Results for "Dániel Apai"

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Mapping Directly Imaged Giant ExoplanetsOct 25 2012With the increasing number of directly imaged giant exoplanets the current atmosphere models are often not capable of fully explaining the spectra and luminosity of the sources. A particularly challenging component of the atmosphere models is the formation ... More
ACCESS: Ground-based Optical Transmission Spectroscopy of the Hot Jupiter WASP-4bDec 18 2018We present an optical transmission spectrum of the atmosphere of WASP-4b obtained through observations of four transits with Magellan/IMACS. Using a Bayesian approach to atmospheric retrieval, we find no evidence for scattering or absorption features ... More
PHENIX results on Lévy analysis of Bose-Einstein correlation functionsOct 17 2016The nature of the quark-hadron phase transition can be investigated through analyzing the space-time structure of the hadron emission source. For this, the Bose-Einstein or HBT correlations of identified charged particles are among the best observables. ... More
Tractable hypergraph properties for constraint satisfaction and conjunctive queriesNov 04 2009Dec 06 2011An important question in the study of constraint satisfaction problems (CSP) is understanding how the graph or hypergraph describing the incidence structure of the constraints influences the complexity of the problem. For binary CSP instances (i.e., where ... More
Quantum $f$-divergence preserving maps on positive semidefinite operators acting on finite dimensional Hilbert spacesFeb 22 2016Mar 18 2016We determine the structure of all bijections on the cone of positive semidefinite operators which preserve the quantum $f$-divergence for an arbitrary strictly convex function $f$ defined on the positive halfline. It turns out that any such transformation ... More
Characterizations of centrality by local convexity of certain functions on $C^*$-algebrasSep 11 2017Feb 15 2018We provide a function class which is useful to distinguish central and non-central elements of a $C^*$-algebra in the following sense: for each element $f$ of this function class, a self-adjoint element $a$ of a $C^*$-algebra is central if and only if ... More
The Transit Light Source Effect: False Spectral Features and Incorrect Densities for M-dwarf Transiting PlanetsNov 15 2017Jan 24 2018Transmission spectra are differential measurements that utilize stellar illumination to probe transiting exoplanet atmospheres. Any spectral difference between the illuminating light source and the disk-integrated stellar spectrum due to starspots and ... More
Magellan Adaptive Optics Imaging of PDS 70: Measuring the Mass Accretion Rate of a Young Giant Planet within a Gapped DiskJul 27 2018PDS 70b is a recently discovered and directly imaged exoplanet within the wide ($\gtrsim$40 au) cavity around PDS 70 (Keppler et al. 2018, M\"uller et al. 2018). Ongoing accretion onto the central star suggests that accretion onto PDS 70b may also be ... More
The Transit Light Source Effect II: The Impact of Stellar Heterogeneity on Transmission Spectra of Planets Orbiting Broadly Sun-like StarsDec 14 2018Transmission spectra probe exoplanetary atmospheres, but they can also be strongly affected by heterogeneities in host star photospheres through the transit light source effect. Here we build upon our recent study of the effects of unocculted spots and ... More
Stellar-Mass-Dependent Disk Structure in Coeval Planet-Forming DisksJul 21 2010Previous studies suggest that the planet-forming disks around very-low-mass stars/brown dwarfs may be flatter than those around more massive stars, in contrast to model predictions of larger scale heights for gas-disks around lower-mass stars. We conducted ... More
PHENIX results on Bose-Einstein correlation functionsFeb 15 2016Measurement of Bose-Einstein or HBT correlations of identified charged particles provide insight into the space-time structure of particle emitting sources in heavy-ion collisions. In this paper we present the latest results from the RHIC PHENIX experiment ... More
Applications of an intersection formula to dual conesApr 03 2017Oct 19 2017We give a succinct proof of a duality theorem obtained by R\'ev\'esz in 1991 which concerns extremal quantities related to trigonomertic polynomials. The key tool of our new proof is an intersection formula on dual cones in real Banach spaces. We show ... More
A class of characterizations of central elements in $C^*$-algebrasAug 18 2016Let $\mathcal{A}$ be a unital $C^*$-algebra. We introduce a quite large function class $\mathcal{F}$ (which includes the power function $x \mapsto x^p$ for any $p \in (1, \infty)$), and show that any function $f \in \mathcal{F}$ provides a characterization ... More
Connections between centrality and local monotonicity of certain functions on $C^*$-algebrasAug 18 2016Apr 12 2017We introduce a quite large class of functions (including the exponential function and the power functions with exponent greater than one), and show that for any element $f$ of this function class, a self-adjoint element $a$ of a $C^*$-algebra is central ... More
A note on the Turán number of a Berge odd cycleMar 03 2019In this note we obtain upper bounds on the number of hyperedges in 3-uniform hypergraphs not containing a Berge cycle of given odd length. We improve the bound given by F\"uredi and \"Ozkahya. The result follows from a more general theorem. We also obtain ... More
Maps on probability measures preserving certain distances --- a survey and some new resultsFeb 09 2018Mar 19 2018Borel probability measures living on metric spaces are fundamental mathematical objects. There are several meaningful distance functions that make the collection of the probability measures living on a certain space a metric space. We are interested in ... More
Connections between centrality and local monotonicity of certain functions on $C^*$-algebrasAug 18 2016Nov 10 2016In 1955, Ogasawara showed that a $C^*$-algebra $\mathcal{A}$ is commutative if and only if the square function is monotone on the positive cone of $\mathcal{A}.$ It was observed later by Pedersen that the above statement remains true for any power function ... More
Maps on quantum states preserving Bregman and Jensen divergencesJan 25 2016Jul 01 2016We describe the structure of the bijective transformations on the set of density operators which preserve the Bregman $f$-divergence for an arbitrary differentiable strictly convex function $f.$ Furthermore, we determine the preservers of the Jensen $f$-divergence ... More
On a problem of Bauschke and BorweinDec 05 2014Aug 03 2015Consider a differentiable convex function $f: \mathbb{R}^n \supset \mathrm{dom} f \rightarrow \mathbb{R}.$ The induced spectral function $F$ is given by $F=f \circ \lambda,$ where $\lambda: \mathbf{M}_n^{sa} \rightarrow \mathbb{R}^{n}$ is the eigenvalue ... More
Jointly convex quantum Jensen divergencesDec 14 2017Mar 08 2018We investigate the quantum Jensen divergences from the viewpoint of joint convexity. It turns out that the set of the functions which generate jointly convex quantum Jensen divergences on positive matrices coincides with the Matrix Entropy Class which ... More
A Physical Model-based Correction for Charge Traps in the Hubble Space Telescope's Wide Field Camera 3 Near-IR Detector and Applications to Transiting Exoplanets and Brown DwarfsMar 03 2017Mar 16 2017The Hubble Space Telescope (HST) Wide Field Camera 3 (WFC3) near-IR channel is extensively used in time-resolved observations, especially for transiting exoplanet spectroscopy and brown dwarf and directly imaged exoplanet rotational phase mapping. The ... More
Retrieval of planetary and stellar properties in transmission spectroscopy with AuraAug 29 2018Transmission spectroscopy provides a powerful probe of the atmospheric properties of transiting exoplanets. To date, studies of exoplanets in transit have focused on inferring their atmospheric properties such as chemical compositions, cloud/haze properties, ... More
50+ Metrics for Calendar MiningJan 01 2016In this report we propose 50+ metrics which can be measured by organizations in order to identify improvements in various areas such as meeting efficiency, capacity planning or leadership skills, just to new a few. The notion of calendar mining is introduced ... More
Cleaning Interval GraphsMar 05 2010We investigate a special case of the Induced Subgraph Isomorphism problem, where both input graphs are interval graphs. We show the NP-hardness of this problem, and we prove fixed-parameter tractability of the problem with non-standard parameterization, ... More
Structure Theorem and Isomorphism Test for Graphs with Excluded Topological SubgraphsNov 04 2011Nov 13 2014We generalize the structure theorem of Robertson and Seymour for graphs excluding a fixed graph $H$ as a minor to graphs excluding $H$ as a topological subgraph. We prove that for a fixed $H$, every graph excluding $H$ as a topological subgraph has a ... More
Obtaining a Planar Graph by Vertex DeletionDec 29 2008In the k-Apex problem the task is to find at most k vertices whose deletion makes the given graph planar. The graphs for which there exists a solution form a minor closed class of graphs, hence by the deep results of Robertson and Seymour, there is an ... More
Observational Constraints on the Stellar Radiation Field Impinging on Transitional Disk AtmospheresSep 18 2012Mid-infrared atomic and ionic line ratios measured in spectra of pre-main sequence stars are sensitive indicators of the hardness of the radiation field impinging on the disk surface. We present a low-resolution Spitzer IRS search for [Ar II] at 6.98 ... More
Evidence Against an Edge-On Disk Around the Extrasolar Planet 2MASS 1207 b and a New Thick Cloud Explanation for its Under-LuminosityMar 09 2011(Abridged) Since the discovery of the first directly-imaged, planetary-mass object, 2MASS 1207 b, several works have sought to explain a disparity between its observed temperature and luminosity. Given its known age, distance, and spectral type, 2MASS ... More
Saturation in random graphsOct 30 2015Apr 13 2016A graph $H$ is $K_s$-saturated if it is a maximal $K_s$-free graph, i.e., $H$ contains no clique on $s$ vertices, but the addition of any missing edge creates one. The minimum number of edges in a $K_s$-saturated graph was determined over 50 years ago ... More
Domination in 3-tournamentsFeb 04 2016A 3-tournament is a complete 3-uniform hypergraph where each edge has a special vertex designated as its tail. A vertex set $X$ dominates $T$ if every vertex not in $X$ is contained in an edge whose tail is in $X$. The domination number of $T$ is the ... More
Path-search in the pyramid and in other graphsApr 27 2011We are given an acyclic directed graph with one source, and a subset of its edges which contains exactly one outgoing edge for every non-sink vertex. These edges determine a unique path from the source to a sink. We can think of it as a switch in every ... More
Rounds in a combinatorial search problemNov 30 2016We consider the following combinatorial search problem: we are given some excellent elements of $[n]$ and we should find at least one, asking questions of the following type: "Is there an excellent element in $A \subset [n]$?". G.O.H. Katona proved sharp ... More
On the joint convexity of the Bregman divergence of matricesMay 30 2014Apr 23 2015We characterize the functions for which the corresponding Bregman divergence is jointly convex on matrices. As an application of this characterization, we derive a sharp inequality for the quantum Tsallis entropy of a tripartite state, which can be considered ... More
Direct Imaging Discovery of a Jovian Exoplanet Within a Triple Star SystemJul 08 2016Direct imaging allows for the detection and characterization of exoplanets via their thermal emission. We report the discovery via imaging of a young Jovian planet in a triple star system and characterize its atmospheric properties through near-infrared ... More
Complexity of counting subgraphs: only the boundedness of the vertex-cover number countsJul 10 2014For a class $\mathcal{H}$ of graphs, #Sub$(\mathcal{H})$ is the counting problem that, given a graph $H\in \mathcal{H}$ and an arbitrary graph $G$, asks for the number of subgraphs of $G$ isomorphic to $H$. It is known that if $\mathcal{H}$ has bounded ... More
Interval Deletion is Fixed-Parameter TractableNov 26 2012May 06 2014We study the minimum \emph{interval deletion} problem, which asks for the removal of a set of at most $k$ vertices to make a graph of $n$ vertices into an interval graph. We present a parameterized algorithm of runtime $10^k \cdot n^{O(1)}$ for this problem, ... More
Prime congruences of idempotent semirings and a Nullstellensatz for tropical polynomialsAug 17 2014Sep 01 2015A new definition of prime congruences in additively idempotent semirings is given using twisted products. This class turns out to exhibit some analogous properties to the prime ideals of commutative rings. In order to establish a good notion of radical ... More
Everything you always wanted to know about the parameterized complexity of Subgraph Isomorphism (but were afraid to ask)Jul 08 2013Aug 25 2013Given two graphs $H$ and $G$, the Subgraph Isomorphism problem asks if $H$ is isomorphic to a subgraph of $G$. While NP-hard in general, algorithms exist for various parameterized versions of the problem: for example, the problem can be solved (1) in ... More
Optimal parameterized algorithms for planar facility location problems using Voronoi diagramsApr 21 2015We study a general family of facility location problems defined on planar graphs and on the 2-dimensional plane. In these problems, a subset of $k$ objects has to be selected, satisfying certain packing (disjointness) and covering constraints. Our main ... More
Subexponential parameterized algorithms for graphs of polynomial growthOct 25 2016We show that for a number of parameterized problems for which only $2^{O(k)} n^{O(1)}$ time algorithms are known on general graphs, subexponential parameterized algorithms with running time $2^{O(k^{1-\frac{1}{1+\delta}} \log^2 k)} n^{O(1)}$ are possible ... More
Triangle-different Hamiltonian pathsAug 18 2016Oct 11 2016Let $G$ be a fixed graph. Two paths of length $n-1$ on $n$ vertices (Hamiltonian paths) are $G$-different if there is a subgraph isomorphic to $G$ in their union. In this paper we prove that the maximal number of pairwise triangle-different Hamiltonian ... More
Forbidden subposet problems with size restrictionsAug 23 2016Upper bounds to the size of a family of subsets of an n-element set that avoids certain configurations are proved. These forbidden configurations can be described by inclusion patterns and some sets having the same size. Our results are closely related ... More
A faster FPT algorithm for Bipartite ContractionMay 13 2013Sep 04 2013The \textsc{Bipartite Contraction} problem is to decide, given a graph $G$ and a parameter $k$, whether we can can obtain a bipartite graph from $G$ by at most $k$ edge contractions. The fixed-parameter tractability of the problem was shown by [Heggernes ... More
Fundamental Analysis of a Developer Support Chat Log for Identifying Process Improvement OpportunitiesMar 18 2015In this report analysis of a support chat log of a development team is shown. Developer support chat is used to provide internal support to other development teams. The report shows how a fundamental data analysis helped to identify gaps and action items ... More
Random walk hierarchy measure: What is more hierarchical, a chain, a tree or a star?Aug 31 2015Signs of hierarchy are prevalent in a wide range of systems in nature and society. One of the key problems is quantifying the importance of hierarchical organisation in the structure of the network representing the interactions or connections between ... More
An exact characterization of tractable demand patterns for maximum disjoint path problemsNov 04 2014We study the following general disjoint paths problem: given a supply graph $G$, a set $T\subseteq V(G)$ of terminals, a demand graph $H$ on the vertices $T$, and an integer $k$, the task is to find a set of $k$ pairwise vertex-disjoint valid paths, where ... More
Fixed-parameter tractability of multicut parameterized by the size of the cutsetOct 18 2010Sep 03 2013Given an undirected graph $G$, a collection $\{(s_1,t_1),..., (s_k,t_k)\}$ of pairs of vertices, and an integer $p$, the Edge Multicut problem ask if there is a set $S$ of at most $p$ edges such that the removal of $S$ disconnects every $s_i$ from the ... More
Orientations of graphs with uncountable chromatic numberAug 24 2016A graph (digraph) has uncountable chromatic number if its vertices cannot be covered by countably many independent (acyclic) sets. Our aim is to investigate digraphs with uncountable chromatic number and orientations of undirected graphs with uncountable ... More
Toric quiver cellsSep 12 2016It is shown that up to dimension four, the toric ideal of a quiver polytope is generated in degree two, with the only exception of the four-dimensional Birkhoff polytope. As a consequence, B{\o}gvad's conjecture holds for quiver polytopes of dimension ... More
Ladder system uniformization on trees I & IIJun 11 2018Jan 04 2019Given a tree $T$ of height $\omega_1$, we say that a ladder system colouring $(f_\alpha)_{\alpha\in \lim\omega_1}$ has a $T$-uniformization if there is a function $\varphi$ defined on a subtree $S$ of $T$ so that for any $s\in S_\alpha$ of limit height ... More
Prime congruences of idempotent semirings and a Nullstellensatz for tropical polynomialsAug 17 2014Sep 13 2017A new definition of prime congruences in additively idempotent semirings is given using twisted products. This class turns out to exhibit some analogous properties to the prime ideals of commutative rings. In order to establish a good notion of radical ... More
Density of 4-edge paths in graphs with fixed edge densityJan 06 2016We investigate the number of 4-edge paths in graphs with a fixed number of vertices and edges. An asymptotically sharp upper bound is given to this quantity. The extremal construction is the quasi-star or the quasi-clique graph, depending on the edge ... More
Kernelization of Packing ProblemsDec 07 2018Kernelization algorithms are polynomial-time reductions from a problem to itself that guarantee their output to have a size not exceeding some bound. For example, d-Set Matching for integers d>2 is the problem of finding a matching of size at least k ... More
Chordal Editing is Fixed-Parameter TractableMay 30 2014Graph modification problems are typically asked as follows: is there a small set of operations that transforms a given graph to have a certain property. The most commonly considered operations include vertex deletion, edge deletion, and edge addition; ... More
Toric quiver cellsSep 12 2016Jul 03 2017It is shown that up to dimension four, the toric ideal of a quiver polytope is generated in degree two, with the only exception of the four-dimensional Birkhoff polytope. As a consequence, B{\o}gvad's conjecture holds for quiver polytopes of dimension ... More
Extremal results for Berge-hypergraphsMay 29 2015Let $G$ be a graph and $\mathcal{H}$ be a hypergraph both on the same vertex set. We say that a hypergraph $\mathcal{H}$ is a \emph{Berge}-$G$ if there is a bijection $f : E(G) \rightarrow E(\mathcal{H})$ such that for $e \in E(G)$ we have $e \subset ... More
On algebraic endomorphisms of the Einstein gyrogroupJun 20 2015We describe the structure of all continuous algebraic endomorphisms of the open unit ball $\mathbf{B}$ of $\mathbb{R}^3$ equipped with the Einstein velocity addition. We show that any nonzero such transformation originates from an orthogonal linear transformation ... More
Peeling and Nibbling the Cactus: Subexponential-Time Algorithms for Counting Triangulations and Related ProblemsMar 23 2016Given a set of $n$ points $S$ in the plane, a triangulation $T$ of $S$ is a maximal set of non-crossing segments with endpoints in $S$. We present an algorithm that computes the number of triangulations on a given set of $n$ points in time $n^{(11+ o(1))\sqrt{n} ... More
Uncountable strongly surjective linear ordersJun 30 2017Jan 30 2018A linear order $L$ is strongly surjective if $L$ can be mapped onto any of its suborders in an order preserving way. We prove various results on the existence and non-existence of uncountable strongly surjective linear orders answering questions of Camerlo, ... More
Continuous Jordan triple endomorphisms of $\mathbb{P}_2$Jun 20 2015We describe the structure of all continuous Jordan triple endomorphisms of the set $\mathbb{P}_2$ of all positive definite $2\times 2$ matrices thus completing a recent result of ours. We also mention an application concerning sorts of surjective generalized ... More
A candidate planetary-mass object with a photoevaporating disk in OrionNov 29 2016In this work, we report the discovery of a candidate planetary-mass object with a photoevaporating protoplanetary disk, Proplyd 133-353, which is near the massive star $\theta^{1}$ Ori C at the center of the Orion Nebula Cluster (ONC). The object was ... More
t-wise Berge and t-heavy hypergraphsFeb 08 2019In many proofs concerning extremal parameters of Berge hypergraphs one starts with analyzing that part of that shadow graph which is contained in many hyperedges. Capturing this phenomenon we introduce two new types of hypergraphs. A hypergraph $\mathcal{H}$ ... More
Cloud Structure of the Nearest Brown Dwarfs II: High-amplitude variability for Luhman 16 A and B in and out of the 0.99 micron FeH featureSep 21 2015The re-emergence of the 0.99 $\mu$m FeH feature in brown dwarfs of early- to mid-T spectral type has been suggested as evidence for cloud disruption where flux from deep, hot regions below the Fe cloud deck can emerge. The same mechanism could account ... More
Stability results on vertex Turán problems in Kneser graphsApr 11 2018Apr 20 2018The vertex set of the Kneser graph $K(n,k)$ is $V = \binom{[n]}{k}$ and two vertices are adjacent if the corresponding sets are disjoint. For any graph $F$, the largest size of a vertex set $U \subseteq V$ such that $K(n,k)[U]$ is $F$-free, was recently ... More
Stability results on vertex Turán problems in Kneser graphsApr 11 2018Mar 07 2019The vertex set of the Kneser graph $K(n,k)$ is $V = \binom{[n]}{k}$ and two vertices are adjacent if the corresponding sets are disjoint. For any graph $F$, the largest size of a vertex set $U \subseteq V$ such that $K(n,k)[U]$ is $F$-free, was recently ... More
On the maximum number of copies of H in graphs with given size and orderOct 01 2018We study the maximum number $ex(n,e,H)$ of copies of a graph $H$ in graphs with given number of vertices and edges. We show that for any fixed graph $H$, $ex(n,e,H)$ is asymptotically realized by the quasi-clique provided that the edge density is sufficiently ... More
Fixed-parameter algorithms for minimum cost edge-connectivity augmentationApr 24 2013Aug 26 2013We consider connectivity-augmentation problems in a setting where each potential new edge has a nonnegative cost associated with it, and the task is to achieve a certain connectivity target with at most p new edges of minimum total cost. The main result ... More
Constraint satisfaction parameterized by solution sizeJun 21 2012Jan 18 2014In the constraint satisfaction problem (CSP) corresponding to a constraint language (i.e., a set of relations) $\Gamma$, the goal is to find an assignment of values to variables so that a given set of constraints specified by relations from $\Gamma$ is ... More
The method of double chains for largest families with excluded subposetsApr 24 2012For a given finite poset $P$, $La(n,P)$ denotes the largest size of a family $\mathcal{F}$ of subsets of $[n]$ not containing $P$ as a weak subposet. We exactly determine $La(n,P)$ for infinitely many $P$ posets. These posets are built from seven base ... More
Infinite combinatorics plain and simpleMay 17 2017Feb 05 2018We explore a general method based on trees of elementary submodels in order to present highly simplified proofs to numerous results in infinite combinatorics. While countable elementary submodels have been employed in such settings already, we significantly ... 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
An Increase in the Mass of Planetary Systems around Lower-Mass StarsOct 08 2015Oct 20 2015Trends in the planet population with host star mass provide an avenue to constrain planet formation theories. We derive the planet radius distribution function for Kepler stars of different spectral types, sampling a range in host star masses. We find ... More
A stellar-mass-dependent drop in planet occurrence ratesJun 28 2014Jan 11 2015The Kepler Spacecraft has discovered a large number of planets up to one-year periods and down to terrestrial sizes. While the majority of the target stars are main-sequence dwarfs of spectral type F, G, and K, Kepler covers stars with effective temperature ... More
Disks around Brown Dwarfs and Cool StarsFeb 10 2007We review the current picture of disks around cool stars and brown dwarfs, including disk fractions, mass estimates, disk structure and dispersal, accretion, dust composition, and the debris disk phase. We discuss these in the framework of recent planet ... More
Generalizations of the Tree Packing ConjectureApr 04 2011Oct 21 2011The Gy\'arf\'as tree packing conjecture asserts that any set of trees with $2,3, ..., k$ vertices has an (edge-disjoint) packing into the complete graph on $k$ vertices. Gy\'arf\'as and Lehel proved that the conjecture holds in some special cases. We ... More
Finding small separators in linear time via treewidth reductionOct 21 2011We present a method for reducing the treewidth of a graph while preserving all of its minimal $s-t$ separators up to a certain fixed size $k$. This technique allows us to solve $s-t$ Cut and Multicut problems with various additional restrictions (e.g., ... More
Known Algorithms on Graphs of Bounded Treewidth are Probably OptimalJul 30 2010We obtain a number of lower bounds on the running time of algorithms solving problems on graphs of bounded treewidth. We prove the results under the Strong Exponential Time Hypothesis of Impagliazzo and Paturi. In particular, assuming that SAT cannot ... More
On subexponential parameterized algorithms for Steiner Tree and Directed Subset TSP on planar graphsJul 07 2017There are numerous examples of the so-called square root phenomenon in the field of parameterized algorithms: many of the most fundamental graph problems, parameterized by some natural parameter $k$, become significantly simpler when restricted to planar ... More
Maps on positive definite matrices preserving Bregman and Jensen divergencesSep 08 2015In this paper we determine those bijective maps of the set of all positive definite $n\times n$ complex matrices which preserve a given Bregman divergence corresponding to a differentiable convex function that satisfies certain conditions. We cover the ... More
$Extrasolar~Storms$: Pressure-dependent Changes In Light Curve Phase In Brown Dwarfs From Simultaneous $Hubble$ and $Spitzer$ ObservationsMay 09 2016We present $Spitzer$/IRAC Ch1 and Ch2 monitoring of six brown dwarfs during 8 different epochs over the course of 20 months. For four brown dwarfs, we also obtained simulataneous $HST$/WFC3 G141 Grism spectra during two epochs and derived light curves ... More
Parallaxes and Infrared Photometry of three Y0 dwarfsMar 30 2017We have followed up the three Y0 dwarfs WISEPA J041022.71+150248.5, WISEPA J173835.53+273258.9 and WISEPC J205628.90+145953.3 using the UKIRT/WFCAM telescope/instruments. We find parallaxes that are more consistent and accurate than previously published ... More
ACCESS I: An Optical Transmission Spectrum of GJ 1214b Reveals a Heterogeneous Stellar PhotosphereDec 01 2016GJ 1214b is the most studied sub-Neptune exoplanet to date. Recent measurements have shown its near-infrared transmission spectrum to be flat, pointing to a high-altitude opacity source in the exoplanet's atmosphere, either equilibrium condensate clouds ... More
Decomposing random graphs into few cycles and edgesApr 12 2014Nov 26 2014Over 50 years ago, Erd\H{o}s and Gallai conjectured that the edges of every graph on $n$ vertices can be decomposed into $O(n)$ cycles and edges. Among other results, Conlon, Fox and Sudakov recently proved that this holds for the random graph $G(n,p)$ ... More
Fixed-parameter Approximability of Boolean MinCSPsJan 19 2016The minimum unsatisfiability version of a constraint satisfaction problem asks for an assignment where the number of unsatisfied constraints is minimum possible, or equivalently, asks for a minimum-size set of constraints whose deletion makes the instance ... More
Rooted grid minorsJul 30 2013Intuitively, a tangle of large order in a graph is a highly-connected part of the graph, and it is known that if a graph has a tangle of large order then it has a large grid minor. Here we show that for any k, if G has a tangle of large order and Z is ... More
Treewidth reduction for constrained separation and bipartization problemsFeb 22 2009Feb 03 2010We present a method for reducing the treewidth of a graph while preserving all the minimal $s-t$ separators. This technique turns out to be very useful for establishing the fixed-parameter tractability of constrained separation and bipartization problems. ... More
Near threshold laser-modified proton emission in nuclear photoeffectMar 06 2013Jun 25 2013The change of the probability of proton emission in nuclear photoeffect due to an intense coherent (laser) field is discussed near the threshold, where the hindering effect of the Coulomb field of the remainder nucleus is essential. The ratio of laser-assisted ... More
Properties of minimally $t$-tough graphsApr 10 2016A graph $G$ is minimally $t$-tough if the toughness of $G$ is $t$ and the deletion of any edge from $G$ decreases the toughness. Kriesell conjectured that for every minimally $1$-tough graph the minimum degree $\delta(G)=2$. We show that in every minimally ... More
Optimal parameter estimation of Pauli channelsNov 20 2015The optimal measurement configuration, i.e., the optimal input quantum state and measurement in the form of a POVM with two elements, is investigated in this paper for qubit and generalized Pauli channels. The channel directions are defined as the contracting ... More
$\mathcal{O}(k)$-robust spanners in one dimensionMar 23 2018A geometric $t$-spanner on a set of points in Euclidean space is a graph containing for every pair of points a path of length at most $t$ times the Euclidean distance between the points. Informally, a spanner is $\mathcal{O}(k)$-robust if deleting $k$ ... More
Towards scalable pattern-based optimization for dense linear algebraMay 11 2018Linear algebraic expressions are the essence of many computationally intensive problems, including scientific simulations and machine learning applications. However, translating high-level formulations of these expressions to efficient machine-level representations ... More
Union-intersecting set systemsMar 01 2014Three intersection theorems are proved. First, we determine the size of the largest set system, where the system of the pairwise unions is l-intersecting. Then we investigate set systems where the union of any s sets intersect the union of any t sets. ... More
The LEECH Exoplanet Imaging Survey: Limits on Planet Occurrence Rates Under Conservative AssumptionsOct 24 2018Dec 06 2018We present the results of the largest $L^{\prime}$ ($3.8~\mu$m) direct imaging survey for exoplanets to date, the Large Binocular Telescope Interferometer (LBTI) Exozodi Exoplanet Common Hunt (LEECH). We observed 98 stars with spectral types from B to ... More
Disorder is good for you: The influence of local disorder on strain localization and ductility of strain softening materialsApr 06 2016We formulate a generic concept model for the deformation of a locally disordered, macroscopically homogeneous material which undergoes irreversible strain softening during plastic deformation. We investigate the influence of the degree of microstructural ... More
A discrete isodiametric result: the Erdős-Ko-Rado theorem for multisetsDec 05 2012Mar 09 2014There are many generalizations of the Erd\H{o}s-Ko-Rado theorem. We give new results (and problems) concerning families of $t$-intersecting $k$-element multisets of an $n$-set and point out connections to coding theory and classical geometry. We establish ... More
Pauli channel tomography with unknown channel directionsApr 16 2013In this paper we estimate the parameters of the qubit Pauli channel using the channel matrix formalism. The main novelty of this work is that we do not assume the directions of the Pauli channel to be known, but they are determined through the tomography ... More
An upper bound on the size of diamond-free families of setsJan 24 2016Let $La(n,P)$ be the maximum size of a family of subsets of $[n]=\{1,2,...,n\}$ not containing $P$ as a (weak) subposet. The diamond poset, denoted $B_{2}$, is defined on four elements $x,y,z,w$ with the relations $x<y,z$ and $y,z<w$. $La(n,P)$ has been ... More
Laser-assisted nuclear photoeffect reexaminedMar 06 2013The S-matrix element and the cross section of the laser-assisted nuclear photoeffect are recalculated in a gauge invariant manner taking into account the effect of the Coulomb field of the remainder nucleus. The \gamma-photon energy dependence of the ... More
Effect of scattering lengths on the dynamics of a two-component Bose-Einstein condensateSep 11 2010We examine the effect of the intra- and interspecies scattering lengths on the dynamics of a two-component Bose-Einstein condensate, particularly focusing on the existence and stability of solitonic excitations. For each type of possible soliton pairs ... More
Minimizing Movement: Fixed-Parameter TractabilityMay 31 2012Nov 23 2012We study an extensive class of movement minimization problems which arise from many practical scenarios but so far have little theoretical study. In general, these problems involve planning the coordinated motion of a collection of agents (representing ... More