Results for "J. H. Viehmann"

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Set-up for multi coincidence experiments of EUV to VIS photons and charged particles -- the solid angle maximization approachJun 11 2019The coincident detection of particles is a powerful method in experimental physics, enabling the investigation of a variety of projectile-target interactions. The vast majority of coincidence experiments is performed with charged particles, as they can ... More
Moduli spaces of p-divisible groupsFeb 15 2005Apr 27 2007We study the global structure of moduli spaces of quasi-isogenies of p-divisible groups introduced by Rapoport and Zink. We determine their dimensions and their sets of connected components and of irreducible components. If the isocrystals of the p-divisible ... More
On the geometry of the Newton stratificationNov 10 2015We give an expository overview over recent results on the global structure and geometry of the Newton stratification of the reduction modulo p of Shimura varieties of Hodge type with hyperspecial level structure. More precisely, we discuss non-emptiness, ... More
Minimal Newton strata in Iwahori double cosetsMar 05 2019The set of Newton strata in a given Iwahori double coset in the loop group of a reductive group $G$ is indexed by a finite subset of the set $B(G)$ of Frobenius-conjugacy classes. For unramified $G$ we show that it has a unique minimal element and determine ... More
Truncations of level 1 of elements in the loop group of a reductive groupJul 14 2009Sep 26 2013We generalize the notion of Ekedahl-Oort strata to elements in the loop group of any connected reductive group, and call the resulting discrete invariant the truncation of level 1 of the element. We give conditions for the Newton points occurring among ... More
VLT L-band mapping of the Galactic Center IRS 3-IRS 13 region Evidence for new Wolf-Rayet type starsJul 07 2005This paper presents L-band ISAAC and NAOS/CONICA (VLT) spectroscopic observations of the IRS~3-IRS~13 Galactic Center region. The ISAAC data allowed us to build the first spectroscopic data cube of the region in the L-band domain corrected for the foreground ... More
Moduli spaces of local G-shtukasMar 13 2018We give an overview of the theory of local G-shtukas and their moduli spaces that were introduced in joint work of U.~Hartl and the author, and in the past years studied by many people. We also discuss relations to moduli of global G-shtukas, properties ... More
The dimension of some affine Deligne-Lusztig varietiesMar 28 2006Jul 21 2006We prove Rapoport's dimension conjecture for affine Deligne-Lusztig varieties for GL_h and superbasic b. From this case the general dimension formula for affine Deligne-Lusztig varieties for special maximal compact subgroups of split groups follows, as ... More
Implementation of batched Sinkhorn iterations for entropy-regularized Wasserstein lossJul 01 2019Jul 05 2019In this report, we review the calculation of entropy-regularised Wasserstein loss introduced by Cuturi and document a practical implementation in PyTorch. Code is available at https://github.com/t-vi/pytorch-tvmisc/blob/master/wasserstein-distance/Pytorch_Wasserstein.ipynb ... More
Variants of the Smith-Wilson method with a view towards applicationsJun 14 2019We propose two variants of the Smith-Wilson method for practical application in the insurance industry. Our first variant relaxes the Smith-Wilson energy and can be used to incorporate less reliable market data with a certain weight rather than disregarding ... More
Implementation of batched Sinkhorn iterations for entropy-regularized Wasserstein lossJul 01 2019In this report, we review the calculation of entropy-regularised Wasserstein loss introduced by Cuturi and document a practical implementation in PyTorch.
Newton strata in the loop group of a reductive groupMay 31 2010May 04 2011We generalize purity of the Newton stratification to purity for a single break point of the Newton point in the context of local G-shtukas respectively of elements of the loop group of a reductive group. As an application we prove that elements of the ... More
The global structure of moduli spaces of polarized p-divisible groupsMar 28 2007We study the global structure of moduli spaces of quasi-isogenies of polarized p-divisible groups introduced by Rapoport and Zink. Using the corresponding results for non-polarized p-divisible groups from a previous paper, we determine their dimensions ... More
Connected components of closed affine Deligne-Lusztig varietiesJul 26 2006Jul 30 2007We determine the set of connected components of closed affine Deligne-Lusztig varieties for special maximal compact subgroups of split connected reductive groups. Especially, we show that such an affine Deligne-Lusztig variety has isolated points if and ... More
Dusty Sources at the Galactic Center: The N- and Q-band view with VISIRJan 19 2006We present mid-infrared N- and Q-band photometry of the Galactic Center from images obtained with the mid-infrared camera VISIR at the ESO VLT in May 2004. The high resolution and sensitivity possible with VISIR enables us to investigate a total of over ... More
L- and M-band imaging observations of the Galactic Center regionNov 30 2004We present near-infrared H-, K-, L- and M-band photometry of the Galactic Center from images obtained at the ESO VLT in May and August 2002, using the NAOS/CONICA (H and K) and the ISAAC (L and M) instruments. The large field of view (70" x 70") of the ... More
VLTI/MIDI measurements of extended mid-infrared emission in the Galactic CenterMay 25 2005We investigated with MIDI the extension of dusty mid-infrared excess sources (IRS 1W, IRS 10W, IRS 2, IRS 8) in immediate vicinity to the black hole (BH) at the GC. We derive 3$\sigma$ upper limits of the correlated fluxes of our target sources which ... More
Compact mid-IR sources east of galactic center source IRS5Dec 19 2007There are four less prominent compact sources east of IRS5, the natures of which were unclear until now. We present near-infrared K-band long slit spectroscopy of the four sources east of IRS5 obtained with the ISAAC spectrograph at the ESO VLT in July ... More
On the Hodge-Newton filtration for p-divisible O-modulesOct 23 2007Nov 27 2007The notions Hodge-Newton decomposition and Hodge-Newton filtration for F-crystals are due to Katz and generalize Messing's result on the existence of the local-\'etale filtration for p-divisible groups. Recently, some of Katz's classical results have ... More
Towards a theory of local Shimura varietiesJan 13 2014Jan 17 2014This is a survey article that advertizes the idea that there should exist a theory of p-adic local analogues of Shimura varieties. Prime examples are the towers of rigid-analytic spaces defined by Rapoport-Zink spaces, and we also review their theory ... More
Affine Deligne-Lusztig varieties and the action of JJul 10 2015Sep 14 2016We propose a new stratification of the reduced subschemes of Rapoport-Zink spaces and of affine Deligne-Lusztig varieties that highlights the relation between the geometry of these spaces and the action of the associated automorphism group. We show that ... More
The enigma of GCIRS 3 - Constraining the properties of the mid-infrared reference star of the central parsec of the Milky Way with optical long baseline interferometryNov 02 2007Feb 15 2008GCIRS3 is the most prominent MIR source in the central pc of the Galaxy. NIR spectroscopy failed to solve the enigma of its nature. The properties of extreme individual objects of the central stellar cluster contribute to our knowledge of star and dust ... More
A feasibility study of future observations with MIDI and other VLTI science instruments: The example of the Galactic CenterMay 11 2005VLT-Interferometry will allow imaging of the Galactic Center (GC) and the nuclei of extragalactic sources at an angular resolution of a few milliarcseconds. VLTI will be a prime instrument to study the immediate environment of the massive black hole at ... More
Dust Embedded Sources at the Galactic Center. 2 to 4$μ$m imaging and spectroscopy in the central parsecJun 07 2004We present the first L-band spectroscopic observations for a dozen stellar sources in the central 0.5 pc of the GC stellar cluster that are bright in the 2-4 micron wavelength domain. With the aid of additional K-band spectroscopic data, we derive optical ... More
Ekedahl-Oort and Newton strata for Shimura varieties of PEL typeNov 14 2010Dec 08 2012We study the Ekedahl-Oort stratification for good reductions of Shimura varieties of PEL type. These generalize the Ekedahl-Oort strata defined and studied by Oort for the moduli space of principally polarized abelian varieties (the "Siegel case"). They ... More
The Newton stratification on deformations of local G-shtukasOct 05 2008Feb 11 2010Bounded local G-shtukas are function field analogs for p-divisible groups with extra structure. We describe their deformations and moduli spaces. The latter are analogous to Rapoport-Zink spaces for p-divisible groups. The underlying schemes of these ... More
Central leaves in loop groupsJun 30 2016This paper analyses the finer structure of Newton strata in loop groups. These can be decomposed into so-called central leaves. We define them, and determine their global geometric structure. We then study the closure of central leaves, both by proving ... More
Irreducible components of minuscule affine Deligne-Lusztig varietiesFeb 27 2017We examine the set of $J_b(F)$-orbits in the set of irreducible components of affine Deligne-Lusztig varieties for a hyperspecial subgroup and minuscule coweight $\mu$. Our description implies in particular that its number of elements is bounded by the ... More
Generalized affine Springer fibersMar 10 2010This paper studies two new kinds of affine Springer fibers that are adapted to the root valuation strata of Goresky-Kottwitz-MacPherson. In addition it develops various linear versions of Katz's Hodge-Newton decomposition.
Generic Newton points and the Newton poset in Iwahori double cosetsFeb 06 2019We consider the Newton stratification on Iwahori double cosets in the loop group of a reductive group. We describe a group-theoretic condition on the generic Newton point, called cordiality, under which the Newton poset (i.e. the index set for non-empty ... More
The generic fiber of moduli spaces of bounded local $G$-shtukasDec 21 2017Moduli spaces of bounded local $G$-shtukas are a group-theoretic generalization of the function field analog of Rapoport and Zink's moduli spaces of $p$-divisible groups. In this article we generalize some very prominent concepts in the theory of Rapoport-Zink ... More
Foliations in deformation spaces of local G-shtukasFeb 11 2010Sep 21 2011We study local G-shtukas with level structure over a base scheme whose Newton polygons are constant on the base. We show that after a finite base change and after passing to an \'etale covering, such a local G-shtuka is isogenous to a completely slope ... More
Irreducible components of minuscule affine Deligne-Lusztig varietiesFeb 27 2017Mar 14 2019We examine the set of $J_b(F)$-orbits in the set of irreducible components of affine Deligne-Lusztig varieties for a hyperspecial subgroup and minuscule coweight $\mu$. Our description implies in particular that its number of elements is bounded by the ... More
Finiteness properties of affine Deligne-Lusztig varietiesFeb 20 2019Affine Deligne-Lusztig varieties are closely related to the special fibre of Newton strata in the reduction of Shimura varieties or of moduli spaces of $G$-shtukas. In almost all cases, they are not quasi-compact. In this note we prove basic finiteness ... More
The Flare Activity of SgrA*; New Coordinated mm to X-Ray ObservationsDec 16 2005We report new simultaneous near-infrared/sub-millimeter/X-ray observations of the SgrA* counterpart associated with the massive 3-4x10**6 solar mass black hole at the Galactic Center. The main aim is to investigate the physical processes responsible for ... More
VLTI observations of IRS~3: The brightest compact MIR source at the Galactic CentreMay 10 2005The dust enshrouded star IRS~3 in the central light year of our galaxy was partially resolved in a recent VLTI experiment. The presented observation is the first step in investigating both IRS~3 in particular and the stellar population of the Galactic ... More
Superradiant Phase Transitions and the Standard Description of Circuit QEDMar 23 2011We investigate the equilibrium behaviour of a superconducting circuit QED system containing a large number of artificial atoms. It is shown that the currently accepted standard description of circuit QED via an effective model fails in an important aspect: ... More
Observing the Nonequilibrium Dynamics of the Quantum Transverse-Field Ising Chain in Circuit QEDAug 07 2012Jan 10 2013We show how a quantum Ising spin chain in a time-dependent transverse magnetic field can be simulated and experimentally probed in the framework of circuit QED with current technology. The proposed setup provides a new platform for observing the nonequilibrium ... More
Reply to Comment on "Superradiant Phase Transitions and the Standard Description of Circuit QED"Feb 14 2012Jun 25 2012A Reply to the Comment by C. Ciuti and P. Nataf [arXiv:1112.0986v1] on our Letter "Superradiant Phase Transitions and the Standard Description of Circuit QED" [Phys. Rev. Lett. 107, 113602 (2011)].
Connected components of affine Deligne-Lusztig varieties in mixed characteristicJul 15 2013Jan 08 2015We determine the set of connected components of minuscule affine Deligne-Lusztig varieties for special maximal compact subgroups of unramified connected reductive groups. Partial results are also obtained for non-minuscule closed affine Deligne-Lusztig ... More
The quantum transverse-field Ising chain in circuit QED: effects of disorder on the nonequilibrium dynamicsJan 16 2013Apr 19 2013We study several dynamical properties of a recently proposed implementation of the quantum transverse-field Ising chain in the framework of circuit QED. Particular emphasis is placed on the effects of disorder on the nonequilibrium behavior of the system. ... More
Rescaling multipartite entanglement measures for mixed statesSep 05 2011Nov 16 2012A relevant problem regarding entanglement measures is the following: Given an arbitrary mixed state, how does a measure for multipartite entanglement change if general local operations are applied to the state? This question is nontrivial as the normalization ... More
Tight Approximation Bounds for Vertex Cover on Dense k-Partite HypergraphsJul 11 2011We establish almost tight upper and lower approximation bounds for the Vertex Cover problem on dense k-partite hypergraphs.
A Taxonomy to Assess and Tailor Risk-based Testing in Recent Testing StandardsMay 25 2019This article provides a taxonomy for risk-based testing that serves as a tool to define, tailor, or assess risk-based testing approaches in general and to instantiate risk-based testing approaches for the current testing standards ISO/IEC/IEEE 29119, ... More
Approximating Subdense Instances of Covering ProblemsOct 30 2010Nov 09 2010We study approximability of subdense instances of various covering problems on graphs, defined as instances in which the minimum or average degree is Omega(n/psi(n)) for some function psi(n)=omega(1) of the instance size. We design new approximation algorithms ... More
Approximating Vertex Cover in Dense HypergraphsDec 12 2010We consider the minimum vertex cover problem in hypergraphs in which every hyperedge has size k (also known as minimum hitting set problem, or minimum set cover with element frequency k). Simple algorithms exist that provide k-approximations, and this ... More
The possibility of detecting Sagittarius A* at 8.6 mumNov 15 2006The Galactic Center was observed at 8.6 mum in order to detect a mid-infrared (MIR) counterpart of Sgr A*, parallel to NIR observations. The goal was to set constraints on possible emission mechanisms.Imaging data were acquired with the adaptive optics ... More
Remarks on T-duality for open stringsFeb 03 1997This contribution gives in sigma-model language a short review of recent work on T-duality for open strings in the presence of abelian or non-abelian gauge fields. Furthermore, it adds a critical discussion of the relation between RG beta-functions and ... More
Remarks on the continuum formulation of noncritical stringsDec 01 1992We discuss various aspects of the calculation of correlation functions in conformal theories coupled to quantized 2-dimensional gravity. The main emphasis lies on the construction of a continuation in the number of insertions of the cosmological constant ... More
$Q\bar Q$ potential from AdS-CFT relation at $T\geq 0$: Dependence on orientation in internal space and higher curvature correctionsJul 14 1998Sep 15 1998Within the classical approximation we calculate the static $Q\bar Q$ potential via the AdS/CFT relation for nonzero temperature and arbitrary internal orientation of the quarks. We use a higher order curvature corrected target space background. For timelike ... More
Analysis of All Dimensionful Parameters Relevant in Gravitational Dressing of Conformal TheoriesApr 28 1992Starting from a covariant and background independent definition of normal ordered vertex operators we give an alternative derivation of the KPZ relation between conformal dimensions and their gravitational dressed partners. With our method we are able ... More
On Correlation Functions for Non-critical Strings with c<1 but d>1Jun 12 1992We construct a Goulian-Li-type continuation in the number of insertions of the cosmological constant operator which is no longer restricted to one dimensional target space. The method is applied to the calculation of the three-point and a special four-point ... More
Fidelity freeze for a random matrix model with off--diagonal perturbationJan 16 2006The concept of fidelity has been introduced to characterize the stability of a quantum-mechanical system against perturbations. The fidelity amplitude is defined as the overlap integral of a wave packet with itself after the development forth and back ... More
Four Pion Final States with Tagged Photons at Electron Positron CollidersAug 24 2000Oct 11 2000A Monte Carlo generator has been constructed to simulate the reaction e^+e^- \to \gamma + 4 \pi, where the photon is assumed to be observed in the detector. Only initial state radiation is considered. Additional collinear photon radiation has been incorporated ... More
A basis of hierarchy of generalized symmetries and their conservation laws for the (3+1)-dimensional diffusion equationDec 06 2017We determine, by hierarchy, dependencies between higher order linear symmetries which occur when generating them using recursion operators. Thus, we deduce a formula which gives the number of independent generalized symmetries (basis) of several orders. ... More
Invariance analysis, reductions and conservation laws for second-order systems of ordinary difference equationsOct 31 2017We present a method to obtain symmetries for second-order systems of ordinary difference equations and how to use them to reduce the order. We also introduce a technique of finding conservation laws for such systems.
On T-duality for open strings in general abelian and nonabelian gauge field backgroundsMar 28 1996Dec 11 1996We discuss T-duality for open strings in general background fields both in the functional integral formulation as well as in the language of canonical transformations. The Dirichlet boundary condition in the dual theory has to be treated as a constraint ... More
Some conclusions for noncritical string theory drawn from two- and three-point functions in the Liouville sectorJan 06 1995Starting from the known expression for the three-point correlation functions for Liouville exponentials with generic real coefficients at we can prove the Liouville equation of motion at the level of three-point functions. Based on the analytical structure ... More
Two and three-point functions in Liouville theoryMar 23 1994Sep 21 1994Based on our generalization of the Goulian-Li continuation in the power of the 2D cosmological term we construct the two and three-point correlation functions for Liouville exponentials with generic real coefficients. As a strong argument in favour of ... More
Canonical Quantum Supergravity in Three Dimensions, (some lines lost during submission)Jun 15 1993Jun 16 1993We discuss the canonical treatment and quantization of matter coupled supergravity in three dimensions, with special emphasis on $N=2$ supergravity. We then analyze the quantum constraint algebra; certain operator ordering ambiguities are found to be ... More
Stripe formation instability in crossing traffic flowsJun 20 2014At the intersection of two unidirectional traffic flows a stripe formation instability is known to occur. In this paper we consider coupled time evolution equations for the densities of the two flows in their intersection area. We show analytically how ... More
Astrometry of brown dwarfs with GaiaApr 15 2014Europe's Gaia spacecraft will soon embark on its five-year mission to measure the absolute parallaxes of the complete sample of 1,000 million objects down to 20 mag. It is expected that thousands of nearby brown dwarfs will have their astrometry determined ... More
On Wilson loops and $Q\bar Q$-potentials from the AdS/CFT relation at $T\geq 0$Dec 14 1998Jan 15 1999We give a short introduction to and a partial review of the work on the calculation of Wilson loops and $Q\bar Q$-potentials via the conjectured AdS/CFT duality. Included is a discussion of the relative weight of the stringy correction to the target space ... More
Effective Lagrangian for SU(3)_c gluodynamics from lattice color dielectricsMar 19 1998Apr 28 1999Small momenta limit of the lattice color dielectric model in the SU(3)_c case is considered. We show that in that limit the model involves a coarse-grained gluon field, a color singlet "bleached gluon" field, and both color singlet and octet rank two ... More
Fabrication of Analog Electronics for Serial Readout of Silicon Strip SensorsApr 11 2007Apr 23 2007A set of analog electronics boards for serial readout of silicon strip sensors was fabricated. A commercially available amplifier is mounted on a homemade hybrid board in order to receive analog signals from silicon strip sensors. Also, another homemade ... More
General Relativistic MHD JetsSep 14 2009Magnetic fields connecting the immediate environs of rotating black holes to large distances appear to be the most promising mechanism for launching relativistic jets, an idea first developed by Blandford and Znajek in the mid-1970s. To enable an understanding ... More
On the PCT--Theorem in the Theory of Local ObservablesDec 11 2000We review the PCT-theorem and problems connected with its demonstration. We add a new proof of the PCT-theorem in the theory of local observables which is similar to that one of Jost in Wightman quantum field theory. We also look at consequences in case ... More
The Quantum InternetJun 25 2008Quantum networks offer a unifying set of opportunities and challenges across exciting intellectual and technical frontiers, including for quantum computation, communication, and metrology. The realization of quantum networks composed of many nodes and ... More
Comment on "Deterministic Single-Photon Source for Distributed Quantum Networking" by Kuhn, Hennrich, and RempeOct 04 2002I comment on the experiment to realize an "on-demand," reversible single-photon source by Kuhn, Hennrich, and Rempe [Phys. Rev. Lett. 89, 067901 (2002)].
Highly ionized Fe X-ray lines at energies 7.7-8.6 keVSep 09 2008Fe XXV lines at 1.85 A (6.70 keV) and nearby Fe XXIV satellites have been widely used for determining the temperature of the hottest parts of solar flare and tokamak plasmas, though the spectral region is crowded and the lines are blended during flare ... More
On the integrability of nonlinear partial differential equationsJul 22 1998We investigate the integrability of Nonlinear Partial Differential Equations (NPDEs). The concepts are developed by firstly discussing the integrability of the KdV equation. We proceed by generalizing the ideas introduced for the KdV equation to other ... More
Eclipsing Binary Stars from SpaceOct 18 2006We have begun a programme to obtain high-precision photometry of bright detached eclipsing binary (dEB) stars with the Wide field InfraRed Explorer (WIRE) satellite. Due to the small aperture of WIRE only stars brighter than V=6 can be observed. We are ... More
The Skyrme Model for BaryonsJul 29 1999We review the Skyrme model approach which treats baryons as solitons of an effective meson theory. We start out with a historical introduction and a concise discussion of the original two flavor Skyrme model and its interpretation. Then we develop the ... More
Particle Conjugation and the $1/N_C$ Corrections to $g_A$Oct 19 1994We impose the requirement that the isovector axial vector current for the soliton sector of the chiral quark model transforms correctly under particle conjugation. This forces us to choose an otherwise arbitrary ordering of collective space operators ... More
Real Time Nonequilibrium Dynamics of Quantum Plasmas. Quantum Kinetics and the Dynamical Renormalization GroupNov 21 2000We implement the dynamical renormalization group (DRG) using the hard thermal loop (HTL) approximation for the real-time nonequilibrium dynamics in hot plasmas. The focus is on the study of the relaxation of gauge and fermionic mean fields and on the ... More
Non-Equilibrium Quantum Field Evolution in FRW CosmologiesMay 21 1994We derive the effective equations for the out of equilibrium time evolution of the order parameter and the fluctuations of a scalar field theory in spatially flat FRW cosmologies. After setting the problem in general we propose a non-perturbative, self-consistent ... More
Bethe Ansatz and Quantum GroupsAug 03 1993Aug 05 1993The formulation and resolution of integrable lattice statistical models in a quantum group covariant way is the subject of this review. The Bethe Ansatz turns to be remarkably useful to implement quantum group symmetries and to provide quantum group representations ... More
Strings in Curved SpacetimesFeb 12 1993Feb 15 1993Progress on the physics of strings in curved spacetime are comprehensively reviewed.We start by showing through renormalization group arguments that a meaningful quantum theory of gravity must be finite and must include all particle physics.Then, we review ... More
The Calogero-Moser equation system and the ensemble average in the Gaussian ensemblesOct 09 2003From random matrix theory it is known that for special values of the coupling constant the Calogero-Moser (CM) equation system is nothing but the radial part of a generalized harmonic oscillator Schroedinger equation. This allows an immediate construction ... More
Magnetized Accretion Inside the Marginally Stable Orbit around a Black HoleFeb 18 1999Qualitative arguments are presented to demonstrate that the energy density of magnetic fields in matter accreting onto a black hole inside the marginally stable orbit is automatically comparable to the rest-mass energy density of the accretion flow. Several ... More
Polarized Parton DensitiesDec 31 2002In this talk we summarize main results of a recent determination of the polarized deeply inelastic parton distributions to NLO from the world data. In the analysis the LO and NLO parton densities and their $1\sigma$ statistical errors were derived and ... More
Millisecond Time Variations of X-Ray BinariesJan 23 1998The Rossi X-Ray Timing Explorer (RXTE) has found that the neutron stars in low-mass X-ray binaries exhibit oscillations in the range 300-1200 Hz. Persistent emission may exhibit one or both of two features. In bursts a nearly coherent pulsation is seen, ... More
Comment: Causal entropic forcesDec 15 2013In this comment I argue that the causal entropy proposed in [1] is state-independent and the entropic force is zero for state-independent noise in a discrete time formulation and that the causal entropy description is incomplete in the continuous time ... More
Concentration of the Stationary Distribution on General Random Directed GraphsSep 18 2013We consider a random model for directed graphs whereby an arc is placed from one vertex to another with a prescribed probability which may vary from arc to arc. Using perturbation bounds as well as Chernoff inequalities, we show that the stationary distribution ... More
Measuring M dwarf Winds with DAZ White DwarfsAug 01 2006Hydrogen atmosphere white dwarfs with metal lines, so-called DAZs, show evidence for ongoing accretion of material onto their surfaces. Some DAZs are known to have unresolved M dwarf companions, which could account for the observed accretion through a ... More
On Super-Liouville Operator ConstructionsApr 15 1994We review the construction of field operators of the N=1 supersymmetric Liouville theory in terms of the components of a quantized free superfield.
O(α^2 L) Radiative Corrections to Deep Inelastic ep ScatteringNov 13 2002The leptonic QED radiative corrections are calculated in the next-to-leading log approximation ${\cal O}[\alpha^2 \ln(Q^2/m_e^2)]$ for unpolarized deeply inelastic $ep$--scattering in the case of mixed variables. The corrections are determined using mass ... More
Penguins, Trees and Final State Interactions in B Decays in Broken SU3Oct 14 1997The availability of data on $B_s$ decays to strange quasi-two-body final states, either with or without charmonium opens new possibilities for understanding different contributions of weak diagrams and in particular the relative contributions of tree ... More
Time discretization of functional integralsMar 22 2000Numerical evaluation of functional integrals usually involves a finite (L-slice) discretization of the imaginary-time axis. In the auxiliary-field method, the L-slice approximant to the density matrix can be evaluated as a function of inverse temperature ... More
On the integrability of PT-symmetric dimersJul 10 2013Dec 05 2013The coupled discrete linear and Kerr nonlinear Schrodinger equations with gain and loss describing transport on dimers with parity-time PT symmetric potentials are considered. The model is relevant among others to experiments in optical couplers and proposals ... More
Note on a q-modified central limit theoremAug 25 2010A q-modified version of the central limit theorem due to Umarov et al. affirms that q-Gaussians are attractors under addition and rescaling of certain classes of strongly correlated random variables. The proof of this theorem rests on a nonlinear q-modified ... More
Asymptotic statistics of the n-sided planar Voronoi cell: II. HeuristicsMar 20 2009We develop a set of heuristic arguments to explain several results on planar Poisson-Voronoi tessellations that were derived earlier at the cost of considerable mathematical effort. The results concern Voronoi cells having a large number n of sides. The ... More
The perimeter of large planar Voronoi cells: a double-stranded random walkDec 21 2004Feb 12 2005Let $p\_n$ be the probability for a planar Poisson-Voronoi cell to have exactly $n$ sides. We construct the asymptotic expansion of $\log p\_n$ up to terms that vanish as $n\to\infty$. We show that {\it two independent biased random walks} executed by ... More
Optimum ground states for spin-$\frac{3}{2}$ chainsFeb 14 1996We present a set of {\em optimum ground states} for a large class of spin-$\frac{3}{2}$ chains. Such global ground states are simultaneously ground states of the local Hamiltonian, i.e. the nearest neighbour interaction in the present case. They are constructed ... More
Grand Equilibrium: vapour-liquid equilibria by a new molecular simulation methodMay 05 2009A new molecular simulation method for the calculation of vapour-liquid equilibria of mixtures is presented. In this method, the independent thermodynamic variables are temperature and liquid composition. In the first step, one isobaric isothermal simulation ... More
Tunnel magnetoresistance and interfacial electronic stateMar 12 2002We study the relation between tunnel magnetoresistance (TMR) and interfacial electronic states modified by magnetic impurities introduced at the interface of the ferromagnetic tunnel junctions, by making use of the periodic Anderson model and the linear ... More
12CO(J=2->1) and CO(J=3->2) observations of Virgo Cluster spiral galaxies with the KOSMA telescope: global propertiesNov 25 2002We present 12CO(J=2->1) and CO(J=3->2) observations of quiescent Virgo Cluster spiral galaxies with the KOSMA 3m submm telescope. The beam sizes of 80" at 345 GHz and 120" at 230 GHz are well suited for the investigation of global properties of Virgo ... More
On the Possibility of Observing the Double Emission Line Feature of H$_2$ and HD from Primordial Molecular Cloud CoresNov 21 2001Nov 26 2002We study the prospects for observing H$_2$ and HD emission during the assembly of primordial molecular cloud cores. The primordial molecular cloud cores, which resemble those at the present epoch, can emerge around $1+z \sim 20$ according to recent numerical ... More
How to obtain a covariant Breit type equation from relativistic Constraint TheoryDec 08 1994It is shown that, by an appropriate modification of the structure of the interaction potential, the Breit equation can be incorporated into a set of two compatible manifestly covariant wave equations, derived from the general rules of Constraint Theory. ... More
Parton distributions in the chiral quark model: a continuum computationNov 16 2000Jan 19 2001We compute the parton distributions for the chiral quark model. We present a new technique for performing such computations based on Green functions. This approach avoids a discretization of the spectrum. It therefore does not need any smoothing procedures. ... More