Results for "Á. Sódor"

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Changes in Mean Global Physical Parameters of Blazhko RR Lyrae stars -- Derived from Multicolor PhotometryApr 12 2010We developed an Inverse Photometric method (IPM) to determine global physical parameters of RR Lyrae stars exclusively from multicolor light curves (S\'odor, Jurcsik & Szeidl, 2009, MNRAS, 394, 261). We showed that for good quality photometric observations ... More
LCfit, a harmonic-function fitting programJun 01 2012In this note I announce and introduce the program LCfit developed for fitting harmonic functions to a data set, particularly to time-series data. LCfit stands for Linear Combination fitting.
The Blazhko behaviour of RR Geminorum II -- long-term photometric resultsApr 25 2007Context. RR Gem is one of the few Blazhko RR Lyrae that has photometric observations available extended enough to study the long-term courses of its pulsation and modulation properties in detail. Aims. We investigate the pulsation and modulation properties ... More
Studying Blazhko RR Lyrae stars with the 24-inch telescope of the Konkoly ObservatoryApr 25 2007About a dozen field RR Lyrae stars have been observed with the 24-inch Heyde-Zeiss telescope of the Konkoly Observatory at Sv\'abhegy, Budapest, since its refurbishment in 2003. Most of the observing time is allocated for the investigation of the Blazhko ... More
White Dwarf Period Tables - I. Pulsators with hydrogen-dominated atmospheresOct 24 2016We aimed at collecting all known white dwarf pulsators with hydrogen-dominated atmospheres and list their main photometric and atmospheric parameters together with their pulsation periods and amplitudes observed at different epochs. For this purpose, ... More
The diversity of light curve variations of Blazhko starsJan 26 2011The ground-based Konkoly Blazhko Survey I and II aim to collect accurate, extended, multicolour light curves of galactic field RRab stars in order to determine the incidence rate of the modulation in the sample, to study the modulation in details, to ... More
A new method for determining physical parameters of fundamental mode RR Lyrae stars from multicolour light curvesNov 19 2008We present a new method for determining physical parameters of RRab variables exclusively from multicolour light curves. Our method is an Inverse Photometric Baade-Wesselink analysis which, using a nonlinear least squares algorithm, searches for the effective ... More
One new variable candidate and six nonvariable stars at the ZZ Ceti instability stripFeb 08 2019We present our results on the continuation of our survey searching for new ZZ Ceti stars, inspired by the recently launched TESS space mission. The seven targets were bright DA-type white dwarfs located close to the empirical ZZ Ceti instability strip. ... More
KIC 2831097 - A 2-year orbital-period RR Lyrae binary candidateSep 21 2016We report the discovery of a new Kepler first-overtone RR Lyrae pulsator, KIC 2831097. The pulsation shows large, 0.1 d amplitude, systematic phase variations that can be interpreted as light travel-time effect caused by orbital motion in a binary system, ... More
Amplitude Modulation in the ZZ Ceti Star GD 244Jun 23 2015Previous studies of GD 244 revealed seven pulsation frequencies (two doublets and three single periods) in the light variations of the star. The data obtained at McDonald Observatory between 2003 and 2006, and our additional measurements in 2006 and 2007 ... More
Binary systems with an RR Lyrae component - progress in 2016Jan 20 2017In this contribution, we summarize the progress made in the investigation of binary candidates with an RR Lyrae component in 2016. We also discuss the actual status of the RRLyrBinCan database.
Finest light curve details, physical parameters, and period fluctuations of CoRoT RR Lyrae starsAug 23 2016The CoRoT satellite supplied the scientific community with a huge data base of variable stars. Among them the RR Lyrae stars have intensively been discussed in numerous papers in the last few years, but the latest runs have not been checked to find RR ... More
Fitting Blazhko light curvesJun 08 2012The correct amplitude and phase modulation formalism of the Blazhko modulation is given. The harmonic order dependent amplitude and phase modulation form is equivalent with the Fourier decomposition of multiplets. The amplitude and phase modulation formalism ... More
Affordable spectroscopy for 1m-class telescopesJan 15 2014Doppler observations of exoplanet systems have been a very expensive technique, mainly due to the high costs of high-resolution stable spectrographs. Recent advances in instrumentation enable affordable Doppler planet detections with surprisingly small ... More
On the interpretation of the long-term cyclic period variations in RR Lyrae starsSep 10 2018Many RR Lyrae stars show long-term variations of their pulsation period, some of them in a cyclic way. Such behaviour can be attributed to the light-travel time effect (LTTE) caused by an unseen companion. Solutions of the LTTE often suggest very eccentric ... More
The light-curve modulation of XY And and UZ Vir - Two Blazhko RR Lyrae stars with additional frequenciesAug 01 2012A thorough analysis of multicolour CCD observations of two modulated RRab-type variables, XY And and UZ Vir is presented. These Blazhko stars show relatively simple light-curve modulation with the usual multiplet structures in their Fourier spectra. One ... More
G 207-9 and LP 133-144: light curve analysis and asteroseismology of two ZZ Ceti starsJun 30 2016G 207-9 and LP 133-144 are two rarely observed ZZ Ceti stars located in the middle and close to the blue edge of the ZZ Ceti instability domain, respectively. We aimed to observe them at least during one observing season at Konkoly Observatory with the ... More
A cautionary tale of interpreting O-C diagrams: period instability in a classical RR Lyr Star Z CVn mimicking as a distant companionOct 18 2017We present a comprehensive study of Z CVn, an RR Lyrae star that shows long-term cyclic variations of its pulsation period. A possible explanation suggested from the shape of the O-C diagram is the light travel-time effect, which we thoroughly examine. ... More
Searching for new white dwarf pulsators for TESS observations at Konkoly ObservatoryMay 25 2018We present the results of our survey searching for new white dwarf pulsators for observations by the TESS space telescope. We collected photometric time-series data on 14 white dwarf variable-candidates at Konkoly Observatory, and found two new bright ... More
The Blazhko modulation of TV Boo in 2010Nov 15 2012We present the analysis of the multicolour CCD observations in the 2010 season of the Blazhko RRc star TV Boo. TV Boo shows a complex Blazhko modulation dominated by two independent modulations with P_{fm1}=9.74 d and P_{fm2}=21.43 d long periods. Both ... More
The shortest modulation period Blazhko RR Lyrae star: SS CncMar 20 2006Extended BV(RI)c CCD observations of SS Cnc, a short period RRab star are presented. Nearly 1400 data points in each band have been obtained spanning over 79 days during the spring of 2005. The star exhibits light curve modulation, the so called Blazhko ... More
The Multi-periodic Blazhko Modulation of CZ LacertaeSep 28 2010Thorough analysis of the multicolour CCD observations of the RRab-type variable, CZ Lacertae is presented. The observations were carried out in two consecutive observing seasons in 2004 and 2005 within the framework of the Konkoly Blazhko Survey of bright, ... More
The triple-mode pulsating variable V823 CasAug 30 2005Based on extended multicolour CCD photometry of the triple-mode radial pulsator V823 Cas we studied the properties of the coupling frequencies invoked by nonlinear processes. Our results support that a resonance connection as suggested by Antonello & ... More
Long-term photometric monitoring of RR Lyr stars in M3Sep 21 2011The period-change behaviour of 134 RR Lyrae stars in the globular cluster Messier 3 (M3) is investigated on the ~120-year time base of the photometric observations. The mean period-change rates (\beta \approx 0.01 d Myr^-1) of the subsamples of variables ... More
Four-colour photometry of EY Dra: a study of an ultra-fast rotating active dM1-2e starJan 12 2010May 06 2010We present more than 1000-day long photometry of EY Draconis in BV(RI)C passbands. The changes in the light curve are caused by the spottedness of the rotating surface. Modelling of the spotted surface shows that there are two large active regions present ... More
The Blazhko behaviour of RR Geminorum I - CCD photometric results in 2004Oct 05 2004Extended CCD monitoring of RR Gem revealed that it is a Blazhko type RRab star with the shortest Blazhko period (7.23d) and smallest modulation amplitude (Delta Mmax<0.1 mag) currently known. The short period of the modulation cycle enabled us to obtain ... More
The Konkoly Blazhko Survey: Is light-curve modulation a common property of RRab stars?Aug 07 2009A systematic survey to establish the true incidence rate of the Blazhko modulation among short-period, fundamental-mode, Galactic field RR Lyrae stars has been accomplished. The Konkoly Blazhko Survey (KBS) was initiated in 2004. Since then more than ... More
On the distribution of the modulation frequencies of RR Lyrae starsAug 01 2005For the first time connection between the pulsation and modulation properties of RR Lyrae stars has been detected. Based on the available data it is found that the possible range of the modulation frequencies, i.e, the possible maximum value of the modulation ... More
KIC 9533489: a genuine gamma Doradus-delta Scuti Kepler hybrid pulsator with transit eventsJun 04 2015Context: Several hundred candidate hybrid pulsators of type A-F have been identified from space-based observations. Their large number allows both statistical analyses and detailed investigations of individual stars. This offers the opportunity to study ... More
Rotation and pulsation in Ap stars: first light results from TESS sectors 1 and 2Jun 03 2019We present the first results from the Transiting Exoplanet Survey Satellite (TESS) on the rotational and pulsational variability of magnetic chemically peculiar A-type stars. We analyse TESS 2-min cadence data from sectors 1 and 2 on a sample of 83 stars. ... More
An extensive photometric study of the Blazhko RR Lyrae star MW Lyr: I. Light curve solutionJul 03 2008We have obtained the most extensive and most accurate photometric data of a Blazhko variable MW Lyr during the 2006-2007 observing seasons. The data within each 0.05 phase bin of the modulation period (P_m=1/f_m) cover the entire light cycle of the primary ... More
What is the difference? Blazhko and non-Blazhko RRab stars and the special case of V123 in M3Sep 20 2013In an extended photometric campaign of RR Lyrae variables of the globular cluster M3, an aberrant light-curve, non-Blazhko RRab star, V123, was detected. Based on its brightness, colors and radial velocity curve, V123 is a bona fide member of M3. The ... More
Comment on "The complete Schwarzschild interior and exterior solution in the harmonic coordinate system" [J. Math. Phys. 39, 6086 (1998)]Dec 21 2007In a recent paper Liu considered the complete Schwarzschild interior and exterior solution in harmonic coordinates. There he argued about the necessity to keep an integration constant, in contrast with previous treatments. The purpose of this comment ... More
Colliding spherically symmetric null dust in equilibriumNov 17 1998We present two recently obtained solutions of the Einstein equations with spherical symmetry and one additional Killing vector, describing colliding null dust streams.
Eötvös branesJun 25 2008Apr 21 2009The high value of brane tension has a crucial role in recovering Einstein's general relativity at low energies. In the framework of a recently developed formalism with variable brane tension one can pose the question, whether it was always that high? ... More
The geometry of the Barbour-Bertotti theories I. The reduction processMar 16 2000The dynamics of $N\geq 3$ interacting particles is investigated in the non-relativistic context of the Barbour-Bertotti theories. The reduction process on this constrained system yields a Lagrangian in the form of a Riemannian line element. The involved ... More
Model compression as constrained optimization, with application to neural nets. Part I: general frameworkJul 05 2017Compressing neural nets is an active research problem, given the large size of state-of-the-art nets for tasks such as object recognition, and the computational limits imposed by mobile devices. We give a general formulation of model compression as constrained ... More
The Electrostatic Properties of Zeros of Exceptional Laguerre and Jacobi Polynomials and stable interpolationOct 03 2014We will examine the electrostatic properties of exceptional and regular zeros of $X_m$-Laguerre and $X_m$-Jacobi polynomials. Since there is a close connection between the electrostatic properties of the zeros and the stability of interpolation on the ... More
Models of Elastic Shells in Contact with a Rigid Foundation: An Asymptotic ApproachNov 22 2016We consider a family of linearly elastic shells with thickness $2\varepsilon$ (where $\varepsilon$ is a small parameter). The shells are clamped along a portion of their lateral face, all having the same middle surface $S$, and may enter in contact with ... More
The energy function with respect to the zeros of the exceptional Hermite polynomialsJan 22 2016We examine the energy function with respect to the zeros of exceptional Hermite polynomials. The localization of the eigenvalues of the Hessian is given in the general case. In some special arrangements we have a more precise result on the behavior of ... More
Degenerate Hessian structures on radiant manifoldsMar 02 2015Oct 17 2016A manifold $M$ is said to be radiant if it is endowed with a distinguished atlas whose coordinate changes are locally linear transformations. Such manifolds are thereby furnished with a flat connection $\bar\nabla$ and a radiant vector field $\rho$ whose ... More
A review of mean-shift algorithms for clusteringMar 02 2015A natural way to characterize the cluster structure of a dataset is by finding regions containing a high density of data. This can be done in a nonparametric way with a kernel density estimate, whose modes and hence clusters can be found using mean-shift ... More
Variable tension brane-worldsFeb 26 2010I present recent work on codimension one brane-world models containing a 3+1 dimensional curved brane with time-dependent brane tension.
Black holes on cosmological branesMar 08 2007While in general relativity black holes can be freely embedded into a cosmological background, the same problem in brane-worlds is much more cumbersome. We present here the results obtained so far in the explicit constructions of such space-times. We ... More
Black holes and dark energy from gravitational collapse on the braneMar 31 2006Feb 22 2007The gravitational collapse of a pressureless fluid in general relativity (Oppenheimer-Snyder collapse) results in a black hole. The study of the same phenomenon in the brane-world scenario has shown that the exterior of the collapsing dust sphere cannot ... More
On Hamiltonian formulations of the Schrödinger systemJan 09 2003We review and compare different variational formulations for the Schr\"{o}dinger field. Some of them rely on the addition of a conveniently chosen total time derivative to the hermitic Lagrangian. Alternatively, the Dirac-Bergmann algorithm yields the ... More
Brane-world cosmology with black stringsMar 30 2006Jun 16 2006We consider the simplest scenario when black strings / cigars penetrate the cosmological brane. As a result, the brane has a Swiss-cheese structure, with Schwarzschild black holes immersed in a Friedmann-Lema\^{\i}tre-Robertson-Walker brane. There is ... More
A Spherically Symmetric Closed Universe as an Example of a 2D Dilatonic ModelFeb 04 1999We study the two-dimensional (2D) dilatonic model describing a massless scalar field minimally coupled to the spherically reduced Einstein-Hilbert gravity. The general solution of this model is given in the case when a Killing vector is present. When ... More
Asymptotics for Recurrence Coefficients of X1-Jacobi Polynomials and Christoffel FunctionMay 27 2019Computing asymptotics of the recurrence coefficients of X1-Jacobi polynomials we investigate the limit of Christoffel function. We also study the relation between the normalized counting measure based on the zeros of the modified average characteristic ... More
Possibility of microscopic liquid water formation at landing sites on Mars and their observational potentialSep 26 2016Microscopic liquid brines, especially calcium-perchlorate could emerge by deliquescence on Mars during night time hours. Using climate model computations and orbital humidity observations, the ideal periods and their annual plus daily characteristics ... More
Debris Disks in Nearby Young Moving Groups in the ALMA EraOct 13 2015Many members of nearby young moving groups exhibit infrared excess attributed to circumstellar debris dust, formed via erosion of planetesimals. With their proximity and well-dated ages, these groups are excellent laboratories for studying the early evolution ... More
Chromatic Derivatives and Expansions with WeightsJan 22 2016Chromatic derivatives and series expansions of bandlimited functions have recently been introduced in signal processing and they have been shown to be useful in practical applications. We extend the notion of chromatic derivative using varying weights. ... More
Is dark matter futile on the brane?Dec 27 2006We investigate whether dark matter can be replaced by various source terms appearing in the effective Einstein equation, valid on a brane embedded into a higher dimensional space-time (the bulk). Such non-conventional source terms include a quadratic ... More
Generalized Friedmann branesAug 21 2003Sep 19 2008We prove that for a large class of generalized Randall-Sundrum II type models the characterization of brane-gravity sector by the effective Einstein equation, Codazzi equation and the twice-contracted Gauss equation is equivalent with the bulk Einstein ... More
No Swiss-cheese universe on the braneJul 02 2004Feb 22 2007We study the possibility of brane-world generalization of the Einstein-Straus Swiss-cheese cosmological model. We find the modifications induced by the brane-world scenario. At a first glance only the motion of the boundary is modified and the fluid in ... More
Linear Einstein equations and Kerr-Schild mapsMar 28 2002We prove that given a solution of the Einstein equations $g_{ab}$ for the matter field $T_{ab}$, an autoparallel null vector field $l^{a}$ and a solution $(l_{a}l_{c}, \mathcal{T}_{ac})$ of the linearized Einstein equation on the given background, the ... More
Spherically symmetric static solution for colliding null dustSep 04 1998The Einstein equations are integrated in the presence of two (incoming and outgoing) streams of null dust, under the assumptions of spherical symmetry and staticity. The solution is also written in double null and radiation coordinates and it is reinterpreted ... More
The HATNet and HATSouth Exoplanet SurveysJan 02 2018The Hungarian-made Automated Telescope Network (HATNet) has been in operation since 2003, with the key science goal being the discovery and accurate characterization of transiting extrasolar planets (TEPs) around bright stars. Using six small, 11\,cm\ ... More
Formulas on hyperbolic volumeOct 26 2010Nov 16 2010This paper collects some important formulas on hyperbolic volume. To determine concrete values of volume function is a very hard question requiring the knowledge of various methods. Our goal to give a non-elementary integral on the volume of the orthosceme ... More
An ADMM algorithm for solving a proximal bound-constrained quadratic programDec 29 2014We consider a proximal operator given by a quadratic function subject to bound constraints and give an optimization algorithm using the alternating direction method of multipliers (ADMM). The algorithm is particularly efficient to solve a collection of ... More
Dark energy from gravitational collapse?Jun 16 2006We discuss the status of both cosmological and black hole type singularities in the framework of the brane-world model of gravity. We point out that the Big Bang is not properly understood yet. We also show new features of the gravitational collapse on ... More
Potential Theory and Quadratic ProgrammingNov 09 2016We extend the notion of some energy-type expressions based on two sets, developed in the abstract potential theory. We also give the discretized version of the quantities defined, similar to Chebyshev constant. This extension allows to apply the potential-theoretic ... More
Weighted Fejér Constants and Fekete SetsJan 28 2013We give the connections among the Fekete sets, the zeros of orthogonal polynomials, $1(w)$-normal point systems, and the nodes of a stable and most economical interpolatory process via the Fej\'er contants. Finally the convergence of a weighted Gr\"unwald ... More
Wandering near the red edge: photometric observations of three cool ZZ Ceti starsOct 23 2018We summarize our findings on three cool ZZ Ceti type pulsating white dwarfs. We determined eight independent modes in HS 0733+4119, of which seven are new findings. For GD 154, we detected two new eigenmodes, and the recurrence of the pulsational behaviour ... More
An extensive photometric study of the Blazhko RR Lyrae star RZ LyrFeb 20 2012Jun 01 2012The analysis of recent, extended multicolour CCD and archive photoelectric, photographic and visual observations has revealed several important properties of RZ Lyr, an RRab-type variable exhibiting large-amplitude Blazhko modulation. On the time-base ... More
Spin-spin effects in radiating compact binariesNov 22 1999The dynamics of a binary system with two spinning components on an eccentric orbit is studied, with the inclusion of the spin-spin interaction terms appearing at the second post-Newtonian order. A generalized true anomaly parametrization properly describes ... More
Friedmann branes with variable tensionJun 24 2008Sep 22 2008We introduce brane-worlds with non-constant tension, strenghtening the analogy with fluid membranes, which exhibit a temperature-dependence according to the empirical law established by E\"otv\"os. This new degree of freedom allows for evolving gravitational ... More
A homogeneous brane-world universeSep 11 2003A homogeneous, Kantowski-Sachs type, bouncing brane-world universe is presented. The bulk has a positive cosmological constant and the Killing algebra $so(1,3)\oplus so(3)$. The totality of the source terms of the effective Einstein equation combine to ... More
Wormholes, naked singularities and universes of ghost radiationApr 03 2002Jan 09 2003Both the static and homogeneous metrics describing the spherically symmetric gravitational field of a crossflow of incoming and outgoing null dust streams are generalized for the case of the two-component ghost radiation. Static solutions represent either ... More
Second post-Newtonian radiative evolution of the relative orientations of angular momenta in spinning compact binariesMar 09 2000The radiative evolution of the relative orientations of the spin and orbital angular momentum vectors ${\bf S}_{{\bf 1}}, {\bf S}_{{\bf 2}}$ and ${\bf L}$, characterizing a binary system on eccentric orbit is studied up to the second post-Newtonian order. ... More
Degenerate Hessian structures on radiant manifoldsMar 02 2015Sep 29 2017We present a rigorous mathematical treatment of Ruppeiner geometry, by considering degenerate Hessian metrics defined on radiant manifolds. A manifold $M$ is said to be radiant if it is endowed with a symmetric, flat connection $\bar\nabla$ and a global ... More
Symmetric hyperbolic systems for Bianchi equationsMay 12 1998We obtain a family of first-order symmetric hyperbolic systems for the Bianchi equations. They have only physical characteristics: the light cone and timelike hypersurfaces. In the proof of the hyperbolicity, new positivity properties of the Bel tensor ... More
Normally distributed probability measure on the metric space of normsMay 19 2011Apr 26 2012In this paper we propose a method to construct probability measures on the space of convex bodies with a given pushforward distribution. Concretely we show that there is a measure on the metric space of centrally symmetric convex bodies, which pushforward ... More
Kerr-Schild metrics revisited I. The ground stateMar 26 2002The Kerr-Schild pencil of metrics $g_{ab}+\La l_al_b$ is investigated in the generic case when it maps an arbitrary vacuum space-time with metric $g_{ab}$ to a vacuum space-time. The theorem is proved that this generic case, with the field $l$ shearing, ... More
New variables for brane-world gravityMar 23 2006Geometric variables naturally occurring in a time-like foliation of brane-worlds are introduced. These consist of the induced metric and two sets of lapse functions and shift vectors, supplemented by two sets of tensorial, vectorial and scalar variables ... More
Gravitational radiation reaction in compact binary systems: Contribution of the quadrupole-monopole interactionNov 07 2002Nov 07 2002The radiation reaction in compact spinning binaries on eccentric orbits due to the quadrupole-monopole interaction is studied. This contribution is of second post-Newtonian order. As result of the precession of spins the magnitude $L$ of the orbital angular ... More
Hamiltonian theory of brane-world gravityDec 08 2006A brane-world universe consists of a 4-dimensional brane embedded into a 5-dimensional space-time (bulk). We apply the Arnowitt-Deser-Misner decomposition to the brane-world, which results in a 3+1+1 break-up of the bulk. We present the canonical theory ... More
No solvable lambda-value term left behindApr 28 2016Jul 13 2016In the lambda calculus a term is solvable iff it is operationally relevant. Solvable terms are a superset of the terms that convert to a final result called normal form. Unsolvable terms are operationally irrelevant and can be equated without loss of ... More
Derivation of models for linear viscoelastic shells by using asymptotic analysisApr 08 2016Feb 15 2017We consider a family of linear viscoelastic shells with thickness $2\varepsilon$ ( $\varepsilon$ , small parameter), clamped along a portion of their lateral face, all having the same middle surface $S$. We formulate the three-dimensional mechanical problem ... More
Linear Viscoelastic Shells: An Asymptotic ApproachApr 08 2016We consider a family of linear viscoelastic shells with thickness $2\varepsilon$ ( $\varepsilon$ , small parameter), clamped along a portion of their lateral face, all having the same middle surface $S$. We formulate the three-dimensional mechanical problem ... More
Testing General Relativity With Laser Accelerated Electron BeamsJul 16 2012Electron accelerations of the order of $10^{21} g$ obtained by laser fields open up the possibility of experimentally testing one of the cornerstones of general relativity, the weak equivalence principle, which states that the local effects of a gravitational ... More
3+1+1 dimensional covariant gravitational dynamics on an asymmetrically embedded braneNov 12 2009We give the evolution and constraint equations on an asymmetrically embedded brane in the form of average and difference equations.
Covariant gravitational dynamics in 3+1+1 dimensionsSep 02 2009May 11 2010We develop a 3+1+1 covariant formalism with cosmological and astrophysical applications. First we give the evolution and constraint equations both on the brane and off-brane in terms of 3-space covariant kinematical, gravito-electro-magnetic (Weyl) and ... More
Gravitational dynamics in s+1+1 dimensions II. Hamiltonian theorySep 13 2007We develop a Hamiltonian formalism of brane-world gravity, which singles out two preferred, mutually orthogonal directions. One is a unit twist-free field of spatial vectors with integral lines intersecting perpendicularly the brane. The other is a temporal ... More
Asymmetric Swiss-cheese brane-worldsAug 27 2006Jul 31 2007We study a brane-world cosmological scenario with local inhomogeneities represented by black holes. The brane is asymmetrically embedded into the bulk. The black strings/cigars penetrating the Friedmann brane generate a Swiss-cheese type structure. This ... More
Kerr-Schild metrics revisited II. The complete vacuum solutionMar 26 2002The complete solution of Einstein's gravitational equations with a vacuum-vacuum Kerr-Schild pencil of metrics $g_{ab}+V l_al_b$ is obtained. Our result generalizes the solution of the Kerr-Schild problem with a flat metric $g_{ab}$ (represented by the ... More
Weak gravitational lensing in brane-worldsFeb 20 2006We derive the deflection angle of light rays caused by a brane black hole with mass m and tidal charge q in the weak lensing approach, up to the second order in perturbation theory. We point out when the newly derived second order contributions become ... More
Solution of the vacuum Kerr-Schild problemMar 26 2002The complete solution of the vacuum Kerr-Schild equations in general relativity is presented, including the space-times with a curved background metric. The corresponding result for a flat background has been obtained by Kerr.
Effective field theory of modified gravity with two scalar fields: dark energy and dark matterFeb 04 2014Mar 29 2014We present a framework for discussing the cosmology of dark energy and dark matter based on two scalar degrees of freedom. An effective field theory of cosmological perturbations is employed. A unitary gauge choice renders the dark energy field into the ... More
Combined cosmological tests of a bivalent tachyonic dark energy scalar field modelAug 16 2014Dec 25 2014A recently investigated tachyonic scalar field dark energy dominated universe exhibits a bivalent future: depending on initial parameters can run either into a de Sitter exponential expansion or into a traversable future soft singularity followed by a ... More
Black hole tidal charge constrained by strong gravitational lensingMar 29 2012Dec 16 2013Spherically symmetric brane black holes have tidal charge, which modifies both weak and strong lensing characteristics. Even if lensing measurements are in agreement with a Schwarzschild lens, the margin of error of the detecting instrument allows for ... More
Bounded representation and radial projections of bisectors in normed spacesJan 30 2010It is well known that the description of topological and geometric properties of bisectors in normed spaces is a non-trivial subject. In this paper we introduce the concept of bounded representation of bisectors in finite dimensional real Banach spaces. ... More
The SERMON project: 48 new field Blazhko stars and an investigation of modulation-period distributionJun 29 2016We investigated 1234 fundamental mode RR Lyrae stars observed by the All Sky Automated Survey (ASAS) to identify the Blazhko (BL) effect. A sample of 1547 BL stars from the literature was collected to compare the modulation-period distribution with stars ... More
Multi-technique investigation of the binary fraction among A-F type candidate hybrid variable stars discovered by KeplerSep 11 2017Hundreds of candidate hybrid pulsators of intermediate type A-F were revealed by the recent space missions. Hybrid pulsators allow to study the full stellar interiors, where p- and g-modes are simultaneously excited. The true hybrid stars must be identified ... More
Irradiated asymmetric Friedmann branesJan 29 2006We consider a Friedmann brane moving in a bulk impregnated by radiation. The setup is strongly asymmetric, with only one black hole in the bulk. The radiation emitted by this bulk black hole can be reflected, absorbed or transmitted through the brane. ... More
Vacuum Kerr-Schild metrics generated by nontwisting congruencesMar 26 2002The Kerr-Schild pencil of metrics $\tilde g_{ab}=g_{ab}+V l_al_b$, with $g_{ab}$ and $\tilde g_{ab}$ satisfying the vacuum Einstein equations, is investigated in the case when the null vector $l$ has vanishing twist. This class of Kerr-Schild metrics ... More
Renormalized 2PN spin contributions to the accumulated orbital phase for LISA sourcesAug 12 2008Apr 21 2009We give here a new third post-Newtonisn (3PN) spin-spin contribution (in the PN parameter $\epsilon $) to the accumulated orbital phase of a compact binary, arising from the spin-orbit precessional motion of the spins. In the equal mass case this contribution ... More
Gravitational dynamics in s+1+1 dimensionsJul 06 2005Mar 06 2006We present the concomitant decomposition of an (s+2)-dimensional spacetime both with respect to a timelike and a spacelike direction. The formalism we develop is suited for the study of the initial value problem and for canonical gravitational dynamics ... More
On the validity of the 5-dimensional Birkhoff theorem: The tale of an exceptional caseDec 21 2007Jun 26 2008The 5-dimensional (5d) Birkhoff theorem gives the class of 5d vacuum space-times containing spatial hypersurfaces with cosmological symmetries. This theorem is violated by the 5d vacuum Gergely-Maartens (GM) space-time, which is not a representant of ... More
The geometry of the Barbour-Bertotti theories II. The three body problemMar 16 2000We present a geometric approach to the three-body problem in the non-relativistic context of the Barbour-Bertotti theories. The Riemannian metric characterizing the dynamics is analyzed in detail in terms of the relative separations. Consequences of a ... More