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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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Imaging Cool Giant Planets in Reflected Light: Science Investigations and Synergy with Habitable PlanetsMar 22 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

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

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

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

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

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

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 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

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

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

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

Buneman instability in a magnetized current-carrying plasma with velocity shearApr 28 2011May 02 2011Buneman instability is often driven in magnetic reconnection. Understanding how velocity shear in the beams driving the Buneman instability affects the growth and saturation of waves is relevant to turbulence, heating, and diffusion in magnetic reconnection. ... 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

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

The Palm measure and the Voronoi tessellation for the Ginibre processOct 07 2006Jan 14 2010We prove that the Palm measure of the Ginibre process is obtained by removing a Gaussian distributed point from the process and adding the origin. We obtain also precise formulas describing the law of the typical cell of Ginibre--Voronoi tessellation. ... More

Optical Manipulation of Magnetic Vortex Visualized in situ by 4D Electron MicroscopyDec 20 2017Understanding the fundamental dynamics of topological vortex and antivortex naturally formed in micro/nanoscale ferromagnetic building blocks under external perturbations is crucial to magnetic vortex based information processing and spintronic devices. ... More

Emergence of the persistent spin helix in semiconductor quantum wellsMar 26 2009Mar 28 2009According to Noethers theorem, for every symmetry in nature there is a corresponding conservation law. For example, invariance with respect to spatial translation corresponds to conservation of momentum. In another well-known example, invariance with ... 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

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

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

Lattice Dynamics and Melting of a Nonequilibrium PatternOct 14 2002Apr 17 2003We present a new description of nonequilibrium square patterns as a harmonically coupled crystal lattice. In a vertically oscillating granular layer, different transverse normal modes of the granular square-lattice pattern are observed for different driving ... 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

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

Magnetic ordering and magnetodielectric phenomena in CoSeO$_4$Mar 19 2010CoSeO$_4$ has a structure consisting of edge-sharing chains of Co$^{2+}$ octahedra which are held together by SeO$_4^{2-}$ tetrahedra via shared oxygen atoms at the edges of the octahedra. DC magnetization measurements indicate a transition to an ordered ... More

The Stabilization of Superconductivity by Magnetic Field in Out-of-Equilibrium NanowiresFeb 10 2010Aug 02 2010A systematic study has been carried out on the previously reported "magnetic-field-induced superconductivity" of Zn nanowires. By varying parameters such as magnetic field orientation and wire length, the results provide evidence that the phenomenon is ... 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

Quantitative Comparison of Open-Source Data for Fine-Grain Mapping of Land UseNov 09 2017This paper performs a quantitative comparison of open-source data available on the Internet for the fine-grain mapping of land use. Three points of interest (POI) data sources--Google Places, Bing Maps, and the Yellow Pages--and one volunteered geographic ... 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

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

Phase Bubbles and Spatiotemporal Chaos in Granular PatternsAug 31 2001We use inelastic hard sphere molecular dynamics simulations and laboratory experiments to study patterns in vertically oscillated granular layers. The simulations and experiments reveal that {\em phase bubbles} spontaneously nucleate in the patterns when ... 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

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

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

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

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

Symmetry Breaking of the Persistent Spin Helix in Quantum TransportJan 17 2018We exploit the high-symmetry spin state obtained for equal Rashba and linear Dresselhaus interactions to derive a closed-form expression for the weak localization magnetoconductivity -- the paradigmatic signature of spin-orbit coupling in quantum transport. ... More

Kepler Data Validation II -- Transit Model Fitting and Multiple-Planet SearchDec 01 2018This paper discusses the transit model fitting and multiple-planet search algorithms and performance of the Kepler Science Data Processing Pipeline, developed by the Kepler Science Operations Center (SOC). Threshold Crossing Events (TCEs), which are transit ... More

The Mapping Class Group acts reducibly on SU(n)-character varietiesSep 06 2005Sep 22 2005When $G$ is a connected compact Lie group, and $\pi$ is a closed surface group, then $Hom(\pi,G)$ contains an open dense $Out(\pi)$-invariant subset which is a smooth symplectic manifold. This symplectic structure is $Out(\pi)$-invariant and therefore ... 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

State Sum Invariants of Three Manifolds from Spherical Multi-fusion CategoriesFeb 23 2017We define a family of quantum invariants of closed oriented $3$-manifolds using spherical multi-fusion categories. The state sum nature of this invariant leads directly to $(2+1)$-dimensional topological quantum field theories ($\text{TQFT}$s), which ... 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

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

Eros 2 proper motion survey for halo white dwarfsAug 24 2000Since 1996 EROS 2 has surveyed 440 square degrees at high Galactic latitude in order to search for high proper motion stars in the Solar neighbourhood. We present here the analysis of 250 square degrees for which we have three years of data. No object ... More

The Robustness of Cosmological Hydrodynamic Simulation Predictions to Changes in Numerics and Cooling PhysicsOct 30 2018We test and improve the numerical schemes in our smoothed particle hydrodynamics (SPH) code for cosmological simulations, including the pressure-entropy formulation (PESPH), a time-dependent artificial viscosity, a refined timestep criterion, and metal-line ... More

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

State-selective intersystem crossing in nitrogen-vacancy centersDec 16 2014Mar 03 2015The intersystem crossing (ISC) is an important process in many solid-state atomlike impurities. For example, it allows the electronic spin state of the nitrogen-vacancy (NV) center in diamond to be initialized and read out using optical fields at ambient ... More

Surfing at the wave fronts: the bidirectional movement of cargo particles driven by molecular motorsMar 18 2008The collective behavior of molecular motor proteins have been investigated in the literature using models to describe the long-time dynamics of a unidimensional continuum motor distribution. Here, we consider the phenomena related to the transport of ... More

Quantum interference of single photons from remote nitrogen-vacancy centers in diamondDec 16 2011Apr 11 2012We demonstrate quantum interference between indistinguishable photons emitted by two nitrogen-vacancy (NV) centers in distinct diamond samples separated by two meters. Macroscopic solid immersion lenses are used to enhance photon collection efficiency. ... More

Affine differential geometry and affine rotation surfaces: algebraic surfaces invariant under non-Euclidean affine rotationsJun 22 2018Affine rotation surfaces are a generalization of the well-known surfaces of revolution. Affine rotation surfaces arise naturally within the framework of affine differential geometry, a field started by Blaschke in the first decades of the past century. ... 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

X-ray Emission from Charge Exchange in the Cygnus Loop SNRFeb 17 2015The Cygnus Loop has been the focus of substantial debate concerning the contribution of charge exchange (CX) to supernova remnant (SNR) X-ray emission. We take advantage of a distinct feature of CX, enhanced K{\alpha} forbidden line emission, and employ ... 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

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

Mixing Flows on Moduli Spaces of Flat Bundles over SurfacesJul 11 2017Jul 31 2017We extend Teichmueller dynamics to a flow on the total space of a flat bundle of deformation spaces of representations of the fundamental group of a fixed surface S in a Lie group G. The resulting dynamical system is a continuous version of the action ... 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

The complement of the Bowditch space in the SL(2,C) character varietyMar 17 2006Let ${\mathcal X}$ be the space of type-preserving $\SL(2,C)$ characters of the punctured torus $T$. The Bowditch space ${\mathcal X}_{BQ}$ is the largest open subset of ${\mathcal X}$ on which the mapping class group acts properly discontinuously, this ... More

Fine-Grained Land Use Classification at the City Scale Using Ground-Level ImagesFeb 07 2018We perform fine-grained land use mapping at the city scale using ground-level images. Mapping land use is considerably more difficult than mapping land cover and is generally not possible using overhead imagery as it requires close-up views and seeing ... 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

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

Only accessible information is useful: insights from gradient-mediated patterningJan 29 2015May 07 2015Information theory is gaining popularity as a tool to characterize performance of biological systems. However, information is commonly quantified without reference to whether or how a system could extract and use it; as a result, information-theoretic ... More

The non-magnetic collapsed tetragonal phase of CaFe2As2 and superconductivity in the iron pnictidesOct 23 2013The relationship between antiferromagnetic spin fluctuations and superconductivity has become a central topic of research in studies of superconductivity in the iron pnictides. We present unambiguous evidence of the absence of magnetic fluctuations in ... More

Suppression of antiferromagnetic spin fluctuations in the collapsed tetragonal phase of CaFe2As2Dec 21 2008Inelastic neutron scattering measurements of CaFe2As2 under applied hydrostatic pressure show that the antiferromagnetic spin fluctuations observed in the ambient pressure, paramagnetic, tetragonal (T) phase are strongly suppressed, if not absent, in ... 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

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

Stellar Turbulent Convection: A Selfconsistent ModelAug 30 1996We present a selfconsistent model for stellar turbulent convection which is similar in spirit to the CM model (Canuto \& Mazzitelli 1991) since it accounts for the full spectrum of the turbulent eddies rather than only one eddy, as done in the mixing ... More

Geometry of error amplification in solving Prony system with near-colliding nodesJan 15 2017Jun 14 2018We 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 $m_k(F)$, $k=0,1,\ldots,2d-1$, are ... 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

Magnetic Field Tuned Quantum Phase Transition in the Insulating Regime of Ultrathin Amorphous Bi FilmsJan 30 2011A surprisingly strong variation of resistance with perpendicular magnetic field, and a peak in the resistance vs. field, R(B) has been found in insulating films of a sequence of homogeneous, quench-condensed films of amorphous Bi undergoing a thickness-tuned ... More

An Infrared Census Of Dust In Nearby Galaxies With Spitzer (DUSTiNGS): V. The Period-luminosity Relation For Dusty Metal-Poor AGB StarsFeb 20 2019Feb 22 2019The survey for DUST In Nearby Galaxies with Spitzer (DUSTiNGS) has identified hundreds of candidate dust-producing Asymptotic Giant Branch (AGB) stars in several nearby metal-poor galaxies. We have obtained multi-epoch follow-up observations for these ... More

Coexistence of Half-Metallic Itinerant Ferromagnetism with Local-Moment Antiferromagnetism in Ba{0.60}K{0.40}Mn2As2Jun 29 2013Jul 22 2013Magnetization, nuclear magnetic resonance, high-resolution x-ray diffraction and magnetic field-dependent neutron diffraction measurements reveal a novel magnetic ground state of Ba{0.60}K{0.40}Mn2As2 in which itinerant ferromagnetism (FM) below a Curie ... More

Hedgehog spin-vortex crystal stabilized in a hole-doped iron-based superconductorJun 04 2017Jul 02 2017Magnetism is widely considered to be a key ingredient of unconventional superconductivity. In contrast to cuprate high-temperature superconductors, antiferromagnetism in Fe-based superconductors (FeSCs) is characterized by a pair of magnetic propagation ... 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

A large-scale regularity theory for the Monge-Ampere equation with rough data and application to the optimal matching problemAug 28 2018The aim of this paper is to obtain quantitative bounds for solutions to the optimal matching problem in dimension two. These bounds show that up to a logarithmically divergent shift, the optimal transport maps are close to be the identity at every scale. ... More

Quantitative estimates for bending energies and applications to non-local variational problemsJan 04 2018Sep 14 2018We discuss a variational model, given by a weighted sum of perimeter, bending and Riesz interaction energies, that could be considered as a toy model for charged elastic drops. The different contributions have competing preferences for strongly localized ... More

Indirect Magnetic-Field-Tuned Superconductor-Insulator Transitions and Weak Localization of Bosons of Quasi-Two Dimensional Metal FilmsFeb 08 2010Magnetic field and electrostatically tuned superconductor-insulator (SI) transitions of ultrathin metal films with levels of disorder that place them near the disorder-tuned SI transition appear to be direct, continuous quantum phase transitions. When ... More

New Universality Class at the Magnetic Field Tuned Superconductor-Insulator Transition?Aug 12 1998The superconductor-insulator transition in ultrathin films of amorphous Bi was tuned by an applied magnetic field. A finite size scaling analysis has been carried out to determine the critical exponent product vz=0.7 for five films of different thicknesses ... 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

Universal quantum computation with weakly integral anyonsJan 28 2014Feb 21 2014Harnessing non-abelian statistics of anyons to perform quantum computational tasks is getting closer to reality. While the existence of universal anyons by braiding alone such as the Fibonacci anyon is theoretically a possibility, accessible anyons with ... More

Improving Trajectory Optimization using a Roadmap FrameworkNov 05 2018We present an evaluation of several representative sampling-based and optimization-based motion planners, and then introduce an integrated motion planning system which incorporates recent advances in trajectory optimization into a sparse roadmap framework. ... More