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Identifying Planetary Biosignature Impostors: Spectral Features of CO and O4 Resulting from Abiotic O2/O3 ProductionFeb 17 2016O2 and O3 have been long considered the most robust individual biosignature gases in a planetary atmosphere, yet multiple mechanisms that may produce them in the absence of life have been described. However, these abiotic planetary mechanisms modify the ... More

Habitable Zones Around Main-Sequence Stars: Dependence on Planetary MassApr 21 2014May 12 2014The ongoing discoveries of extrasolar planets are unveiling a wide range of terrestrial mass (size) planets around their host stars. In this letter, we present estimates of habitable zones (HZs) around stars with stellar effective temperatures in the ... More

The Habitability of Proxima Centauri b I: Evolutionary ScenariosAug 24 2016Mar 06 2018We analyze the evolution of the potentially habitable planet Proxima Centauri b to identify environmental factors that affect its long-term habitability. We consider physical processes acting on size scales ranging from the galactic to the stellar system ... More

VPLanet: The Virtual Planet SimulatorMay 15 2019We describe a software package called VPLanet that simulates fundamental aspects of planetary system evolution over Gyr timescales, with a focus on investigating habitable worlds. In this first version, eleven physics modules are included that model internal, ... More

Understanding Stellar Contamination in Exoplanet Transmission Spectra as an Essential Step in Small Planet CharacterizationMar 23 2018Transmission spectroscopy during planetary transits is expected to be a major source of information on the atmospheres of small (approximately Earth-sized) exoplanets in the next two decades. This technique, however, is intrinsically affected by stellar ... More

Exoplanet Science Priorities from the Perspective of Internal and Surface Processes for Silicate and Ice Dominated WorldsApr 13 2018The geophysics of extrasolar planets is a scientific topic often regarded as standing largely beyond the reach of near-term observations. This reality in no way diminishes the central role of geophysical phenomena in shaping planetary outcomes, from formation, ... More

Effects of Extreme Obliquity Variations on the Habitability of ExoplanetsApr 14 2014We explore the impact of obliquity variations on planetary habitability in hypothetical systems with high mutual inclination. We show that large amplitude, high frequency obliquity oscillations on Earth-like exoplanets can suppress the ice-albedo feedback, ... More

A Model for Collective Dynamics in Ant RaidsAug 17 2015Ant raiding, the process of identifying and returning food to the nest or bivouac, is a fascinating example of collective motion in nature. During such raids ants lay pheromones to form trails for others to find a food source. In this work a coupled PDE/ODE ... More

Testing the Early Mars H2-CO2 Greenhouse Hypothesis with a 1-D Photochemical ModelJul 09 2015A recent study by Ramirez et al. (2014) demonstrated that an atmosphere with 1.3-4 bar of CO2 and H2O, in addition to 5-20% H2, could have raised the mean annual and global surface temperature of early Mars above the freezing point of water. Such warm ... More

Impacts of Quantum Chemistry Calculations on Exoplanetary Science, Planetary Astronomy, and AstrophysicsApr 15 2019Several of NASA missions (TESS, JWST, WFIRST, etc.) and mission concepts (LUVOIR, HabEx, and OST) emphasize the exploration and characterization of exoplanets, and the study of the interstellar medium. We anticipate that a much broader set of chemical ... More

Constraining Stellar Photospheres as an Essential Step for Transmission Spectroscopy of Small ExoplanetsMar 14 2019Transmission spectra probe the atmospheres of transiting exoplanets, but these observations are also subject to signals introduced by magnetic active regions on host stars. Here we outline scientific opportunities in the next decade for providing useful ... More

On the Frequency of Potential Venus Analogs from Kepler DataSep 09 2014The field of exoplanetary science has seen a dramatic improvement in sensitivity to terrestrial planets over recent years. Such discoveries have been a key feature of results from the {\it Kepler} mission which utilizes the transit method to determine ... More

Imaging Cool Giant Planets in Reflected Light: Science Investigations and Synergy with Habitable PlanetsMar 22 2019Mar 26 2019Planned astronomical observatories of the 2020s will be capable of obtaining reflected light photometry and spectroscopy of cool extrasolar giant planets. Here we explain that such data are valuable both for understanding the origin and evolution of giant ... More

Abiotic Ozone and Oxygen in Atmospheres Similar to Prebiotic EarthJul 09 2014The search for life on planets outside our solar system will use spectroscopic identification of atmospheric biosignatures. The most robust remotely-detectable potential biosignature is considered to be the detection of oxygen (O_2) or ozone (O_3) simultaneous ... More

The Need for Laboratory Measurements and Ab Initio Studies to Aid Understanding of Exoplanetary AtmospheresMay 16 2019We are now on a clear trajectory for improvements in exoplanet observations that will revolutionize our ability to characterize their atmospheric structure, composition, and circulation, from gas giants to rocky planets. However, exoplanet atmospheric ... More

Exoplanet Exploration Program Analysis Group (ExoPAG) Report to Paul Hertz Regarding Large Mission Concepts to Study for the 2020 Decadal SurveyDec 31 2015This is a joint summary of the reports from the three Astrophysics Program Analysis Groups (PAGs) in response to the "Planning for the 2020 Decadal Survey" charge given by the Astrophysics Division Director Paul Hertz. This joint executive summary contains ... More

Detecting and Constraining N$_2$ Abundances in Planetary Atmospheres Using Collisional PairsJul 28 2015Characterizing the bulk atmosphere of a terrestrial planet is important for determining surface pressure and potential habitability. Molecular nitrogen (N$_2$) constitutes the largest fraction of Earth$'$s atmosphere and is likely to be a major constituent ... More

Would contact with extraterrestrials benefit or harm humanity? A scenario analysisApr 22 2011Aug 16 2011While humanity has not yet observed any extraterrestrial intelligence (ETI), contact with ETI remains possible. Contact could occur through a broad range of scenarios that have varying consequences for humanity. However, many discussions of this question ... More

Explicit cloud representation in the Atmos 1D climate model for Earth and rocky planet applicationsNov 27 20181D climate models are less sophisticated than 3D global circulation models (GCMs), however their computational time is much less expensive, allowing a large number of runs in a short period of time to explore a wide parameter space. Exploring parameter ... More

Lower Limits on Aperture Size for an ExoEarth-Detecting Coronagraphic MissionJun 04 2015The yield of Earth-like planets will likely be a primary science metric for future space-based missions that will drive telescope aperture size. Maximizing the exoEarth candidate yield is therefore critical to minimizing the required aperture. Here we ... More

Homological action of the modular group on some cubic moduli spacesFeb 03 2004We describe the action of the automorphism group of the complex cubic x^2+y^2+z^2-xyz-2 on the homology of its fibers. This action includes the action of the mapping class group of a punctured torus on the subvarieties of its SL(2,C) character variety ... More

Pale Orange Dots: The Impact of Organic Haze on the Habitability and Detectability of Earthlike ExoplanetsFeb 09 2017Hazes are common in known planet atmospheres, and geochemical evidence suggests early Earth occasionally supported an organic haze with significant environmental and spectral consequences. The UV spectrum of the parent star drives organic haze formation ... More

ATLAST detector needs for direct spectroscopic biosignature characterization in the visible and near-IRAug 26 2015Are we alone? Answering this ageless question will be a major focus for astrophysics in coming decades. Our tools will include unprecedentedly large UV-Optical-IR space telescopes working with advanced coronagraphs and starshades. Yet, these facilities ... More

Stellar Activity Effects on Moist Habitable Terrestrial Atmospheres Around M dwarfsFeb 11 2019Transit spectroscopy of terrestrial planets around nearby M dwarfs is a primary goal of space missions in coming decades. 3-D climate modeling has shown that slow-synchronous rotating terrestrial planets may develop thick clouds at the substellar point, ... More

The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean EarthOct 14 2016Recognizing whether a planet can support life is a primary goal of future exoplanet spectral characterization missions, but past research on habitability assessment has largely ignored the vastly different conditions that have existed in our planet's ... More

Habitability of Planets Orbiting Cool StarsDec 08 2010Terrestrial planets are more likely to be detected if they orbit M dwarfs due to the favorable planet/star size and mass ratios. However, M dwarf habitable zones are significantly closer to the star than the one around our Sun, which leads to different ... More

Habitable Zones Around Main-Sequence Stars: New EstimatesJan 28 2013Feb 07 2013Identifying terrestrial planets in the habitable zones (HZs) of other stars is one of the primary goals of ongoing radial velocity and transit exoplanet surveys and proposed future space missions. Most current estimates of the boundaries of the HZ are ... More

Exoplanet Biosignatures: A Framework for Their AssessmentMay 18 2017May 03 2018Finding life on exoplanets from telescopic observations is an ultimate goal of exoplanet science. Life produces gases and other substances, such as pigments, which can have distinct spectral or photometric signatures. Whether or not life is found with ... More

Exoplanet Classification and Yield Estimates for Direct Imaging MissionsFeb 26 2018Future NASA concept missions that are currently under study, like Habitable Exoplanet Imaging Mission (HabEx) & Large Ultra-Violet Optical Infra Red (LUVOIR) Surveyor, would discover a large diversity of exoplanets. We propose here a classification scheme ... More

Biosignature Anisotropy Modeled on Temperate Tidally Locked M-dwarf PlanetsOct 30 2018Dec 26 2018A planet's atmospheric constituents (e.g., O$_2$, O$_3$, H$_2$O$_v$, CO$_2$, CH$_4$, N$_2$O) can provide clues to its surface habitability, and may offer biosignature targets for remote life detection efforts. The plethora of rocky exoplanets found by ... More

Small hyperbolic polyhedraFeb 01 2011Nov 18 2011We classify the 3-dimensional hyperbolic polyhedral orbifolds that contain no embedded essential 2-suborbifolds, up to decomposition along embedded hyperbolic triangle orbifolds (turnovers). We give a necessary condition for a 3-dimensional hyperbolic ... More

Technology Needs for Detecting Life Beyond the Solar System: A White Paper in Support of the Astrobiology Science StrategyJan 23 2018Jan 31 2018In support of the Astrobiology Science Strategy, this whitepaper outlines some key technology challenges pertaining to the remote search for life in exoplanetary systems. Finding evidence for life on rocky planets outside of our solar system requires ... More

Key Technology Challenges for the Study of Exoplanets and the Search for Habitable WorldsMar 12 2018In support of the National Acadamies' Exoplanet Science Strategy, this whitepaper outlines key technology challenges for studying the diversity of worlds in the Galaxy and in searching for habitable planets. Observations of habitable planets outside of ... More

The Habitable Exoplanet Observatory (HabEx) Mission Concept Study Interim ReportSep 25 2018For the first time in human history, technologies have matured sufficiently to enable a mission capable of discovering and characterizing habitable planets like Earth orbiting sunlike stars other than the Sun. At the same time, such a platform would enable ... More

Coefficient growth in square chainsFeb 27 2019Suppose $((\cdots((x^{2}-c_{1})^{2}-c_{2})^{2}\cdots)^{2}-c_{k-1})^{2}-c_{k}$ splits into linear factors over $\mathbb{Z}$ and $c_{k}\neq0$. We show that for each $j$ and each prime $p$, if $p\leq2^{j-1}$ then $p$ divides $c_{j}$. Consequently, $$\ln ... More

Bayesian Deep Learning for Exoplanet Atmospheric RetrievalNov 08 2018Dec 02 2018Over the past decade, the study of extrasolar planets has evolved rapidly from plain detection and identification to comprehensive categorization and characterization of exoplanet systems and their atmospheres. Atmospheric retrieval, the inverse modeling ... More

Anomaly Detection in Cyber Network Data Using a Cyber Language ApproachAug 15 2018As the amount of cyber data continues to grow, cyber network defenders are faced with increasing amounts of data they must analyze to ensure the security of their networks. In addition, new types of attacks are constantly being created and executed globally. ... More

The remote detectability of Earth's biosphere through time and the importance of UV capability for characterizing habitable exoplanetsMar 13 2019Thousands of planets beyond our solar system have been discovered to date, dozens of which are rocky in composition and are orbiting within the circumstellar habitable zone of their host star. The next frontier in life detection beyond our solar system ... More

A comprehensive understanding of planet formation is required for assessing planetary habitability and for the search for lifeMar 23 2018Dozens of habitable zone, approximately earth-sized exoplanets are known today. An emerging frontier of exoplanet studies is identifying which of these habitable zone, small planets are actually habitable (have all necessary conditions for life) and, ... More

Extension of ATLAST/LUVOIR's Capabilities to 5 Microns, or BeyondMay 14 2016ATLAST is a particular realization of LUVOIR, the Large Ultraviolet Optical Infrared telescope, a ~10 m diameter space telescope being defined for consideration in the 2020 Decadal Review of astronomy and astrophysics. ATLAST/LUVOIR is generally thought ... More

A note related to the CS decomposition and the BK inequality for discrete determinantal processesMay 09 2019We prove that for a discrete determinantal process the BK inequality occurs for increasing events generated by simple points. We give also some elementary, but nonetheless appealing relationship, between a discrete determinantal process and the well-known ... More

The Habitability of Proxima Centauri b I: Evolutionary ScenariosAug 24 2016We analyze the evolution of the potentially habitable planet Proxima Centauri b to identify environmental factors that affect its long-term habitability. We consider physical processes acting on size scales ranging between the galactic scale, the scale ... More

The Habitability of Proxima Centauri b: II: Environmental States and Observational DiscriminantsAug 30 2016Proxima Centauri b provides an unprecedented opportunity to understand the evolution and nature of terrestrial planets orbiting M dwarfs. Although Proxima Cen b orbits within its star's habitable zone, multiple plausible evolutionary paths could have ... More

Optical Control of a Single Nuclear Spin in the Solid StateAug 13 2018We demonstrate a novel method for coherent optical manipulation of individual nuclear spins in the solid state, mediated by the electronic states of a proximal quantum emitter. Specifically, using the nitrogen-vacancy (NV) color center in diamond, we ... More

Phylogenetic quantification of intra-tumour heterogeneityJun 07 2013Background: Intra-tumour heterogeneity (ITH) is the result of ongoing evolutionary change within each cancer. The expansion of genetically distinct sub-clonal populations may explain the emergence of drug resistance and if so would have prognostic and ... More

Families of Artin-Schreier curves with Cartier-Manin matrix of constant rankFeb 19 2012Let k be an algebraically closed field of characteristic p > 0. Every Artin-Schreier k-curve X has an equation of the form y^p - y = f(x) for some f(x) in k(x) such that p does not divide the least common multiple L of the orders of the poles of f(x). ... More

Continuum-type stability balloon in oscillated granular layersFeb 25 1998The stability of convection rolls in a fluid heated from below is limited by secondary instabilities, including the skew-varicose and crossroll instabilities. We observe a stability boundary defined by the same instabilities in stripe patterns in a vertically ... More

Retrieval of Planetary Rotation and Albedo from DSCOVR dataNov 12 2015The field of exoplanets has rapidly expanded from the exclusivity of exoplanet detection to include exoplanet characterization. A key step towards this characterization will be retrieval of planetary albedos and rotation rates from highly undersampled ... More

Modules of constant Jordan type, pullbacks of bundles and generic kernel filtrationsApr 08 2015Let $kE$ denote the group algebra of an elementary abelian $p$-group of rank $r$ over an algebraically closed field of characteristic $p$. We investigate the functors $\mathcal{F}_i$ from $kE$-modules of constant Jordan type to vector bundles on $\mathbb{P}^{r-1}(k)$, ... More

The Importance of Multiple Observation Methods to Characterize Potentially Habitable Exoplanets: Ground- and Space-Based SynergiesMar 08 2018The discovery of a truly habitable exoplanet would be one of the most important events in the history of science. However, the nature and distribution of habitable environments on exoplanets is currently unconstrained. The exoplanet revolution teaches ... More

Exoplanet Biosignatures: Observational ProspectsMay 19 2017Aug 19 2018Exoplanet hunting efforts have revealed the prevalence of exotic worlds with diverse properties, including Earth-sized bodies, which has fueled our endeavor to search for life beyond the Solar System. Accumulating experiences in astrophysical, chemical, ... More

Venus: The Making of an Uninhabitable WorldJan 09 2018The goals of the astrobiology community are focussed on developing a framework for the detection of biosignatures, or evidence thereof, on objects inside and outside of our solar system. A fundamental aspect of understanding the limits of habitable environments ... More

Life Beyond the Solar System: Observation and Modeling of Exoplanet EnvironmentsJan 23 2018The search for life on planets outside our solar system has largely been the province of the astrophysics community until recently. A major development since the NASA Astrobiology Strategy 2015 document (AS15) has been the integration of other NASA science ... More

Locally homogeneous geometric manifoldsMar 14 2010Apr 21 2010Motivated by Felix Klein's notion that geometry is governed by its group of symmetry transformations, Charles Ehresmann initiated the study of geometric structures on topological spaces locally modeled on a homogeneous space of a Lie group. These locally ... More

Crooked surfaces and anti-de Sitter geometryFeb 20 2013Nov 25 2014Crooked planes were defined by Drumm to bound fundamental polyhedra in Minkowski space for Margulis spacetimes. They were extended by Frances to closed polyhedral surfaces in the conformal compactification of Minkowski space (Einstein space) which we ... More

Magnetic ordering in EuRh2As2 studied by x-ray resonant magnetic scatteringFeb 05 2009Feb 05 2009Element-specific x-ray resonant magnetic scattering investigations were performed to determine the magnetic structure of Eu in EuRh2As2. In the temperature range from 46 K down to 6 K, an incommensurate antiferromagnetic (ICM)structure with a temperature ... More

Phase segregation for binary mixtures of Bose-Einstein CondensatesMay 27 2015Nov 30 2016We study the strong segregation limit for mixtures of Bose-Einstein condensates modelled by a Gross-Pitaievskii functional. Our first main result is that in presence of a trapping potential, for different intracomponent strengths, the Thomas-Fermi limit ... More

Dynamics of the Automorphism Group of the GL(2,R)-Characters of a Once-puncutred TorusSep 04 2003Let pi be a free group of rank 2. Its outer automorphism group Out(pi) acts on the space of equivalence classes of representations in Hom(pi, SL(2,C)). Let SLm(2,R) denote ths subset of GL(2,R) consisting of matrices of determinant -1 and let ISL(2,R) ... More

The Modular Group Action on Real SL(2)-characters of a One-Holed TorusMay 06 2003Aug 22 2003The group Gamma of automorphisms of the polynomial kappa(x,y,z) = x^2 + y^2 + z^2 - xyz -2 is isomorphic to PGL(2,Z) semi-direct product with (Z/2+Z/2). For t in R, Gamma-action on ktR = kappa^{-1}(t) intersect R displays rich and varied dynamics. The ... More

Optimal Control Of Surface ShapeJul 16 2014Dec 08 2014Controlling the shapes of surfaces provides a novel way to direct self-assembly of colloidal particles on those surfaces and may be useful for material design. This motivates the investigation of an optimal control problem for surface shape in this paper. ... More

Universal Quantum Computation with Metaplectic AnyonsMay 30 2014Mar 15 2015We show that braidings of the metaplectic anyons $X_\epsilon$ in $SO(3)_2=SU(2)_4$ with their total charge equal to the metaplectic mode $Y$ supplemented with measurements of the total charge of two metaplectic anyons are universal for quantum computation. ... More

On Two Invariants of Three Manifolds from Hopf AlgebrasOct 26 2017Dec 21 2017We prove a 20-year-old conjecture concerning two quantum invariants of three manifolds that are constructed from finite dimensional Hopf algebras, namely, the Kuperberg invariant and the Hennings-Kauffman-Radford invariant. The two invariants can be viewed ... More

Exoplanet Biosignatures: Understanding Oxygen as a Biosignature in the Context of Its EnvironmentMay 22 2017Here we review how environmental context can be used to interpret whether O2 is a biosignature in extrasolar planetary observations. This paper builds on the overview of current biosignature research discussed in Schwieterman et al. (2017), and provides ... More

Microlensing Evidence That A Type 1 Quasar Is Viewed Face OnOct 19 2009Feb 09 2010Using a microlensing analysis of 11-years of OGLE V-band photometry of the four image gravitational lens Q2237+0305, we measure the inclination i of the accretion disk to be cos i > 0.66 at 68% confidence. Very edge on (cos i < 0.39) solutions are ruled ... More

Non-convex functionals penalizing simultaneous oscillations along independent directions: rigidity estimatesMay 20 2019We study a family of non-convex functionals $\{\mathcal{E}\}$ on the space of measurable functions$u: \Omega_1\times\Omega_2 \subset \mathbb{R}^{n_1}\times\mathbb{R}^{n_2} \to \mathbb{R}$. These functionals vanish on the non-convex subset $S(\Omega_1\times\Omega_2)$ ... More

Bulging deformations of convex $RP^2$-manifoldsFeb 04 2013We define deformations of $RP^2$-manifolds.

Higgs Bundles and Geometric Structures on SurfacesMay 12 2008This paper concerns the relationship between locally homogeneous geometric structures on topological surfaces and the moduli of polystable Higgs bundles on Riemann surfaces, due to Hitchin and Simpson. In particular we discuss the uniformization of Riemann ... More

On the regularity of stationary points of a nonlocal isoperimetric problemMay 18 2014In this article we establish $C^{3,\alpha}$-regularity of the reduced boundary of stationary points of a nonlocal isoperimetric problem in a domain $\Omega \subset \mathbb{R}^n$. In particular, stationary points satisfy the corresponding Euler-Lagrange ... More

A 3-Manifold with no Real Projective StructureJul 09 2012Jan 04 2015We show that the connected sum of two copies of real projective 3-space does not admit a real projective structure. This is the first known example of a connected 3-manifold without a real projective structure.

Phonon-Induced Population Dynamics and Intersystem Crossing in Nitrogen-Vacancy CentersJun 16 2014Mar 03 2015We report direct measurement of population dynamics in the excited state manifold of a nitrogen-vacancy (NV) center in diamond. We quantify the phonon-induced mixing rate and demonstrate that it can be completely suppressed at low temperatures. Further, ... More

Structural, magnetic and superconducting phase transitions in CaFe2As2 under ambient and applied pressureJan 29 2009At ambient pressure CaFe2As2 has been found to undergo a first order phase transition from a high temperature, tetragonal phase to a low temperature orthorhombic / antiferromagnetic phase upon cooling through T ~ 170 K. With the application of pressure ... More

Affine Schottky Groups and Crooked TilingsMay 08 2010In his 1990 doctoral thesis, Todd Drumm showed that proper affine deformations of free Fuchsian groups could be constructed as Schottky groups using a new family of hypersurfaces called "crooked planes." The existence of proper affine deformations of ... More

Single crystal growth and physical properties of the layered arsenide BaRh_2As_2Aug 22 2008Single crystals of BaRh_2As_2 have been synthesized from a Pb flux. We present the room temperature crystal structure, single crystal x-ray diffraction measurements as a function of temperature T, anisotropic magnetic susceptibility \chi versus T, electrical ... More

Exoplanet Biosignatures: Future DirectionsMay 23 2017Aug 08 2017Exoplanet science promises a continued rapid accumulation of new observations in the near future, energizing a drive to understand and interpret the forthcoming wealth of data to identify signs of life beyond our Solar System. The large statistics of ... More

Geodesics on Margulis spacetimesFeb 02 2011Aug 15 2011Let M be a Margulis spacetime whose associated complete hyperbolic surface S has compact convex core. Generalizing the correspondence between closed geodesics on M and closed geodesics on S, we establish an orbit equivalence between recurrent spacelike ... More

Confinement, Crossing Symmetry, and GlueballsOct 18 1994We suggest that the quark-confining force is related by crossing symmetry to a color-singlet glueball ${\cal G}$ which is well described as a loop of one quantum of color magnetic flux. Electron pair annihilation as high as $\approx 2 GeV$ above the $\Upsilon$ ... More

McShane-type Identities for Affine DeformationsJul 07 2015Oct 07 2016We derive an identity for Margulis invariants of affine deformations of a complete orientable one-ended hyperbolic sur- face following the identities of McShane, Mirzakhani and Tan- Wong-Zhang. As a corollary, a deformation of the surface which infinitesimally ... More

Affine cubic surfaces and relative SL(2)-character varieties of compact surfacesJun 19 2010Jun 30 2011A natural family of affine cubic surfaces arises from SL(2)-characters of the 4-holed sphere and the 1-holed torus. The ideal locus is a tritangent plane which is generic in the sense that the cubic curve at infinity consists of three lines pairwise intersecting ... More

What Is It Like Down There? Generating Dense Ground-Level Views and Image Features From Overhead Imagery Using Conditional Generative Adversarial NetworksJun 13 2018Sep 23 2018This paper investigates conditional generative adversarial networks (cGANs) to overcome a fundamental limitation of using geotagged media for geographic discovery, namely its sparse and uneven spatial distribution. We train a cGAN to generate ground-level ... More

Spatial Morphing Kernel Regression For Feature InterpolationFeb 21 2018May 04 2018In recent years, geotagged social media has become popular as a novel source for geographic knowledge discovery. Ground-level images and videos provide a different perspective than overhead imagery and can be applied to a range of applications such as ... More

The prime spectra of relative stable module categoriesNov 10 2015Jun 08 2017For a finite group $G$ and an arbitrary commutative ring $R$, Brou\'e has placed a Frobenius exact structure on the category of finitely generated $RG$-modules by taking the exact sequences to be those that split upon restriction to the trivial subgroup. ... More

The Need for Laboratory Work to Aid in The Understanding of Exoplanetary AtmospheresFeb 19 2016Feb 23 2016Advancements in our understanding of exoplanetary atmospheres, from massive gas giants down to rocky worlds, depend on the constructive challenges between observations and models. We are now on a clear trajectory for improvements in exoplanet observations ... More

Stripe Antiferromagnetic Spin Fluctuations in SrCo$_{2}$As$_{2}$Jun 21 2013Oct 14 2013Inelastic neutron scattering measurements of paramagnetic SrCo$_{2}$As$_{2}$ at T=5 K reveal antiferromagnetic (AFM) spin fluctuations that are peaked at a wavevector of $\textbf{Q}_{\mathrm{AFM}}=(1/2,1/2,1)$ and possess a large energy scale. These stripe ... More

Single Stage Prediction with Embedded Topic Modeling of Online Reviews for Mobile App ManagementJul 26 2016Feb 19 2018Mobile apps are one of the building blocks of the mobile digital economy. A differentiating feature of mobile apps to traditional enterprise software is online reviews, which are available on app marketplaces and represent a valuable source of consumer ... More

A Finite Element Method for a Phase Field Model of Nematic Liquid Crystal DropletsAug 08 2017Sep 12 2017We develop a novel finite element method for a phase field model of nematic liquid crystal droplets. The continuous model considers a free energy comprised of three components: the Ericksen's energy for liquid crystals, the Cahn-Hilliard energy representing ... More

Using Conditional Generative Adversarial Networks to Generate Ground-Level Views From Overhead ImageryFeb 19 2019This paper develops a deep-learning framework to synthesize a ground-level view of a location given an overhead image. We propose a novel conditional generative adversarial network (cGAN) in which the trained generator generates realistic looking and ... More

The prime spectra of relative stable module categoriesNov 10 2015Dec 09 2015For a finite group $G$ and an arbitrary commutative ring $R$, Benson, Iyengar and Krause have defined a Frobenius exact structure on the category of finitely generated $RG$-modules by letting the exact sequences be those that split on restriction to the ... More

A Statistical Comparative Planetology Approach to Maximize the Scientific Return of Future Exoplanet Characterization EffortsMar 12 2019Provided that sufficient resources are deployed, we can look forward to an extraordinary future in which we will characterize potentially habitable planets. Until now, we have had to base interpretations of observations on habitability hypotheses that ... More

A gradient flow approach to relaxation rates for the multi-dimensional Cahn-Hilliard equationFeb 22 2018The aim of this paper is to study relaxation rates for the Cahn-Hilliard equation in dimension larger than one. We follow the approach of Otto and Westdickenberg based on the gradient flow structure of the equation and establish differential and algebraic ... More

HealthcareMar 03 2017The complexity of the healthcare ecosystem and the trans-disciplinary convergence which is essential for its function, makes it difficult to address healthcare as one domain. Data curation and analysis of the information may boost our health related knowledge. ... More

Action of the Johnson-Torelli group on Representation VarietiesMar 14 2010Oct 15 2011Let \Sigma be a compact orientable surface with genus g and n boundary components B = (B_1,..., B_n). Let c = (c_1,...,c_n) in [-2,2]^n. Then the mapping class group MCG of \Sigma acts on the relative SU(2)-character variety X_c := Hom_C(\pi, SU(2))/SU(2), ... More

Geometry of error amplification in solving Prony system with near-colliding nodesJan 15 2017May 13 2019We consider a reconstruction problem for ``spike-train'' signals $F$ of an a priori known form $ F(x)=\sum_{j=1}^{d}a_{j}\delta\left(x-x_{j}\right),$ from their moments $m_k(F)=\int x^kF(x)dx.$ We assume that the moments $m_k(F)$, $k=0,1,\ldots,2d-1$, ... More

Life Beyond the Solar System: Remotely Detectable BiosignaturesJan 20 2018For the first time in human history, we will soon be able to apply the scientific method to the question "Are We Alone?" The rapid advance of exoplanet discovery, planetary systems science, and telescope technology will soon allow scientists to search ... More

SN1987A - a Testing Ground for the KARMEN AnomalyDec 22 1999May 02 2000We show, that SN1987A can serve as an astrophysical laboratory for testing the viability of the assertion that a new massive neutral fermion is implied by the KARMEN data. We show that a wide range of the parameters characterizing the proposed particle ... More

Nonlinear dynamics of Aharonov-Bohm cagesOct 17 2018Mar 12 2019The interplay of $\pi$-flux and lattice geometry can yield full localization of quantum dynamics in lattice systems, a striking interference phenomenon known as Aharonov-Bohm caging. At the level of the single-particle energy spectrum, this full-localization ... More

Proper affine actions and geodesic flows of hyperbolic surfacesJun 12 2004Sep 24 2008We give necessary and sufficient conditions for an affine deformation of a Schottky subgroup of O(2,1) to act properly on affine space. There exists a real-valued biaffine map between the cohomology of the Schottky group and the space of geodesic currents ... More

Study of island formation in epitaxially strained films on unbounded domainsFeb 17 2014Sep 11 2014We consider a variational model for the formation of islands in heteroepitaxial growth on unbounded domains. We first derive the scaling regimes of the minimal energy in terms of the volume of the film and the amplitude of the crystallographic misfit. ... More

Wide-Orbit Exoplanet DemographicsMar 19 2019The Kepler, K2 and TESS transit surveys are revolutionizing our understanding of planets orbiting close to their host stars and our understanding of exoplanet systems in general, but there remains a gap in our understanding of wide-orbit planets. This ... More

Identifying topological edge states in 2D optical lattices using light scatteringSep 10 2012Feb 11 2013We recently proposed in a Letter [Physical Review Letters 108 255303] a novel scheme to detect topological edge states in an optical lattice, based on a generalization of Bragg spectroscopy. The scope of the present article is to provide a more detailed ... More

Super-resolution of near-colliding point sourcesApr 19 2019We consider the problem of stable recovery of sparse signals of the form $$F(x)=\sum_{j=1}^d a_j\delta(x-x_j),\quad x_j\in\mathbb{R},\;a_j\in\mathbb{C}, $$ from their spectral measurements, known in a bandwidth $\Omega$ with absolute error not exceeding ... More