Multiwinner Approval Rules as Apportionment MethodsNov 26 2016We establish a link between multiwinner elections and apportionment problems by showing how approval-based multiwinner election rules can be interpreted as methods of apportionment. We consider several multiwinner rules and observe that they induce apportionment ... More
Systems described by Volterra type integral operatorsNov 19 2013In the paper some sufficient condition for the nonlinear integral operator of the Volterra type to be a diffeomorphism defined on the space of absolutely continuous functions are formulated. The proof relies on consideration of the linearized equation ... More
Achieving Fully Proportional Representation: Approximability ResultsDec 14 2013We study the complexity of (approximate) winner determination under the Monroe and Chamberlin--Courant multiwinner voting rules, which determine the set of representatives by optimizing the total (dis)satisfaction of the voters with their representatives. ... More
Collective Schedules: Scheduling Meets Computational Social ChoiceMar 20 2018When scheduling public works or events in a shared facility one needs to accommodate preferences of a population. We formalize this problem by introducing the notion of a collective schedule. We show how to extend fundamental tools from social choice ... More
MOA-2010-BLG-353Lb A Possible Saturn RevealedOct 05 2015We report the discovery of a possible planet in microlensing event MOA-2010-BLG-353. This event was only recognised as having a planetary signal after the microlensing event had finished, and following a systematic analysis of all archival data for binary ... More
MOA-2011-BLG-293Lb: A test of pure survey microlensing planet detectionsJan 04 2012Jul 03 2012Because of the development of large-format, wide-field cameras, microlensing surveys are now able to monitor millions of stars with sufficient cadence to detect planets. These new discoveries will span the full range of significance levels including planetary ... More
$Spitzer$ Microlensing Parallax for OGLE-2017-BLG-0896 Reveals a Counter-Rotating Low-Mass Brown DwarfMay 22 2018Jan 18 2019The kinematics of isolated brown dwarfs in the Galaxy, beyond the solar neighborhood, is virtually unknown. Microlensing has the potential to probe this hidden population, as it can measure both the mass and five of the six phase-space coordinates (all ... More
Spectroscopic Mass and Host-star Metallicity Measurements for Newly Discovered Microlensing Planet OGLE-2018-BLG-0740LbMay 01 2019We report the discovery of the microlensing planet OGLE-2018-BLG-0740Lb. The planet is detected with a very strong signal of $\Delta\chi^2\sim 4630$, but the interpretation of the signal suffers from two types of degeneracies. One type is caused by the ... More
OGLE-2018-BLG-0022: First Prediction of an Astrometric Microlensing Signal from a Photometric Microlensing EventMar 30 2019Apr 04 2019In this work, we present the analysis of the binary microlensing event OGLE-2018-BLG-0022 that is detected toward the Galactic bulge field. The dense and continuous coverage with the high-quality photometry data from ground-based observations combined ... More
OGLE-2018-BLG-0022: First Prediction of an Astrometric Microlensing Signal from a Photometric Microlensing EventMar 30 2019Apr 02 2019In this work, we present the analysis of the binary microlensing event OGLE-2018-BLG-0022 that is detected toward the Galactic bulge field. The dense and continuous coverage with the high-quality photometry data from ground-based observations combined ... More
$Spitzer$ Parallax of OGLE-2018-BLG-0596: A Low-mass-ratio Planet around an M-dwarfMay 14 2019We report the discovery of a $Spitzer$ microlensing planet OGLE-2018-BLG-0596Lb, with preferred planet-host mass ratio $q \sim 2\times10^{-4}$. The planetary signal, which is characterized by a short $(\sim 1~{\rm day})$ "bump" on the rising side of the ... More
MOA-2013-BLG-220Lb: Massive Planetary Companion to Galactic-Disk HostMar 10 2014May 30 2014We report the discovery of MOA-2013-BLG-220Lb, which has a super-Jupiter mass ratio $q=3.01\pm 0.02\times 10^{-3}$ relative to its host. The proper motion, $\mu=12.5\pm 1\, {\rm mas}\,{\rm yr}^{-1}$, is one of the highest for microlensing planets yet ... More
Mass Measurements of Isolated Objects from Space-based MicrolensingOct 07 2015Apr 21 2016We report on the mass and distance measurements of two single-lens events from the 2015 \emph{Spitzer} microlensing campaign. With both finite-source effect and microlens parallax measurements, we find that the lens of OGLE-2015-BLG-1268 is very likely ... More
MOA-2010-BLG-311: A planetary candidate below the threshold of reliable detectionOct 22 2012Oct 10 2013We analyze MOA-2010-BLG-311, a high magnification (A_max>600) microlensing event with complete data coverage over the peak, making it very sensitive to planetary signals. We fit this event with both a point lens and a 2-body lens model and find that the ... More
A Super-Jupiter orbiting a late-type star: A refined analysis of microlensing event OGLE-2012-BLG-0406Oct 09 2013Dec 05 2013We present a detailed analysis of survey and follow-up observations of microlensing event OGLE-2012-BLG-0406 based on data obtained from 10 different observatories. Intensive coverage of the lightcurve, especially the perturbation part, allowed us to ... More
Microlensing Discovery of a Population of Very Tight, Very Low-mass Binary Brown DwarfsFeb 18 2013Mar 20 2013Although many models have been proposed, the physical mechanisms responsible for the formation of low-mass brown dwarfs are poorly understood. The multiplicity properties and minimum mass of the brown-dwarf mass function provide critical empirical diagnostics ... More
Characterizing Low-Mass Binaries From Observation of Long Time-scale Caustic-crossing Gravitational Microlensing EventsApr 13 2012Jun 13 2012Despite astrophysical importance of binary star systems, detections are limited to those located in small ranges of separations, distances, and masses and thus it is necessary to use a variety of observational techniques for a complete view of stellar ... More
Generation of Schrödinger's cat states in a planar semiconductor heterostructureOct 20 2016We propose a nanodevice based on a typical planar semiconductor heterostructure with lateral confinement potential created by voltages applied to local electrodes. We show how to obtain near parabolical confinement along the nanodevice, and how to use ... More
Spanning trees of the World Trade Web: real-world data and the gravity model of tradeDec 04 2014In this paper, we investigate the statistical features of the weighted international-trade network. By finding the maximum weight spanning trees for this network we make the extraction of the truly relevant connections forming the network's backbone. ... More
Mixed Integer Programming with Convex/Concave Constraints: Fixed-Parameter Tractability and Applications to Multicovering and VotingSep 08 2017Nov 20 2017A classic result of Lenstra [Math.~Oper.~Res.~1983] says that an integer linear program can be solved in fixed-parameter tractable (FPT) time for the parameter being the number of variables. We extend this result by incorporating non-decreasing piecewise ... More
The Dynamics of Emotional Chats with Bots: Experiment and Agent-Based SimulationsApr 16 2014Quantitative research of emotions in psychology and machine-learning methods for extracting emotion components from text messages open an avenue for physical science to explore the nature of stochastic processes in which emotions play a role, e.g., in ... More
Emotional persistence in online chatting communitiesMay 11 2012How do users behave in online chatrooms, where they instantaneously read and write posts? We analyzed about 2.5 million posts covering various topics in Internet relay channels, and found that user activity patterns follow known power-law and stretched ... More
Fair KnapsackNov 13 2017Nov 12 2018We study the following multiagent variant of the knapsack problem. We are given a set of items, a set of voters, and a value of the budget; each item is endowed with a cost and each voter assigns to each item a certain value. The goal is to select a subset ... More
Proportional RankingsDec 05 2016In this paper we extend the principle of proportional representation to rankings. We consider the setting where alternatives need to be ranked based on approval preferences. In this setting, proportional representation requires that cohesive groups of ... More
Entropy-growth-based model of emotionally charged online dialoguesJan 26 2012We analyze emotionally annotated massive data from IRC (Internet Relay Chat) and model the dialogues between its participants by assuming that the driving force for the discussion is the entropy growth of emotional probability distribution. This process ... More
Applying a Text-Based Affective Dialogue System in Psychological Research: Case Studies on the Effects of System Behavior, Interaction Context and Social ExclusionApr 28 2014This article presents two studies conducted with an affective dialogue system in which text-based system-user communication was used to model, generate, and present different affective and social interaction scenarios. We specifically investigated the ... More
Properties of Multiwinner Voting RulesJun 09 2015The goal of this paper is to propose and study properties of multiwinner voting rules which can be consider as generalisations of single-winner scoring voting rules. We consider SNTV, Bloc, k-Borda, STV, and several variants of Chamberlin--Courant's and ... More
Repeating microlensing events in the OGLE dataNov 17 2008Microlensing events are usually selected among single-peaked non-repeating light curves in order to avoid confusion with variable stars. However, a microlensing event may exhibit a second microlensing brightening episode when the source or/and the lens ... More
Hydrogen-rich supernovae beyond the neutrino-driven core-collapse paradigmSep 29 2017We present our study of OGLE-2014-SN-073, one of the brightest Type II SN ever discovered, with an unusually broad lightcurve combined with high ejecta velocities. From our hydrodynamical modelling we infer a remarkable ejecta mass of $60^{+42}_{-16}$~M$_\odot$, ... More
Equilibria of Plurality Voting: Lazy and Truth-biased VotersSep 15 2014We present a systematic study of Plurality elections with strategic voters who, in addition to having preferences over election winners, have secondary preferences, which govern their behavior when their vote cannot affect the election outcome. Specifically, ... More
Multiwinner Elections with Diversity ConstraintsNov 17 2017Nov 22 2017We develop a model of multiwinner elections that combines performance-based measures of the quality of the committee (such as, e.g., Borda scores of the committee members) with diversity constraints. Specifically, we assume that the candidates have certain ... More
The Condorcet Principle for Multiwinner Elections: From Shortlisting to ProportionalityJan 27 2017We study two notions of stability in multiwinner elections that are based on the Condorcet criterion. The first notion was introduced by Gehrlein: A committee is stable if each committee member is preferred to each non-member by a (possibly weak) majority ... More
Committee Scoring Rules: Axiomatic Characterization and HierarchyFeb 19 2018Committee scoring voting rules are multiwinner analogues of positional scoring rules which constitute an important subclass of single-winner voting rules. We identify several natural subclasses of committee scoring rules, namely, weakly separable, representation-focused, ... More
Optimal Average Satisfaction and Extended Justified Representation in Polynomial TimeApr 02 2017In this short note, we describe an approval-based committee selection rule that admits a polynomial-time algorithm and satisfies the Extended Justified Representation (EJR) axiom. This rule is based on approximately maximizing the PAV score, by means ... More