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A Note on the Convex Hull of Finitely Many Projections of SpectrahedraAug 24 2009A spectrahedron is a set defined by a linear matrix inequality. A projection of a spectrahedron is often called a semidefinitely representable set. We show that the convex hull of a finite union of such projections is again a projection of a spectrahedron. ... More

Extreme Rays of the Hankel Spectrahedra for Ternary FormsJun 07 2014Jun 20 2015Hankel spectrahedra are the dual convex cones to the cone of sums of squares of real polynomials, and we study them from the point of view of convex algebraic geometry. We show that the Zariski closure of the union of all extreme rays of Hankel spectrahedra ... More

Algebraic Boundaries of Convex Semi-algebraic SetsMay 30 2014Nov 03 2014We study the algebraic boundary of a convex semi-algebraic set via duality in convex and algebraic geometry. We generalize the correspondence of facets of a polytope to the vertices of the dual polytope to general semi-algebraic convex bodies. In the ... More

The Algebraic Boundary of SO(2)-OrbitopesAug 15 2011Let $X\subset\A^{2r}$ be a real curve embedded into an even-dimensional affine space. In the main result of this paper, we characterise when the r-th secant variety to $X$ is an irreducible component of the algebraic boundary of the convex hull of the ... More

Conic Programming: Infeasibility Certificates and Projective GeometryOct 28 2018We revisit facial reduction from the point of view of projective geometry. This leads us to a homogenization strategy in conic programming that eliminates the phenomenon of weak infeasibility. For semidefinite programs (and others), this yields infeasibility ... More

Real Rank with Respect to VarietiesNov 22 2015We study the real rank of points with respect to a real variety $X$. This is a generalization of various tensor ranks, where $X$ is in a specific family of real varieties like Veronese or Segre varieties. The maximal real rank can be bounded in terms ... More

Maximum Likelihood Threshold and Generic Completion Rank of GraphsMar 22 2017May 23 2017The minimum number of observations such that the maximum likelihood estimator in a Gaussian graphical model exists with probability one is called the maximum likelihood threshold of the underlying graph G. The natural algebraic relaxation is the generic ... More

Generic Spectrahedral ShadowsJul 19 2014Apr 27 2015Spectrahedral shadows are projections of linear sections of the cone of positive semidefinite matrices. We characterize the polynomials that vanish on the boundaries of these convex sets when both the section and the projection are generic.

Positive Semidefinite Univariate Matrix PolynomialsJul 26 2017We study sum-of-squares representations of symmetric univariate real matrix polynomials that are positive semidefinite along the real line. We give a new proof of the fact that every positive semidefinite univariate matrix polynomial of size $n\times ... More

Do Sums of Squares Dream of Free Resolutions?Jul 13 2016We associate to a real projective variety $X$ two convex cones which are fundamental in real algebraic geometry: the cone $P_X$ of quadratic forms nonnegative on $X$, and the cone $\Sigma_X$ of sums of squares of linear forms. The dual cone $\Sigma_X^\ast$ ... More

Do Sums of Squares Dream of Free Resolutions?Jul 13 2016Dec 03 2016We associate to a real projective variety $X$ two convex cones which are fundamental in real algebraic geometry: the cone $P_X$ of quadratic forms nonnegative on $X$, and the cone $\Sigma_X$ of sums of squares of linear forms. The dual cone $\Sigma_X^\ast$ ... More

Kippenhahn's Theorem for joint numerical ranges and quantum statesJul 10 2019Kippenhahn's Theorem asserts that the numerical range of a matrix is the convex hull of a certain algebraic curve. Here, we show that the joint numerical range of finitely many hermitian matrices is similarly the convex hull of a semi-algebraic set. We ... More

Typical and Generic Ranks in Matrix CompletionFeb 26 2018We consider the problem of exact low-rank matrix completion from a geometric viewpoint: given a partially filled matrix M, we keep the positions of specified and unspecified entries fixed, and study how the minimal completion rank depends on the values ... More

Weyl-Heisenberg Spaces for Robust Orthogonal Frequency Division MultiplexingNov 24 2013Design of Weyl-Heisenberg sets of waveforms for robust orthogonal frequency division multiplex- ing (OFDM) has been the subject of a considerable volume of work. In this paper, a complete parameterization of orthogonal Weyl-Heisenberg sets and their corresponding ... More

Low-Rank Sum-of-Squares Representations on Varieties of Minimal DegreeJun 14 2016A celebrated result by Hilbert says that every real nonnegative ternary quartic is a sum of three squares. We show more generally that every nonnegative quadratic form on a real projective variety $X$ of minimal degree is a sum of $\dim(X)+1$ squares ... More

Gram SpectrahedraJul 31 2016May 02 2018Representations of nonnegative polynomials as sums of squares are central to real algebraic geometry and the subject of active research. The sum-of-squares representations of a given polynomial are parametrized by the convex body of positive semidefinite ... More

Sums of Squares and Quadratic Persistence on Real Projective VarietiesFeb 07 2019We bound the Pythagoras number of a real projective subvariety: the smallest positive integer $r$ such that every sum of squares of linear forms in its homogeneous coordinate ring is a sum of at most $r$ squares. Enhancing existing methods, we exhibit ... More

Gram SpectrahedraJul 31 2016Representations of nonnegative polynomials as sums of squares are central to real algebraic geometry and the subject of active research. The sum-of-squares representations of a given polynomial are parametrized by the convex body of positive semidefinite ... More

Computing Hermitian determinantal representations of hyperbolic curvesApr 23 2015Every real hyperbolic form in three variables can be realized as the determinant of a linear net of Hermitian matrices containing a positive definite matrix. Such representations are an algebraic certificate for the hyperbolicity of the polynomial and ... More

Low-Rank Sum-of-Squares Representations on Varieties of Minimal DegreeJun 14 2016Mar 04 2017A celebrated result by Hilbert says that every real nonnegative ternary quartic is a sum of three squares. We show more generally that every nonnegative quadratic form on a real projective variety $X$ of minimal degree is a sum of $\dim(X)+1$ squares ... More

Topological Classifying Spaces of Lie Algebras and the Natural Completion of ContractionsAug 15 1995The space K^n of all n-dimensional { Lie} algebras has a natural non-Hausdorff topology k^n, which has characteristic limits, called transitions, A -> B, between distinct Lie algebras A and B. The entity of these transitions are the natural transitive ... More

Alternatives to the neoBayesian Theorem, avoiding several of its inconsistencies: The rMPE-MethodJan 10 2005May 02 2005Some drawbacks of the formalism of Bayes Theorem can be avoided by the rMPE-Method, a modification of the cMPE-Method that permits (i): Adding probabilities in spite of non-linearity. (ii): Taking into account extensional evidence and weight-bearing evidence ... More

Spin-dependent Fragmentation FunctionsJun 26 2002I will give an overview on fragmentation functions with particular emphasis on spin-dependence. A straightforward classification scheme permits to label all independent fragmentation functions for a given physical situation in an unambiguous way. In the ... More

Vacuum Fluctuations, Geometric Modular Action and Relativistic Quantum Information TheoryDec 08 2005A summary of some lines of ideas leading to model-independent frameworks of relativistic quantum field theory is given. It is followed by a discussion of the Reeh-Schlieder theorem and geometric modular action of Tomita-Takesaki modular objects associated ... More

Wigner-Cusp in Kaon Decays and Determination of pi pi Scattering LengthsDec 04 2007Jun 06 2008In the last few years it has become possible to study low energy pi pi scattering in kaon decays to three pions, thanks to the high statistics measurement of K+- -> pi+- pi0 pi0 decays performed by the NA48/2 experiment at the CERN SPS. At the pi+ pi- ... More

Lepton Universality Tests with KaonsJul 16 2007Sep 21 2007Precision data on Kl3 and Kl2 decay rates and form factors allow us to perform significant tests of lepton universality and to constrain the strength of non-standard interactions. The present status of these tests and new physics searches are discussed, ... More

New Results on Xi0 Hyperon DecaysFeb 09 2007In the recent years many new measurements of the decay of the neutral Xi0 hyperon have been reported both by the NA48/1 and the KTeV collaboration. The results are based on data samples of more than 2 billion Xi0 decays. In this report new measurements ... More

Model structures, categorial quotients and representations of super commutative Hopf algebras II, The case Gl(m,n)Oct 15 2010Oct 19 2010We construct a tensor functor from the category of super representations of the superlinear group Gl(m,n) over a field of characteristic zero to the category of super representations of the linear group Gl(m-n) over some extension field (for m at least ... More

Ideal Quantum Gases with Planck Scale LimitationsMar 14 2015A thermodynamic system of non-interacting quantum particles changes its statistical distribution formulas if there is a universal limitation for the size of energetic quantum leaps (magnitude of quantum leaps smaller than Planck energy). By means of a ... More

The Orbit of GG Tau AApr 12 2011Apr 27 2011We present a study of the orbit of the pre-main-sequence binary system GG Tau A and its relation to its circumbinary disk, in order to find an explanation for the sharp inner edge of the disk. Three new relative astrometric positions of the binary were ... More

Higher Spin Quantum Fields as Twisted Dirac FieldsMar 24 2011Apr 14 2011We pursue the idea of constructing higher spin fields as solutions to twisted Dirac operators. As general results we find that twisted prenormally hyperbolic first order operators (such as the Dirac operator) on globally hyperbolic Lorentzian spacetime ... More

Remarks on the nonvanishing of cohomology groups for perverse sheaves on abelian varietiesDec 05 2016It is shown that for a perverse sheaf $K$ on an abelian variety $X$ the integers $i$ for which the cohomology $H^i(X,K)$ does not vanish define an interval in the number line (under certain conditions on the field of definition of $K$)

Dirac Equation and Planck-Scale QuantitiesFeb 08 2016This work investigates in which form quantities with Planck dimensions occur already in the common quantum theory with local Lorentz symmetry. Since such Planck quantities as Planck length or Planck mass involve the Planck constant h, the velocity of ... More

Magnetic fields in the nearby spiral galaxy IC 342: A multi-frequency radio polarization studyFeb 18 2015May 28 2015The total and polarized radio continuum emission of IC 342 was observed in four wavelength bands with the Effelsberg and VLA telescopes. The frequency dependence of the radial scalelength of synchrotron emission indicates energy-dependent propagation ... More

The Role of Magnetic Fields in Spiral GalaxiesDec 12 2002Interstellar magnetic fields are strong: up to 25 muG in spiral arms and 40 muG in nuclear regions. In the spiral galaxy NGC 6946 the average magnetic energy density exceeds that of the thermal gas. Magnetic fields control the evolution of dense clouds ... More

Magnetism in the spiral galaxy NGC 6946: magnetic arms, depolarization rings, dynamo modes and helical fieldsMay 29 2007Jun 05 2007The spiral galaxy NGC 6946 was observed in total intensity and linear polarization in five radio bands between 3cm and 21cm. At the inner edge of the inner gas spiral arm the ordered magnetic field is only mildly compressed and turns smoothly, to become ... More

Arc-smooth functions on closed setsJan 25 2018Jan 08 2019By an influential theorem of Boman, a function $f$ on an open set $U$ in $\mathbb R^d$ is smooth ($\mathcal C^\infty$) if and only if it is arc-smooth, i.e., $f\circ c$ is smooth for every smooth curve $c : \mathbb R \to U$. In this paper we investigate ... More

Quasianalytic ultradifferentiability cannot be tested in lower dimensionsOct 25 2018Mar 11 2019We show that, in contrast to the real analytic case, quasianalytic ultradifferentiability can never be tested in lower dimensions. Our results are based on a construction due to Jaffe.

The $Λ$-parameter and $m_s$ of quenched QCDDec 01 1997We explain how scale dependent renormalized quantities can be computed using lattice QCD. Two examples are used: the running coupling and quark masses. A reliable computation of the $\Lambda$-parameter in the quenched approximation is presented.

Determining fundamental parameters of QCD on the latticeJul 08 2006We summarize the status of determinations of fundamental parameters of QCD by the ALPHA Collaboration.

Non-perturbative Heavy Quark Effective Theory: a test and its matching to QCDDec 15 2004We give an introduction to the special problems encountered in a treatment of HQET beyond perturbation theory in the gauge coupling constant. In particular, we report on a recent test of HQET as an effective theory for QCD and discuss how HQET can be ... More

Non-perturbative renormalization of HQET and QCDSep 26 2002We discuss the necessity of non-perturbative renormalization in QCD and HQET and explain the general strategy for solving this problem. A few selected topics are discussed in some detail, namely the importance of off-shell improvement in the MOM-scheme ... More

Orbit projections as fibrationsOct 17 2006The orbit projection $\pi : M \to M/G$ of a proper $G$-manifold $M$ is a fibration if and only if all points in $M$ are regular. Under additional assumptions we show that $\pi$ is a quasifibration if and only if all points are regular. We get a full answer ... More

Orbit projections of proper Lie groupoids as fibrationsDec 05 2007Let $\mathcal{G} \rightrightarrows M$ be a source locally trivial proper Lie groupoid such that each orbit is of finite type. The orbit projection $M \to M/\mathcal{G}$ is a fibration if and only if $\mathcal{G} \rightrightarrows M$ is regular.

On an Elasto-Acoustic Transmission Problem in Anisotropic, Inhomogeneous MediaJan 10 2018We consider a coupled system describing the interaction between acoustic and elastic regions, where the coupling occurs not via material properties but through an interaction on an interface separating the two regimes. Evolutionary well-posedness in the ... More

Perturbation of complex polynomials and normal operatorsNov 21 2006Aug 03 2009We study the regularity of the roots of complex monic polynomials $P(t)$ of fixed degree depending smoothly on a real parameter $t$. We prove that each continuous parameterization of the roots of a generic $C^\infty$ curve $P(t)$ (which always exists) ... More

Standard Cosmology in the DGP Brane ModelOct 17 2001Oct 19 2001Large extra dimensions provide interesting extensions of our parameter space for gravitational theories. There exist now brane models which can perfectly reproduce standard four-dimensional Friedmann cosmology. These models are not motivated by observations, ... More

Brane worldsMay 31 2001This is an introductory review of gravity on branes with an emphasis on codimension 1 models. However, for a new result it is also pointed out that the cosmological evolution of the 3-brane in the model of Dvali, Gabadadze and Porrati may follow the standard ... More

Remarks on chiral symmetry breaking with massless fermionsJun 29 1995Jul 06 1995In this talk I present recent results on Lorentz covariant correlation functions $\langle q(p_1)\overline{q}(p_2)\rangle$ on the cone $p^2=0$. In particular, chiral symmetry breaking terms are constructed which resemble fermionic 2--point functions of ... More

Confinement from a massive scalar in QCDFeb 28 1998A model is introduced with a massive scalar coupling to the Yang--Mills term in four--dimensional gauge theory. It is shown that the resulting potential of colour sources consists of a short range Coulomb interaction and a long range confining part. Far ... More

New embedding of Schwarzschild geometry. I. Exterior solutionNov 22 2001We propose a global minimal embedding of the Schwarzschild theory in a five-dimensional flat space by using two surfaces. Covariant field equations are deduced for the gravitational forces.

Tests of Chiral Perturbation Theory in Rare Kaon DecaysJul 01 2002The neutral Kaon decays Ks->gamma gamma and Kl->pi0 gamma gamma are very sensitive to higher order loop effects of Chiral Perturbation Theory (ChPT). New measurements of the NA48 experiment show that ChPT contributions of O(p^6) cannot be neglected in ... More

Connecting generalized parton distributions and light-cone wave functionsSep 26 2000The relation of generalized (skewed) quark distributions to nucleon wave functions is discussed in the context of light-cone quantization.

Wide Angle Compton ScatteringOct 16 2000We present the handbag contribution to Wide Angle Compton Scattering (WACS) at moderately large momentum transfer obtained with a proton distribution amplitude close to the asymptotic form. In comparison it is found to be significantly larger than results ... More

Proton-Proton Elastic Scattering; Landshoff Contributions in the Diquark ModelJun 08 1994Independent multiple scattering (`Landshoff') contributions to proton-proton elastic scattering at wide angles are calculated in the quark-diquark model. Results confirm previous observations about the magnitude of these contributions. The use of the ... More

Precision Standard Model Tests with KaonsJul 17 2008In kaon physics, several new precision measurements on flavour variables and CP violation have performed in the recent years. Presented are a new precise determination of the CKM parameter |V_us|, which combines the results of all experiments together ... More

Kerr interior surfacesNov 30 2007A recently found interior for the Kerr metric is re-investigated by means of geometrical methods. A surface with nonholonomicity is matched to the surface of the exterior solution.

Correction. Efficient parameter estimation for self-similar processesJul 04 2006Correction to The Annals of Statistics (1989) 17 1749--1766 [URL: http://links.jstor.org/sici?sici=0090-5364%28198912%2917%3A4%3C1749%3AEPEFSP%3E 2.0.CO%3B2-9]

Semisimple algebraic tensor categoriesSep 09 2009Sep 09 2009A semisimple algebraic tensor category over an algebraically closed field k of characteristic zero is the representation category of all finite dimensional twisted super representations of an affine reductive supergroup G over k. Such a supergroup is ... More

The Norm Index Theorem (An Analytic Proof)Jul 09 2007We give an analytic proof of the norm index theorem $[I_:K^* N(I_L)] =[L:K]$ for cyclic extensions of number fields using spectral theory of the idele class group.

Siegel modular forms mod pApr 19 2008We prove a vanishing theorem for one forms on the moduli stack of principally polarized abelian varieties of genus g>1 with level structure N over fields of characteristic p different from two. This is used to compute the Picard groups of these stacks. ... More

Tannakian Categories attached to abelian VarietiesApr 10 2007Jun 13 2007Starting from certain perverse sheaves on an abelian variety, including the intersection cohomology sheaves of curves and smooth ample divisors, we construct a semisimple super-Tannakian category.

Galactic and extragalactic magnetic fieldsDec 19 2000The current state of research of the Galactic magnetic field is reviewed critically. The average (equipartition) strength of the total field derived from radio synchrotron data is 6 +/- 2 muG locally and about 10 +/- 3 muG at 3 kpc Galactic radius. These ... More

Magnetic Visions: Mapping Cosmic Magnetism with LOFAR and SKAApr 29 2008The origin of magnetic fields in the Universe is an open problem in astrophysics and fundamental physics. "Cosmic Magnetism" has been accepted as Key Science Project both for the Low Frequency Array (LOFAR, under construction) and the planned Square Kilometre ... More

Magnetic fields in nearby galaxies: prospects with future radio telescopesSep 01 2009The origin of magnetic fields in the Universe is an open problem in astrophysics and fundamental physics. Our present-day knowledge is limited to regions of strong magnetic fields and to star-forming disks of galaxies. Low-energy electrons emitting at ... More

Galactic Dynamos and Galactic WindsNov 29 2007Apr 24 2008Spiral galaxies host dynamically important magnetic fields which can affect gas flows in the disks and halos. Total magnetic fields in spiral galaxies are strongest (up to 30 \muG) in the spiral arms where they are mostly turbulent or tangled. Polarized ... More

On the distribution of Galois groupsOct 26 2010Let $G$ be a subgroup of the symmetric group $S_n$, and let $\delta_G=|S_n/G|^{-1}$ where $|S_n/G|$ is the index of $G$ in $S_n$. Then there are at most $O_{n, \epsilon}(H^{n-1+\delta_G+\epsilon})$ monic integer polynomials of degree $n$ having Galois ... More

Weyl's inequality and systems of formsAug 09 2012Apr 06 2014By providing a variant of Weyl's inequality for general systems of forms we establish the Hardy-Littlewood asymptotic formula for the density of integer zeros of systems of quadratic or cubics forms under weaker rank conditions than previously known. ... More

Differentiable roots, eigenvalues, and eigenvectorsNov 17 2012Jan 22 2013We determine the conditions for the existence of $C^p$-roots of curves of monic complex polynomials as well as for the existence of $C^p$-eigenvalues and $C^p$-eigenvectors of curves of normal complex matrices.

Which action for brane worlds?Jul 09 2000Sep 21 2000In his pioneering work on singular shells in general relativity, Lanczos had derived jump conditions across energy-momentum carrying hypersurfaces from the Einstein equation with codimension 1 sources. However, on the level of the action, the discontinuity ... More

The string scale and the Planck scaleJul 23 1997A particle spectrum below the string scale in accordance with predictions from heterotic string theory yields a Planck mass $m_{Pl}=(8\pi G_N)^{-1/2}$ which exceeds the string scale by a factor $\simeq 61.9$. A Planck mass $m_{Pl}=2.43\times 10^{18}$ ... More

Non-Standard Fermion Propagators from Conformal Field TheoryAug 04 1994It is shown that Weyl spinors in 4D Minkowski space are composed of primary fields of half-integer conformal weights. This yields representations of fermionic 2-point functions in terms of correlators of primary fields with a factorized transformation ... More

The dilaton as a candidate for dark matterSep 25 1996Oct 01 1996We examine consequences of the stabilization of the dilaton through the axion. An estimate of the resulting dilaton potential yields a relation between the axion parameter $m_a f_{PQ}$ and the average instanton radius, and predicts the ratio between the ... More

The onefold truthJun 06 2005Some features of the Schwarzschild and Kruskal metric are being discussed under the assumption that the Schwarzschild model can be explained geometrically.

Brill-Noether SheavesOct 30 2006Nov 05 2007We construct a $\bar Q_l$-linear Tannakian category attached to a smooth projective curve C equivalent to the category of finite dimensional $\bar Q_l$-representations Rep(G), where G is $Sp(2g-2,\bar Q_l)$ or $Sl(2g-2,\bar Q_l)$ depending on whether ... More

Torelli's theorem from the topological point of viewOct 15 2006Torelli's theorem is proven by the study of the convolution product of the intersection cohomology sheaf of the thetadivisor.

Supertranslations to all ordersAug 14 2009The transformation laws of the general linear superfield and chiral superfields under N=1 supertranslations are tabulated to all orders in the supertranslation parameters.

The butterfly diagram in the 18th centuryDec 11 2008Digitized images of the drawings by J.C. Staudacher were used to determine sunspot positions for the period of 1749-1796. From the entire set of drawings, 6285 sunspot positions were obtained for a total of 999 days. Various methods have been applied ... More

On the electronic structure of the charge-ordered phase in epitaxial and polycrystalline La1-xCaxMnO3 (x = 0.55, 0.67) perovskite manganitesMar 28 2008In this work the charge transport properties of charge ordered (CO) La1-xCaxMnO3 (LCMO) (x= 0.55, 0.67) epitaxial thin films and polycrystals are discussed following the recent controversy of localised electron states vs. weakly or de- localised charge ... More

Galactic and Extragalactic Magnetic FieldsOct 16 2008Jan 12 2009The strength of the total magnetic field in our Milky Way from radio Zeeman and synchrotron measurements is about 6 muG near the Sun and several mG in dense clouds, pulsar wind nebulae, and filaments near the Galactic Center. Diffuse polarized radio emission ... More

Radio continuum emission from M31 and M33Sep 28 2000The radio emission from M31 (like HI, CO, FIR and H\alpha) is concentrated in the '10 kpc ring', giving an impressive example that cosmic rays are produced in star-forming regions. M31 and M33 have similar strengths of the total magnetic field, but very ... More

New Perspectives for B-Physics from the LatticeSep 29 2003Oct 09 2003We give an introduction to the problems faced on the way to a reliable lattice QCD computation of B-physics matrix elements. In particular various approaches for dealing with the large scale introduced by the heaviness of the b-quark are mentioned and ... More

Crosstalk between DGP branesFeb 12 2015If two DGP branes carry U(1) gauge theories and overlap, particles of one brane can interact with the photons from the other brane. This coupling modifies in particular the Coulomb potentials between charges from the same brane in the overlapping regions. ... More

Minimal energy solutions for repulsive nonlinear Schrödinger systemsMar 19 2013In this paper we establish existence and nonexistence results concerning fully nontrivial minimal energy solutions of the nonlinear Schr\"odinger system \begin{align*} \begin{gathered} -\Delta u + \, u = |u|^{2q-2}u + b|u|^{q-2}u|v|^q \quad\text{in}\R^n, ... More

Parallelisms of $\mathop{\rm PG}(3,\mathbb R)$ admitting a 3-dimensional groupJun 11 2018Jun 28 2018Betten and Riesinger constructed Parallelisms of $\mathop{\rm PG}(3,\mathbb R)$ with automorphism group $\mathop{\rm SO}(3,\mathbb R)$ by applying the reducible $\mathop{\rm SO}(3,\mathbb R)$-action to a rotational Betten spread. This was generalized ... More

Rotational spreads and rotational parallelisms and oriented parallelisms of PG(3,R)Apr 20 2018Jun 01 2018We introduce topological parallelisms of oriented lines (briefly called oriented parallelisms). Every topological parallelism (of lines) on PG(3,R) gives rise to a parallelism of oriented lines, but we show that even the most homogeneous parallelisms ... More

A characterization of Clifford parallelism by automorphismsFeb 10 2017Betten and Riesinger have shown that Clifford parallelism on real projective space is the only topological parallelism that is left invariant by a group of dimension at least 5. We improve the bound to 4. Examples of different parallelisms admitting a ... More

Well-posedness and exponential decay of solutions for the Blackstock-Crighton-Kuznetsov equationMay 26 2014Aug 13 2015The present work provides well-posedness and exponential decay results for the Blackstock-Crighton-Kuznetsov equation arising in the modeling of nonlinear acoustic wave propagation in thermally relaxing viscous fluids. First, we treat the associated linear ... More

A Class of Evolutionary Problems with an Application to Acoustic Waves with Impedance Type Boundary ConditionsApr 25 2012A class of evolutionary operator equations is studied. As an application the equations of linear acoustics are considered with complex material laws. A dynamic boundary condition is imposed which in the time-harmonic case corresponds to an impedance or ... More

Perturbation theory for normal operatorsNov 18 2011Apr 12 2012Let $E \ni x\mapsto A(x)$ be a $\mathscr{C}$-mapping with values unbounded normal operators with common domain of definition and compact resolvent. Here $\mathscr{C}$ stands for $C^\infty$, $C^\omega$ (real analytic), $C^{[M]}$ (Denjoy--Carleman of Beurling ... More

Lifting quasianalytic mappings over invariantsJul 06 2010Jan 12 2011Let $\rho : G \to \operatorname{GL}(V)$ be a rational finite dimensional complex representation of a reductive linear algebraic group $G$, and let $\sigma_1,\sigma_n$ be a system of generators of the algebra of invariant polynomials $\mathbb{C}[V]^G$. ... More

The trace of Hecke operators on the space of classical holomorphic Siegel modular forms of genus twoSep 09 2009We prove multiplicity one for vector valued holomorphic Siegel modular forms of weights greater or equal to 3 and the full Siegel modular group and give a trace formula for the action of the Hecke operators T(p) in the regular cases.

Existence of Whittaker models related to four dimensional symplectic Galois representationsMar 08 2007We show that an irreducible cuspidal automorphic representation of the group GSp(4,A), which is not CAP and whose infinite component belongs to the discrete series, is weakly equivalent to an irreducible generic automorphic cuspidal representation, whose ... More

Reissner exterior and interiorFeb 05 2009The Reissner-Nordstroem metric is re-examined and supplemented with an interior solution. Both metrics are embedded in a 5-dimensional flat space.

Measurements of the CKM Angle betaNov 04 2005In this article I report on new and updated measurements of the CP-violating parameter beta (phi_1), which is related to the phase of the Cabibbo-Kobayashi-Maskawa (CKM) quark-mixing matrix of the electroweak interaction. Over the past few years, beta ... More

The ALICE detector at LHCSep 23 2005Oct 05 2005The ALICE experiment at the Large Hadron Collider LHC is presented, and an overview of its physics program is given. A few specific observables are discussed in order to illustrate the physics potential of ALICE.

The Milky Way Nuclear Star Cluster in ContextJan 24 2010Jan 29 2010Nuclear star clusters are located at the dynamical centers of the majority of galaxies. They are usually the densest and most massive star cluster in their host galaxy. In this article, I will give a brief overview of our current knowledge on nuclear ... More

Continuity of symplectically adjoint maps and the algebraic structure of Hadamard vacuum representations for quantum fields on curved spacetimeSep 30 1996Nov 18 1996We derive for a pair of operators on a symplectic space which are adjoints of each other with respect to the symplectic form (that is, they are sympletically adjoint) that, if they are bounded for some scalar product on the symplectic space dominating ... More

Freely falling observersOct 18 2004We show that the field equations of the Schwarzschild geometry are invariant under passive Lorentz transformations to a freely falling system. We decompose the field equations with respect to the accelerated system and find that the force of gravity is ... More

Self-trapping of the dilatonSep 22 1995The dilaton in three dimensions does not roll. Witten's conjecture that duality between theories in three and four dimensions solves the cosmological constant problem thus may also solve the dilaton problem in string theory.