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A monotonic relationship between the variability of the infectious period and final size in pairwise epidemic modellingDec 16 2017Dec 24 2018For a recently derived pairwise model of network epidemics with non-Markovian recovery, we prove that under some mild technical conditions on the distribution of the infectious periods, smaller variance in the recovery time leads to higher reproduction ... More

Optimal experimental designs for inverse quadratic regression modelsSep 29 2008In this paper optimal experimental designs for inverse quadratic regression models are determined. We consider two different parameterizations of the model and investigate local optimal designs with respect to the $c$-, $D$- and $E$-criteria, which reflect ... More

Reducible means and reducible inequalitiesJul 14 2016It is well-known that if a real valued function acting on a convex set satisfies the $n$-variable Jensen inequality, for some natural number $n\geq 2$, then, for all $k\in\{1,\dots, n\}$, it fulfills the $k$-variable Jensen inequality as well. In other ... More

On the X-ray number of almost smooth convex bodies and of convex bodies of constant widthMar 27 2009The X-ray numbers of some classes of convex bodies are investigated. In particular, we give a proof of the X-ray Conjecture as well as of the Illumination Conjecture for almost smooth convex bodies of any dimension and for convex bodies of constant width ... More

Chip-firing games on Eulerian digraphs and NP-hardness of computing the rank of a divisor on a graphJul 25 2014Sep 06 2015Baker and Norine introduced a graph-theoretic analogue of the Riemann-Roch theory. A central notion in this theory is the rank of a divisor. In this paper we prove that computing the rank of a divisor on a graph is NP-hard. The determination of the rank ... More

A characterization of $n$-associative, monotone, idempotent functions on an interval that have neutral elementsSep 01 2016Oct 16 2017We investigate monotone idempotent $n$-ary semigroups. One of the main result of this article is the generalisation of Czogala-Drewniak Theorem, which describes the idempotent monotone associative functions having neutral element. Furthermore we present ... More

Determination of confusion noise for far-infrared measurementsSep 14 2004We present a detailed assessment of the far-infrared confusion noise imposed on measurements with the ISOPHOT far-infrared detectors and cameras aboard the ISO satellite. We provide confusion noise values for all measurement configurations and observing ... More

Epidemic spread in networks: Existing methods and current challengesMar 08 2014We consider the spread of infectious disease through contact networks of Configuration Model type. We assume that the disease spreads through contacts and infected individuals recover into an immune state. We discuss a number of existing mathematical ... More

A note on $m$-factorizations of complete multigraphs arising from designsJul 21 2014Some new infinite families of simple, indecomposable $m$-factorizations of the complete multigraph $\lambda K_v$ are presented. Most of the constructions come from finite geometries.

High precision $^{113}$In($α,α$)$^{113}$In elastic scattering at energies around the Coulomb barrier for the astrophysical $γ$ processNov 02 2013The $\gamma$ process in supernova explosions is thought to explain the origin of proton-rich isotopes between Se and Hg, the so-called $p$ nuclei. The majority of the reaction rates for $\gamma$ process reaction network studies has to be predicted in ... More

Far-infrared loops in the 2nd Galactic QuadrantJan 15 2004We present the results of an investigation of the large scale structure of the diffuse interstellar medium in the 2nd Galactic Quadrant (90 <= l <= 180). 145 loops were identified on IRAS based far-infrared maps. Our catalogue lists their basic physical ... More

Catalogue of far-infrared loops in the GalaxyOct 16 2006Aims: An all-sky survey of loop- and arc-like intensity enhancements has been performed in order to investigate the large-scale structure of the diffuse far-infrared emission. Methods: We used maps made of 60 and 100 micrometer processed IRAS data (Sky ... More

Pushing the limits: K2 observations of the trans-Neptunian objects 2002 GV31 and (278361) 2007 JJ43Apr 14 2015Apr 15 2015We present the first photometric observations of trans-Neptunian objects (TNOs) taken with the Kepler space telescope, obtained in the course of the K2 ecliptic survey. Two faint objects have been monitored in specifically designed pixel masks that were ... More

Mass and orbit constraints of the gamma-ray binary LS 5039Aug 16 2011We present the results of space-based photometric and ground-based spectroscopic observing campaigns on the gamma-ray binary LS 5039. The new orbital and physical parameters of the system are similar to former results, except we found a lower eccentricity. ... More

F10-SGD: Fast Training of Elastic-net Linear Models for Text Classification and Named-entity RecognitionFeb 27 2019Voice-assistants text classification and named-entity recognition (NER) models are trained on millions of example utterances. Because of the large datasets, long training time is one of the bottlenecks for releasing improved models. In this work, we develop ... More

On the complexity of the chip-firing reachability problemJul 12 2015Oct 04 2016In this paper, we study the complexity of the chip-firing reachability problem. We show that for Eulerian digraphs, the reachability problem can be decided in strongly polynomial time, even if the digraph has multiple edges. We also show a special case ... More

Characterization of field homomorphisms through Pexiderized functional equationsOct 29 2018The aim of this paper is to prove characterization theorems for field homomorphisms. More precisely, the main result investigates the following problem. Let $n\in \mathbb{N}$ be arbitrary, $\mathbb{K}$ a field and $f_{1}, \ldots, f_{n}\colon \mathbb{K}\to ... More

On a class of linear functional equations without range conditionMar 19 2019The main purpose of this work is to provide the general solutions of a class of linear functional equations. Let $n\geq 2$ be an arbitrarily fixed integer, let further $X$ and $Y$ be linear spaces over the field $\mathbb{K}$ and let $\alpha_{i}, \beta_{i}\in ... More

Pointwise regularity of parameterized affine zipper fractal curvesAug 16 2016Jul 12 2017We study the pointwise regularity of zipper fractal curves generated by affine mappings. Under the assumption of dominated splitting of index-1, we calculate the Hausdorff dimension of the level sets of the pointwise H\"older exponent for a subinterval ... More

Large primes in generalized Pascal trianglesNov 15 2011In this paper, after presenting the results of the generalization of Pascal triangle (using powers of base numbers), we examine some properties of the 112-based triangle, most of all regarding to prime numbers. Additionally, an effective implementation ... More

Spectral signatures of disk eccentricity in young binary systems: I. Circumprimary caseJan 10 2011Jan 27 2011Star formation occurs via fragmentation of molecular clouds, which means that the majority of stars born are a members of binaries. There is growing evidence that planets might form in circumprimary disks of medium-separation binaries. The tidal forces ... More

Interior Structures and Tidal Heating in the TRAPPIST-1 PlanetsDec 15 2017Jan 24 2018With seven planets, the TRAPPIST-1 system has the largest number of exoplanets discovered in a single system so far. The system is of astrobiological interest, because three of its planets orbit in the habitable zone of the ultracool M dwarf. Assuming ... More

Conditions for one-dimensional supersonic flow of quantum gasesMay 01 2004Aug 18 2004One can use transsonic Bose-Einstein condensates of alkali atoms to establish the laboratory analog of the event horizon and to measure the acoustic version of Hawking radiation. We determine the conditions for supersonic flow and the Hawking temperature ... More

Herschel Footprint Database and ServiceFeb 02 2016We created the Herschel Footprint Database and web services for the Herschel Space Observatory imaging data. For this database we set up a unified data model for the PACS and SPIRE Herschel instruments, from the pointing and header information of each ... More

Absolute resonance strengths in the 6,7Li(alpha,gamma)10,11B reactionsFeb 26 2004The absolute strengths of the Ea=1175keV resonance in the 6Li(a,g)10B reaction and of the Ea=814 keV resonance in the 7Li(a,g)11B reaction have been measured to $\omega\gamma$=366+-38 meV and $\omega\gamma$=300+-32 meV, respectively, in good agreement ... More

Tidal Heating and the Habitability of the TRAPPIST-1 ExoplanetsFeb 11 2019Context. New estimates of the masses and radii of the seven planets orbiting the ultracool M-dwarf TRAPPIST-1 star permit improved modelling of their compositions, heating by tidal dissipation, and removal of tidal heat by solid-state convection. Aims. ... More

"TNOs are Cool": A survey of the trans-Neptunian region XIV. Size/albedo characterization of the Haumea family observed with Herschel and SpitzerApr 12 2019A group of trans-Neptunian objects (TNO) are dynamically related to the dwarf planet 136108 Haumea. Ten of them show strong indications of water ice on their surfaces, are assumed to have resulted from a collision, and are accepted as the only known TNO ... More

Sky Confusion Noise in the Far-Infrared: Cirrus, Galaxies and the Cosmic Far-Infrared BackgroundOct 05 2001We examined the sky confusion noise in 40 sky regions by analysing 175 far-infrared (90--200 $\mu$m) maps obtained with ISOPHOT, the photometer on-board the Infrared Space Observatory. For cirrus fields with $\rm < \rm B > > 5$ MJysr$^{-1}$ the formula ... More

On the relationship between the theory of cointegration and the theory of phase synchronizationJan 03 2012May 11 2018The theory of cointegration has been a leading theory in econometrics with powerful applications to macroeconomics during the last decades. On the other hand the theory of phase synchronization for weakly coupled complex oscillators has been one of the ... More

The mass and density of the dwarf planet (225088) 2007 OR10Mar 13 2019The satellite of (225088) 2007 OR10 was discovered on archival Hubble Space Telescope images and along with new observations with the WFC3 camera in late 2017 we have been able to determine the orbit. The orbit's notable eccentricity, e$\approx$0.3, may ... More

High-resolution spectroscopic view of planet formation sitesNov 10 2010Dec 03 2010Theories of planet formation predict the birth of giant planets in the inner, dense, and gas-rich regions of the circumstellar disks around young stars. These are the regions from which strong CO emission is expected. Observations have so far been unable ... More

The impact of main belt asteroids on infrared--submillimetre photometry and source countsNov 24 2007Nov 28 2007<<>> Among the components of the infrared and submillimetre sky background, the closest layer is the thermal emission of dust particles and minor bodies in the Solar System. This contribution is especially important for current and future infrared and ... More

Fast variables determine the epidemic threshold in the pairwise model with an improved closureSep 11 2018Pairwise models are used widely to model epidemic spread on networks. These include the modelling of susceptible-infected-removed (SIR) epidemics on regular networks and extensions to SIS dynamics and contact tracing on more exotic networks exhibiting ... More

Photometric Observations of Three High Mass X-Ray Binaries and a Search for Variations Induced by Orbital MotionMay 10 2011We searched for long period variation in V-band, Ic-band and RXTE X-ray light curves of the High Mass X-ray Binaries (HMXBs) LS 1698 / RX J1037.5-5647, HD 110432 / 1H 1249-637 and HD 161103 / RX J1744.7-2713 in an attempt to discover orbitally induced ... More

Nearby debris disk systems with high fractional luminosity reconsideredMar 27 2006Mar 31 2006By searching the IRAS and ISO databases we compiled a list of 60 debris disks which exhibit the highest fractional luminosity values (fd>10^-4) in the vicinity of the Sun (d<120pc). Eleven out of these 60 systems are new discoveries. Special care was ... More

The heart of the swarm: K2 photometry and rotational characteristics of 56 Jovian Trojan asteroidsSep 09 2016We present fully covered phased light curves for 56 Jovian Trojan asteroids as acquired by the K2 mission of the Kepler space telescope. This set of objects has been monitored during Campaign 6 and represents a nearly unbiased subsample of the population ... More

Uninterrupted optical light curves of main-belt asteroids from the K2 MissionSep 09 2016Due to the failure of the second reaction wheel, a new mission was conceived for the otherwise healthy Kepler space telescope. In the course of the K2 Mission, the telescope is staring at the plane of the Ecliptic, hence thousands of Solar System bodies ... More

Unveiling new members in five nearby young moving groupsSep 06 2013In the last decade many kinematic groups of young stars (<100 Myr) were discovered in the solar neighbourhood. Since the most interesting period of planet formation overlaps with the age of these groups, their well dated members are attractive targets ... More

Evidence for fresh frost layer on the bare nucleus of comet Hale--Bopp at 32 AU distanceOct 10 2012Here we report that the activity of comet Hale--Bopp ceased between late 2007 and March, 2009, at about 28 AU distance from the Sun. At that time the comet resided at a distance from the Sun that exceeded the freeze-out distance of regular comets by an ... More

Determining the 7Li(n,gamma) cross section via Coulomb dissociation of 8LiDec 12 2013The applicability of Coulomb dissociation reactions to determine the cross section for the inverse neutron capture reaction was explored using the reaction 8Li(gamma,n)7Li. A 69.5 MeV/nucleon 8Li beam was incident on a Pb target, and the outgoing neutron ... More

Visual characterization of associative quasitrivial nondecreasing operations on finite chainsSep 21 2017Oct 26 2018In this paper we provide visual characterization of associative quasitrivial nondecreasing operations on finite chains. We also provide a characterization of bisymmetric quasitrivial nondecreasing binary operations on finite chains. Finally, we estimate ... More

A note on Talagrand's variance bound in terms of influencesJul 05 2010Jul 26 2011Let X_1,..., X_n be independent Bernoulli random variables and $f$ a function on {0,1}^n. In the well-known paper (Talagrand1994) Talagrand gave an upper bound for the variance of f in terms of the individual influences of the X_i's. This bound turned ... More

Educational Challenges of Rubik's CubeApr 30 2015The first 2x2x2 twisty cube was created as a demonstration tool by Erno Rubik in 1974 to help his students understand the complexity of space and the movements in 3D. He fabricated a novel 3x3x3 mechanism where the 26 cubies were turning, and twisting ... More

Ambarzumian theorem on graphsOct 04 2016We consider an inverse problem for Schr\"odinger operators on a connected equilateral graph with standard matching conditions. We prove an Ambarzumian-type result, i.e., if a specific part of the spectrum is the same as in the case of zero potential, ... More

An Ambarzumian type theorem on graphs with odd cyclesOct 20 2017We consider an inverse problem for Schr\"odinger operators on a connected equilateral graph $G$ with standard matching conditions. The graph $G$ consists of at least two odd cycles glued together at a common vertex. We prove an Ambarzumian type result, ... More

Classification of bounded Baire class $ξ$ functionsJun 02 2015Jan 25 2016Kechris and Louveau showed that each real-valued bounded Baire class 1 function defined on a compact metric space can be written as an alternating sum of a decreasing countable transfinite sequence of upper semi-continuous functions. Moreover, the length ... More

A game characterizing Baire class 1 functionsApr 26 2017Feb 14 2019Duparc introduced a two-player game for a function $f$ between zero-dimensional Polish spaces in which Player II has a winning strategy iff $f$ is of Baire class 1. We generalize this result by defining a game for an arbitrary function $f : X \to Y$ between ... More

Constructing, sampling and counting graphical realizations of restricted degree sequencesJan 31 2013Dec 02 2013With the current burst of network theory (especially in connection with social and biological networks) there is a renewed interest on realizations of given degree sequences. In this paper we propose an essentially new degree sequence problem: we want ... More

Rate Analysis or a Possible Interpretation of AbundancesFeb 11 2015Feb 24 2015Heavy elements are formed in nucleosynthesis processes. Abundances of these elements can be classified as elemental abundance, isotopic abundance, and abundance of nuclei. In this work we propose to change nucleon identification from the usual (Z,A) to ... More

Large deviation bounds for the volume of the largest cluster in 2D critical percolationApr 08 2014Let M_n denote the number of sites in the largest cluster in critical site percolation on the triangular lattice inside a box side length n. We give lower and upper bounds on the probability that M_n / E(M_n) > x of the form exp(- C x^(2/alpha)) for x ... More

Spectral determinants and an Ambarzumian type theorem on graphsOct 04 2016Mar 01 2017We consider an inverse problem for Schr\"odinger operators on connected equilateral graphs with standard matching conditions. We calculate the spectral determinant and prove that the asymptotic distribution of a subset of its zeros can be described by ... More

Dynamic control of modern, network-based epidemic modelsFeb 10 2014In this paper we make the first steps to bridge the gap between classic control theory and modern, network-based epidemic models. In particular, we apply nonlinear model predictive control (NMPC) to a pairwise ODE model which we use to model a susceptible-infectious-susceptible ... More

Neutron Capture NucleosynthesisJan 23 2016Aug 17 2016Heavy elements (beyond iron) are formed in neutron capture nucleosynthesis processes. We have proposed a simple unified model to investigate the neutron capture nucleosynthesis in arbitrary neutron density environment. We have also investigated what neutron ... More

2-semiarcs in $\mathrm{PG}(2,q)$, $q\leq 13$Jul 22 2014A $2$-semiarc is a pointset ${\mathcal S}_k$ with the property that the number of tangent lines to ${\mathcal S}_k$ at each of its points is two. Using some theoretical results and computer aided search, the complete classification of $2$-semiarcs in ... More

On a conjecture of Erdős about sets without $k$ pairwise coprime integersMay 16 2017Let $\mathbb{Z}^{+}$ be the set of positive integers. Let $C_{k}$ denote all subsets of $\mathbb{Z}^{+}$ such that neither of them contains $k + 1$ pairwise coprime integers and $C_k(n)=C_k\cap \{1,2,\ldots,n\}$. Let $f(n, k) = \text{max}_{A \in C_{k}(n)}|A|$, ... More

Small-scale structure of the galactic cirrus emissionDec 04 2002We examined the Fourier power spectrum characteristics of cirrus structures in 13 sky fields with faint to bright cirrus emission observed with ISOPHOT in the 90--200µm wavelength range in order to study variations of the spectral index $\alpha$. ... More

Frozen percolation in two dimensionsFeb 27 2013Jul 12 2013Aldous introduced a modification of the bond percolation process on the binary tree where clusters stop growing (freeze) as soon as they become infinite. We investigate the site version of this process on the triangular lattice where clusters freeze as ... More

Growth Rates of Algebras, II: Wiegold DichotomyNov 25 2013Jan 11 2014We investigate the function $d_\mathbf{A}(n)$, which gives the size of a least size generating set for $\mathbf{A}^n$, in the case where $\mathbf{A}$ has a cube term. We show that if $\mathbf{A}$ has a $k$-cube term and $\mathbf{A}^k$ is finitely generated, ... More

On the metric dimension of affine planes, biaffine planes and generalized quadranglesJun 20 2017In this paper the metric dimension of (the incidence graphs of) particular partial linear spaces is considered. We prove that the metric dimension of an affine plane of order $q\geq13$ is $3q-4$ and describe all resolving sets of that size if $q\geq 23$. ... More

Edge-based compartmental modelling of an SIR epidemic on a dual-layer static-dynamic multiplex network with tunable clusteringJan 04 2018Apr 04 2018The duration, type and structure of connections between individuals in real-world populations play a crucial role in how diseases invade and spread. Here, we incorporate the aforementioned heterogeneities into a model by considering a dual-layer static-dynamic ... More

Determination of the cosmic far-infrared background level with the ISOPHOT instrumentApr 20 2009The cosmic infrared background (CIRB) consists mainly of the integrated light of distant galaxies. In the far-infrared the current estimates of its surface brightness are based on the measurements of the COBE satellite. Independent confirmation of these ... More

Discovery of the spectroscopic binary nature of six southern CepheidsJan 31 2013We present the analysis of photometric and spectroscopic data of six bright Galactic Cepheids: GH Carinae, V419 Centauri, V898 Centauri, AD Puppis, AY Sagittarii, and ST Velorum. Based on new radial velocity data (in some cases supplemented with earlier ... More

Main-belt asteroids in the K2 Uranus fieldJun 19 2017Dec 13 2017We present the K2 light curves of a large sample of untargeted Main Belt asteroids (MBAs) detected with the Kepler space telescope. The asteroids were observed within the Uranus superstamp, a relatively large, continuous field with low stellar background ... More

The first CCD photometric study of the open cluster NGC 2126Aug 26 2003We present the first CCD photometric observations of the northern open cluster NGC 2126. Data were taken on eight nights in February and December 2002 with a total time span of ~57 hours. Almost 1000 individual V-band frames were examined to find short-period ... More

Nereid from space: Rotation, size and shape analysis from Kepler/K2, Herschel and Spitzer observationsJan 11 2016In this paper we present an analysis of Kepler K2 mission Campaign 3 observations of the irregular Neptune satellite, Nereid. We determined a rotation period of P=11.594(+/-)0.017 h and amplitude of dm=0.0328(+/-)00018, confirming previous short rotation ... More

Main-Belt Asteroids in the K2 Engineering Field of ViewJan 23 2015Unlike NASA's original Kepler Discovery Mission, the renewed K2 Mission will stare at the plane of the Ecliptic, observing each field for approximately 75 days. This will bring new opportunities and challenges, in particular the presence of a large number ... More

Thermal Infrared Observations of Asteroid (99942) Apophis with HerschelApr 23 2014The near-Earth asteroid (99942) Apophis is a potentially hazardous asteroid. We obtained far-infrared observations of this asteroid with the Herschel Space Observatory's PACS instrument at 70, 100, and 160 micron. These were taken at two epochs in January ... More

Mean-field models for non-Markovian epidemics on networks: from edge-based compartmental to pairwise modelsNov 12 2016This paper presents a novel extension of the edge-based compartmental model for epidemics with arbitrary distributions of transmission and recovery times. Using the message passing approach we also derive a new pairwise-like model for epidemics with Markovian ... More

Constraints on the nature of dust particles by infrared observationsSep 25 2006The far-infrared (FIR) emissivity of dust is an important parameter characterizing the physical properties of the grains. With the availability of stellar databases and far-infrared data from Infrared Space Observatory (ISO) it is possible to compare ... More

Epidemic threshold in pairwise models for clustered networks: closures and fast correlationsJun 15 2018The epidemic threshold is probably the most studied quantity in the modelling of epidemics on networks. For a large class of networks and dynamics the epidemic threshold is well studied and understood. However, it is less so for clustered networks where ... More

New debris disks in nearby young moving groupsJun 29 2016A significant fraction of nearby young moving group members harbor circumstellar debris dust disks. Due to their proximity and youth, these disks are attractive targets for studying the early evolution of debris dust and planetesimal belts. Here we present ... More

Investigation of 74As decay branching ratio dependence on the host materialJun 27 2008The branching ratio between the beta- and beta+/electron capture decay of 74As has been measured in different host materials such as Ta, Al, Ge and mylar. No significant dependence of the branching ratio on the host material has been observed. The half-life ... More

Extending the limits of globule detection -- ISOPHOT Serendipity Survey Observations of interstellar cloudsFeb 28 2002A faint $I_{\rm 170}=4$ MJysr$^{-1}$ bipolar globule was discovered with the ISOPHOT 170 $\mu$m Serendipity Survey (ISOSS). ISOSS J 20246+6541 is a cold ($T_{\rm d}\approx 14.5$ K) FIR source without an IRAS pointsource counterpart. In the Digitized Sky ... More

New clues on outburst mechanisms and improved spectroscopic elements of the black-hole binary V4641 SagittariiAug 03 2005We present spectroscopic observations of the black-hole binary V4641 Sagittarii, obtained between 4th July 2004 and 28th March 2005, which cover the minor outburst of the star in early July 2004 and quiescence variations on 19 nights scattered over six ... More

Dense cores in the dark cloud complex LDN1188Sep 19 2013We present a molecular line emission study of the LDN1188 dark cloud complex located in Cepheus. In this work we focused on the densest parts of the cloud and on the close neighbourhood of infrared point sources. We made ammonia mapping with the Effelsberg ... More

Comet C/2013 A1 (Siding Spring) as seen with the Herschel Space ObservatoryOct 08 2014Dec 25 2014The thermal emission of comet C/2013 A1 (Siding Spring) was observed on March 31, 2013, at a heliocentric distance of 6.48 au using the PACS photometer camera of the Herschel Space Observatory. The comet was clearly active, showing a coma that could be ... More

PACS photometer calibration block analysisOct 10 2013The absolute stability of the PACS bolometer response over the entire mission lifetime without applying any corrections is about 0.5% (standard deviation) or about 8% peak-to-peak. This fantastic stability allows us to calibrate all scientific measurements ... More

Herschel survey of brown dwarf disks in Rho OphiuchiOct 01 2013Recent observations of the Rho Ophiuchi cluster with the Herschel Space Observatory allow us to probe the spectral energy distribution (SED) of the brown dwarf population in the far-IR, where the disk emission peaks. We performed aperture photometry at ... More

Molecular gas in young debris disksSep 11 2011Gas-rich primordial disks and tenuous gas-poor debris disks are usually considered as two distinct evolutionary phases of the circumstellar matter. Interestingly, the debris disk around the young main-sequence star 49 Ceti possesses a substantial amount ... More

The discovery of new warm debris disks around F-type starsJun 05 2009We report the discovery of four rare debris disks with warm excesses around F-stars, significantly increasing the number of such systems known in the solar neighborhood. Three of the disks are consistent with the predictions of steady state planetesimal ... More

Structure and evolution of debris disks around F-type stars: I. Observations, database and basic evolutionary aspectsDec 16 2010Although photometric and spectroscopic surveys with the Spitzer Space Telescope increased remarkably the number of well studied debris disks around A-type and Sun-like stars, detailed analyzes of debris disks around F-type stars remained less frequent. ... More

Cycloidally modulated magnetic order stabilized by thermal fluctuations in the Néel-type skyrmion host GaV$_4$S$_8$Apr 12 2017We report small-angle neutron scattering studies of the lacunar spinel GaV$_4$S$_8$, which reveal the long-wavelength magnetic states to be cycloidally modulated. This provides direct support for the formation of N\'eel-type skyrmions recently claimed ... More

Subtle flickering in CepheidsJan 20 2014Fundamental mode classical Cepheids have light curves which repeat accurately enough that we can watch them evolve (change period). The new level of accuracy and quantity of data with the {\it Kepler} and {\it MOST} satellites probes this further. An ... More

Activation measurement of the 3He(a,g)7Be reaction cross section at high energiesApr 17 2013The astrophysically important 3He(a,g)7Be reaction was studied at high energies where the available experimental data are in contradiction. A thin window 3He gas cell was used and the cross section was measured with the activation method. The obtained ... More

Resonant impurity states in chemically disordered half-Heusler Dirac semimetalsOct 23 2015We address the electron transport characteristics in bulk half-Heusler alloys with their compositions tuned to the borderline between topologically nontrivial semi-metallic and trivial semiconducting phases. The precise first-principles calculations based ... More

Frustration induced one-dimensionality in the isosceles triangular antiferromagnetic lattice of $δ$-(EDT-TTF-CONMe$_{2}$)$_{2}$AsF$_6$Nov 19 2016The $1/4$-filled organic compound, $\delta$-(EDT-TTF-CONMe$_{2}$)$_{2}$AsF$_6$ is a frustrated two-dimensional triangular magnetic system as shown by high-frequency (111.2 and 222.4 GHz) electron spin resonance (ESR) and structural data in the literature. ... More

Astrophysical analysis of the measurement of (alpha,gamma) and (alpha,n) cross sections of 169TmJun 26 2012Reaction cross sections of 169Tm(alpha,gamma)173Lu and 169Tm(alpha,n)172Lu have been measured in the energy range 12.6<=E_alpha<=17.5 MeV and 11.5<=E_alpha<=17.5 MeV, respectively, using the recently introduced method of combining activation with X-ray ... More

Phenomenological description of neutron capture cross sections at 30 keVApr 01 2011Studying published data of Maxwellian averaged neutron capture cross sections, we found simple phenomenological rules obeyed by the cross sections as a function of proton and neutron number. We use these rules to make predictions for cross sections of ... More

N=8 Supergravity in Central Charge SuperspaceSep 04 2002Apr 17 2003We present a geometrical description of N=8 supergravity, using central charge superspace. The essential properties of the multiplet, like self-duality properties of the vectors or the non-linear sigma model structure of the scalars, are found as consequences ... More

Equations of motion for N=4 supergravity with antisymmetric tensor from its geometric description in central charge superspaceJan 29 2002Mar 30 2004We consider the geometrical formulation in central charge superspace of the N=4 supergravity containing an antisymmetric tensor gauge field. The theory is on-shell, so clearly, the constraints used for the identification of the multiplet together with ... More

Derivations and differential operators on rings and fieldsMar 02 2018Apr 06 2018Let $R$ be an integral domain of characteristic zero. We prove that a function $D\colon R\to R$ is a derivation of order $n$ if and only if $D$ belongs to the closure of the set of differential operators of degree $n$ in the product topology of $R^R$, ... More

$n$-dimensional ratio-dependent predator-prey systems with memoryAug 05 2008This paper deals with ratio-dependent predator-prey systems with delay. We will investigate under what conditions delay cannot cause instability in higher dimension. We give an example when delay causes instability.

On line colorings of finite projective spacesFeb 22 2017May 28 2018In this paper, we prove lower and upper bounds on the achromatic and the pseudoachromatic indices of the $n$-dimensional finite projective space of order $q$.

How large dimension guarantees a given angle?Jan 07 2011Apr 06 2012We study the following two problems: (1) Given $n\ge 2$ and $\al$, how large Hausdorff dimension can a compact set $A\su\Rn$ have if $A$ does not contain three points that form an angle $\al$? (2) Given $\al$ and $\de$, how large Hausdorff dimension can ... More

Scalar order: possible candidate for order parameters in skutteruditesApr 16 2008Phenomenological Landau analysis shows that the properties of ordered phases in some skutterudites are consistently accounted for by a scalar order parameter which preserves the cubic symmetry, even in the ordered phase. A universal value is found for ... More

Decomposition of balls in $\mathbb{R}^d$Jan 30 2014We investigate the decomposition problem of balls into finitely many congruent pieces in dimension $d=2k$. In addition, we prove that the $d$ dimensional unit ball $B_d$ can be divided into finitely many congruent pieces if $d=4$ or $d\ge 6$. We show ... More

Characterizations of biselective operationsJun 06 2018Jun 18 2018Let $X$ be a nonempty set and let $i,j \in \{1,2,3,4\}$. We say that a binary operation $F:X^2\to X$ is $(i,j)$-selective if $$ F(F(x_1,x_2),F(x_3,x_4))~=~F(x_i,x_j), $$ for all $x_1,x_2,x_3,x_4\in X$. In this paper we provide characterizations of the ... More

Unions of regular polygons with large perimeter-to-area ratioFeb 21 2014Jun 22 2014T. Keleti asked, whether the ratio of the perimeter and the area of a finite union of unit squares is always at most 4. In this paper we present an example where the ratio is greater than 4. We also answer the analogous question for regular triangles ... More

Low-field octupoles and high-field quadrupoles in URu2Si2Apr 05 2004The recent experimental finding of large-amplitude antiferromagnetism induced by uniaxial strain shows that the "hidden" low-field order of URu2Si2 breaks time reversal invariance. We propose a new crystal field model which supports T(beta)z octupolar ... More

Implications between generalized convexity properties of real functionsJul 19 2015Motivated by the well-known implications among $t$-convexity properties of real functions, analogous relations among the upper and lower $M$-convexity properties of real functions are established. More precisely, having an $n$-tuple $(M_1,\dots,M_n)$ ... More