Results for "G. Hartmann"

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Gaussian quantum fluctuations in interacting many particle systemsDec 17 2003Apr 13 2004We consider a many particle quantum system, in which each particle interacts only with its nearest neighbours. Provided that the energy per particle has an upper bound, we show, that the energy distribution of almost every product state becomes a Gaussian ... More
Diluted antiferromagnets in a field seem to be in a different universality class than the random-field Ising modelFeb 11 2013Nov 13 2013We perform large-scale Monte Carlo simulations using the Machta-Newman-Chayes algorithms to study the critical behavior of both the diluted antiferromagnet in a field with 30% dilution and the random-field Ising model with Gaussian random fields for different ... More
On the asymptotic behavior of the length of the longest increasing subsequences of random walksJun 30 2019We numerically estimate the leading asymptotic behavior of the length $L_{n}$ of the longest increasing subsequence of random walks with step increments following Student's $t$-distribution with parameter in the range $\frac{1}{2} \leq \nu \leq 5$. We ... More
On Rational Points of Varieties over Local Fields having a Model with Tame Quotient SingularitiesDec 20 2012Oct 23 2013We study rational points on a smooth variety X over a complete local field K with algebraically closed residue field, and models of X with tame quotient singularities. If a model of X is the quotient of a Galois action on a weak N\'eron model of the base ... More
A pullback diagram in the coarse categoryJul 04 2019This paper studies the limit of a pullback diagram in the coarse category.
Twisted Coefficients on coarse Spaces and their CoronaMar 31 2019To a metric space $X$ we associate a compact topological space $\nu' X$ called the corona of $X$. Then a coarse map $f:X\to Y$ between metric spaces is mapped to a continuous map $\nu' f:\nu' X\to \nu' Y$ between coronas. Sheaf cohomology on coarse spaces ... More
Coarse Cohomology with twisted CoefficientsSep 30 2017Jul 04 2019This paper studies sheaf cohomology on coarse spaces.
Some results on the lattice parameters of quaternionic Gabor framesJul 17 2015Gabor frames play a vital role not only modern harmonic analysis but also in several fields of applied mathematics, for instances, detection of chirps, or image processing. In this work we present a non-trivial generalization of Gabor frames to the quaternionic ... More
Interpolation and harmonic majorants in big Hardy-Orlicz spacesMar 27 2006Mar 28 2006Free interpolation in Hardy spaces is caracterized by the well-known Carleson condition. The result extends to Hardy-Orlicz spaces contained in the scale of classical Hardy spaces $H^p$, $p>0$. For the Smirnov and the Nevanlinna classes, interpolating ... More
Equivariant motivic integration on formal schemes and the motivic zeta functionNov 27 2015For a formal scheme over a complete discrete valuation ring with a good action of a finite group, we define equivariant motivic integration, and we prove a change of variable formula for that.To do so, we construct and examine an induced group action ... More
Why Do We See a Classical World?Dec 29 2011Jul 18 2012From a general abstract system theoretical perspective, a quantum-like system description in the spirit of a generalized Quantum Theory may appear to be simpler and more natural than a classically inspired description. We investigate the reasons why we ... More
A criteria of strong H-differentiabilityJul 19 2016Dec 01 2016We give a criteria for a Malliavin differentiable function to be strongly H-differentiable.
Quantum Many-Body Phenomena in Coupled Cavity ArraysAug 19 2008The increasing level of experimental control over atomic and optical systems gained in the past years have paved the way for the exploration of new physical regimes in quantum optics and atomic physics, characterised by the appearance of quantum many-body ... More
A polaritonic two-component Bose-Hubbard modelJun 15 2007We show that polaritons in an array of interacting micro-cavities with strong atom-photon coupling can form a two-component Bose-Hubbard model. Both polariton species are thereby protected against spontaneous emission as their atomic part is stored in ... More
Long-term Evolution of Protostellar and Protoplanetary Disks. I. OutburstsMar 08 2010As an initial investigation into the long-term evolution of protostellar disks, we explore the conditions required to explain the large outbursts of disk accretion seen in some young stellar objects. We use one-dimensional time-dependent disk models with ... More
The X-ray Telescope of the CAST ExperimentNov 14 2005The CERN Axion Solar Telescope (CAST) searches for solar axions employing a 9 Tesla superconducting dipole magnet equipped with 3 independent detection systems for X-rays from axion-photon conversions inside the 10 m long magnetic field. Results of the ... More
From Nanopores to Macropores: Fractal Morphology of GraphiteSep 18 2015We present a comprehensive structural characterization of two different highly pure nuclear graphites that compasses all relevant length scales from nanometers to sub-mm. This has been achieved by combining several experiments and neutron techniques: ... More
Direct observation of nanometer-scale pinning sites in (Nd$_{0.33}$,Eu$_{0.20}$,Gd$_{0.47}$)Ba$_2$Cu$_3$O$_{7-δ}$ single crystalsJul 25 2008We report on the observation of self-organized stripe-like structures on the as-grown surface and in the bulk of (Nd,Eu,Gd)Ba$_2$Cu$_3$O$_y$ single crystals. The periodicity of the stripes on the surface lies between 500 and 800 nm. These are possibly ... More
Effective spin systems in coupled micro-cavitiesApr 23 2007We show that atoms trapped in micro-cavities that interact via exchange of virtual photons can model an anisotropic Heisenberg spin-1/2 chain in an external magnetic field. All parameters of the effective Hamiltonian can individually be tuned via external ... More
Strongly Interacting Polaritons in Coupled Arrays of CavitiesJun 12 2006Nov 29 2006The experimental observation of quantum phenomena in strongly correlated many particle systems is difficult because of the short length- and timescales involved. Obtaining at the same time detailed control of individual constituents appears even more ... More
Light-shift-induced photonic nonlinearitiesMay 16 2007We propose a new method to produce self- and cross-Kerr photonic nonlinearities, using light-induced Stark shifts due to the interaction of a cavity mode with atoms. The proposed experimental set-up is considerably simpler than in previous approaches, ... More
Quantum phase transitions with Photons and PolaritonsJan 31 2007We show that a system of polaritons - combined atom and photon excitations - in an array of coupled cavities, under an experimental set-up usually considered in electromagnetically induced transparency, is described by the Bose-Hubbard model. This opens ... More
Are Abell Clusters Correlated with Gamma-Ray Bursts?Feb 21 1997A recent study has presented marginal statistical evidence that gamma-ray burst sources are correlated with Abell clusters, based on analyses of bursts in the BATSE 3B catalog. Using precise localization information from the 3rd Interplanetary Network, ... More
The Robotic Super-LOTIS Telescope: Results & Future PlansFeb 29 2008We provide an overview of the robotic Super-LOTIS (Livermore Optical Transient Imaging System) telescope and present results from gamma-ray burst (GRB) afterglow observations using Super-LOTIS and other Steward Observatory telescopes. The 0.6-m Super-LOTIS ... More
Relativistic Particle-In-Cell Simulation Studies of Prompt and Early Afterglows from GRBsFeb 18 2008Nonthermal radiation observed from astrophysical systems containing relativistic jets and shocks e.g. gamma-ray bursts (GRBs) active galactic nuclei (AGNs) and microquasars commonly exhibit power-law emission spectra. Recent PIC simulations of relativistic ... More
Explicit Model Checking of Very Large MDP using Partitioning and Secondary StorageApr 11 2015May 19 2016The applicability of model checking is hindered by the state space explosion problem in combination with limited amounts of main memory. To extend its reach, the large available capacities of secondary storage such as hard disks can be exploited. Due ... More
Quantum Phase Transition with Inhomogeneous Driving in the LHZ modelJun 27 2019We study the zero-temperature phase diagram of the LHZ model. An analytic expression for the free energy and critical coefficients for finite-size systems and in the thermodynamic limit are derived and numerically verified. With the aim to improve standard ... More
Efficient Rare Event Simulation by Optimal Nonequilibrium ForcingAug 15 2012Aug 17 2012Rare event simulation and estimation for systems in equilibrium are among the most challenging topics in molecular dynamics. As was shown by Jarzynski and others, nonequilibrium forcing can theoretically be used to obtain equilibrium rare event statistics. ... More
Order Effects in Sequential Measurements of Non-Commuting Psychological ObservablesJan 23 2012Jun 26 2012Sequential measurements of non-commuting observables produce order effects that are well-known in quantum physics. But their conceptual basis, a significant measurement interaction, is relevant for far more general situations. We argue that non-commutativity ... More
Infinite-dimensional bilinear and stochastic balanced truncation with error boundsJun 14 2018Nov 26 2018Along the ideas of Curtain and Glover, we extend the balanced truncation method for infinite-dimensional linear systems to bilinear and stochastic systems. Specifically , we apply Hilbert space techniques used in many-body quantum mechanics to establish ... More
An extension of the Cheeger-Müller theorem for a coneAug 18 2010Oct 02 2014We prove the equality of the $L^2$-analytic torsion and the intersection R torsion of the even dimensional finite metric cone over an odd dimensional compact manifold.
Fractional EchoesMar 03 2016We report the observation of fractional echoes in a double-pulse excited nonlinear system. Unlike standard echoes which appear periodically at delays which are integer multiple of the delay between the two exciting pulses, the fractional echoes appear ... More
High-redshift blazars through nustar eyesMar 30 2017The most powerful sources among the blazar family are MeV blazars. Often detected at $z>2$, they usually display high X- and \gm-ray luminosities, larger-than-average jet powers and black hole masses $\gtrsim 10^9 M_{\odot}$. In the present work we perform ... More
Nano-Thermodynamics: On the minimal length scale for the existence of temperatureFeb 02 2005We consider a quantum system consisting of a regular chain of elementary subsystems with nearest neighbor interactions and assume that the total system is in a canonical state with temperature $T$. We analyze under what condition the state factors into ... More
Local Versus Global Thermal States: Correlations and the Existence of Local TemperaturesApr 29 2004Dec 01 2004We consider a quantum system consisting of a regular chain of elementary subsystems with nearest neighbor interactions and assume that the total system is in a canonical state with temperature $T$. We analyze under what condition the state factors into ... More
Girsanov reweighting for path ensembles and Markov state modelsMar 16 2017The sensitivity of molecular dynamics on changes in the potential energy function plays an important role in understanding the dynamics and function of complex molecules.We present a method to obtain path ensemble averages of a perturbed dynamics from ... More
Fundamentals of Nano-ThermodynamicsAug 06 2004Recent progress in the synthesis and processing of nano-structured materials and systems calls for an improved understanding of thermal properties on small length scales. In this context, the question whether thermodynamics and, in particular, the concept ... More
Strongly Coupled Plasma LiquidsOct 27 2007This paper intends to review some of the prominent properties of strongly coupled classical plasmas having in mind the possible link with the quark-gluon plasma created in heavy-ion collisions. Thermodynamic and transport properties of classical liquid-state ... More
An experiment for the measurement of the bound-beta decay of the free neutronFeb 26 2006The hyperfine-state population of hydrogen after the bound-beta decay of the neutron directly yields the neutrino left-handedness or a possible right-handed admixture and possible small scalar and tensor contributions to the weak force. Using the through-going ... More
Ferromagnetism in the Hubbard model on the square lattice: Improved instability criterion for the Nagaoka stateDec 08 1995The instability of the fully polarized ferromagnetic state (Nagaoka state) with respect to single spin flips is re-examined for the Hubbard model on the square lattice with a large family of variational wave functions which include correlation effects ... More
Ultrametricity and clustering of states in spin glasses: A one-dimensional viewJul 22 2008Jan 26 2009We present results from Monte Carlo simulations to test for ultrametricity and clustering properties in spin-glass models. By using a one-dimensional Ising spin glass with random power-law interactions where the universality class of the model can be ... More
Exciton-Dominated Core-Level Absorption Spectra of Hybrid Organic-Inorganic Lead Halide PerovskitesApr 18 2018In a combined theoretical and experimental work, we investigate X-ray Absorption Near-Edge Structure (XANES) spectroscopy of the I $L_3$ and the Pb $M_5$ edges of the methylammonium lead iodide ($\textrm{MAPbI}_3$) hybrid inorganic-organic perovskite ... More
Kondo-like phonon scattering in thermoelectric clathratesNov 23 2017Crystalline solids are generally known as excellent heat conductors, amorphous materials or glasses as thermal insulators. It has thus come as a surprise that certain crystal structures defy this paradigm. A prominent example are type-I clathrates and ... More
Triplet superconductivity in a one-dimensional ferromagnetic t-J modelJul 27 1999In this paper we study the ground state phase diagram of a one-dimensional $t-U-J$ model, at half-filling. In the large-bandwidth limit and for ferromagnetic exchange with easy-plane anisotropy, a phase with gapless charge and massive spin excitations, ... More
Interaction of Infall and Winds in Young Stellar ObjectsOct 14 1999The interaction of a stellar or disk wind with a collapsing environment holds promise for explaining a variety of outflow phenomena observed around young stars. In this paper we present the first simulations of these interactions. The focus here is on ... More
New Relativistic Particle-In-Cell Simulation Studies of Prompt and Early Afterglows from GRBsSep 30 2008Oct 15 2008Nonthermal radiation observed from astrophysical systems containing relativistic jets and shocks, e.g., gamma-ray bursts (GRBs), active galactic nuclei (AGNs), and microquasars commonly exhibit power-law emission spectra. Recent PIC simulations of relativistic ... More
Complex Algebras of ArithmeticNov 27 2009Dec 01 2009An 'arithmetic circuit' is a labeled, acyclic directed graph specifying a sequence of arithmetic and logical operations to be performed on sets of natural numbers. Arithmetic circuits can also be viewed as the elements of the smallest subalgebra of the ... More
Cointegrated Continuous-time Linear State Space and MCARMA ModelsNov 23 2016Dec 30 2017In this paper we define and characterize cointegrated continuous-time linear state-space models. A main result is that a cointegrated continuous-time linear state-space model can be represented as a sum of a L\'evy process and a stationary linear state-space ... More
Rare-Event Properties of the Nagel-Schreckenberg ModelAug 13 2019We have studied the distribution of traffic flow $q$ for the Nagel-Schreckenberg model by computer simulations. We applied a large-deviation approach, which allowed us to obtain the distribution $P(q)$ over more than one hundred decades in probability, ... More
Floquet engineering in superconducting circuits: from arbitrary spin-spin interactions to the Kitaev honeycomb modelAug 09 2018We derive a theory for the generation of arbitrary spin-spin interactions in superconducting circuits via periodic time modulation of the individual qubits or the qubit-qubit interactions. The modulation frequencies in our approach are in the microwave ... More
Functions Definable by Numerical Set-ExpressionsOct 31 2009A "numerical set-expression" is a term specifying a cascade of arithmetic and logical operations to be performed on sets of non-negative integers. If these operations are confined to the usual Boolean operations together with the result of lifting addition ... More
Nonlinear cotunneling through an artificial moleculeDec 03 2002May 05 2003We study electron transport through a system of two lateral quantum dots coupled in series. We consider the case of weak coupling to the leads and a bias point in the Coulomb blockade. After a generalized Schrieffer-Wolf transformation, cotunneling through ... More
Nonequilibrium stabilization of charge states in double quantum dotsFeb 27 2003Apr 29 2004We analyze the decoherence of charge states in double quantum dots due to cotunneling. The system is treated using the Bloch-Redfield generalized master equation for the Schrieffer-Wolff transformed Hamiltonian. We show that the decoherence, characterized ... More
Contributions of GRBs and Cen A-like Radio Galaxies to the Cosmic Gamma-ray BackgroundMay 10 2001The contribution to the cosmic diffuse gamma-ray background (CGB) from Gamma Ray Bursts (GRBs) is studied in the 40 keV - 2 MeV regime. We use High Energy Resolution (HER) data from the Burst And Transient Source Experiment (BATSE) aboard the Compton ... More
Robust estimation of continuous-time ARMA models via indirect inferenceApr 03 2018In this paper we present a robust estimator for the parameters of a continuous-time ARMA(p,q) (CARMA(p,q)) process sampled equidistantly which is not necessarily Gaussian. Therefore, an indirect estimation procedure is used. It is an indirect estimation ... More
Efficient Algorithms for Time- and Cost-Bounded Probabilistic Model CheckingMay 18 2016In the design of probabilistic timed systems, bounded requirements concerning behaviour that occurs within a given time, energy, or more generally cost budget are of central importance. Traditionally, such requirements have been model-checked via a reduction ... More
Magnetism of PdNi alloys near the critical concentration for ferromagnetismFeb 19 2014We report results of a muon spin rotation and relaxation ($\mu$SR) study of dilute Pd$_{1-x}$Ni$_x$ alloys, with emphasis on Ni concentrations $x =$ 0.0243 and 0.025. These are close to the critical value $x_\mathrm{cr}$ for the onset of ferromagnetic ... More
On the Incommensurate Phase in Modulated Heisenberg ChainsMar 08 1998Using the density matrix renormalization group method (DMRG) we calculate the magnetization of frustrated S=1/2 Heisenberg chains for various modulation patterns of the nearest neighbour coupling: commensurate, incommensurate with sinusoidal modulation ... More
Molecular dynamics simulation of strongly coupled QCD plasmasJan 06 2006The properties of a strongly interacting quark plasma are investigated by molecular dynamics method including non-abelian quark-quark potential. Our main goal is to study the thermalization process in this system. We find an interesting resonance-like ... More
Energy size effects of two-dimensional Ising spin glassesFeb 25 2004Sep 04 2004We analyze exact ground-state energies of two-dimensional Ising spin glasses with either Gaussian or bimodal nearest-neighbor interactions for large system sizes and for three types of boundary conditions: free on both axes, periodic on both axes, and ... More
Ultrametric probe of the spin-glass state in a fieldMay 18 2012Nov 06 2012We study the ultrametric structure of phase space of one-dimensional Ising spin glasses with random power-law interaction in an external random field. Although in zero field the model in both the mean-field and non-mean-field universality classes shows ... More
Gravitational Focusing and the Star Cluster Initial Mass FunctionJan 30 2017We discuss the possibility that gravitational focusing, is responsible for the power-law mass function of star clusters $N(\log M) \propto M^{-1}$. This power law can be produced asymptotically when the mass accretion rate of an object depends upon the ... More
Signatures of star cluster formation by cold collapseOct 28 2015Nov 13 2015Sub-virial gravitational collapse is one mechanism by which star clusters may form. Here we investigate whether this mechanism can be inferred from observations of young clusters. To address this question, we have computed SPH simulations of the initial ... More
Tail probabilities of random linear functions of regularly varying random vectorsApr 15 2019We provide a new extension of Breiman's Theorem on computing tail probabilities of a product of random variables to a multivariate setting. In particular, we give a complete characterization of regular variation on cones in $[0,\infty)^d$ under random ... More
Steady state entanglement in open and noisy quantum systems at high temperatureDec 23 2005We show that quantum mechanical entanglement can prevail even in noisy open quantum systems at high temperature and far from thermodynamical equilibrium, despite the deteriorating effect of decoherence. The system consists of a number N of interacting ... More
Analysis of the loop length distribution for the negative weight percolation problem in dimensions d=2 through 6Jul 12 2012We consider the negative weight percolation (NWP) problem on hypercubic lattice graphs with fully periodic boundary conditions in all relevant dimensions from d=2 to the upper critical dimension d=6. The problem exhibits edge weights drawn from disorder ... More
Scaling behavior of interactions in a modular quantum system and the existence of local temperatureDec 18 2003We consider a quantum system of fixed size consisting of a regular chain of $n$-level subsystems, where $n$ is finite. Forming groups of $N$ subsystems each, we show that the strength of interaction between the groups scales with $N^{- 1/2}$. As a consequence, ... More
Band-Insulator-Metal-Mott-Insulator transition in the half--filled $t-t^{\prime}$ ionic-Hubbard chainNov 15 2006We investigate the ground state phase diagram of the half-filled $t-t^{\prime}$ repulsive Hubbard model in the presence of a staggered ionic potential $\Delta$, using the continuum-limit bosonization approach. We find, that with increasing on-site-repulsion ... More
QCD Tests in High Energy CollisionsJun 26 1998Recent measurements and theoretical developments on the hadronic final state in deep-inelastic scattering, pp and ee collisions are presented.
Finding Low-Temperature States with Parallel Tempering, Simulated Annealing and Simple Monte CarloSep 11 2002Monte Carlo simulation techniques, like simulated annealing and parallel tempering, are often used to evaluate low-temperature properties and find ground states of disordered systems. Here we compare these methods using direct calculations of ground states ... More
The Truncated Disk of CoKu Tau/4Nov 18 2004We present a model of a dusty disk with an inner hole which accounts for the Spitzer Space Telescope Infrared Spectrograph observations of the low-mass pre-main sequence star CoKu Tau/4. We have modeled the mid-IR spectrum (between 8 and 25 mic) as arising ... More
Spin Waves in Quantum AntiferromagnetsJun 02 1995Using a self-consistent mean-field theory for the $S=1/2$ Heisenberg antiferromagnet Kr\"uger and Schuck recently derived an analytic expression for the dispersion. It is exact in one dimension ($d=1$) and agrees well with numerical results in $d=2$. ... More
Probing tails of energy distributions using importance-sampling in the disorder with a guiding functionMar 10 2006Apr 26 2006We propose a simple and general procedure based on a recently introduced approach that uses an importance-sampling Monte Carlo algorithm in the disorder to probe to high precision the tails of ground-state energy distributions of disordered systems. Our ... More
Modelling Radioactivities and other Observables from OB AssociationsMay 18 2000Recent observations of the diffuse Galactic gamma-ray glow at 1.809 MeV, attributed to the radioactive decay of 26Al, point towards a massive star origin of this radioactive isotope. Wolf Rayet stars and core-collapse supernovae appear to dominate the ... More
IRAC Colors of Young Stellar ObjectsMay 31 2004We compare the infrared colors predicted by theoretical models of protostellar envelopes and protoplanetary disks with initial observations of young stellar objects made with the Infrared Array Camera (IRAC) on the Spitzer Space Telescope (Werner et al. ... More
Radioactive 26Al and massive stars in the GalaxyJan 01 2006Jan 04 2006Gamma-rays from radioactive 26Al (half life ~7.2 10^5 yr) provide a 'snapshot' view of ongoing nucleosynthesis in the Galaxy. The Galaxy is relatively transparent to such gamma-rays, and emission has been found concentrated along the plane of the Galaxy. ... More
EXIST: A High Sensitivity Hard X-ray Imaging Sky Survey Mission for ISSDec 18 1999A deep all-sky imaging hard x-ray survey and wide-field monitor is needed to extend soft (ROSAT) and medium (ABRIXAS2) x-ray surveys into the 10-100 keV band (and beyond) at comparable sensitivity (~0.05 mCrab). This would enable discovery and study of ... More
Recovery of high-energy photoelectron circular dichroism through Fano interferenceJun 25 2019It is commonly accepted that the magnitude of a photoelectron circular dichroism (PECD) is governed by the ability of an outgoing photoelectron wave packet to probe the chiral asymmetry of a molecule. To be able to accumulate this characteristic asymmetry ... More
Overcoming system-size limitations in spin glassesSep 18 2005In order to overcome the limitations of small system sizes in spin-glass simulations, we investigate the one-dimensional Ising spin chain with power-law interactions. The model has the advantage over traditional higher-dimensional Hamiltonians in that ... More
Extended scaling for ferromagnetic Ising models with zero-temperature transitionsSep 06 2008Nov 12 2008We study the second-moment correlation length and the reduced susceptibility of two ferromagnetic Ising models with zero-temperature ordering. By introducing a scaling variable motivated by high-temperature series expansions, we are able to scale data ... More
Radiation from relativistic shocks with turbulent magnetic fieldsJun 26 2009Jan 24 2011Using our new 3-D relativistic electromagnetic particle (REMP) code parallelized with MPI, we investigated long-term particle acceleration associated with a relativistic electron-positron jet propagating in an unmagnetized ambient electron-positron plasma. ... More
New Insights from One-Dimensional Spin GlassesMar 24 2008The concept of replica symmetry breaking found in the solution of the mean-field Sherrington-Kirkpatrick spin-glass model has been applied to a variety of problems in science ranging from biological to computational and even financial analysis. Thus it ... More
The Orion OB1 Association II. The Orion-Eridanus BubbleMar 03 1995Observations of the interstellar medium in the vicinity of the Orion OB1 association show a cavity filled with hot ionized gas, surrounded by an expanding shell of neutral hydrogen (the Orion-Eridanus Bubble). In this paper we examine this cavity and ... More
Government and Social Media: A Case Study of 31 Informational World CitiesJan 18 2014Feb 28 2014Social media platforms are increasingly being used by governments to foster user interaction. Particularly in cities with enhanced ICT infrastructures (i.e., Informational World Cities) and high internet penetration rates, social media platforms are valuable ... More
Dust Processing in Disks around T Tauri StarsMay 17 2006The 8-14 micron emission spectra of 12 T Tauri stars in the Taurus/Auriga dark clouds and in the TW Hydrae association obtained with the Infrared Spectrograph (IRS; The IRS is a collaborative venture between Cornell University and Ball Aerospace Corporation ... More
Zeta-determinants of Sturm-Liouville operators with quadratic potentials at infinityJul 25 2016Dec 05 2016We consider Sturm-Liouville operators on a half line $[a,\infty), a>0$, with potentials that are growing at most quadratically at infinity. Such operators arise naturally in the analysis of hyperbolic manifolds, or more generally manifolds with cusps. ... More
Depinning of elastic manifoldsJul 11 2002We compute roughness exponents of elastic d-dimensional manifolds in (d+1)-dimensional embedding spaces at the depinning transition for d=1,...,4. Our numerical method is rigorously based on a Hamiltonian formulation; it allows to determine the critical ... More
The Spiral Wave Instability Induced by a Giant Planet: I. Particle Stirring in the Inner Regions of Protoplanetary DisksOct 26 2016We have recently shown that spiral density waves propagating in accretion disks can undergo a parametric instability by resonantly coupling with and transferring energy into pairs of inertial waves (or inertial-gravity waves when buoyancy is important). ... More
Evolution of Disk AccretionFeb 23 1999We review the present knowledge of disk accretion in young low mass stars, and in particular, the mass accretion rate and its evolution with time. The methods used to obtain mass accretion rates from ultraviolet excesses and emission lines are described, ... More
Weierstrass preparation and algebraic invariantsSep 28 2011Aug 31 2012We prove a form of the Weierstrass Preparation Theorem for normal algebraic curves over complete discrete valuation rings. While the more traditional algebraic form of Weierstrass Preparation applies just to the projective line over a base, our version ... More
Optimal control of Markov jump processes : Asymptotic analysis, algorithms and applications to the modelling of chemical reaction systemsDec 01 2015Jul 04 2017Markov jump processes are widely used to model natural and engineered processes. In the context of biological or chemical applications one typically refers to the chemical master equation (CME), which models the evolution of the probability mass of any ... More
Jarzynski's equality, fluctuation theorems, and variance reduction: Mathematical analysis and numerical algorithmsMar 25 2018Apr 08 2019In this paper, we study Jarzynski's equality and fluctuation theorems for diffusion processes. While some of the results considered in the current work are known in the (mainly physics) literature, we review and generalize these nonequilibrium theorems ... More
Mott metal-insulator transition induced by utilizing a glass-like structural ordering in low-dimensional molecular conductorsOct 30 2014Nov 14 2014We utilize a glass-like structural transition in order to induce a Mott metal-insulator transition in the quasi-two-dimensional organic charge-transfer salt $\kappa$-(BEDT-TTF)$_2$Cu[N(CN)$_2$]Br. In this material, the terminal ethylene groups of the ... More
Infall models of Class 0 protostarsOct 02 2000We have carried out radiative transfer calculations of infalling, dusty envelopes surrounding embedded protostars to understand the observed properties of the recently identified ``Class 0'' sources. To match the far-infrared peaks in the spectral energy ... More
Static solutions of a 6-dimensional Einstein-Yang-Mills modelJun 03 2004We study the Einstein-Yang-Mills equations in a 6-dimensional space-time. We make a self-consistent static, spherically symmetric ansatz for the gauge fields and the metric. The metric of the manifold associated with the two extra dimensions contains ... More
Spherically symmetric Yang-Mills solutions in a (4+n)- dimensional space-timeMar 03 2004May 07 2004We consider the Einstein-Yang-Mills Lagrangian in a (4+n)-dimensional space-time. Assuming the matter and metric fields to be independent of the n extra coordinates, a spherical symmetric Ansatz for the fields leads to a set of coupled ordinary differential ... More
Constraining the Spectrum of Supernova Neutrinos from Neutrino-Process-Induced Light-Element SynthesisMay 02 2005May 31 2005We constrain energy spectra of supernova neutrinos through the avoidance of an overproduction of the 11B abundance during Galactic chemical evolution. In supernova nucleosynthesis calculations with a parametrized neutrino spectrum as a function of temperature ... More
Deep Reinforcement Learning for Time Optimal Velocity Control using Prior KnowledgeNov 28 2018Mar 12 2019While autonomous navigation has recently gained great interest in the field of reinforcement learning, only a few works in this field have focused on the time optimal velocity control problem, i.e. controlling a vehicle such that it travels at the maximal ... More
Large-Scale, Low-Energy Excitations in the Two-Dimensional Ising Spin GlassMay 31 2002Oct 30 2002We study large-scale, low-energy excitations in the Ising spin glass with Gaussian interactions in two-dimensions at zero temperature, using an optimization algorithm to determine exact ground states. Periodic boundary conditions are applied. Our results ... More
Comment on: "Self-Diffusion in 2D Dusty-Plasma Liquids: Numerical-Simulation Results" [arXiv:0812.0338]Apr 20 2009Sep 01 2009An analysis of superdiffusion in two-dimensional strongly correlated Yukawa liquids is presented. In particular, we report a regular, montonic behavior of the diffusion exponent on the screening parameter.