Results for "D. J. O. Göransson"

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Coulomb Blockade from the Shell of an InP-InAs Core-Shell Nanowire with a Triangular Cross SectionJan 28 2019We report on growth of InP-InAs core-shell nanowires and demonstration of the formation of single quantum structures, which show Coulomb blockade effect, over entire lengths of the nanowires. The core-shell nanowires are grown by a selective area growth ... More
Measurements of strain and bandgap of coherently epitaxially grown wurtzite InAsP-InP core-shell nanowiresApr 12 2019We report on experimental determination of the strain and bandgap of InAsP in epitaxially grown InAsP-InP core-shell nanowires. The core-shell nanowires are grown via metal-organic vapor phase epitaxy. The as-grown nanowires are characterized by transmission ... More
Coupled Mode Effects on Energy Transfer Rates in Two Temperature PlasmasJan 20 2009We investigate the effects of collective modes on the temperature relaxation rates in fully coupled electron-ion systems. Firstly, the well-understood limit of weakly coupled plasmas is considered and the coupled mode formula within the random phase approximation ... More
Mapping Colossal Magnetoresistance Phase Transitions with the Charge-Carrier Density Collapse ModelMay 12 2011We explain the observed specific heat anomaly (and hence entropy change) in the colossal magnetoresistive manganite Sm0.55Sr0.45MnO3, by introducing phase separation into the current carrier density collapse theory via the notion of the ferromagnetic ... More
Critical exponents for an impurity in a bosonic Josephson junction: Position measurement as a phase transitionOct 01 2014Dec 19 2014We use fidelity susceptibility to calculate quantum critical scaling exponents for a system consisting of $N$ identical bosons interacting with a single impurity atom in a double well potential (bosonic Josephson junction). Above a critical value of the ... More
Parameter estimation in modelling frequency response of coupled systems using a stepwise approachAug 15 2018This paper studies the problem of parameter estimation in resonant, acoustic fluid-structure interaction problems over a wide frequency range. Problems with multiple resonances are known to be subjected to local minima, which represents a major challenge ... More
Particle-in-cell simulations of the relaxation of electron beams in inhomogeneous solar wind plasmasDec 06 2016Previous theoretical considerations of electron beam relaxation in inhomogeneous plasmas have indicated that the effects of the irregular solar wind may account for the poor agreement of homogeneous modelling with the observations. Quasi-linear theory ... More
Self-consistent particle-in-cell simulations of fundamental and harmonic plasma radio emission mechanismsSep 23 2015Aims. The simulation of three-wave interaction based plasma emission, thought to be the underlying mechanism for Type III solar radio bursts, is a challenging task requiring fully-kinetic, multi-dimensional models. This paper aims to resolve a contradiction ... More
Comparison of electron-ion energy transfer in dense plasmas obtained from numerical simulations and quantum kinetic theoryJul 25 2013We evaluate various analytical models for the electron-ion energy transfer and compare the results to data from molecular dynamics (MD) simulations. The models tested includes energy transfer via strong binary collisions, Landau-Spitzer rates with different ... More
Low-Complexity OFDM Spectral PrecodingMay 16 2019This paper proposes a new large-scale mask-compliant spectral precoder (LS-MSP) for orthogonal frequency division multiplexing systems. In this paper, we first consider a previously proposed mask-compliant spectral precoding scheme that utilizes a generic ... More
Morphology of a quantum catastropheOct 25 2016Thom's seven elementary catastrophes are the only structurally stable singularities in up to four dimensions \cite{thom75}. Their stability against perturbations removes any symmetry requirement which accounts for their ubiquity in nature, e.g.\ as caustics. ... More
On increasing subsequences of iid samplesMar 10 1998We study the fluctuations, in the large deviations regime, of the longest increasing subsequence of a random i.i.d. sample on the unit square. In particular, our results yield the precise upper and lower exponential tails for the length of the longest ... More
The Quark Structure of PentaquarksSep 23 2005Motivated by the possible observation of the $\Theta^+(1530)$, we study the quark structure of pentaquark states in quenched lattice QCD. The complete set of 19 local sources that have the proper symmetry for positive or negative parity isoscalar pentaquarks ... More
Condensation and Slow Dynamics of Polar Nanoregions in Lead RelaxorsMar 01 2003It is now well established that the unique properties of relaxor ferroelectrics are due to the presence of polar nanoregions (PNR's). We present recent results from Neutron and Raman scattering of single crystals of PZN, PZN-xPT, and PMN. Both sets of ... More
Extragalactic Foreground Contamination in Temperature-based CMB Lens ReconstructionOct 28 2013We discuss the effect of unresolved point source contamination on estimates of the CMB lensing potential, from components such as the thermal Sunyaev-Zel'dovich effect, radio point sources, and the Cosmic Infrared Background. We classify the possible ... More
Parametric amplification of light in a cavity with a moving dielectric membrane: Landau-Zener problem for the Maxwell fieldJul 06 2016We perform a theoretical investigation into the classical and quantum dynamics of an optical field in a cavity containing a moving membrane ("membrane-in-the-middle" set-up). Our approach is based on the Maxwell wave equation, and complements previous ... More
Hyperbolic Twistor SpacesDec 18 2003In contrast to the classical twistor spaces whose fibres are 2-spheres, we introduce twistor spaces over manifolds with almost quaternionic structures of the second kind in the sense of P. Libermann whose fibres are hyperbolic planes. We discuss two natural ... More
Glueball spectral densities from the latticeOct 29 2012The propagator of a physical degree of freedom ought to obey a K\"{a}ll\'{e}n-Lehmann spectral representation, with positive spectral density. The latter quantity is directly related to a cross section based on the optical theorem. The spectral density ... More
Representation of Finite Abelian Group Elements by Subsequence SumsJun 02 2008Let $G\cong C_{n_1}\oplus ... \oplus C_{n_r}$ be a finite and nontrivial abelian group with $n_1|n_2|...|n_r$. A conjecture of Hamidoune says that if $W=w_1... w_n$ is a sequence of integers, all but at most one relatively prime to $|G|$, and $S$ is a ... More
Electric field sensing near the surface microstructure of an atom chip using cold Rydberg atomsJun 29 2012The electric fields near the heterogeneous metal/dielectric surface of an atom chip were measured using cold atoms. The atomic sensitivity to electric fields was enhanced by exciting the atoms to Rydberg states that are 10^8 times more polarizable than ... More
Future Directions in Astronomy VisualisationFeb 20 2006Despite the large budgets spent annually on astronomical research equipment such as telescopes, instruments and supercomputers, the general trend is to analyse and view the resulting datasets using small, two-dimensional displays. We report here on alternative ... More
Comparative analysis of Gallex and GNO solar neutrino dataSep 06 2004Jun 20 2006Since the GALLEX and GNO datasets were derived from closely related experiments, there is a natural tendency to merge them. This is perhaps appropriate for any analysis based on the hypothesis that the solar neutrino flux is constant, but it is not necessarily ... More
Evolution loops and spin-1/2 systemsOct 03 1999The derivation of a new family of magnetic fields inducing exactly solvable spin evolutions is presented. The conditions for which these fields generate the evolution loops (dynamical processes for which any spin state evolves cyclically) are studied. ... More
Absorption spectra of Fe L-lines in Seyfert 1 galaxiesMar 19 2003Absorption L-lines of iron ions are observed, in absorption, in spectra of Seyfert 1 galaxies by the new generation of X-ray satellites: Chandra (NASA) and XMM-Newton (ESA). Lines associated to Fe23+ to Fe17+ are well resolved. Whereas, those corresponding ... More
Effects of Annealing Conditions on the Microstructure and Magnetic Properties of the Perovskite Manganite, La0.75Sr0.25MnO3May 13 2011The effects of annealing conditions upon the microstructure and the magnetic properties of the colossal magnetoresistive manganite La0.75Sr0.25MnO3 have been investigated. Increasing the annealing temperature and time of annealing is seen to increase ... More
Debye mass at the QCD transition in the PNJL modelAug 21 2015Aug 28 2015We consider colour-electric screening as expressed by the quark contribution to the Debye mass calculated in a PNJL model with emphasis on confining and chiral symmetry breaking effects. We observe that the screening mass is entirely determined by the ... More
Can LSND be included in a 3-Neutrino framework?May 08 2000May 11 2000We study the special features emerging from a three lepton generation analysis of the available neutrino oscillation data (solar, atmospheric and LSND). First we find that it is possible to explain all three sets of data in terms of the standard left ... More
Revealing short-range non-Newtonian gravity through Casimir-Polder shieldingNov 13 2018We carry out a realistic, yet simple, calculation of the Casimir-Polder interaction in the presence of a metallic shield in order to aid the design of experiments to test non-Newtonian gravity. In particular, we consider a rubidium atom near a movable ... More
Two-loop two-point functions with masses: asymptotic expansions and Taylor series, in any dimensionApr 27 1993In all mass cases needed for quark and gluon self-energies, the two-loop master diagram is expanded at large and small $q^2$, in $d$ dimensions, using identities derived from integration by parts. Expansions are given, in terms of hypergeometric series, ... More
Resistively-limited current sheet implosions in planar anti-parallel (1D) and null-point containing (2D) magnetic field geometriesJun 21 2018Jul 11 2018Implosive formation of current sheets is a fundamental plasma process. Previous studies focused on the early time evolution, while here our primary aim is to explore the longer-term evolution, which may be critical for determining the efficiency of energy ... More
Three-dimensional oscillatory magnetic reconnectionJun 29 2017Here we detail the dynamic evolution of localised reconnection regions about three-dimensional (3D) magnetic null points by using numerical simulation. We demonstrate for the first time that reconnection triggered by the localised collapse of a 3D null ... More
On the periodicity of linear and nonlinear oscillatory reconnectionNov 21 2018(Abridged for ArXiv) An injection of energy towards a magnetic null point can drive reversals of current sheet polarity leading to time-dependent Oscillatory Reconnection, which is a possible explanation of how periodic phenomena can be generated when ... More
QED$_{4}$ Ward Identity for fermionic field in the light-frontAug 07 2008In a covariant gauge we implicitly assume that the Green's function propagates information from one point of the space-time to another, so that the Green's function is responsible for the dynamics of the relativistic particle. In the light front form, ... More
Coupling of Finite-Element and Plane Waves Discontinuous Galerkin methods for time-harmonic problemsJan 15 2018A coupling approach is presented to combine a wave-based method to the standard finite element method. This coupling methodology is presented here for the Helmholtz equation but it can be applied to a wide range of wave propagation problems. While wave-based ... More
Ground-State Ordering of the $J_1$--$J_2$ Model on the Simple Cubic and Body-Centered Cubic LatticesJun 01 2016The $J_1$--$J_2$ Heisenberg model is a "canonical" model in the field of quantum magnetism in order to study the interplay between frustration and quantum fluctuations as well as quantum phase transitions driven by frustration. Here we apply the Coupled ... More
Background of gravitational waves from pre-galactic black hole formationFeb 20 2002We study the generation of a gravitational wave (GW) background produced from a population of core-collapse supernovae, which form black holes in scenarios of structure formation of the Universe. We obtain, for example, that a pre-galactic population ... More
Observing an invisible Higgs bosonSep 13 2000Given its weak coupling to bottom quarks and tau leptons, the Higgs boson may predominantly decay into invisible particles like gravitinos, neutralinos, or gravitons. We consider the manifestation of such an invisibly decaying Higgs boson in weak boson ... More
The late stages of evolution of helium star-neutron star binaries and the formation of double neutron star systemsJun 03 2003With a view to understanding the formation of double neutron-stars (DNS), we investigate the late stages of evolution of helium stars with masses of 2.8 - 6.4 Msun in binary systems with a 1.4 Msun neutron-star companion. We found that mass transfer from ... More
Diffusion and Transport Coefficients in Synthetic OpalsOct 22 1999Opals are structures composed of the closed packing of spheres in the size range of nano-to-micro meter. They are sintered to create small necks at the points of contact. We have solved the diffusion problem in such structures. The relation between the ... More
Construction of bosons and fermions out of quonsJul 06 2001Oct 24 2001The quon algebra describes particles, ``quons,'' that are neither fermions nor bosons, using a label $q$ that parametrizes a smooth interpolation between bosons ($q = 1$) and fermions ($q = -1$). Understanding the relation of quons on the one side and ... More
TFAW: wavelet-based signal reconstruction to reduce photometric noise in time-domain surveysFeb 21 2017Sep 17 2018There have been many efforts to correct systematic effects in astronomical light curves to improve the detection and characterization of planetary transits and astrophysical variability. Algorithms like the Trend Filtering Algorithm (TFA) use simultaneously-observed ... More
Temperature-dependent Raman scattering of DyScO3 and GdScO3 single crystalsApr 12 2010We report a temperature-dependent Raman scattering investigation of DyScO3 and GdScO3 single crystals from room temperature up to 1200 {\deg}C. With increasing temperature, all modes decrease monotonously in wavenumber without anomaly, which attests the ... More
The transition from the adiabatic to the sudden limit in core level photoemission: A model study of a localized systemApr 23 1999We consider core electron photoemission in a localized system, where there is a charge transfer excitation. The system is modelled by three electron levels, one core level and two outer levels. The model has a Coulomb interaction between these levels ... More
Low-density, one dimensional quantum gases in the presence of a localised attractive potentialJun 26 2008We investigate low-density, quantum-degenerate gases in the presence of a localised attractive potential in the centre of a one-dimensional harmonic trap.The attractive potential is modelled using a parameterised delta-function, allowing us to determine ... More
Nontrivial ghost-gluon vertex and the match of RGZ, DSE and lattice Yang-Mills propagatorsJul 21 2012Either by solving the ghost propagator DSE or through a one-loop computation in the RGZ (Refined Gribov-Zwanziger) formalism, we show that a non-trivial ghost-gluon vertex is anyhow required to obtain a ghost propagator prediction compatible with the ... More
(Lattice) Propagators and Extraction of Spectral DensitiesJan 14 2013In this proceeding, we explain a few steps for an alternative extraction of the spectral density of a two-point function (propagator) based on a discrete set of data points. We present a so-called Tikhonov regularization of this particular inverse problem. ... More
Planetary nebulae in the inner Milky Way: new abundancesMar 01 2010The study of planetary nebulae in the inner-disk and bulge gives important information on the chemical abundances of elements such as He, N, O, Ar, Ne, and on the evolution of these abundances, which is associated with the evolution of intermediate-mass ... More
A Dark Matter Candidate with New Strong InteractionsJun 02 2005Jun 16 2005We study the possibility that dark matter is a baryon of a new strongly interacting gauge theory, which was introduced in the low energy theory of Cosmological SUSY Breaking (CSB). This particle can fit the observed dark matter density if an appropriate ... More
Tensor Representation of Spin StatesSep 03 2014Feb 26 2015We propose a generalization of the Bloch sphere representation for arbitrary spin states. It provides a compact and elegant representation of spin density matrices in terms of tensors that share the most important properties of Bloch vectors. Our representation, ... More
Planetary nebulae in the inner Milky Way II: the Bulge-Disk transitionJan 17 2011In this work, a sample of planetary nebulae located in the inner-disk and bulge of the Galaxy is used in order to find the galactocentric distance which better separates these two populations, from the point of view of abundances. Statistical distance ... More
Radial abundance gradients from planetary nebulae at different distances from the galactic planeMay 28 2015We investigate the variations of the radial O/H abundance gradients from planetary nebulae (PN) located at different distances from the galactic plane. In particular, we determine the abundance gradients at different heights from the plane in order to ... More
Three-frequency resonances in dynamical systemsJul 22 2000We investigate numerically and experimentally dynamical systems having three interacting frequencies: a discrete mapping (a circle map), an exactly solvable model (a system of coupled ordinary differential equations), and an experimental device (an electronic ... More
Thermal activation at moderate-to-high and high damping: finite barrier effects and force spectroscopyDec 18 2012Mar 11 2013We study the thermal escape problem in the moderate-to-high and high damping regime of a system with a parabolic barrier. We present a formula that matches our numerical results accounting for finite barrier effects, and compare it with previous works. ... More
Integrable Chiral Theories in 2+1 DimensionsMay 15 1998Following a recent proposal for integrable theories in higher dimensions based on zero curvature, new Lorentz invariant submodels of the principal chiral model in 2+1 dimensions are found. They have infinite local conserved currents, which are explicitly ... More
Implosive collapse about magnetic null points: A quantitative comparison between 2D and 3D nullsFeb 20 2018Null collapse is an implosive process whereby MHD waves focus their energy in the vicinity of a null point, forming a current sheet and initiating magnetic reconnection. We consider, for the first time, the case of collapsing 3D magnetic null points in ... More
On the Periodicity of Oscillatory ReconnectionDec 05 2012Oscillatory reconnection is a time-dependent magnetic reconnection mechanism that naturally produces periodic outputs from aperiodic drivers. This paper aims to quantify and measure the periodic nature of oscillatory reconnection for the first time. We ... More
Ground-state properties of the triangular-lattice Heisenberg antiferromagnet with arbitrary spin quantum number $s$Aug 25 2015We apply the coupled cluster method to high orders of approximation and exact diagonalizations to study the ground-state properties of the triangular-lattice spin-$s$ Heisenberg antiferromagnet. We calculate the fundamental ground-state quantities, namely, ... More
Tidally Heated Terrestrial Exoplanets: Viscoelastic Response ModelsDec 10 2009Tidal friction in exoplanet systems, driven by orbits that allow for durable nonzero eccentricities at short heliocentric periods, can generate internal heating far in excess of the conditions observed in our own solar system. Secular perturbations or ... More
Clustering around the radio-galaxy MRC0316-257 at z=3.14Sep 03 1996We report here the spectroscopic identification of galaxies in the neighborhood of the radio-galaxy MRC0316-257, at a redshift $z\sim3.14$. Candidate cluster galaxies were selected from deep V and I images combined with narrow band imaging at the wavelength ... More
Three Additional Quiescent Low-Mass X-ray Binary Candidates in 47 TucanaeDec 06 2004We identify through their X-ray spectra one certain (W37) and two probable (W17 and X4) quiescent low-mass X-ray binaries (qLMXBs) containing neutron stars in a long Chandra X-ray exposure of the globular cluster 47 Tucanae, in addition to the two previously ... More
Mid-infrared microlensing of accretion disc and dusty torus in quasars: effects on flux ratio anomaliesMar 05 2013Jun 06 2013Multiply-imaged quasars and AGNs observed in the mid-infrared (MIR) range are commonly assumed to be unaffected by the microlensing produced by the stars in their lensing galaxy. In this paper, we investigate the validity domain of this assumption. Indeed, ... More
Exact mean exit time for surface-mediated diffusionNov 15 2012We present an exact expression for the mean exit time through the cap of a confining sphere for particles alternating phases of surface and of bulk diffusion. The present approach is based on an integral equation which can be solved analytically. In contrast ... More
Time asymptotics of the Schroedinger wave function in time-periodic potentialsAug 13 2006We study the transition to the continuum of an initially bound quantum particle in $\RR^d$, $d=1,2,3$, subjected, for $t\ge 0$, to a time periodic forcing of arbitrary magnitude. The analysis is carried out for compactly supported potentials, satisfying ... More
Thermal transport in the Falicov-Kimball model on a Bethe latticeOct 22 2003We calculate thermal transport in the Falicov-Kimball model on an infinite-coordination-number Bethe lattice. We perform numerical calculations of the thermoelectric characteristics and concentrate on finding materials parameters for which the electronic ... More
Power Law Distributions of Patents as Indicators of InnovationApr 30 2012The total number of patents produced by a country (or the number of patents produced per capita) is often used as an indicator for innovation. Here we present evidence that the distribution of patents amongst applicants within many OECD countries is well-described ... More
Role of heavy-meson exchange in pion production near thresholdApr 06 1993Recent calculations of $s$-wave pion production have severely underestimated the accurately known $pp\rightarrow pp\pi^0$\ total cross section near threshold. In these calculations, only the single-nucleon axial-charge operator is considered. We have ... More
Castaing's instability in a trapped ultra-cold gasSep 21 2002Oct 01 2002We consider a trapped ultra-cold gas of (non-condensed) bosons with two internal states (described by a pseudo spin) and study the stability of a longitudinal pseudo spin polarization gradient. For this purpose, we numerically solve a kinetic equation ... More
A simple table-top demonstration of radiation pressure on a macroscopic objectMay 27 2016We report a simple demonstration of radiation pressure on a table-top experiment. Utilizing dynamic force microscopy in ambient environment, the resonant motion of a cm-sized cantilever driven by an amplitude-modulated diode laser is directly observed. ... More
Line-driven ablation of circumstellar disks: I. Optically thin decretion disks of classical Oe/Be starsFeb 25 2016The extreme luminosities of hot, massive stars drive strong stellar winds through UV line-scattering. For OB stars with an orbiting circumstellar disk, we explore the effect of such line-scattering in ablating disk material, initially focusing on the ... More
Remarks on the Charged, Magnetized Tomimatsu-Sato $δ=2$ SolutionNov 09 1999The full metric describing a charged, magnetized generalization of the Tomimatsu-Sato (TS) $\delta=2$ solution is presented in a concise explicit form. We use it to investigate some physical properties of the solution; in particular, we point out the ... More
Statistical crossover and nonextensive behavior of the neuronal short-term depressionDec 27 2016Nov 17 2017The theoretical basis of neuronal coding, associated with short term degradation in synaptic transmission, is a matter of debate in the literature. In fact, electrophysiological signals are commonly characterized as inversely proportional to stimulus ... More
Multilayer Thermionic Refrigerator and GeneratorJan 19 1998A new method of refrigeration is proposed. Cooling is obtained by thermionic emission of electrons over periodic barriers in a multilayer geometry. These could be either Schottky barriers between metals and semiconductors or else barriers in a semiconductor ... More
The Effect of Jupiter's Formation on the Distribution of Refractory Elements and Inclusions in MeteoritesOct 10 2017Aug 09 2018We present a comprehensive evolutionary model of the Sun's protoplanetary disk, constructed to resolve the "CAI Storage" problem of meteoritics. We predict the abundances of calcium-rich, aluminum-rich inclusions (CAIs) and refractory lithophile elements ... More
A solution for galactic disks with Yukawian gravitational potentialFeb 15 2007We present a new solution for the rotation curves of galactic disks with gravitational potential of the Yukawa type. We follow the technique employed by Toomre in 1963 in the study of galactic disks in the Newtonian theory. This new solution allows an ... More
SDSS White Dwarf mass distribution at low effective temperaturesDec 02 2008The DA white dwarfs in the Sloan Digital Sky Survey, as analyzed in the papers for Data Releases 1 and 4, show an increase in surface gravity towards lower effective temperatures below 11500 K. We study the various possible explanations of this effect, ... More
Pushmepullyou: An efficient micro-swimmerJan 18 2005Apr 21 2005The swimming of a pair of spherical bladders that change their volumes and mutual distance is efficient at low Reynolds numbers and is superior to other models of artificial swimmers. The change of shape resembles the wriggling motion known as {\it metaboly} ... More
Impurity in a bosonic Josephson junction: swallowtail loops, chaos, self-trapping and the poor man's Dicke modelSep 30 2013We study a model describing $N$ identical bosonic atoms trapped in a double-well potential together with a single impurity atom, comparing and contrasting it throughout with the Dicke model. As the boson-impurity coupling strength is varied, there is ... More
Detailed Models of super-Earths: How well can we infer bulk properties?Apr 25 2007May 09 2007The field of extrasolar planets has rapidly expanded to include the detection of planets with masses smaller than that of Uranus. Many of these are expected to have little or no hydrogen and helium gas and we might find Earth analogs among them. In this ... More
Relevance of a magnetic moment distribution and scaling law methods to study the magnetic behavior of antiferromagnetic nanoparticlesAug 06 2004In antiferromagnetic nanoparticles magnetization the linear component, $\chi_{AF}$H superposed to the saturation one usually complicates the fit of experimental data. We present a method based on scaling laws to determine the variation of $\chi_{AF}$ ... More
Evolution of a model quantum system under time periodic forcing: conditions for complete ionizationNov 01 2000We analyze the time evolution of a one-dimensional quantum system with an attractive delta function potential whose strength is subjected to a time periodic (zero mean) parametric variation $\eta(t)$. We show that for generic $\eta(t)$, which includes ... More
Apparent first-order wetting and anomalous scaling in the two-dimensional Ising modelOct 30 2014Jan 03 2016The global phase diagram of wetting in the two-dimensional (2d) Ising model is obtained through exact calculation of the surface excess free energy. Besides a surface field for inducing wetting, a surface-coupling enhancement is included. The wetting ... More
Long cycles in fullerene graphsJan 24 2008Jan 24 2011It is conjectured that every fullerene graph is hamiltonian. Jendrol' and Owens proved [J. Math. Chem. 18 (1995), pp. 83--90] that every fullerene graph on n vertices has a cycle of length at least 4n/5. In this paper, we improve this bound to 5n/6-2/3. ... More
Variable cosmological term $Λ(t)$Oct 08 2015We present the case of time-varying cosmological term $\Lambda(t)$. The main idea arises by proposing that as in the cosmological constant case, the scalar potential is identified as $ V(\phi)=2\Lambda$, with $\Lambda$ a constant, this identification ... More
Incipient superconductivity in TaB$_{2}$Mar 27 2001Mar 28 2001Magnetic properties of TaB$_{2}$ were studied by means of DC and AC susceptibility measurements. It has been found that the compound becomes superconducting at T$_{c}$ = 9.5 K. From upper critical field measurements the superconducting parameters have ... More
Backaction-Driven Transport of Bloch Oscillating Atoms in Ring CavitiesFeb 19 2014Aug 19 2014We predict that an atomic Bose-Einstein condensate strongly coupled to an intracavity optical lattice can undergo resonant tunneling and directed transport when a constant and uniform bias force is applied. The bias force induces Bloch oscillations, causing ... More
Catastrophes in many-body wave functions: universality and critical scalingSep 15 2016As part of the quest to uncover universal features of quantum dynamics, we study catastrophes that form in simple many-body wave functions after a quench, focusing on two-mode systems that include the two-site Bose Hubbard model, and under some circumstances ... More
Band structure loops and multistability in cavity-QEDJan 08 2011Jun 07 2011We calculate the band structure of ultracold atoms located inside a laser-driven optical cavity. For parameters where the atom-cavity system exhibits bistability, the atomic band structure develops loop structures akin to the ones predicted for Bose-Einstein ... More
Gravitational wave background from Population III black hole formationFeb 01 2002We study the generation of a stochastic gravitational wave (GW) background produced from a population of core-collapse supernovae, which form black holes in scenarios of structure formation. We obtain, for example, that the formation of a population (Population ... More
Stochastic background of gravitational wavesApr 28 2000A continuous stochastic background of gravitational waves (GWs) for burst sources is produced if the mean time interval between the occurrence of bursts is smaller than the average time duration of a single burst at the emission, i.e., the so called duty ... More
Pitch Perception of Complex Sounds: Nonlinearity RevisitedMay 05 1995The ability of the auditory system to perceive the fundamental frequency of a sound even when this frequency is removed from the stimulus is an interesting phenomenon related to the pitch of complex sounds. This capability is known as ``residue'' or ``virtual ... More
Comment on ``On spin-1 massive particles coupled to a Chern-Simons field''Dec 16 1999In this comment we discuss some serious inconsistencies presented by Gomes, Malacarne and da Silva in their paper, Phys.Rev. D60 (1999) 125016 (hep-th/9908181).
The hydrogen equation of state at high densitiesAug 24 2011We use a two-fluid model combining the quantum Green's function technique for the electrons and a classical HNC description for the ions to calculate the high-density equation of state of hydrogen. This approach allows us to describe fully ionized plasmas ... More
Chemical abundances of photoionized nebulae in the Local GroupDec 14 2016Photoionized nebulae comprise basically HII regions and planetary nebulae, and their abundances give important clues on the nucleosynthesis and chemical evolution of their host galaxies. There is presently a large amount of data on these objects, especially ... More
The Diversity of Extrasolar Terrestrial PlanetsJan 22 2010Extrasolar planetary host stars are enriched in key planet-building elements. These enrichments have the potential to drastically alter the building blocks available for terrestrial planet formation. Here we report on the combination of dynamical models ... More
Abundances in photoionized nebulae of the Local Group and nucleosynthesis of intermediate mass starsFeb 13 2017Photoionized nebulae, comprising HII regions and planetary nebulae, are excellent laboratories to investigate the nucleosynthesis and chemical evolution of several elements in the Galaxy and other galaxies of the Local Group. Our purpose in this investigation ... More
Planetary nebulae in the inner Milky WayDec 10 2009New abundances of planetary nebulae located towards the bulge of the Galaxy are derived based on observations made at LNA (Brazil). We present accurate abundances of the elements He, N, S, O, Ar, and Ne for 56 PNe located towards the galactic bulge. The ... More
Magnetic field topology and chemical abundance distributions of the young, rapidly rotating chemically peculiar star HR5624May 14 2017The young, rapidly rotating Bp star HR5624 (HD133880) shows an unusually strong non-sinusoidal variability of its longitudinal magnetic field. This behaviour was previously interpreted as the signature of an exceptionally strong, quadrupole-dominated ... More
An optomechanical elevator: Transport of a Bloch oscillating Bose-Einstein condensate up and down an optical lattice by cavity sideband amplification and coolingNov 26 2015Feb 04 2016We analyze the optomechanics of an atomic Bose-Einstein condensate interacting with the optical lattice inside a laser-pumped optical cavity and subject to a uniform bias force such as gravity. An atomic wave packet in a tilted lattice undergoes Bloch ... More
Electronic structure of the pyrochlore metals Cd2Os2O7 and Cd2Re2O7Aug 14 2001First principles density functional calculations within the local spin density approximation (LSDA) and the generalized gradient approximation (GGA) are reported for pyrochlore Cd$_2$Os$_2$O$_7$ and Cd$_{2}$Re$_{2}$O$_7$. The transition metal $t_{2g}$ ... More
d-Wave Model for Microwave Response of High-Tc SuperconductorsMar 06 1994Mar 11 1994We develop a simple theory of the electromagnetic response of a d- wave superconductor in the presence of potential scatterers of arbitrary s-wave scattering strength and inelastic scattering by antiferromagnetic spin fluctuations. In the clean London ... More