Searching Arxiv, refresh for possibly better results.

Results for "Joerg Riemann"

total 1280took 0.09s
The line shape of the $Z$ bosonJan 05 1995At LEP~1, cross sections and cross section asymmetries may be analysed model independently. Cross sections depend on four, asymmetries on two free parameters. As an example, I discuss the model independent $Z$ boson mass determination from the $Z$ line ... More
Z' Signals from Kaluza-Klein Dark MatterAug 11 2005Aug 12 2005In a minimal model of universal extra dimensions the lightest Kalzua-Klein particle is neutral and stable because of Kaluza-Klein parity conservation and it is a dark matter candidate. The corresponding level 2 mode of the lightest Kaluza-Klein particle ... More
Study of Z' Couplings to Leptons and Quarks at NLCOct 28 1996The discovery of a Z' and the measurement of Z' couplings to fermions are main tasks of future colliders. Here, the possibilities to measure Z' f \bar f couplings at an NLC operating below a Z' resonance are studied. In dependence on the mass of the Z' ... More
Verification of the global gyrokinetic stellarator code XGC-S for linear ion temperature gradient driven modesMay 14 2019XGC (X-point Gyrokinetic Code) is a whole-volume, total-f gyrokinetic particle-in-cell code developed for modelling tokamaks. In recent work, XGC has been extended to model more general 3D toroidal magnetic configurations, such as stellarators. These ... More
Cross-Section Asymmetries Around the $Z$ PeakJun 21 1995A simple model-independent formula for cross-section asymmetries $A$ in fermion-pair production is derived, which may be used for the analysis of LEP~1 data, $A = \sum_n A_n (s - M_Z^2)^n$. The coefficient $A_0$ depends on the $Z$ boson exchange, $A_1$ ... More
S-matrix approach to the Z resonanceOct 14 2016The proposed $e^+e^-$-collider FCC-ee aims at an unprecedented accuracy for $e^+e^-$ collisions into fermion pairs at the $Z$ peak, based on about $10^{13}$ events. The S-matrix approach to the $Z$ boson line shape allows the model-independent quantitative ... More
ZZ' Mixing in Presence of Standard Weak Loop CorrectionsAug 20 1998We derive a method for a common treatment of Z' exchange, QED corrections, and weak loops. It is based on the form factor approach to the description of weak loop corrections to partial Z widths and cross sections. Problems connected with ZZ' mixing are ... More
ZZ' Mixing and Radiative Corrections at LEP IJul 27 1995We present a method for a common treatment of $Z'$ exchange, QED corrections, and weak loops in $e^+ e^-$ annihilation. QED corrections are taken into account by convoluting a hard-scattering cross section containing $\gamma,\ Z,$ and $Z'$ exchange. Weak ... More
Off-shell W pair production with anomalous couplings: The CC11 processMay 18 1998Jan 21 1999The differential cross-sections for processes of the type e+ e- to W+ W- to l nu q anti-q are determined with account of background contributions and of anomalous triple gauge boson couplings. Analytic expressions for dsigma/ds1 ds2 dcostheta, where theta ... More
Off shell W pair production in e+ e- annihilation: The CC11 processSep 20 1995The various four-fermion production channels in $e^+ e^-$ annihilation are discussed and the {\tt CC11} process $e^+ e^- \rightarrow {\bar f}_1^u f_1^d f^u_2 {\bar f}_2^d$, {\mbox{$f$$\neq$$e$}}, is studied in detail. The cross section $d^2\sigma/ds_1ds_2$, ... More
Z' Constraints from e+e- to f fbar at NLCApr 15 1996Constraints on extra neutral gauge bosons are obtained from $e^+e^-\rightarrow f\bar f$ at NLC energies. Model independent limits on the $Z'f\bar f$ couplings and lower limits on the $Z'$ mass are discussed. Typical GUTs with $M_{Z'}$ up to (3 -- 6) $\sqrt{s}$ ... More
Low emittance lattice design from first principles: reverse bending and longitudinal gradient bendsOct 26 2018The well-known relaxed theoretical minimum emittance (TME) cell is commonly used in the design of multi-bend achromat (MBA) lattices for the new generation of diffraction limited storage rings. But significantly lower emittance at moderate focusing properties ... More
Semi-analytic predictions for W pair production at 500 GeVSep 01 1997We give a short review on the semi-analytic approach to off-shell W pair production at 500 GeV and above. Numerical calculations are performed with the Fortran program GENTLE v. 2.0 and its upgrade. Recent extensions include: (i) angular distribution ... More
An approach for a business-driven cloudcompliance analysis covering public sector process improvement requirementsOct 08 2013The need for process improvement is an important target that does affect as well the government processes. Specifically in the public sector there are specific challenges to face.New technology approaches within government processes such as cloud services ... More
A Fundamental Solution to the Schrödinger Equation with Doss Potentials and its SmoothnessMar 17 2015We construct a fundamental solution to the Schr\"odinger equation for a class of potentials of polynomial type by a complex scaling approach as in [Doss1980]. The solution is given as the generalized expectation of a white noise distribution. Moreover, ... More
Radiative corrections to e+e- --> f+f-Feb 04 2000Aug 02 2000The past ten years of physics with e+e- colliding experiments at LEP and SLAC have shown the success of these experiments on not only impressively proving the theoretical predictions of the Standard Model (SM), but also to help provide stringent bounds ... More
Predictions for Lepton Flavour Violation in Z decaysJun 06 2000Sep 28 2000Recent experimental results suggest that the neutrinos of the Standard Model are massive, though light. Therefore they may mix with each other giving rise to lepton flavour or even lepton number violating processes, depending on whether they are Dirac ... More
ZFITTER 1985-2013Feb 06 2013Jun 12 2014The ZFITTER project is aimed at the computation of high-precision theoretical predictions for various observables in high-energy electron-positron annihilation and other processes. The stages of the project development are described. Accent is made on ... More
Nearby cycles and characteristic classes of singular spacesMar 11 2010May 04 2010In this paper we give an introduction to our recent work on characteristic classes of complex hypersurfaces based on some talks given at conferences in Strasbourg, Oberwolfach and Kagoshima. We explain the relation between nearby cycles for constructible ... More
On the SEDs of passively heated condensed coresNov 13 2010The dust emission spectrum and the brightness profile of passively heated condensed cores is analyzed in relation to their astrophysical environment. The cores are modeled as critically stable self-gravitating spheres embedded at the center of self-gravitating ... More
On the probability distribution function of the mass surface density of molecular clouds IMar 03 2014The probability distribution function (PDF) of the mass surface density is an essential characteristic of the structure of molecular clouds or the interstellar medium in general. Observations of the PDF of molecular clouds indicate a composition of a ... More
Real and complex operator idealsApr 12 1994The powerful concept of an operator ideal on the class of all Banach spaces makes sense in the real and in the complex case. In both settings we may, for example, consider compact, nuclear, or $2$--summing operators, where the definitions are adapted ... More
Polymer dynamics, fluorescence correlation spectroscopy, and the limits of optical resolutionMar 13 2012In recent years, fluorescence correlation spectroscopy has been increasingly applied for the study of polymer dynamics on the nanometer scale. The core idea is to extract, from a measured autocorrelation curve, an effective mean-square displacement function ... More
Lagrangian studies in convective turbulenceApr 06 2009May 04 2009We present high-resolution direct numerical simulations of turbulent three-dimensional Rayleigh-Benard convection with a focus on the Lagrangian properties of the flow. The volume is a Cartesian slab with an aspect ratio of four bounded by free-slip planes ... More
Lagrangian dispersion and heat transport in convective turbulenceMar 11 2008Lagrangian studies of the local temperature mixing and heat transport in turbulent Rayleigh-Benard convection are presented, based on three-dimensional direct numerical simulations. Contrary to vertical pair distances, the temporal growth of lateral pair ... More
Relation between shear parameter and Reynolds number in statistically stationary turbulent shear flowsMay 01 2004Jul 08 2004Studies of the relation between the shear parameter S^* and the Reynolds number Re are presented for a nearly homogeneous and statistically stationary turbulent shear flow. The parametric investigations are in line with a generalized perspective on the ... More
Strong fields and recycled accelerator parts as a laboratory for fundamental physicsAug 05 2009Over the last few years it has become increasingly clear that low energy, but high precision experiments provide a powerful and complementary window to physics beyond the Standard Model. In this note we illuminate this by using minicharged particles as ... More
WISP hunting - some new experimental ideasJul 31 2008We present several new ideas on how to search for weakly interacting sub-eV particles in laboratory experiments. The first experiment is sensitive to minicharged particles. It exploits that in strong electric fields particle - antiparticle pairs are produced ... More
Probing Minicharged Particles with Tests of Coulomb's LawApr 09 2009Minicharged particles arise in many extensions of the Standard Model. Their contribution to the vacuum polarization modifies Coulomb's law via the Uehling potential. In this note we argue that tests for electromagnetic fifth forces can therefore be a ... More
On Divergence in Radiation FieldsMay 02 2016Nov 11 2016Three thought experiments demonstrate that under certain circumstances electromagnetic fields have to be attenuated or amplified multiplicatively in order not to violate the conservation of energy. Modulation of radiation by means other than superposition ... More
On global regularity and singularities of Navier-Stokes- and Euler equation solutionsDec 29 2014Jul 20 2015Euler-Leray data functions of first and second order are defined by first and second order derivatives of the nonlinear spatial part of the incompressible Euler equation operator in Leray projection form applied to Cauchy data. The Lipschitz continuity ... More
Singular vorticity solutions of the incompressible Euler equation via inviscid limitsAug 28 2013Apr 05 2016Singular vorticty solutions of the incompressible 3D-Euler equation are constructed which satisfy the BKM criterion (cf. [2]). The construction is done by inviscid limits of vorticity solutions of transformed incompressible Navier Stokes type equations ... More
The dilemma of turbulence modellingAug 25 2016Sep 14 2016A new construction technique of multiple solutions of the Euler equa- tion in strong spaces is introduced which reveals the relationship to multi- ple Navier Stokes equation solutions with special force terms while avoid- ing viscosity limit constructions. ... More
On the local pressure of the Navier-Stokes equations and related systemsNov 04 2016In the study of local regularity of weak solutions to systems related to incompressible viscous fluids local energy estimates serve as important ingredients. However, this requires certain informations on the pressure. This fact has been used by V. Scheffer ... More
Existence of triangular Lie bialgebra structures IISep 20 2004We characterize finite-dimensional Lie algebras over an arbitrary field of characteristic zero which admit a non-trivial (quasi-) triangular Lie bialgebra structure.
On local analytic expansions of densities in the context of (micro-)hypoelliptic and classes of semi-elliptic equationsDec 02 2010Dec 06 2010Explicit representations of densities for linear parabolic partial differential equations are useful in order to design computation schemes of high accuracy for a considerable class of diffusion models. Approximations of lower order based on the WKB-expansion ... More
On the Cohomology of Modular Lie AlgebrasAug 21 2006In this paper we establish a connection between the cohomology of a modular Lie algebra and its p-envelopes. We also compute the cohomology of Zassenhaus algebras and their minimal p-envelopes with coefficients in generalized baby Verma modules and in ... More
A different way to read off the time - A new idea for a binary clockJun 07 2010A new idea for a binary clock is presented. It displays the time using a triangular array of 15 bits. It is shown that such a geometric, triangular arrangement is only possible because our system of time divisions is based on a sexagesimal system in which ... More
Photons as a Probe of Minicharged ParticlesMay 31 2007Low energy experiments with photons can provide deep insights into fundamental physics. In this note we concentrate on minicharged particles. We discuss how they can arise in extensions of the standard model and how we can search for them using a variety ... More
Understanding the Fierz Ambiguity of Partially Bosonized TheoriesMay 15 2002A useful tool in non perturbative studies of fermionic theories is partial bosonization. However, partial bosonization is often connected to an ambiguity due to Fierz rearrangement in the original theory. We discuss two different approximations for the ... More
Metastable SUSY Breaking - Predicting the Fate of the UniverseOct 29 2008The possibility that supersymmetry (SUSY) could be broken in a metastable vacuum has recently attracted renewed interest. In these proceedings we will argue that metastability is an attractive and testable scenario. The recent developments were triggered ... More
The Physics Case for Axions, WIMPs, WISPs and Other Weird StuffSep 18 2008We argue that there exists an excellent `physics case' motivating the search for axions, WIMPs, WISPs and other phenomena testable at low energies. This physics case arises from both experimental and observational evidence as well as the desire to test ... More
Entire curves, Integral sets and Principal bundlesAug 24 2008We compare the behaviour of entire curves and integral sets, in particular in relation to locally trivial fiber bundles, algebraic groups and finite ramified covers over semi-abelian varieties.
Failed theories of superconductivityAug 03 2010Aug 05 2010Almost half a century passed between the discovery of superconductivity by Kamerlingh Onnes and the theoretical explanation of the phenomenon by Bardeen, Cooper and Schrieffer. During the intervening years the brightest minds in theoretical physics tried ... More
On the thermal behaviour of small iron grainsDec 16 2004Dec 22 2004The optical properties of small spherical iron grains are derived using a Kramers-Kronig-consistent model of the dielectric function including its dependence on temperature and size. Especially discussed is the effect of the size dependence, which results ... More
Dust Attenuation caused by Isothermal Turbulent MediaDec 16 2004Our ability to correct the observational photometry of galaxies depends upon our knowledge of the attenuation of light produced by the dust contained in the interstellar medium. We will present a model based on the statistical properties of the local ... More
Trotter product formulas and global regular upper bounds of the Navier Stokes equation solutionJan 13 2014Oct 20 2015Global upper bounds with respect to regular norms of the incompressible Navier Stokes equation solution with regular data are constructed by an infinite scheme, where we work in bounded ZFC with bounded quantifiers and explicit infinitesimals. Trotter ... More
Constructive analysis of the Navier-Stokes equationApr 26 2010Jul 11 2012A global time-discretized scheme for the Navier-Stokes equation system in its Leray projection form is defined. It is shown that the scheme converges to a bounded global classical solution for smooth data which have polynomial decay at infinity. Furthermore, ... More
Neutral Higgs boson contributions to the decays B_{d,s}->mu^+ mu^- in the MSSM at large tan[beta]Oct 21 2002It is well known that the Minimal Supersymmetric Standard Model (MSSM) can enhance Br[B_{d,s}->mu^+ mu^-] by orders of magnitude, even if we assume the Cabibbo-Kobayashi-Maskawa (CKM) matrix to be the only source of flavour violation. Of particular interest ... More
Analyzing Search Topology Without Running Any Search: On the Connection Between Causal Graphs and h+Jan 16 2014The ignoring delete lists relaxation is of paramount importance for both satisficing and optimal planning. In earlier work, it was observed that the optimal relaxation heuristic h+ has amazing qualities in many classical planning benchmarks, in particular ... More
One-dimensional atomic superfluids as a model system for quantum thermodynamicsMay 29 2018In this chapter we will present the one-dimensional (1d) quantum degenerate Bose gas (1d superfluid) as a testbed to experimentally illustrate some of the key aspects of quantum thermodynamics. Hard-core bosons in one-dimension are described by the integrable ... More
Injective Modules and Prime Ideals of Universal Enveloping AlgebrasApr 26 2005Aug 18 2006In this paper we study injective modules over universal enveloping algebras of finite-dimensional Lie algebras over fields of arbitrary characteristic. Most of our results are dealing with fields of prime characteristic but we also elaborate on some of ... More
On the dimension formula for the hyperfunction solutions of some holonomic D-modulesApr 24 2003Dec 15 2004In this short note we improve a dimension formula of Takeuchi for the dimension of the hyperfunction solutions of some holonomic D-modules. Besides the constructibility result and local index formula of Kashiwara for the holomorphic solution complex, ... More
A generalized Verdier-type Riemann-Roch theorem for Chern-Schwartz-MacPherson classesFeb 18 2002We give a general formula for the defect appearing in the Verdier-type Riemann-Roch formula for Chern-Schwartz-MacPherson classes in the case of a regular embedding. Our proof of this formula uses the constructible function version of Verdier's specialization ... More
On a class of singular solutions to the incompressible 3-D Euler equationSep 27 2012Oct 02 2012A class of singular 3D-velocity vector fields is constructed which satisfy the incompressible 3D-Euler equation. It is shown that such a solution scheme does not exist in dimension 2. The solutions constructed are bounded and smooth up to finite time ... More
A 3D Euler equation solution with 2D sets of singularities and data with Hoelder continuous first order derivativesNov 17 2015Mar 16 2016An example of a solution branch of the three dimensional Euler equation Cauchy problem is constructed which develops a singular velocity component and a singular vorticity component after finite time for some data which have Hoelder continuous first order ... More
A projective manifold where Brody and entire curves behave very differentlyNov 05 2005We give an example of a projective manifold with dense entire curves such that every Brody curve is degenerate.
Generalisation of Hajek s stochastic comparison results to stochastic sumsAug 13 2014Hajek's stochastic comparison result is generalised to multivariate stochastic sum processes with univariate convex data functions and for univariate monoton nondecreasing convex data functions for processes with and without drift respectively. The univariate ... More
On partial convolution and mean comparisonApr 12 2018We prove mean comparison from a different perspective, where we introduce the concept of partial convolution.
Regular polynomial interpolation and approximation of global solutions of linear partial differential equationsJul 09 2008We consider regular polynomial interpolation algorithms on recursively defined sets of interpolation points which approximate global solutions of arbitrary well-posed systems of linear partial differential equations. Convergence of the 'limit' of the ... More
On Meromorphic Functions which are Brody CurvesSep 25 2007We discuss meromorphic functions on the complex plane which are Brody curves regarded as holomorphic maps to P_1, i.e., which have bounded spherical derivative.
Realizing Connected Lie Groups As Automorphism Groups Of Complex ManifoldsApr 18 2002Apr 19 2002We show that every connected real Lie group can be realized as the full automorphism group of a Stein hyperbolic complex manifold.
Maximal treesNov 24 2016We show that, consistently, there can be maximal subtrees of P (omega) and P (omega) / fin of arbitrary regular uncountable size below the size of the continuum. We also show that there are no maximal subtrees of P (omega) / fin with countable levels. ... More
Large Discrete Sets in Stein manifoldsAug 19 1998Rosay and Rudin constructed examples of discrete subsets of C^n with remarkable properties. We generalize these constructions from C^n to arbitrary Stein manifolds. We prove: Given a Stein manifold X and a affine variety V of the same dimension there ... More
Surface Foliations with Compact complex leaves are holomorphicSep 03 2004Let X be a compact complex surface with a real foliation. If all leaves are compact complex curves, the foliation must be holomorphic.
A force beyond the Standard Model - Status of the quest for hidden photonsMar 07 2013In this note we discuss the search for new gauge forces beyond the Standard Model. In particular we give an overview for the simplest case of a new U(1), kinetically mixed with the Standard Model photon (hypercharge boson), a so-called hidden photon (also ... More
Axions, their Relatives and Prospects for the FutureFeb 05 2007The observation of a non-vanishing rotation of linear polarized laser light after passage through a strong magnetic field by the PVLAS collaboration has renewed the interest in light particles coupled to photons. Axions are a species of such particles ... More
Effective Actions for Strongly Interacting Fermionic SystemsSep 09 2003We compare different non-perturbative methods for calculating the effective action for fermionic systems featuring bosonic bound states (BBS) and spontaneous symmetry breaking (SSB). In a purely fermionic language proceeding into the SSB phase requires ... More
Ideal norms and trigonometric orthonormal systemsApr 12 1994In this article, we characterize the $UMD$--property of a Banach space $X$ by ideal norms associated with trigonometric orthonormal systems. The asymptotic behavior of that numerical parameters can be used to decide whether or not $X$ is a $UMD$--space. ... More
Financial markets with volatility uncertaintyDec 07 2010Dec 15 2010We investigate financial markets under model risk caused by uncertain volatilities. For this purpose we consider a financial market that features volatility uncertainty. To have a mathematical consistent framework we use the notion of G-expectation and ... More
Heights for line bundles on arithmetic surfacesAug 06 1995For line bundles on arithmetic varieties we construct height functions using arithmetic intersection theory. In the case of an arithmetic surface, generically of genus g, for line bundles of degree g equivalence is shown to the height on the Jacobian ... More
Quantum critical point with competing propagating and diffusive spin excitationsOct 05 1998Feedback effects due to spin fluctuation induced precursors in the fermionic quasiparticle spectrum are taken into account in the description of a quantum critical point of itinerant spin systems. A correlation length dependent spin damping occurs, leading ... More
Weak singularities of 3-D Euler equations and restricted regularity of Navier Stokes equation solutions with time dependent force termsSep 17 2014Apr 28 2016Classical vorticity solution branches of the three dimensional incompressible Euler equation are constructed where a velocity component can blow up at some point after finite time for regular data in H2. Furthermore, vorticity can blow up after finite ... More
Global analytic expansion of solution for a class of linear parabolic systems with coupling of first order derivatives termsJan 27 2009Jul 17 2009We derive global analytic representations of fundamental solutions for a class of linear parabolic systems with full coupling of first order derivative terms where coefficient may depend on space and time. Pointwise convergence of the global analytic ... More
Construction of unshielded singular solutions of the harmonic field equationsFeb 11 2014Mar 29 2016Singular solutions of the harmonic Einstein evolution equation are constructed which are related to spatially global and time-local solutions for a certain class of quasilinear hyperbolic systems of second order. The constructed singularities of curvature ... More
On a special class of complex toriSep 03 2004We investigate which complex tori admits complex Lie subgroups whose closure is not complex.
On tameness and growth conditionsSep 25 2007We study discrete subsets of C^d, relating "tameness" with growth conditions.
A Barth-Lefschetz theorem for toric varietiesDec 19 2001Jun 06 2002The theorem of Barth-Lefschetz is a statement about the cohomology of a submanifold X of some projective space, in a range depending on the codimension of the embedding. Here this is generalized to the case of a submanifold X of a smooth projective toric ... More
The one-dimensional stratum in the boundary of the moduli stack of stable curvesDec 27 2007The moduli stack of Deligne-Mumford stable curves of genus g admits a stratification, so that the number of nodes of the curves belonging to one stratum is constant. The irreducible components of the stratum corresponding to curves with exactly 3g-4 nodes ... More
One-dimensional substacks of the moduli stack of Deligne-Mumford stable curvesDec 27 2006There is a well-known stratification of the moduli space $M_g$ of Deligne-Mumford stable curves of genus $g$ by the loci of stable curves with a fixed number $i$ of nodes, where $i \le 3g-3$. The associated moduli stack ${\cal M}_g$ admits an analogous ... More
Singular solutions of Navier Stokes equations with time-dependent external force terms in L2May 09 2014Mar 20 2016It is shown that Navier Stokes equation models with time dependent external forces in L2 can have singular solutions.
Pairing due to Spin Fluctuations in Layered Organic SuperconductorsJul 02 1998I show that for a \kappa-type organic (BEDT-TTF)_2-X molecular crystal, a superconducting state with T_c ~ 10 K and gap nodes on the Fermi surface can be caused by short-ranged antiferromagnetic spin fluctuations. Using a two-band description for the ... More
Determiniation of the homotopy class of maps on compact orientable surfaces of positive genus g with infinitely many periodic points (part I)Jun 13 2010We consider the homotopical dynamics on compact orientable surfaces of positive genus g. We establish a sufficient and necessary algebraic criterion for homotopy classes with infinitely many periodic points of maps on such surfaces in terms of the characteristic ... More
Some infinite matrix analysis, a Trotter product formula for dissipative operators, and an algorithm for the incompressible Navier-Stokes equationDec 11 2012Nov 17 2014We introduce a global scheme on the n-torus of a controlled incompressible Navier-Stokes equation in terms of a coupled controlled infinite ODE-system of Fourier-modes with smooth data. We construct a scheme of global approximations related to linear ... More
Generalized Brownian motion from a logical point of viewDec 20 2011Jan 06 2012We describe generalized Brownian motion related to parabolic equation systems from a logical point of view, i.e., as a generalization of Anderson's random walk. The connection to classical spaces is based on the Loeb measure. It seems that the construction ... More
Vector-valued Walsh-Paley martingales and geometry of Banach spacesAug 01 1995The concept of Rademacher type $p$ ($1\leq p\leq2$) plays an important role in the local theory of Banach spaces. In \cite{mas88} Mascioni considers a weakening of this concept and shows that for a Banach space $X$ weak Rademacher type $p$ implies Rademacher ... More
Mean Convergence of Vector--valued Walsh SeriesOct 30 1992Given any Banach space $X$, let $L_2^X$ denote the Banach space of all measurable functions $f:[0,1]\to X$ for which ||f||_2:=(int_0^1 ||f(t)||^2 dt)^{1/2} is finite. We show that $X$ is a UMD--space (see \cite{BUR:1986}) if and only if \lim_n||f-S_n(f)||_2=0 ... More
Immunity and Simplicity for Exact Counting and Other Counting ClassesSep 01 1998Ko [RAIRO 24, 1990] and Bruschi [TCS 102, 1992] showed that in some relativized world, PSPACE (in fact, ParityP) contains a set that is immune to the polynomial hierarchy (PH). In this paper, we study and settle the question of (relativized) separations ... More
Derivative moments in stationary homogeneous shear turbulenceMay 13 2001Jul 29 2001A statistically stationary and nearly homogeneous turbulent shear flow is established by an additional volume forcing in combination with stress-free boundary conditions in the shear direction. Both turbulent energy and enstrophy are stationary to a much ... More
QNov 24 2016A Q-set is an uncountable set of reals all of whose subsets are relative $G_\delta$ sets. We prove that, for an arbitrary uncountable cardinal kappa, there is consistently a Q-set of size $\kappa$ whose square is not Q. This answers a question of A. Miller. ... More
Nonuniformly weighted Schwarz smoothers for spectral element multigridDec 08 2015A hybrid Schwarz/multigrid method for spectral element solvers to the Poisson equation in $\mathbb R^2$ is presented. It is based on an additive Schwarz method studied by J. Lottes and P. Fischer (J. Sci. Comput. 24:45--78, 2005), which makes use of the ... More
A Family of WISPy Dark Matter CandidatesNov 04 2013Jan 10 2014Dark matter made from non-thermally produced bosons can have very low, possibly sub-eV masses. Axions and hidden photons are prominent examples of such "dark" very weakly interacting light (slim) particles (WISPs). A suitable mechanism for their non-thermal ... More
Low energy laboratory searches for WISPsNov 02 2010We present an overview over the current status of laboratory experiments searching for (very) weakly coupled slim particles (WISPs). These experiments at the high precision frontier explore new physics beyond the standard model in a complementary way ... More
Light particles - A window to fundamental physicsMar 12 2010In these proceedings we illustrate that light, very weakly interacting particles can arise naturally from physics which is fundamentally connected to very high energy scales. Searching for them therefore may give us interesting new insights into the structure ... More
Holomorphic functions on an algebraic group invariant under a Zariski-dense subgroupJan 16 1994Jan 18 1994Let G be complex linear-algebraic group, H a subgroup, which is dense in G in the Zariski-topology. Assume that G/[G,G] is reductive and furthermore that (1) G is solvable, or (2) the semisimple elements in G'=[G,G] are dense. Then every H-invariant holomorphic ... More
Non-degenerate Maps and SetsMay 12 2003We construct certain non-degenerate maps and sets, mainly in the complex-analytic category. For example, we show that for every countable subset S in an irreducible complex space X there exists a holomorphic map from the unit disk to X such that S is ... More
Phase-dependent interference mechanisms in a three-level Lambda system driven by a quantized laser fieldApr 20 2005The dynamics of an atomic few-level system can depend on the phase of driving fields coupled to the atom if certain conditions are satisfied. This is of particular interest to control interference effects, which can alter the system properties considerably. ... More
Density estimates for differential equations of second order satisfying a weak Hoermander conditionJul 20 2013We prove an extension of Hoermander's classical result on hypoelliptic second order equations, where the coefficients of the related vector fields are globally Lipschitz and satisfy the classical Hoermander condition on a dense set while the density still ... More
Superreflexivity and J-convexity of Banach spacesOct 15 1997A Banach space X is superreflexive if each Banach space Y that is finitely representable in X is reflexive. Superreflexivity is known to be equivalent to J-convexity and to the non-existence of uniformly bounded factorizations of the summation operators ... More
Tame discrete subsets in Stein manifoldsAug 09 2017For discrete subsets in ${\bf C}^n$ the notion of being "tame" was defined by Rosay and Rudin. We propose a general definition of "tameness" for arbitrary complex manifolds and show that many results classically known for ${\bf C}^n$ may be generalized ... More