Results for "M. Tuomi"

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Bayesian analysis of the radial velocities of HD 11506 reveals another planetary companionFeb 18 2009We aim to demonstrate the efficiency of a Bayesian approach in analysing radial velocity data by reanalysing a set of radial velocity measurements. We present Bayesian analysis of a recently published set of radial velocity measurements known to contain ... More
The complementarity of astrometric and radial velocity exoplanet observations - Determining exoplanet mass with astrometric snapshotsJul 15 2008Dec 16 2008We obtain full information on the orbital parameters by combining radial velocity and astrometric measurements by means of Bayesian inference. We sample the parameter probability densities of orbital model parameters with a Markov chain Monte Carlo (McMC) ... More
A new cold sub-Saturnian candidate planet orbiting GJ 221Jan 16 2014We re-analyse the recently published HARPS and PFS velocities of the nearby K dwarf GJ 221 that have been reported to contain the signatures of two planets orbiting the star. Our goal is to see whether the earlier studies discussing the system fell victims ... More
Bayesian re-analysis of the radial velocities of Gliese 581. Evidence in favour of only four planetary companionsFeb 16 2011The Gliese 581 planetary system has received attention because it has been proposed to host a low-mass planet in its habitable zone. We re-analyse the radial velocity measurements reported to contain six planetary signals to see whether these conclusions ... More
Signals embedded in the radial velocity noiseJan 15 2013Bayesian data analysis techniques, together with suitable statistical models, can be used to obtain much more information from noisy data than the traditional frequentist methods. For instance, when searching for periodic signals in noisy data, the Bayesian ... More
Evidence for 9 planets in the HD 10180 systemApr 05 2012We re-analyse the HARPS radial velocities of HD 10180 and calculate the probabilities of models with differing numbers of periodic signals in the data. We test the significance of the seven signals, corresponding to seven exoplanets orbiting the star, ... More
Frequency of planets orbiting M dwarfs in the Solar neighbourhoodJun 11 2019Jul 27 2019The most abundant stars in the Galaxy, M dwarfs, are very commonly hosts to diverse systems of low-mass planets. Their abundancy implies that the general occurrence rate of planets is dominated by their occurrence rate around such M dwarfs. In this article, ... More
A Goldilocks principle for modeling radial velocity noiseJun 16 2016The doppler measurements of stars are diluted and distorted by stellar activity noise. Different choices of noise models and statistical methods have led to much controversy in the confirmation of exoplanet candidates obtained through analysing radial ... More
Leaf litter decomposition -- Estimates of global variability based on Yasso07 modelJun 04 2009Litter decomposition is an important process in the global carbon cycle. It accounts for most of the heterotrophic soil respiration and results in formation of more stable soil organic carbon (SOC) which is the largest terrestrial carbon stock. Litter ... More
The curious case of HD41248. A pair of static signals buried behind red-noiseJun 12 2014Gaining a better understanding of the effects of stellar induced radial velocity noise is critical for the future of exoplanet studies, since the discovery of the lowest-mass planets using this method will require us to go below the intrinsic stellar ... More
Up to four planets around the M dwarf GJ 163. Sensitivity of Bayesian planet detection criteria to prior choiceJun 07 2013Exoplanet Doppler surveys are currently the most efficient means to detect low-mass companions to nearby stars. Among these stars, the light M dwarfs provide the highest sensitivity to detect low-mass exoplanet candidates. Evidence is accumulating that ... More
A planetary system with gas giants and super-Earths around the nearby M dwarf GJ 676A. Optimizing data analysis techniques for the detection of multi-planetary systemsJun 29 2012Oct 15 2012Several M dwarfs are targets of systematical monitoring in searches for Doppler signals caused by low-mass exoplanet companions. As a result, an emerging population of high-multiplicity planetary systems around low-mass stars are being detected as well. ... More
Comment on "Stellar activity masquerading as planets in the habitable zone of the M dwarf Gliese 581"Mar 06 2015Robertson et al.(Reports, July 25 2014, p440-444)(1) claimed that activity-induced variability is responsible for the Doppler signal of the proposed planet candidate GJ 581d. We point out that their analysis using periodograms of residual data is incorrect, ... More
Counting the number of planets around GJ 581. False positive rate of Bayesian signal detection methodsNov 06 2012The four-planet system around GJ 581 has received attention because it has been claimed that there are possibly two additional low-mass companions as well - one of them being a planet in the middle of the stellar habitable zone. We re-analyse the available ... More
Recovering planet radial velocity signals in the presence of starspot activity in fully convective starsDec 03 2016Accounting for stellar activity is a crucial component of the search for ever-smaller planets orbiting stars of all spectral types. We use Doppler imaging methods to demonstrate that starspot induced radial velocity variability can be effectively reduced ... More
Precision radial velocities of 15 M5 - M9 dwarfsJan 21 2014Jan 23 2014We present radial velocity measurements of a sample of M5V-M9V stars from our Red-Optical Planet Survey, ROPS, operating at 0.65-1.025 micron. Radial velocities for 15 stars, with r.m.s. precision down to 2.5 m/s over a week long time scale are achieved ... More
ROPS: A New Search for Habitable Earths in the Southern SkyApr 27 2012May 04 2012We present the first results from our Red Optical Planet Survey (ROPS) to search for low mass planets orbiting late type dwarfs (M5.5V - M9V) in their habitable zones (HZ). Our observations, with the red arm of the MIKE spectrograph (0.5 - 0.9 microns) ... More
Probabilities of exoplanet signals from posterior samplingsDec 27 2011Jun 25 2012Estimating the marginal likelihoods is an essential feature of model selection in the Bayesian context. It is especially crucial to have good estimates when assessing the number of planets orbiting stars when the models explain the noisy data with different ... More
The Anglo-Australian Planet Search. XXII. Two New Multi-Planet SystemsMay 12 2012May 15 2012We report the detection of two new planets from the Anglo-Australian Planet Search. These planets orbit two stars each previously known to host one planet. The new planet orbiting HD 142 has a period of 6005\pm427 days, and a minimum mass of 5.3M_Jup. ... More
Agatha: disentangling periodic signals from correlated noise in a periodogram frameworkMay 08 2017Periodograms are used as a key significance assessment and visualisation tool to display the significant periodicities in unevenly sampled time series. We introduce a framework of periodograms, called "Agatha", to disentangle periodic signals from correlated ... More
Soil carbon model Yasso07 graphical user interfaceMay 25 2011In this article, we present a graphical user interface software for the litter decomposition and soil carbon model Yasso07 and an overview of the principles and formulae it is based on. The software can be used to test the model and use it in simple applications. ... More
Application of Bayesian model inadequacy criterion for multiple data sets to radial velocity models of exoplanet systemsJun 29 2011We present a simple mathematical criterion for determining whether a given statistical model does not describe several independent sets of measurements, or data modes, adequately. We derive this criterion for two data sets and generalise it to several ... More
An improved quantification of HD 147379 bJan 31 2018We reanalyze the CARMENES and HIRES/KECK radial velocity data for HD 147379, and also analyze the SOPHIE data using the Agatha software in combination with MCMC posterior sampling. The analysis confirms the existence of HD 147379 b and improves the parameter ... More
Detection of the closest Jovian exoplanet in the Epsilon Indi triple systemMar 21 2018We confirm the trend in the radial velocity data for Epsilon Indi A suggesting a long-period planetary companion and find significant curvature is present, sufficient to quantify Epsilon Indi Ab as a cold Jupiter with a minimum mass of $2.71_{-0.44}^{+2.19}~M_{\rm ... More
Evidence for at least three planet candidates orbiting HD20794May 15 2017May 31 2017We explore the feasibility of detecting Earth analogs around Sun-like stars using the radial velocity method by investigating one of the largest radial velocities datasets for the one of the most stable radial-velocity stars HD20794. We proceed by disentangling ... More
Minimizing the bias in exoplanet detection - application to radial velocities of LHS 1140Jul 06 2018A rocky planet orbiting LHS 1140 with a period of 24.7d has been found based on the discovery of transits in its light and high precision radial velocity data (Dittmann et al. 2017). This discovery by two independent methods is an observational tour-de-force, ... More
The Debris Disk of Solar Analogue $τ$ Ceti: Herschel Observations and Dynamical Simulations of the Proposed Multiplanet SystemAug 12 2014$\tau$ Ceti is a nearby, mature G-type star very similar to our Sun, with a massive Kuiper Belt analogue (Greaves et al. 2004) and possible multiplanet system (Tuomi et al. 2013) that has been compared to our Solar System. We present Herschel Space Observatory ... More
Analysis of combined radial velocities and activity of BD+20 1790: evidence supporting the existence of a planetary companionFeb 18 2015This paper presents the simultaneous Bayesian analysis of the radial velocity and activity indices for the K5Ve active star BD+20 1790, that was proposed to host a close-in massive planet by Hern\'an-Obispo et al. (2010). The Bayesian analysis supports ... More
Radial-Velocity Fitting Challenge. II. First results of the analysis of the data setSep 13 2016Radial-velocity (RV) signals induce RV variations an order of magnitude larger than the signal created by the orbit of Earth-twins, thus preventing their detection. The goal of this paper is to compare the efficiency of the different methods used to deal ... More
Two planets around Kapteyn's star : a cold and a temperate super-Earth orbiting the nearest halo red-dwarfJun 03 2014Exoplanets of a few Earth masses can be now detected around nearby low-mass stars using Doppler spectroscopy. In this paper, we investigate the radial velocity variations of Kapteyn's star, which is both a sub-dwarf M-star and the nearest halo object ... More
Frequency of planets orbiting M dwarfs in the Solar neighbourhoodJun 11 2019The most abundant stars in the Galaxy, M dwarfs, are very commonly hosts to diverse systems of low-mass planets. Their abundancy implies that the general occurrence rate of planets is dominated by their occurrence rate around such M dwarfs. In this article, ... More
New Planetary Systems from the Calan-Hertfordshire Extrasolar Planet Search and the Core Accretion Mass LimitMar 30 2016We report the discovery of eight new giant planets, and updated orbits for four known planets, orbiting dwarf and subgiant stars, using the CORALIE, HARPS, and MIKE instruments as part of the Calan-Hertfordshire Extrasolar Planet Search. We include radial ... More
GJ 832c: A super-earth in the habitable zoneJun 21 2014We report the detection of GJ 832c, a super-Earth orbiting near the inner edge of the habitable zone of GJ 832, an M dwarf previously known to host a Jupiter analog in a nearly-circular 9.4-year orbit. The combination of precise radial-velocity measurements ... More
No evidence for activity correlations in the radial velocities of Kapteyn's starJun 30 2015Stellar activity may induce Doppler variability at the level of a few m/s which can then be confused by the Doppler signal of an exoplanet orbiting the star. To first order, linear correlations between radial velocity measurements and activity indices ... More
Two Super-Earths Orbiting the Solar Analogue HD41248 on the edge of a 7:5 Mean Motion ResonanceApr 27 2013Apr 30 2013The number of multi-planet systems known to be orbiting their host stars with orbital periods that place them in mean motion resonances is growing. For the most part, these systems are in first-order resonances and dynamical studies have focused their ... More
New Planetary Systems from the Calan-Hertfordshire Extrasolar Planet SearchMar 30 2016Nov 02 2016We report the discovery of eight new giant planets, and updated orbits for four known planets, orbiting dwarf and subgiant stars using the CORALIE, HARPS, and MIKE instruments as part of the Calan-Hertfordshire Extrasolar Planet Search. The planets have ... More
Filtering out activity-related variations from radial velocities in a search for low-mass planetsMay 08 2014Variations related to stellar activity and correlated noise can prevent the detections of low-amplitude signals in radial velocity data if not accounted for. This can be seen as the greatest obstacle in detecting Earth-like planets orbiting nearby stars ... More
Bayesian search for low-mass planets around nearby M dwarfs. Estimates for occurrence rate based on global detectability statisticsMar 03 2014Due to their higher planet-star mass-ratios, M dwarfs are the easiest targets for detection of low-mass planets orbiting nearby stars using Doppler spectroscopy. Furthermore, because of their low masses and luminosities, Doppler measurements enable the ... More
A terrestrial planet candidate in a temperate orbit around Proxima CentauriSep 12 2016At a distance of 1.295 parsecs, the red-dwarf Proxima Centauri ($\alpha$ Centauri C, GL 551, HIP 70890, or simply Proxima) is the Sun's closest stellar neighbor and one of the best studied low-mass stars. It has an effective temperature of only $\sim$ ... More
Color difference makes a difference: four planet candidates around tau CetiAug 07 2017The removal of noise typically correlated in time and wavelength is one of the main challenges for using the radial velocity method to detect Earth analogues. We analyze radial velocity data of tau Ceti and find robust evidence for wavelength dependent ... More
AD Leonis: Radial velocity signal of stellar rotation or spin-orbit resonance?Feb 16 2018Feb 21 2018AD Leonis is a nearby magnetically active M dwarf. We find Doppler variability with a period of 2.23 days as well as photometric signals: (1) a short period signal which is similar to the radial velocity signal albeit with considerable variability; and ... More
A candidate super-Earth planet orbiting near the snow line of Barnard's starNov 14 2018Nov 23 2018At a distance of 1.8 parsecs, Barnard's star (Gl 699) is a red dwarf with the largest apparent motion of any known stellar object. It is the closest single star to the Sun, second only to the alpha Centauri triple stellar system. Barnard's star is also ... More
Habitable-zone super-Earth candidate in a six-planet system around the K2.5V star HD 40307Nov 07 2012The K2.5 dwarf HD 40307 has been reported to host three super-Earths. The system lacks massive planets and is therefore a potential candidate for having additional low-mass planetary companions. We re-derive Doppler measurements from public HARPS spectra ... More
Stellar activity analysis of Barnard's Star: Very slow rotation and evidence for long-term activity cycleDec 17 2018Jul 23 2019The search for Earth-like planets around late-type stars using ultra-stable spectrographs requires a very precise characterization of the stellar activity and the magnetic cycle of the star, since these phenomena induce radial velocity (RV) signals that ... More
A dynamically-packed planetary system around GJ667C with three super-Earths in its habitable zoneJun 25 2013Since low-mass stars have low luminosities, orbits at which liquid water can exist on Earth-sized planets are relatively close-in, which produces Doppler signals that are detectable using state-of-the-art Doppler spectroscopy. GJ 667C is already known ... More
Stellar activity analysis of Barnard's Star: Very slow rotation and evidence for long-term activity cycleDec 17 2018Aug 06 2019The search for Earth-like planets around late-type stars using ultra-stable spectrographs requires a very precise characterization of the stellar activity and the magnetic cycle of the star, since these phenomena induce radial velocity (RV) signals that ... More
Stellar activity analysis of Barnard's Star: Very slow rotation and evidence for long-term activity cycleDec 17 2018The search for Earth-like planets around late-type stars using ultra-stable spectrographs requires a very precise characterization of the stellar activity and the magnetic cycle of the star, since these phenomena induce radial velocity (RV) signals that ... More
The LCES HIRES/Keck Precision Radial Velocity Exoplanet SurveyFeb 12 2017We describe a 20-year survey carried out by the Lick-Carnegie Exoplanet Survey Team (LCES), using precision radial velocities from HIRES on the Keck-I telescope to find and characterize extrasolar planetary systems orbiting nearby F, G, K, and M dwarf ... More
A Hot Uranus Orbiting the Super Metal-rich Star HD77338 and the Metallicity - Mass ConnectionJul 04 2012Dec 13 2012We announce the discovery of a low-mass planet orbiting the super metal-rich K0V star HD77338 as part of our on-going Calan-Hertfordshire Extrasolar Planet Search. The best fit planet solution has an orbital period of 5.7361\pm0.0015 days and with a radial ... More
The test case of HD26965: difficulties disentangling weak Doppler signals from stellar activityJan 11 2018We report the discovery of a radial velocity signal that can be interpreted as a planetary-mass candidate orbiting the K dwarf HD26965, with an orbital period of 42.364$\pm$0.015 days, or alternatively, as the presence of residual, uncorrected rotational ... More
A Six-Planet System Around the Star HD 34445Oct 19 2017We present a new precision radial velocity dataset that reveals a multi-planet system orbiting the G0V star HD 34445. Our 18-year span consists of 333 precision radial velocity observations, 56 of which were previously published, and 277 which are new ... More
Status of the Calan-Hertfordshire Extrasolar Planet SearchFeb 22 2013Feb 25 2013In these proceedings we give a status update of the Calan-Hertfordshire Extrasolar Planet Search, an international collaboration led from Chile that aims to discover more planets around super metal-rich and Sun-like stars, and then follow these up with ... More
The Anglo-Australian Planet Search. XXIII. Two New Jupiter AnalogsJan 22 2014We report the discovery of two long-period giant planets from the Anglo-Australian Planet Search. HD 154857c is in a multiple-planet system, while HD 114613b appears to be solitary. HD 114613b has an orbital period P=10.5 years, and a minimum mass m sin ... More
Benchmarking the power of amateur observatories for TTV exoplanets detectionJan 27 2015Apr 08 2015We perform an analysis of ~80000 photometric measurements for the following 10 stars hosting transiting planets: WASP-2, -4, -5, -52, Kelt-1, CoRoT-2, XO-2, TrES-1, HD 189733, GJ 436. Our analysis includes mainly transit lightcurves from the Exoplanet ... More
Signals embedded in the radial velocity noise. Periodic variations in the tau Ceti velocitiesDec 18 2012The abilities of radial velocity exoplanet surveys to detect the lowest-mass extra-solar planets are currently limited by a combination of instrument precision, lack of data, and "jitter". Jitter is a general term for any unknown features in the noise, ... More
A new signal for scalar top bound state productionOct 01 1993We study the production and decay of a scalar \stst\ bound state \sigst\ at hadron supercolliders, where \st\ is the lighter stop eigenstate. If \st\ has no tree--level 2--body decays, the dominant decay modes of \sigst\ are $gg$ or, if $m_h < \mst \ll ... More
Lorentz Conserving Noncommutative Standard ModelMar 29 2007May 10 2007We consider Lorentz conserving noncommutative field theory to construct the Lorentz conserving noncommutative standard model based on the gauge group $SU(3)\times SU(2)\times U(1)$. We obtain the enveloping algebra-valued of Higgs field up to the second ... More
Shelving and Probe Efficiency in Trapped Ion ExperimentsFeb 24 2014A generalized probe sequence typical of trapped ion experiments using shelving is studied. Detection efficiency is analyzed for finite shelved state lifetimes and using multi-modal count distributions. Multi-modal distributions are more appropriate for ... More
The Neutralino Relic Density in Minimal N=1 SupergravityJul 10 1992We compute the cosmic relic (dark matter) density of the lightest supersymmetric particle (LSP) in the framework of minimal $N=1$ Supergravity models with radiative breaking of the electroweak gauge symmetry. To this end, we re--calculate the cross sections ... More
Quantization and $2π$ Periodicity of the Axion Action in Topological InsulatorsJun 17 2010Nov 10 2010The Lagrangian describing the bulk electromagnetic response of a three-dimensional strong topological insulator contains a topological `axion' term of the form '\theta E dot B'. It is often stated (without proof) that the corresponding action is quantized ... More
Massive Neutrino in Non-commutative Space-timeDec 24 2007Apr 01 2008We consider the noncommutative standard model based on $SU(3)\times SU(2)\times U(1)$. We study the gauge transformation of right handed neutrino and its direct interaction with photon in the noncommutative space-time. We show that the massive Dirac neutrinos, ... More
Infinite order excitonic Bloch equations for asymmetric nanostructuresJul 04 2003We present a new exciton-based formalism for calculating the coherent response of asymmetric semiconductor multiple quantum well structures to ultra-short optical pulses valid to infinite order in the optical field and including the self-generated intraband ... More
Scalar StoponiumAug 18 1993We study the decays of a scalar \stst\ bound state \sigst, where \st\ is the lighter stop eigenstate. If \st\ has no tree--level 2--body decays, the dominant decay modes of \sigst\ are $gg$ or, if $m_h < \mst \ll \mstt$, a pair of light scalar Higgs bosons ... More
Photon Neutrino Scattering in Non-Commutative SpaceNov 04 2005Jan 19 2006We extend the non-commutative standard model based on the minimal $SU(3)\times SU(2)\times U(1)$ gauge group to include the interaction of photon with neutrino. We show that, in the gauge invariant manner, only the right handed neutrino can directly couple ... More
Production and Decay of Scalar Stoponium Bound StatesDec 02 1993In this paper we discuss possible signatures for the production of scalar \stst\ (stoponium) bound states \sigst\ at hadron colliders, where \st\ is the lighter scalar top eigenstate. We first study the decay of \sigst; explicit expressions are given ... More
Parton Model in Lorentz Invariant Non-Commutative SpaceMay 26 2004Aug 22 2004We consider the Lorentz invariant non-commutative QED and complete the Feynman rules for the theory up to the order $\theta^2$. In the Lorentz invariant version of the non-commutative QED the particles with fractional charges can be also considered. We ... More
Electromagnetic Response of Weyl SemimetalsMar 22 2013Jun 27 2013It has been suggested recently, based on subtle field-theoretical considerations, that the electromagnetic response of Weyl semimetals and the closely related Weyl insulators can be characterized by an axion term E.B with space and time dependent axion ... More
The Charm Quark Contribution to the Proton Structure FunctionOct 14 2006Dec 27 2006The charm quark structure function $F^c_2$ and the longitudinal structure function $F_l^p$ are directly sensitive to the gluon content of proton and therefore are crucial in understanding of proton structure function, in particular at low momentum transfer ... More
The decay of singlet scalar dark matter to unparticle and photonMay 06 2008We consider the unparticle physics introduced by Georgi and show that if the standard model is extended to include a singlet scalar as a dark matter candidate, there is a channel which leads to its decay to photon and unparticle. We calculate the decay ... More
On the effect of the thermal gas component to the stability of vortices in trapped Bose-Einstein condensatesMar 12 2002We study the stability of vortices in trapped single-component Bose-Einstein condensates within self-consistent mean-field theories--especially we consider the Hartree-Fock-Bogoliubov-Popov theory and its recently proposed gapless extensions. It is shown ... More
Phase boundaries of a spin-3/2 Blume-Emery-Griffiths model on a honeycomb latticeOct 11 2013The spin-3/2 Blume-Emery-Griffiths model on a honeycomb lattice is studied by Monte Carlo simulations with the goal to determine phase diagrams for a range of the model parameters and to investigate the nature of the phase transitions between the respective ... More
Flares on A-type stars: Evidence for heating of solar corona by nanoflares?Aug 11 2016We analyzed the occurrence rates of flares on stars of spectral types K, G, F, and A, observed by Kepler. We found that the histogram of occurrence frequencies of stellar flares is systematically shifted towards a high-energy tail for A-type stars compared ... More
The Formation Rates of Population III Stars and Chemical Enrichment of Halos during the Reionization EraJan 06 2009[abridged] The First Stars in the Universe form out of pristine primordial gas clouds that have been radiatively cooled to a few hundreds of degrees Kelvin either via molecular or atomic (Lyman-Alpha) hydrogen lines. This primordial mode of star formation ... More
Symmetry Adaptation Techniques in n-Photon Absorption SpectroscopyOct 27 1998We present some recent progress achieved in the application of symmetry adaptation techniques to n-photon absorption spectroscopy of rare earth ions in finite symmetry. More specifically, this work is concerned with the determination of the intensity ... More
Two-Photon Spectroscopy of Transition-Metal Ions in Cubical SymmetryOct 26 1998Symmetry adaptation techniques are applied to the determination of intensities of intra-configurational two-photon transitions for transition-metal ions in cubical symmetry. This leads to a simple model giving the polarization dependence of intensities ... More
An Alternative Basis for the Wigner-Racah Algebra of the Group SU(2)Dec 17 1997The Lie algebra of the classical group SU(2) is constructed from two quon algebras for which the deformation parameter is a common root of unity. This construction leads to (i) a not very well-known polar decomposition of the ladder generators of the ... More
Enhanced Sampling in the Well-Tempered EnsembleOct 26 2009Apr 13 2010We introduce the well-tempered ensemble (WTE) which is the biased ensemble sampled by well-tempered metadynamics when the energy is used as collective variable. WTE can be designed so as to have approximately the same average energy as the canonical ensemble ... More
Berry's Phase Induced Bose-Einstein condensation into a Vortex StateNov 23 1998The existence of a geometric phase in magnetic traps can be used to Bose condense a magnetically trapped atomic gas into a vortex state. We propose an experimental setup where a magnetic trap together with a blue detuned laser beam form a multiply connected ... More
Superconducting state in Fe-based materials and spin-fluctuation theory of pairingOct 28 2015Short review of the spin-fluctuation theory of superconductive pairing in iron-based pnictides and chalcogenides.
QCD_{1+1} with Static Quarks as Supersymmetric Quantum MechanicsFeb 09 1998We reexamine the solvable model problem of two static, fundamental quarks interacting with a SU(2) Yang-Mills field on a spatial circle, introduced by Engelhardt and Schreiber. If the quarks are at the same point, the model exhibits a quantum mechanical ... More
Massive Binary Black Holes in the Cosmic LandscapeJun 23 2009Binary black holes occupy a special place in our quest for understanding the evolution of galaxies along cosmic history. If massive black holes grow at the center of (pre-)galactic structures that experience a sequence of merger episodes, then dual black ... More
Effect of inelastic scattering on parametric pumpingAug 03 2001Pumping of charge in phase-coherent mesoscopic systems due to the out-of-phase modulation of two parameters has recently found considerable interest. We investigate the effect of inelastic processes on the adiabatically pumped current through a two terminal ... More
Hidden quantum pump effects in quantum coherent ringsFeb 27 2003Time periodic perturbations of an electron system on a ring are examined. For small frequencies periodic small amplitude perturbations give rise to side band currents which in leading order are inversely proportional to the frequency. These side band ... More
Dynamic scattering channels of a double barrier structureApr 02 2008We calculate analytically the Floquet scattering matrix for a periodically driven double-barrier structure. Our approach takes into account dynamical effects which become necessarily important when electrons propagate through a system subject to a fast ... More
Dissipation and noise in adiabatic quantum pumpsJan 16 2002We investigate the distribution function, the heat flow and the noise properties of an adiabatic quantum pump for an arbitrary relation of pump frequency $\omega$ and temperature. To achieve this we start with the scattering matrix approach for ac-transport. ... More
Remarks on the high-energy behaviour of cross-sections in weak-scale string theoriesSep 20 2001We consider the high-energy behaviour of processes involving Kaluza-Klein (KK) gravitons of weak-scale string theories. We discuss how form-factors derived within string theory modify the couplings of KK gravitons and thereby lead to an exponential fall-off ... More
Metastability in Two Dimensions and the Effective PotentialApr 12 1993We study analytically and numerically the decay of a metastable phase in (2+1)-dimensional classical scalar field theory coupled to a heat bath, which is equivalent to two-dimensional Euclidean quantum field theory at zero temperature. By a numerical ... More
New analyticity constraints on the high energy behavior of hadron-hadron cross sectionsJan 25 2006Mar 16 2006We here comment on a series of recent papers by Igi and Ishida[K. Igi and M. Ishida, Phys. Lett B 622, 286 (2005)] and Block and Halzen[M. M. Block and F. Halzen, Phys. Rev D 72, 036006 (2005)] that fit high energy $pp$ and $\bar pp$ cross section and ... More
Factorization Theorems for High Energy nn, gamma p and gamma gamma ScatteringFeb 17 2003The robustness of the factorization theorem for total cross sections, $\sigma_{nn}/\sigma_{\gamma p}=\sigma_{\gamma p}/\sigma_{\gamma\gamma}$, originally proved by Block and Kaidalov\cite{bk} for $nn$ (the even portion of $pp$ and $\pbar p$ scattering), ... More
Visualising a FuseOct 27 2010Nov 09 2010In this brief article I describe an experiment to illustrate how a fuse works. I have used this as part of lessons for my year 11 classes to demonstrate how an electrical fuse 'blows' when too high a current passes through it.
General models of Einstein gravity with a non-Newtonian weak-field limitJan 08 2009We investigate Einstein theories of gravity, coupled to a scalar field \vphi and point-like matter, which are characterized by a scalar field-dependent matter coupling function e^{H(\vphi)}. We show that under mild constraints on the form of the potential ... More
Two Loop Electroweak Bosonic Corrections to the Muon Decay LifetimeNov 04 2002Nov 19 2002A review of the calculation of the two loop bosonic corrections to $\Delta r$ is presented. Factorization and matching onto the Fermi model are discussed. An approximate formula, describing the quantity over the interesting range of Higgs boson mass values ... More
Structure and stability of Al$_2$FeJul 01 2011We employ first principles total energy and phonon calculations to address the structure and stability of Al$_2$Fe. This structure, which is reported as stable in the assessed Al-Fe phase diagram, is distinguished by an unusually low triclinic symmetry. ... More
Stability of Fe-based alloys with structure type C6Cr23Jul 23 2004Bulk metallic glass forms when liquid metal alloys solidify without crystalization. In the search for Iron-based bulk glass-forming alloys of the metal-metalloid type (Fe-B- and Fe-C-based), crystals based on the structural prototype C6Cr23 often preempt ... More
Cohesive energies of Fe-based glass-forming alloysMay 13 2004We calculate the cohesive energies of Fe-based glass-forming alloys in the B-Fe-Y-Zr quaternary system. Our {\it ab-initio} calculations fully relax atomic positions and lattice parameters yielding enthalpies of mixing at T=0K. We examine both the known ... More
Efficiently Extracting Energy from Cosmological NeutrinosJul 02 2013Aug 20 2013Detecting the extremely low-energy neutrinos that form the Cosmic Neutrino Background (CNB) presents many experimental challenges, but pursuing this elusive goal is still worthwhile because these weakly-interacting particles could provide a new window ... More
Are the sungrazing comets the inner source of pickup ions and energetic neutral atoms?May 07 2004Feb 11 2005We present arguments that at least part of the inner source of pickup ions in the solar wind might be the material released by sungrazing comets. Based on a statistical analysis of sungrazing comets detected over almost eight years of LASCO operation ... More
Beyond the Kolmogorov Johnson Mehl Avrami kinetics: inclusion of the spatial correlationApr 16 2003The Kolmogorov-Johnson-Mehl-Avrami model, which is a nucleation and growth poissonian process in space, has been implemented by taking into account spatial correlation among nuclei. This is achieved through a detailed study of a system of distinguishable ... More
On the stability operator for MOTS and the 'core' of Black HolesOct 13 2012Small deformations of marginally (outer) trapped surfaces are considered by using their stability operator. In the case of spherical symmetry, one can use these deformations on any marginally trapped round sphere to prove several interesting results. ... More
On the boundary of the region containing trapped surfacesDec 15 2008The boundary of the region in spacetime containing future-trapped closed surfaces is considered. In asymptotically flat spacetimes, this boundary does not need to be the event horizon nor a dynamical/trapping horizon. Some properties of this boundary ... More