Results for "B. Buysschaert"

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Period spacings of gravity modes in rapidly rotating magnetic stars I. Axisymmetric fossil field with poloidal and toroidal componentsMar 13 2019Context. Stellar magnetic fields are one of the candidates often invoked to explain the missing transport of angular momentum observed in the models of stellar interiors. However, the properties of an internal magnetic field and the consequences of its ... More
Preparing and correcting extracted BRITE observationsOct 18 2016Extracted BRITE lightcurves must be carefully prepared and corrected for instrumental effects before a scientific analysis can be performed. Therefore, we have created a suite of Python routines to prepare and correct the lightcurves, which is publicly ... More
Studying the photometric and spectroscopic variability of the magnetic hot supergiant $ζ$ Orionis AaApr 03 2017Massive stars play a significant role in the chemical and dynamical evolution of galaxies. However, much of their variability, particularly during their evolved supergiant stage, is poorly understood. To understand the variability of evolved massive stars ... More
Understanding the photometric variability of ζ Ori AaOct 18 2016We studied the variability of the magnetic O-type supergiant $\zeta$ Ori Aa using multi-colour BRITE photometry. We confirmed the known rotation frequency $f_{\rm rot} = 0.15 \pm 0.02$ c/d, and detected some of its higher harmonics, of which $4f_{\rm ... More
K2 space photometry reveals rotational modulation and stellar pulsations in chemically peculiar A and B starsMay 04 2018May 11 2018The physics of magnetic hot stars and how a large-scale magnetic field affects their interior properties is largely unknown. Few studies have combined high-quality observations and modelling of magnetic pulsating stars, known as magneto-asteroseismology, ... More
The Most Massive Heartbeat: An In-depth Analysis of ι OrionisMar 06 2017{\iota} Ori is a well studied massive binary consisting of an O9 III + B1 III/IV star. Due to its high eccentricity (e = 0.764) and short orbital period (P orb = 29.13376 d), it has been considered to be a good candidate to show evidence of tidal effects; ... More
Binary Asteroseismic Modelling: isochrone-cloud methodology and application to Kepler gravity-mode pulsatorsOct 01 2018The simultaneous presence of variability due to both pulsations and binarity is no rare phenomenon. Unfortunately, the complexities of dealing with even one of these sources of variability individually means that the other signal is often treated as a ... More
Detection of magnetic fields in chemically peculiar stars observed with the K2 space missionMay 02 2018We report the results of an observational study aimed at searching for magnetic pulsating hot stars suitable for magneto-asteroseismology. A sample of sixteen chemically peculiar stars was selected and analysed using both high-resolution spectropolarimetry ... More
Forward seismic modelling of the pulsating magnetic B-type star HD 43317May 02 2018May 31 2018The large-scale magnetic fields detected at the surface of about 10% of hot stars extend into the stellar interior, where they may alter the structure. Deep inner regions of stars are only observable using asteroseismology. Here, we investigated the pulsating ... More
Testing the asymptotic relation for period spacings from mixed modes of red giants observed with the Kepler missionFeb 08 2016Dipole mixed pulsation modes of consecutive radial order have been detected for thousands of low-mass red-giant stars with the NASA space telescope Kepler. Such modes have the potential to reveal information on the physics of the deep stellar interior. ... More
Kepler's first view of O-star variability: K2 data of five O stars in Campaign 0 as a proof-of-concept for O-star asteroseismologyJul 11 2015We present high-precision photometric light curves of five O-type stars observed with the refurbished {\it Kepler\/} satellite during its Campaign 0. For one of the stars, we also assembled high-resolution ground-based spectroscopy with the {\sc hermes} ... More
Forward asteroseismic modeling of stars with a convective core from gravity-mode oscillations: parameter estimation and stellar model selectionJun 18 2018We propose a methodological framework to perform forward asteroseismic modeling of stars with a convective core, based on gravity-mode oscillations. These probe the near-core region in the deep stellar interior. The modeling relies on a set of observed ... More
Photometric detection of internal gravity waves in early-type stars observed by CoRoTNov 30 2018Early-type stars are predicted to excite an entire spectrum of internal gravity waves (IGWs) at the interface of their convective cores and radiative envelopes. Numerical simulations of IGWs predict stochastic low-frequency variability in photometric ... More
On the photometric detection of Internal Gravity Waves in upper main-sequence stars I. Methodology and application to CoRoT targetsNov 19 2018Context. Main sequence stars with a convective core are predicted to stochastically excite Internal Gravity Waves (IGWs), which effectively transport angular momentum throughout the stellar interior and explain the observed near-uniform interior rotation ... More
K2 photometry and HERMES spectroscopy of the blue supergiant rho Leo: rotational wind modulation and low-frequency wavesFeb 02 2018We present an 80-d long uninterrupted high-cadence K2 light curve of the B1Iab supergiant rho Leo (HD 91316), deduced with the method of halo photometry. This light curve reveals a dominant frequency of $f_{\rmrot}=0.0373$d$^{-1}$ and its harmonics. This ... More
On the sensitivity of gravito-inertial modes to differential rotation in intermediate-mass main-sequence starsJun 10 2018Jun 26 2018Context. While rotation has a major impact on stellar structure and evolution, its effects are not well understood. Thanks to high- quality and long timebase photometric observations obtained with recent space missions, we are now able to study stellar ... More
K2 photometry and HERMES spectroscopy of the blue supergiant rho Leo: rotational wind modulation and low-frequency wavesFeb 02 2018Feb 13 2018We present an 80-d long uninterrupted high-cadence K2 light curve of the B1Iab supergiant rho Leo (HD 91316), deduced with the method of halo photometry. This light curve reveals a dominant frequency of $f_{\rmrot}=0.0373$d$^{-1}$ and its harmonics. This ... More
Discovery of two new bright magnetic B stars: i Car and AtlasAug 27 2015The BRITE (BRIght Target Explorer) constellation of nano-satellites performs seismology of bright stars via high precision photometry. In this context, we initiated a high resolution, high signal-to-noise, high sensitivity, spectropolarimetric survey ... More
The evolution of magnetic fields in hot starsFeb 22 2017Over the last decade, tremendous strides have been achieved in our understanding of magnetism in main sequence hot stars. In particular, the statistical occurrence of their surface magnetism has been established (~10%) and the field origin is now understood ... More
Discovery of magnetic A supergiants: the descendants of magnetic main sequence B starsJul 03 2017In the context of the high resolution, high signal-to-noise ratio, high sensitivity, spectropolarimetric survey BritePol, which complements observations by the BRITE constellation of nanosatellites for asteroseismology, we are looking for and measuring ... More
BRITE-Constellation high-precision time-dependent photometry of the early-O-type supergiant $ζ$ Puppis unveils the photospheric drivers of its small- and large-scale wind structuresOct 23 2017From $5.5$ months of dual-band optical photometric monitoring at the $1$ mmag level, BRITE-Constellation has revealed two simultaneous types of variability in the O4I(n)fp star $\zeta$ Puppis: one single periodic non-sinusoidal component superimposed ... More
Continuum Lowering -- A New PerspectiveSep 05 2013Apr 23 2014What is meant by continuum lowering and ionization potential depression (IPD) in a Coulomb system depends upon precisely what question is being asked. It is shown that equilibrium (equation-of-state) phenomena and non-equilibrium dynamical processes like ... More
Gauge symmetries decrease the number of Dp-brane dimensions. II. Inclusion of the Liouville termNov 17 2006Apr 26 2007The presence of the antisymmetric background field $B_{\mu\nu}$ leads to the noncommutativity of the Dp-brane manifold, while the linear dilaton field in the form $\Phi(x)=\Phi_0+a_\mu x^\mu$, causes the appearance of the commutative Dp-brane coordinate, ... More
A Riemannian approach to low-rank algebraic Riccati equationsDec 17 2013May 28 2014We propose a Riemannian optimization approach for computing low-rank solutions of the algebraic Riccati equation. The scheme alternates between fixed-rank optimization and rank-one updates. The fixed-rank optimization is on the set of fixed-rank symmetric ... More
Inclusive Charmed-Baryon Decays and LifetimesApr 30 1997Jul 11 1997We have quantitatively reanalyzed the inclusive charmed-baryon decays. New ingredients are the Voloshin preasymptotic effects in semileptonic decays and the Cabibbo-subleading contributions to both semileptonic and nonleptonic decays. It has been found ... More
Power spectrum of electron number density perturbations at cosmological recombination epochDec 12 2008Feb 19 2009The power spectrum of number density perturbations of free electrons is obtained for the epoch of cosmological recombination of hydrogen. It is shown that amplitude of the electron perturbations power spectrum of scales larger than acoustic horizon exceeds ... More
Energy dependence of particle multiplicities in central Au+Au collisionsAug 08 2001We present the first measurement of the pseudorapidity density of primary charged particles in Au+Au collisions at sqrt(s_NN) = 200GeV. For the 6% most central collisions, we obtain dN_ch/deta|_|eta|<1 = 650 +/- 35 (syst). Compared to collisions at sqrt(s_NN) ... More
Transverse Momentum and Rapidity Dependence of HBT Correlations in Au+Au Collisions at sqrt(s_NN) = 62.4 and 200 GeVSep 01 2004Two-particle correlations of identical charged pion pairs from Au+Au collisions at sqrt(s_NN) = 62.4 and 200 GeV were measured by the PHOBOS experiment at RHIC. Data for the 15% most central events were analyzed with Bertsch-Pratt and Yano-Koonin-Podgoretskii ... More
Dirichlet boundary conditions in type IIB superstring theory and fermionic T-dualityFeb 01 2012Jul 02 2012In this article we investigate the relation between consequences of Dirichlet boundary conditions (momenta noncommutativity and parameters of the effective theory) and background fields of fermionic T-dual theory. We impose Dirichlet boundary conditions ... More
Noncommutativity relations in type IIB theory and their supersymmetryMay 07 2010In the present paper we investigate noncommutativity of $D9$ and $D5$-brane world-volumes embedded in space-time of type IIB superstring theory. Boundary conditions, which preserve half of the initial supersymmetry, are treated as canonical constraints. ... More
Noncommutativity in space-time extended by Liouville fieldNov 28 2007Oct 09 2009The world-sheet quantum conformal invariance can be realized in the presence of the conformal factor $F$, by inclusion of Liouville term. In the background with linear dilaton field, $\Phi(x)=\Phi_0+a_\mu x^\mu$, the field $F$ becomes a new noncommutative ... More
The Magnus property for direct productsMay 05 2016Jun 14 2016A group G is said to have the Magnus property if the following holds: whenever two elements x,y have the same normal closure, then x is conjugate to y or its inverse. We prove: Let p be an odd prime, and let G,H be residually finite-p groups with the ... More
Four-point correlator constraints on electromagnetic chiral parameters and resonance effective LagrangiansMay 21 2004Jun 01 2004We pursue the analysis of a set of generalized DGMLY sum rules for the electromagnetic chiral parameters at order $e^2p^2$ and discuss implications for effective Lagrangians with resonances. We exploit a formalism in which charge spurions are introduced ... More
Electromagnetic corrections in the anomaly sectorMay 21 2002Chiral perturbation theory in the anomaly sector for $N_f=2$ is extended to include dynamical photons, thereby allowing a complete treatment of isospin breaking. A minimal set of independent chiral lagrangian terms is determined and the divergence structure ... More
Breaking and restoring of diffeomorphism symmetry in discrete gravitySep 30 2009We discuss the fate of diffeomorphism symmetry in discrete gravity. Diffeomorphism symmetry is typically broken by the discretization. This has repercussions for the observable content and the canonical formulation of the theory. It might however be possible ... More
Centrality dependence of charged antiparticle to particle ratios near mid-rapidity in d+Au collisions at sqrt(s_NN)=200 GeVSep 17 2003The ratios of the yields of charged antiparticles to particles have been obtained for pions, kaons, and protons near mid-rapidity for d+Au collisions at sqrt(s_NN) = 200 GeV as a function of centrality. The reported values represent the ratio of the yields ... More
Centrality dependence of charged hadron transverse momentum spectra in d+Au collisions at sqrt(s_NN) = 200 GeVJun 18 2003We have measured transverse momentum distributions of charged hadrons produced in d+Au collisions at sqrt(s_NN) = 200 GeV. The spectra were obtained for transverse momenta 0.25 < p_T < 6.0 GeV/c, in a pseudorapidity range of 0.2 < eta < 1.4 in the deuteron ... More
Scaling Variable for Nuclear Shadowing in Deep-Inelastic ScatteringSep 22 1995A new scaling variable is introduced in terms of which nuclear shadowing in deep-inelastic scattering is universal, i.e. independent of $A$, $Q^2$ and $x$. This variable can be interpreted as a measure of the number of gluons probed by the hadronic fluctuations ... More
Type I background fields in terms of type IIB onesApr 16 2008We choose such boundary conditions for open IIB superstring theory which preserve N=1 SUSY. The explicite solution of the boundary conditions yields effective theory which is symmetric under world-sheet parity transformation $\Omega:\sigma\to-\sigma$. ... More
Gauge symmetries decrease the number of Dp-brane dimensionsApr 19 2006Aug 09 2006It is known that the presence of antisymmetric background field $B_{\mu\nu}$ leads to noncommutativity of Dp-brane manifold. Addition of the linear dilaton field in the form $\Phi(x)=\Phi_0+a_\mu x^\mu$, causes the appearance of the commutative Dp-brane ... More
Open strings in relativistic ion trapsFeb 20 2003Apr 04 2003Electromagnetic plane waves provide examples of time-dependent open string backgrounds free of $\alpha'$ corrections. The solvable case of open strings in a quadrupolar wave front, analogous to pp-waves for closed strings, is discussed. In light-cone ... More
Charged Particle Multiplicities in Ultra-relativistic Au+Au and Cu+Cu CollisionsApr 26 2006The PHOBOS collaboration has carried out a systematic study of charged particle multiplicities in Cu+Cu and Au+Au collisions at the Relativistic Heavy-Ion Collider (RHIC) at Brookhaven National Laboratory. A unique feature of the PHOBOS detector is its ... More
The significance of the fragmentation region in ultrarelativistic heavy ion collisionsOct 09 2002We present measurements of the pseudorapidity distribution of primary charged particles produced in Au+Au collisions at three energies, sqrt(s_{NN}) = 19.6, 130, and 200 GeV, for a range of collision centralities. The centrality dependence is shown to ... More
Uniform semiclassical expansions for the direct part of Franck-Condon transitionsOct 13 1997Semiclassical expansions for traces involving Greens functions have two contributions, one from the periodic or recurrent orbits of the classical system and one from the phase space volume, i.e. the paths of infinitesimal length. Quantitative calculations ... More
RF depolarizing resonances in the presence of a full Siberian snake and full snake spin-flippingApr 18 2003Frequent polarization reversals, or spin-flips, of a stored polarized beam in a high energy scattering asymmetry experiments may greatly reduce systematic errors of spin asymmetry measurements. A spin-flipping technique is being developed by using rf ... More
Lower estimates of transition densities and bounds on exponential ergodicity for stochastic PDE'sFeb 18 2004Sep 25 2006A formula for the transition density of a Markov process defined by an infinite-dimensional stochastic equation is given in terms of the Ornstein--Uhlenbeck bridge and a useful lower estimate on the density is provided. As a consequence, uniform exponential ... More
Quantum dot with spin-orbit interaction in noncommutative phase space and analog Landau levelsJun 30 2009We have studied a quantum dot with Rashba spin orbit interaction on a plane where the position and momentum coordinates are considered to be noncommutative. The energy spectrum of the system is found to be equivalent to that of a quantum dot with Rashba ... More
Content based video retrievalNov 20 2012Content based video retrieval is an approach for facilitating the searching and browsing of large image collections over World Wide Web. In this approach, video analysis is conducted on low level visual properties extracted from video frame. We believed ... More
Content based video retrieval systemsMay 08 2012With the development of multimedia data types and available bandwidth there is huge demand of video retrieval systems, as users shift from text based retrieval systems to content based retrieval systems. Selection of extracted features play an important ... More
Non-commutative Zariski geometries and their classical limitJul 05 2007We undertake a case study of two series of nonclassical Zariski geometries. We show that these geometries can be realised as representations of certain noncommutative $C^*$-algebras and introduce a natural limit construction which for each of the two ... More
Simulating space and timeNov 26 2010This chapter asks if a virtual space-time could appear to those within it as our space-time does to us. A processing grid network is proposed to underlie not just matter and energy, but also space and time. The suggested "screen" for our familiar three ... More
Bonding and Electronic Properties of Ice at High PressureMay 31 2011The properties of water ice at megabar pressure are characterized with ab initio computer simulations. The focus lies on the metallic Cmcm phase and its insulating distorted analogue with Pnma symmetry. Both phases were recently predicted to occur at ... More
Testing the $ΔS=ΔQ$ Rule with Exclusive Semi-Leptonic Kaon DecaysApr 01 1995We consider the possibility of violations of the selection rule $\Delta S=\Delta Q$ at an appreciable level in {\it exclusive} semi-leptonic decays of Kaons. At $\Phi$-Factories, intense Kaon beams will be available and will probe among others, the semi-leptonic ... More
Quantum Computing of Poincare Recurrences and Periodic OrbitsJul 31 2003Jan 30 2004Quantum algorithms are built enabling to find Poincar\'e recurrence times and periodic orbits of classical dynamical systems. It is shown that exponential gain compared to classical algorithms can be reached for a restricted class of systems. Quadratic ... More
Photoproduction of mesons off nucleiOct 02 2011Recent results for the photoproduction of mesons off nuclei are reviewed. These experiments have been performed for two major lines of research related to the properties of the strong interaction. The investigation of nucleon resonances requires light ... More
Photoproduction of eta-mesons from light nucleiApr 02 2003In a series of experiments coherent and quasifree eta-photoproduction from light nuclei (4He, 3He, 2H) was investigated with the TAPS-detector at the Mainz MAMI-accelerator. The experiments were motivated by two different subjects: the determination of ... More
Quiescent X-ray emission from an evolved brown dwarf ?Sep 27 2004I report on the X-ray detection of Gl569Bab. During a 25ksec Chandra observation the binary brown dwarf is for the first time spatially separated in X-rays from the flare star primary Gl569A. Companionship to Gl569A constrains the age of the brown dwarf ... More
X-ray Luminosity Functions of Young Stars in Taurus-Auriga-PerseusNov 23 2000X-ray luminosity functions (XLF) are frequently used to assess the properties of the X-ray emission from a given sample of stars, and particularly important for a comparison of different groups of stars. I present the results from a detailed analysis ... More
The Role of Temperature in the occurrence of some Zeno PhenomenaApr 04 2012Temperature can be responsible for strengthening effective couplings between quantum states, determining a hierarchy of interactions, and making it possible to establish such dynamical regimes known as Zeno dynamics, wherein a strong coupling can hinder ... More
Eigenvalue statistics in quantum ideal gasesSep 04 1998The eigenvalue statistics of quantum ideal gases with single particle energies $e_n=n^\alpha$ are studied. A recursion relation for the partition function allows to calculate the mean density of states from the asymptotic expansion for the single particle ... More
Fractional Authorship in Nuclear PhysicsSep 25 2015Large, multi-institutional groups or collaborations of scientists are engaged in nuclear physics research projects, and the number of research facilities is dwindling. These collaborations have their own authorship rules, and they produce a large number ... More
On the intrinsic origin of 1/f noiseMay 05 2003The problem of the intrinsic origin of 1/f noise is considered. Currents and signals consisting of a sequence of pulses are analysed. It is shown that intrinsic origin of 1/f noise is a random walk of the average time between subsequent pulses of the ... More
A solvable model for scattering on a junction and a modified analytic perturbation procedureFeb 24 2009We consider a one-body spin-less electron spectral problem for a resonance scattering system constructed of a quantum well weakly connected to a noncompact exterior reservoir, where the electron is free. The simplest kind of the resonance scattering system ... More
Ratio between two $Λ$ and $\barΛ$ production mechanisms in $p$ scatteringApr 18 2016We consider $\Lambda$ and $\bar{\Lambda}$ production in a wide range of proton scattering experiments. The produced $\Lambda$ and $\bar{\Lambda}$ may or may not contain a diquark remnant of the beam proton. The ratio of these two production mechanisms ... More
OvershootingJan 06 2010Overshooting occurs in stars when convective elements penetrate into adjacent radiative zones. In the Sun, it leads to the so-called `tachocline' at the base of the outer convection zone and this region is becoming a key ingredient of the standard solar ... More
Search for Light New Physics at B FactoriesSep 05 2012Many extensions of the Standard Model include the possibility of light new particles, such as light Higgs bosons or dark matter candidates. These scenarios can be probed using the large datasets collected by B factories, complementing measurements performed ... More
Quantization of Lie bialgebras and shuffle algebras of Lie algebrasAug 16 2000Sep 28 2000To any field K of characteristic 0, we associate a set Sha(K). Elements of Sha(K) are equivalence classes of families of Lie polynomials subject to associativity relations. We construct an injection and a retraction between Sha(K) and the set of quantization ... More
On correlation functions of Drinfeld currents and shuffle algebrasSep 07 1998We express the vanishing conditions satisfied by the correlation functions of Drinfeld currents of quantum affine algebras, imposed by the quantum Serre relations. We discuss the relation of these vanishing conditions with a shuffle algebra description ... More
Quantum principal commutative subalgebra in the nilpotent part of $U_q\widehat{s\ell}_2$ and lattice KdV variablesFeb 25 1994We propose a quantum lattice version of Feigin and E. Frenkel's constructions, identifying the KdV differential polynomials with functions on a homogeneous space under the nilpotent part of $\widehat{s\ell}_2$. We construct an action of the nilpotent ... More
Compressed quantum simulation of the Ising modelSep 12 2011In [R. Jozsa, B. Kraus, A. Miyake, J. Watrous, Proc. R. Soc. A {\bf 466}, 809-830 (2010)] it has been shown that a match gate circuit running on n qubits can be compressed to a universal quantum computation on \log(n)+3 qubits. Here, we show how this ... More
A short overview of the "Topological recursion"Dec 10 2014Dec 12 2014This review is an extended version of the Seoul ICM 2014 proceedings.It is a short overview of the "topological recursion", a relation appearing in the asymptotic expansion of many integrable systems and in enumerative problems. We recall how computing ... More
Master loop equations, free energy and correlations for the chain of matricesSep 03 2003Oct 30 2003The loop equations for a chain of hermitian random matrices are computed explicitely, including the 1/N^2 corrections. To leading order, the master loop equation reduces to an algebraic equation, whose solution can be written in terms of geometric properties ... More
Some examples of absolute continuity of measures in stochastic fluid dynamicsJan 03 2008A non linear Ito equation in a Hilbert space is studied by means of Girsanov theorem. We consider a non linearity of polynomial growth in suitable norms, including that of quadratic type which appears in the Kuramoto-Sivashinsky equation and in the Navier-Stokes ... More
Quantum quenches and Generalized Gibbs Ensemble in a Bethe Ansatz solvable lattice model of interacting bosonsJul 31 2014Sep 20 2014We consider quantum quenches in the so-called $q$-boson lattice model. We argue that the Generalized Eigenstate Thermalization Hypothesis holds in this model, therefore the Generalized Gibbs Ensemble (GGE) gives a valid description of the stationary states ... More
Overlaps between eigenstates of the XXZ spin-1/2 chain and a class of simple product statesSep 18 2013May 20 2014We consider a class of quantum quenches in the spin-1/2 XXZ chain, where the initial state is of a simple product form. Specific examples are the N\'eel state, the dimer state and the q-deformed dimer state. We compute determinant formulas for finite ... More
The Inner Boundary Condition for a Thin Disk Accreting Into a Black HoleApr 10 2000Contrary to some recent claims the `no torque inner boundary condition' as applied at the marginally stable orbit is correct for geometrically thin disks accreting into black holes.
A Note on QCD Corrections to the forward backward Asymmetry of b-Quarks using Thrust to determine the b-DirectionDec 24 1998I discuss one-loop QCD corrections to the forward backward asymmetry of the b-quark at LEP in a way appropriate to the present experimental procedure. I try to give insight into the structure of the corrections and elucidate some questions which have ... More
Photoproduction of single inclusive jets at future ep colliders in next-to-leading order QCDJul 01 2008A next-to-leading order QCD calculation for single-inclusive jet photoproduction in unpolarized and longitudinally polarized lepton-hadron collisions is presented which consistently includes ``direct'' and ``resolved'' photon contributions. The computation ... More
The Yrast Spectra of Weakly Interacting Bose-Einstein CondensatesMay 05 1999The low energy quantal spectrum is considered as a function of the total angular momentum for a system of weakly interacting bosonic atoms held together by an external isotropic harmonic potential. It is found that besides the usual condensation into ... More
Dynamics of geometric phase in the adiabatic limit of quantum phase transitionAug 23 2009May 10 2010The geometric phase associated with a many body ground state exhibits a signature of quantum phase transition. In this context, we have studied the behaviour of the geometric phase during a linear quench caused by a gradual turning off of the magnetic ... More
Topological Aspects of High Temperature Superconductivity and Berry PhaseMay 29 2003We propose a mechanism of high temperature superconductivity from the viewpoint of chirality and Berry phase. It is observed that spin pairing and charge pairing is caused by a gauge force generated by magnetic flux quanta attached to them. From the renormalization ... More
Modelling the optically dark side of high--redshift galaxiesSep 14 1998The recent detection of the Cosmic Infrared Background in FIRAS and DIRBE residuals, and the observations of IR/submm sources by the ISOPHOT and SCUBA instruments have shed new light on the optically dark side of galaxy formation. It turns out that our ... More
Dephasing-enabled triplet Andreev conductanceMar 12 2009We study the conductance of normal-superconducting quantum dots with strong spin-orbit scattering, coupled to a source reservoir using a single-mode spin-filtering quantum point contact. The choice of the system is guided by the aim to study triplet Andreev ... More
Generalization of the Poisson kernel to the superconducting random-matrix ensemblesFeb 12 2009We calculate the distribution of the scattering matrix at the Fermi level for chaotic normal-superconducting systems for the case of arbitrary coupling of the scattering region to the scattering channels. The derivation is based on the assumption of uniformly ... More
Gauge Invariant Exact Renormalization Group and Perfect Actions in the Open Bosonic String TheoryMay 23 2007The exact renormalization group is applied to the world sheet theory describing bosonic open string backgrounds to obtain the equations of motion for the fields of the open string. Using loop variable techniques the equations can be constructed to be ... More
Wave Functionals, Gauge Invariant Equations for Massive Modes and the Born-Infeld Equation in the Loop Variable Approach to String TheoryFeb 05 2001In earlier papers on the loop variable approach to gauge invariant interactions in string theory, a ``wave functional'' with some specific properties was invoked. It had the purpose of converting the generalized momenta to space time fields. In this paper ... More
On Covariant Derivatives and Gauge Invariance in the Proper Time Formalism for String TheoryNov 22 1995Nov 23 1995It is shown that the idea of ``minimal'' coupling to gauge fields can be conveniently implemented in the proper time formalism by identifying the equivalent of a ``covariant derivative''. This captures some of the geometric notion of the gauge field as ... More
Proper Time Formalism and Gauge Invariance in Open String InteractionsSep 02 1993The issue of gauge invariances in the sigma model formalism is discussed at the free and interacting level. The problem of deriving gauge invariant interacting equations can be addressed using the proper time formalism. This formalism is discussed, both ... More
Fluctuation Diffusion in Quark matterNov 24 2008A unique transition state is a precursor of quark matter formation. We point out the hallmarks of this state and evaluate the quark diffusion coefficient in the vicinity of the QCD critical line.
Strangeness Photoproduction from the Deuteron and Hyperon-Nucleon InteractionOct 15 1999Pronounced effects due to final state hyperon-nucleon interaction are predicted in strangeness photoproduction reaction on the deuteron. Use is made of the covariant reaction formalism and the P- matrix approach to the hyperon-nucleon interaction.
Neutrino Factory R&D - a global perspectiveNov 15 2002The current world status of plans for future particle-physics accelerators and accelerator research and development is outlined. The developments for a neutrino factory are placed in this context. Finally, a specific initiative relevant for Europe is ... More
Lectures on HERA physicsJun 05 2002In these lectures I introduce the basics of HERA physics and give a survey of the major aspects, discussing in somewhat more depth the subject of low $x$ physics.
First-principles study of the polar O-terminated ZnO surface in thermodynamic equilibrium with oxygen and hydrogenFeb 27 2003Using density-functional theory in combination with a thermodynamic formalism we calculate the relative stability of various structural models of the polar O-terminated (000-1)-O surface of ZnO. Model surfaces with different concentrations of oxygen vacancies ... More
Energy barrier in the two-Higgs modelAug 11 1998Jun 24 1999The electroweak model is extended by a second Higgs doublet and a numerical investigation of static, finite energy classical solutions is performed. The results indicate that for a large domain of the parameters of the Higgs potential, the energy barrier ... More
Role of the baryon resonances in the eta and K+ photoproduction processes on the protonAug 23 2004Very recent eta and K+ photoproduction data on the proton from threshold up to E = 2.6 GeV are interpreted within a chiral constituent quark formalism, which embodies all known nucleon and hyperon resonances. Possible contributions from an additional ... More
Non-thermal emission from high-energy binaries through interferometric radio observationsMar 30 2016High-mass binary systems involve extreme environments that produce non-thermal emission from radio to gamma rays. Only three types of these systems are known to emit persistent gamma-ray emission: colliding-wind binaries, high-mass X-ray binaries and ... More
Differential calculus on quantum groups: Constructive procedureSep 01 1994A brief review of the construction and classifiaction of the bicovariant differential calculi on quantum groups is given.
Introduction to Chiral Perturbation TheoryMar 28 2007A brief introduction to chiral perturbation theory, the effective field theory of quantum chromodynamics at low energies, is given.
SU(3) Chiral Effective Field Theories -- A Status Report --Feb 27 2004A personal overview on the present status of SU(3) chiral perturbation theory in the baryonic sector is given. Recent developments are presented and remaining challenges are pointed out.
Monte Carlo Simulations of Critical Dynamics with Conserved Order ParameterMar 06 2001Taking the two-dimensional Ising model for example, short-time behavior of critical dynamics with a conserved order parameter is investigated by Monte Carlo simulations. Scaling behavior is observed, but the dynamic exponent $z$ is updating schemes dependent. ... More