total 82065took 0.13s

Exotic Branes in M-TheoryMar 25 2019We revisit curious objects in string and M-theory called exotic brane---objects that are highly non-perturbative, possessing a tension that scales less than $g_s^{-2}$ and are generically of low-codimension. They are non-geometric in the sense that they ... More

Dynamics of branes in Double Field TheoryApr 04 2019In this contribution the construction of the Wess-Zumino term for Dp-branes and NS 5-branes invariant under T-duality is described. The cases of the massless Type IIA/B and the massive Type IIA theories are covered. Mass parameter is introduced by generalized ... More

Exceptional field theory: $SL(5)$Dec 07 2015Dec 09 2015In this work the exceptional field theory formulation of supergravity with SL(5) gauge group is considered. This group appears as a U-duality group of $D=7$ maximal supergravity. In the formalism presented the hidden global duality group is promoted into ... More

Gauged supergravities in 5 and 6 dimensions from generalised Scherk-Schwarz reductionsJan 03 2013Jun 15 2013It is shown that the Scherk-Schwarz reduction of M-theory in the Berman-Perry duality invariant formalism to 6 and 5 dimensions reproduces the known structures of gauged supergravities that are normally associated to non-geometric compactifications. The ... More

Exceptional Field Theory for $E_{6(6)}$ supergravityMar 29 2015Apr 07 2015A brief description of the supersymmetric and duality covariant approach to supergravity is presented. The formalism is based on exceptional geometric structures and turns the hidden U-duality group into a manifest gauge symmetry. Tensor hierarchy of ... More

Integrability properties of Motzkin polynomialsJun 01 2017Dec 05 2017We consider a Hamiltonian system which has its origin in a generalization of exact renormalization group flow of matrix scalar field theory and describes a non-linear generalization of the shock-wave equation that is known to be integrable. Analyzing ... More

U-dualities in Type II string theories and M-theoryNov 13 2013Dec 29 2013In this thesis the recently developed duality covariant approach to string and M-theory is investigated. In this formalism the U-duality symmetry of M-theory or T-duality symmetry of Type II string theory becomes manifest upon extending coordinates that ... More

O(d+1,d+1) enhanced double field theoryJul 20 2017Oct 17 2017Double field theory yields a formulation of the low-energy effective action of bosonic string theory and half-maximal supergravities that is covariant under the T-duality group O$(d,d)$ emerging on a torus $T^d$. Upon reduction to three spacetime dimensions ... More

Symmetry breaking gives rise to energy spectra of three states of matterJun 08 2013Oct 04 2013A fundamental task of statistical physics is to start with a microscopic Hamiltonian, predict the system's statistical properties and compare them with observable data. A notable current fundamental challenge is to tell whether and how an interacting ... More

Five-brane actions in double field theoryDec 05 2017Mar 25 2018We construct an action for NSNS 5-branes which is manifestly covariant under O(d,d). This is done by doubling $d$ of the spacetime coordinates which appear in the worldvolume action. By formulating the DBI part of the action in a manner similar to a "gauged ... More

T-duality and entanglement entropy for NS five-branesJun 06 2018Aug 06 2018In this work an algorithm is proposed to calculate entropy for field theories living on NS five branes, which gives a result invariant under T-duality. This is a deformation of the well known Ryu-Takayanagi formula, which takes into account dependence ... More

Exceptional field theory: $SO(5,5)$Apr 07 2015Jun 23 2015We construct Exceptional Field Theory for the group $SO(5,5)$ based on the extended (6+16)-dimensional spacetime, which after reduction gives the maximal $D=6$ supergravity. We present both a true action and a duality-invariant pseudo-action formulations. ... More

U-dualities in Type II string theories and M-theoryNov 13 2013Dec 29 2017In this thesis the recently developed duality covariant approach to string and M-theory is investigated. In this formalism the U-duality symmetry of M-theory or T-duality symmetry of Type II string theory becomes manifest upon extending coordinates that ... More

Non-geometric branes are DFT monopolesJul 19 2016The double field theory monopole solution by Berman and Rudolph is shown to reproduce non-geometric backgrounds with non-vanishing Q- and R-flux upon an appropriate choice of physical and dual coordinates. The obtained backgrounds depend non-trivially ... More

Boundary Terms in Generalized Geometry and doubled field theoryOct 14 2011Oct 19 2011We propose a boundary action to complement the recently developed duality manifest actions in string and M-theory using generalized geometry. This boundary action combines the Gibbons-Hawking term with boundary pieces that were previously neglected in ... More

Classical Yang-Baxter equation from beta-supergravityNov 22 2018Jan 26 2019Yang-Baxter deformations of superstring sigma-models have recently inspired a supergravity solution generating technique. Using the open/closed string map and a Killing bi-vector as a deformation parameter, new solutions can be built, such that the (generalised) ... More

The different faces of branes in Double Field TheoryMar 13 2019We show how the Wess-Zumino terms of the different branes in string theory can be embedded within double field theory. Crucial ingredients in our construction are the identification of the correct brane charge tensors {and the use of the} double field ... More

The different faces of branes in Double Field TheoryMar 13 2019Mar 27 2019We show how the Wess-Zumino terms of the different branes in string theory can be embedded within double field theory. Crucial ingredients in our construction are the identification of the correct brane charge tensors and the use of the double field theory ... More

Fermions and Supersymmetry in $\rm E_{6(6)}$ Exceptional Field TheoryDec 23 2014We construct the supersymmetric completion of E$_{6(6)}$-covariant exceptional field theory. The theory is based on a $(5+27)$-dimensional generalized space-time subject to a covariant section constraint. The fermions are tensors under the local Lorentz ... More

Exotic Branes in Exceptional Field Theory: $E_{7(7)}$ and BeyondJun 01 2018Jul 24 2018In recent years, it has been widely argued that the duality transformations of string and M-theory naturally imply the existence of so-called `exotic branes'---low codimension objects with highly non-perturbative tensions, scaling as $g_s^{\alpha}$ for ... More

Order $α'$ heterotic domain walls with warped nearly Kähler geometrySep 01 2014Dec 04 2014We consider 1+3-dimensional domain wall solutions of heterotic supergravity on a six-dimensional warped nearly K\"ahler manifold $X_6$ in the presence of gravitational and gauge instantons of tanh-kink type as constructed in [arXiv:1109.3552]. We include ... More

Duality Invariant M-theory: Gauged supergravities and Scherk-Schwarz reductionsJul 31 2012Oct 20 2012We consider the reduction of the duality invariant approach to M-theory by a U-duality group valued Scherk-Schwarz twist. The result is to produce potentials for gauged supergravities that are normally associated with non-geometric compactifications. ... More

Unified phonon-based approach to the thermodynamics of solid, liquid and gas statesDec 22 2015We introduce a unified approach to states of matter (solid, liquid and gas) and describe the thermodynamics of the pressure-temperature phase diagram in terms of phonon excitations. We derive the effective Hamiltonian with low-energy cutoff in two transverse ... More

Exotic branes in Exceptional Field Theory: the SL(5) duality groupOct 26 2017Aug 11 2018We study how exotic branes, i.e. branes whose tensions are proportional to $g_s^{-\alpha}$, with $\alpha>2$, are realised in Exceptional Field Theory (EFT). The generalised torsion of the Weitzenb\"ock connection of the $\operatorname{SL}(5)$ EFT which, ... More

Large-scale Biological Meta-database ManagementMar 26 2015Feb 22 2016Up-to-date meta-databases are vital for the analysis of biological data. However,the current exponential increase in biological data leads to exponentially increasing meta-database sizes. Large-scale meta-database management is therefore an important ... More

Comments on QED with background electric fieldsJan 05 2009Feb 23 2009It is well known that there is a total cancellation of the \emph{factorizable} IR divergences in unitary interacting field theories, such as QED and quantum gravity. In this note we show that such a cancellation does not happen in QED with background ... More

An exact statement for Wilsonian and Holographic renormalization groupJan 22 2010Mar 03 2010We show that Polchinski equations in the D--dimensional matrix scalar field theory can be reduced at large $N$ to the Hamiltonian equations in a (D+1)-dimensional theory. In the subsector of the $\Tr \phi^l$ (for all $l$) operators we find the exact form ... More

Hints on integrability in the Wilsonian/holographic renormalization groupJun 10 2010Sep 20 2011The Polchinski equations for the Wilsonian renormalization group in the $D$--dimensional matrix scalar field theory can be written at large $N$ in a Hamiltonian form. The Hamiltonian defines evolution along one extra holographic dimension (energy scale) ... More

Experimental study of an advanced concept of moderate-resolution holographic spectrographsApr 17 2018We present the results of an experimental study of an advanced moderate-resolution spectrograph based on a cascade of narrow-band holographic gratings. The main goal of the project is to achieve a moderately high spectral resolutionwith R up to 5000 simultaneously ... More

Determining gravitational lensing effects on supernovae observationsOct 24 2000In this paper we use a generalized version of a method originally proposed by Holz and Wald to investigate the effects from gravitational lensing on Type Ia supernovae measurements. We find that results for different mass distributions in smooth dark ... More

Cosmological histories in bimetric gravity: A graphical approachJan 02 2017Mar 01 2017The bimetric generalization of general relativity has been proven to be able to give an accelerated background expansion consistent with observations. Apart from the energy densities coupling to one or both of the metrics, the expansion will depend on ... More

Cosmological histories from the Friedmann equation: The universe as a particleJun 27 2016In this note, we discuss how possible expansion histories of the universe can be inferred in a simple way, for arbitrary energy contents. No new physical results are obtained, but the goal is rather to discuss an alternative way of writing the Friedmann ... More

Calibrating Milky Way dust extinction using cosmological sourcesOct 08 2012Jan 16 2013We constrain the light extinction properties of Milky Way dust. We investigated the correlations between dust column density as inferred from infrared data and the observed colours of celestial objects at cosmological distances with low levels of colour ... More

On a theorem concerning the elliptic functionsDec 26 2012This is a literal word-for-word translation from the French of Phragmen's proof (the first such published) of Weierstrass' famous theorem characterizing all analytic functions which possess an algebraic addition theorem.

Discovery of the secondary star of the HgMn binary kappa CancriMay 12 1998A careful investigation of a CCD spectrum of the SB1 system kappa Cnc in the spectral region 3800 A - 8000 A resulted in the discovery of the lines of the secondary star. We then analyzed several short-wavelength range Reticon spectra obtained at different ... More

Strong lensing, cosmology and lensing halosOct 05 2005Jan 12 2006With future wide and deep cosmological sky surveys, a large number of gravitationally lensed, multiply imaged systems will be found. In addition to multiply imaged galaxies and quasars, sources will include transient events like supernovae and gamma ray ... More

Does the Hubble constant tension call for new physics?Jan 22 2018The $\Lambda$ Cold Dark Matter model ($\Lambda$CDM) represents the current standard model in cosmology. Within this, there is a tension between the value of the Hubble constant, $H_0$, inferred from local distance indicators and the angular scale of fluctuations ... More

Scalar instabilities in bimetric gravity: The Vainshtein mechanism and structure formationJun 16 2015Jul 06 2015We investigate the observational consequences of scalar instabilities in bimetric theory, under the assumption that the Vainshtein mechanism restores general relativity within a certain distance from gravitational sources. We argue that early time instabilities ... More

Supernovae as seen by off-center observers in a local voidSep 25 2009May 18 2010Inhomogeneous universe models have been proposed as an alternative explanation for the apparent acceleration of the cosmic expansion that does not require dark energy. In the simplest class of inhomogeneous models, we live within a large, spherically ... More

Model independent constraints on the cosmological expansion rateNov 06 2008Jan 28 2009We investigate what current cosmological data tells us about the cosmological expansion rate in a model independent way. Specifically, we study if the expansion was decelerating at high redshifts and is accelerating now, without referring to any model ... More

On the use of black hole binaries as probes of local dark energy propertiesOct 13 2009Dec 21 2009Accretion of dark energy onto black holes will take place when dark energy is not a cosmological constant. It has been proposed that the time evolution of the mass of the black holes in binary systems due to dark energy accretion could be detectable by ... More

Constraints on intergalactic dust from quasar coloursAug 04 2003Sep 02 2003Colour measurements of quasars are used to constrain the abundance and properties of intergalactic dust and the related extinction effects on high-z sources. For Type Ia supernovae at z = 1, we derive an upper limit on the possible dimming from intergalactic ... More

Combined constraints on intergalactic dust from quasar colours and the soft X-ray backgroundSep 04 2012Unless properly corrected for, the existence of intergalactic dust will introduce a redshift dependent magnitude offset to standard candle sources. This would lead to overestimated luminosity distances compared to a dust-free universe and bias the cosmological ... More

Cosmological constraints on the dark energy equation of state and its evolutionJul 13 2004Jul 19 2004We have calculated constraints on the evolution of the equation of state of the dark energy, w(z), from a joint analysis of data from the cosmic microwave background, large scale structure and type-Ia supernovae. In order to probe the time-evolution of ... More

Spherically Symmetric Solutions in Massive Gravity and Constraints from GalaxiesNov 25 2011In this paper, analytical solutions describing static and spherically symmetric sources in the decoupling limit of massive gravity are derived. We analyze the model parameter range and specify when a Vainshtein mechanism is possible. Furthermore, we use ... More

A model independent measure of the large scale curvature of the UniverseFeb 22 2011Cosmological distances as a function of redshift depend on the effective curvature density via the effect on the geometrical path of photons from large scale spatial curvature and its effect on the expansion history, H(z). Cosmological time, however, ... More

Limiting the dimming of distant type Ia supernovaeOct 21 2004Feb 14 2005Distant supernovae have been observed to be fainter than what is expected in a matter dominated universe. The most likely explanation is that the universe is dominated by an energy component with negative pressure -- dark energy. However, there are several ... More

Probing the dark side: Constraints on the dark energy equation of state from CMB, large scale structure and Type Ia supernovaeMay 07 2002Aug 31 2002We have reanalysed constraints on the equation of state parameter, w_Q = P/rho, of the dark energy, using several cosmological data sets and relaxing the usual constraint w_Q > -1. We find that combining Cosmic Microwave Background, large scale structure ... More

The lensing time delay between gravitational and electromagnetic wavesAug 17 2018Aug 30 2018The recent detection of gravitational waves (GWs) and electromagnetic (EM) waves originating from the same source marks the start of a new multi-messenger era in astronomy. The arrival time difference between the GW and EM signal can be used to constrain ... More

Strong lensing constraints on bimetric massive gravityJun 05 2013Feb 13 2014We derive dynamical and gravitational lensing properties of local sources in the Hassan-Rosen bimetric gravity theory. Observations of elliptical galaxies rule out values of the effective length-scale of the theory, in units of the Hubble radius, in the ... More

Constraining photon-axion oscillations using quasar spectraMar 04 2003Using quasar spectra from the SDSS survey, we constrain the possibility of photon-axion oscillations as a source of dimming of high redshift objects. Such a process has been suggested as an explanation of the apparent faintness of distant Type Ia supernovae. ... More

On stars, galaxies and black holes in massive bigravityJul 03 2015Dec 04 2015In this paper we study the phenomenology of stars and galaxies in massive bigravity. We give parameter conditions for the existence of viable star solutions when the radius of the star is much smaller than the Compton wavelength of the graviton. If these ... More

Abundance analysis of two late A-type stars HD 32115 and HD 37594Jun 10 2002We have performed abundance analysis of two slowly rotating, late A-type stars, HD 32115 (HR 1613) and HD 37594 (HR 1940), based on obtained echelle spectra covering the spectral range 4000-9850 AAngstrom. These spectra allowed us to identify an extensive ... More

On generalization of the Freudental's theorem for compact irreducible standard polyhedric representation for superparacompact complete metrizable spacesApr 02 2013In this paper for superparacompact complete metrizable spaces the Freudenthal's theorem for compact irreducible standard polyhedric representation is generalized. Furthermore, for superparacompact metric spaces are reinforced: 1) the Morita's theorem ... More

Probing galaxy density profiles with future supernova surveysJun 15 2004Oct 12 2004In this paper we discuss the possibility to measure the Hubble parameter and the slope of galaxy density profiles using future supernova data. With future supernova surveys such as SNAP, large numbers of core collapse supernovae will be discovered, a ... More

Extinction properties of lensing galaxiesNov 27 2007May 02 2008Context. Observations of quasars shining through foreground galaxies, offer a way to probe the dust extinction curves of distant galaxies. Interesting objects for this study are found in strong gravitational lensing systems, where the foreground galaxies ... More

Measuring the properties of extragalactic dust and implications for the Hubble diagramJan 02 2002Scattering and absorption of light by a homogeneous distribution of intergalactic large dust grains has been proposed as an alternative, non-cosmological explanation for the faintness of Type Ia supernovae at $z\s im 0.5$. We investigate the differential ... More

The effect of inhomogeneities on dark energy constraintsOct 06 2017Jun 27 2018Constraints on models of the late time acceleration of the universe assume the cosmological principle of homogeneity and isotropy on large scales. However, small scale inhomogeneities can alter observational and dynamical relations, affecting the inferred ... More

Gravitational lensing of the farthest known supernova SN1997ffMay 21 2001Feb 06 2003We investigate the effects of gravitational lensing due to intervening galaxies on the recently discovered Type Ia supernova at z=1.7, SN1997ff, in the Hubble Deep Field North. We find that it is possible to obtain a wide range of magnifications by varying ... More

Constraining dark energy fluctuations with supernova correlationsJun 23 2010Oct 28 2010We investigate constraints on dark energy fluctuations using type Ia supernovae. If dark energy is not in the form of a cosmological constant, that is if the equation of state is not equal to -1, we expect not only temporal, but also spatial variations ... More

Photon-axion oscillations and Type Ia supernovaeFeb 07 2002Apr 15 2002We compute the probability of photon-axion oscillations in the presence of both intergalactic magnetic fields and an electron plasma and investigate the effect on Type Ia supernovae observations. The conversion probability is calculated using a density ... More

Classification and asymptotic structure of black holes in bimetric theoryMar 22 2017Sep 07 2017We study general properties of static and spherically symmetric bidiagonal black holes in Hassan-Rosen bimetric theory. In particular, we explore the behaviour of the black hole solutions both at the common Killing horizon and at the large radii. The ... More

Bimetric cosmology is compatible with local tests of gravityDec 20 2018Recently, Kenna-Allison et.al. claimed that bimetric gravity cannot give rise to a viable cosmological expansion history while at the same time being compatible with local gravity tests. In this note we review that claim and combine various results from ... More

Probing Dark Energy Inhomogeneities with SupernovaeJun 03 2008Jun 30 2008We discuss the possibility to identify anisotropic and/or inhomogeneous cosmological models using type Ia supernova data. A search for correlations in current type Ia peak magnitudes over a large range of angular scales yields a null result. However, ... More

The dynamics of laser droplet generationMar 01 2010We propose an experimental setup allowing for the characterization of laser droplet generation in terms of the underlying dynamics, primarily showing that the latter is deterministically chaotic by means of nonlinear time series analysis methods. In particular, ... More

Can a void mimic the $Λ$ in $Λ$CDM?Mar 27 2015Dec 16 2015We investigate Lema\^itre-Tolman-Bondi (LTB) models, whose early time evolution and bang time are homogeneous and the distance - redshift relation and local Hubble parameter are inherited from the $\Lambda$CDM model. We show that the obtained LTB models ... More

Experimental observation of a chaos-to-chaos transition in laser droplet generationAug 03 2010We examine the dynamics of laser droplet generation in dependence on the detachment pulse power. In the absence of the detachment pulse, undulating pendant droplets are formed at the end of a properly fed metal wire due to the impact of the primary laser ... More

Tuning Gravitationally Lensed Standard SirensNov 10 2006Gravitational waves emitted by chirping supermassive black hole binaries could in principle be used to obtain very accurate distance determinations. Provided they have an electromagnetic counterpart from which the redshift can be determined, these standard ... More

Reducing the gravitational lensing scatter of Type Ia supernovae without introducing any extra biasOct 23 2008Magnification and de-magnification due to gravitational lensing will contribute to the brightness scatter of Type Ia supernovae (SNe Ia). The purpose of this paper is to investigate the possibility to decrease this scatter by correcting individual SNe ... More

The evolutionary status of the UX Orionis star RZ PisciumSep 13 2011The star RZ Psc is one of the most enigmatic members of the UX Ori star family. It shows all properties that are typical for these stars (the light variability, high linear polarization in deep minima, the blueing effect) except for one: it lacks any ... More

About the chemical composition of delta Scuti - the prototype of the class of pulsating variablesOct 13 2004We present chemical abundances in the photosphere of $\delta$ Scuti -- the prototype of the class of pulsating variables -- determined from the analysis of a spectrum obtained at Terskol observatory 2 meter telescope with resolution $R=52,000$, signal ... More

Prospects and pitfalls of gravitational lensing in large supernova surveysJun 09 2008To investigate the effect of gravitational lensing of supernovae in large ongoing surveys, we simulate the effect of gravitational lensing magnification on individual supernovae using observational data input from two large supernova surveys. To estimate ... More

Algebraic Properties of Einstein Solutions in Ghost-Free Bimetric TheoryJun 02 2017A known fact is that an Einstein solution in one sector in ghost-free bimetric theory implies an Einstein solution in the other sector. Earlier studies have also shown that some classes of bimetric models necessitate proportional solutions between the ... More

Growth Histories in Bimetric Massive GravityJun 15 2012We perform cosmological perturbation theory in Hassan-Rosen bimetric gravity for general homogeneous and isotropic backgrounds. In the de Sitter approximation, we obtain decoupled sets of massless and massive scalar gravitational fluctuations. Matter ... More

Narrowing down the possible explanations of cosmic acceleration with geometric probesMay 16 2017Recent re-calibration of the Type Ia supernova (SNe~Ia) magnitude-redshift relation combined with cosmic microwave background (CMB) and baryon acoustic oscillation (BAO) data have provided excellent constraints on the standard cosmological model. Here, ... More

Lensing effects in an inhomogeneous universeDec 09 1999Apr 14 2000Recently, Holz & Wald have presented a new method for determining gravitational lensing effects on, e.g., supernova luminosity versus redshift measurements in inhomogeneous universes. In this paper, their method is generalized in several ways: First, ... More

On Birkhoff's theorem in ghost-free bimetric theoryAug 25 2017We consider the Hassan-Rosen bimetric field equations in vacuum when the two metrics share a single common null direction in a spherically symmetric configuration. By solving these equations, we obtain a class of exact solutions of the generalized Vaidya ... More

Cosmic expansion histories in massive bigravity with symmetric matter couplingSep 09 2014Jan 10 2015We study the cosmic expansion history of massive bigravity with a viable matter coupling which treats both metrics on equal footing. We derive the Friedmann equation for the effective metric through which matter couples to the two metrics, and study its ... More

Covariant BSSN formulation in bimetric relativityApr 16 2019Numerical integration of the field equations in bimetric relativity is necessary to obtain solutions describing realistic systems. Thus, it is crucial to recast the equations into a well-posed form. In general relativity, under certain assumptions, the ... More

Spectroscopic variability of IRAS22272+5435Nov 11 2015A time series of high-resolution spectra was observed in the optical wavelength region for the bright proto-planetary nebula IRAS22272+5435 (HD235858), along with a simultaneous monitoring of its radial velocity and $BVR_C$ magnitudes. The object is known ... More

Tentative detection of the gravitational magnification of type Ia supernovaeDec 12 2006The flux from distant type Ia supernovae (SN) is likely to be amplified or de-amplified by gravitational lensing due to matter distributions along the line-of-sight. A gravitationally lensed SN would appear brighter or fainter than the average SN at a ... More

Corrections for gravitational lensing of supernovae: better than average?Jun 30 2005Nov 08 2005We investigate the possibility of correcting for the magnification due to gravitational lensing of standard candle sources, such as Type Ia supernovae. Our method uses the observed properties of the foreground galaxies along the lines-of-sight to each ... More

Weighing dark matter haloes with gravitationally lensed supernovaeOct 21 2009High redshift Type Ia supernovae (SNe Ia) are likely to be gravitationally lensed by dark matter haloes of galaxies in the foreground. Since SNe Ia have very small dispersion after light curve shape and colour corrections, their brightness can be used ... More

The neutrino mass bound from WMAP-3, the baryon acoustic peak, the SNLS supernovae and the Lyman-alpha forestFeb 07 2006May 29 2006We have studied bounds on the neutrino mass using new data from the WMAP 3 year data, the Sloan Digital Sky Survey measurement of the baryon acoustic peak, the Type Ia supernovae from SNLS, and the Lyman-alpha forest. We find that even in the most general ... More

Spacetime symmetries and topology in bimetric relativityOct 17 2017Apr 19 2018We explore spacetime symmetries and topologies of the two metric sectors in Hassan-Rosen bimetric theory. We show that, in vacuum, the two sectors can either share or have separate spacetime symmetries. If stress-energy tensors are present, a third case ... More

Spherical dust collapse in bimetric relativity: Bimetric polytropesApr 18 2019We present a method for solving the constraint equations in the Hassan-Rosen bimetric theory to determine the initial data for the gravitational collapse of spherically symmetric dust. The setup leads to equations similar to those for a polytropic fluid ... More

Atmospheric abundances of CP SB2 star components of equal masses. II. 66 EridaniMay 15 1998We report the results of abundance determination for the components of the SB2 star 66 Eri (M_A/M_B=0.97) from high resolution CCD echelle spectra with S/N>=100 taken with the 1-m telescope of Special Astrophysical Observatory (Zelenchuck, Russia). The ... More

On metal-deficient barium stars and their link with yellow symbiotic starsJun 24 2005This paper addresses the question of why metal-deficient barium stars are not yellow symbiotic stars (YSyS). Samples of (suspected) metal-deficient barium (mdBa) stars and YSyS have been collected from the literature, and their properties reviewed. It ... More

Quantum transitions induced by the third cumulant of current fluctuationsJun 23 2005Oct 14 2005We investigate the transitions induced by external current fluctuations on a small probe quantum system. The rates for the transitions between the energy states are calculated using the real-time Keldysh formalism for the density matrix evolution. We ... More

Momentum-space structure of surface states in a topological semimetal with a nexus point of Dirac linesApr 21 2016Jun 27 2016Three-dimensional topological semimetals come in different variants, either containing Weyl points or Dirac lines. Here we describe a more complicated momentum-space topological defect where several separate Dirac lines connect with each other, forming ... More

The chemical composition of a mild barium star HD202109Aug 20 2003Oct 08 2003We present the result of chemical abundances of a mild barium star HD202109 (zeta Cyg) determined from the analysis of spectrum obtained by using a 2-m telescope at the Peak Terskol Observatory and a high-resolution spectrometer with R=80,000, signal ... More

The structure and kinematics of the the Galaxy thin gaseous disc outside the solar orbitJan 06 2015The rotation curve of the Galaxy is generally thought to be flat. However, using radial velocities from interstellar molecular clouds, which is common in rotation curve determination, seems to be incorrect and may lead to incorrectly inferring that the ... More

The spectral variations of the O-type runaway supergiant HD 188209Feb 21 2000We report spectral time series of the late O-type runaway supergiant HD 188209. Radial velocity variations of photospheric absorption lines with a possible quasi-period ~ 6.4 days have been detected in high-resolution echelle spectra. Night-to-night variations ... More

The evolved pulsating CEMP star HD112869Nov 16 2015Nov 20 2015Radial velocity measurements, $BVR_C$ photometry, and high-resolution spectroscopy in the wavelength region from blue to near infrared are employed in order to clarify the evolutionary status of the carbon-enhanced metal-poor star HD112869 with unique ... More

Explicit Global Coordinates for Schwarzschild and Reissner-NordstroemJul 05 1995Mar 16 1996We construct coordinate systems that cover all of the Reissner-Nordstroem solution with m>|q| and m=|q|, respectively. This is possible by means of elementary analytical functions. The limit of vanishing charge q provides an alternative to Kruskal which, ... More

Classical and Quantum Gravity in 1+1 Dimensions, Part I: A Unifying ApproachAug 08 1995Aug 11 1997We provide a concise approach to generalized dilaton theories with and without torsion and coupling to Yang-Mills fields. Transformations on the space of fields are used to trivialize the field equations locally. In this way their solution becomes accessible ... More

QCD Phenomenology based on a Chiral Effective LagrangianJan 23 1994We review the Nambu-Jona-Lasinio (NJL) approach to the dynamical breaking of chiral symmetry in Quantum Chromodynamics (QCD). The subjects treated in Part I include the vacuum structure of QCD, mass spectra and coupling constants of hadrons, flavor mixing ... More

Perturbative calculation of the spin-wave dispersion in a disordered double-exchange modelJun 05 2004We study the spin-wave dispersion of localized spins in a disordered double-exchange model using the perturbation theory with respect to the strength of the disorder potential. We calculate the dispersion upto the next-leading order, and extensively examine ... More

A Solution to the Doublet-Triplet Splitting Problem in the Type IIB SupergravityAug 11 2002The doublet--triplet mass splitting problem is one of the most serious problems in supersymmetric grand unified theories (GUTs). A class of models based on a product gauge group, such as the SU(5)_{GUT} times U(3)_H or the SU(5)_{GUT} times U(2)_H, realize ... More

Semiclassical ionization dynamics of the hydrogen molecular ion in an electric field of arbitrary orientationOct 12 2004Quasi-static models of barrier suppression have played a major role in our understanding of the ionization of atoms and molecules in strong laser fields. Despite their success, in the case of diatomic molecules these studies have so far been restricted ... More