Results for "Mathias Steiner"

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Room-Temperature Quantum-Confined Stark Effect in Atomically Thin SemiconductorFeb 08 2018Electric field-controlled, two-dimensional (2D) exciton dynamics in transition metal dichalcogenide monolayers is a current research focus in condensed matter physics. We have experimentally investigated the spectral and temporal properties of the A-exciton ... More
A metric for wettability at the nanoscaleAug 29 2016Wettability is the affinity of a liquid for a solid surface. For energetic reasons, macroscopic drops of liquid are nearly spherical away from interfaces with solids, and any local deformations due to molecular-scale surface interactions are negligible. ... More
A black phosphorus photo-detector for multispectral, high-resolution imagingJul 09 2014Jul 30 2014Black phosphorus is a layered semiconductor that is intensely researched in view of applications in optoelectronics. In this Letter, we investigate a multi-layer black phosphorus photo-detector that is capable of acquiring high-contrast (V>0.9) images ... More
On the Delone property of (-β)-integersAug 18 2011The (-\beta)-integers are natural generalisations of the \beta-integers, and thus of the integers, for negative real bases. They can be described by infinite words which are fixed points of anti-morphisms. We show that they are not necessarily uniformly ... More
Bots vs. Wikipedians, Anons vs. Logged-InsFeb 03 2014Feb 05 2014Wikipedia is a global crowdsourced encyclopedia that at time of writing is available in 287 languages. Wikidata is a likewise global crowdsourced knowledge base that provides shared facts to be used by Wikipedias. In the context of this research, we have ... More
Wikipedia Tools for Google SpreadsheetsFeb 08 2016In this paper, we introduce the Wikipedia Tools for Google Spreadsheets. Google Spreadsheets is part of a free, Web-based software office suite offered by Google within its Google Docs service. It allows users to create and edit spreadsheets online, while ... More
Photospheric processes and magnetic flux tubesSep 01 2007In the first part of these lecture notes, new high-resolution observations of small-scale magnetic flux concentrations are presented and compared to results from new three-dimensional magnetohydrodynamic simulations. Special attention is paid to the physics ... More
Recent progresses in the simulation of small-scale magnetic fieldsMay 13 2007New high-resolution observations reveal that small-scale magnetic flux concentrations have a delicate substructure on a spatial scale of 0.1''. Its basic structure can be interpreted in terms of a magnetic flux sheet or tube that vertically extends through ... More
Telling Breaking News Stories from Wikipedia with Social Multimedia: A Case Study of the 2014 Winter OlympicsMar 17 2014With the ability to watch Wikipedia and Wikidata edits in realtime, the online encyclopedia and the knowledge base have become increasingly used targets of research for the detection of breaking news events. In this paper, we present a case study of the ... More
Simple omega-categories and chain complexesAug 28 2006Apr 04 2007The category of strict omega-categories has an important full subcategory whose objects are the simple omega-categories freely generated by planar trees or by globular cardinals. We give a simple description of this subcategory in terms of chain complexes, ... More
The algebra of the nerves of omega-categoriesJul 16 2013We show that the nerve of a strict omega-category can be described algebraically as a simplicial set with additional operations subject to certain identities. The resulting structures are called sets with complicial identities. We also construct an equivalence ... More
Complicial structures in the nerves of omega-categoriesAug 07 2013Sep 02 2013It is known that strict omega-categories are equivalent through the nerve functor to complicial sets and to sets with complicial identities. It follows that complicial sets are equivalent to sets with complicial identities. We discuss these equivalences. ... More
Origin of photoresponse in black phosphorus photo-transistorsJul 27 2014We study the origin of photocurrent generated in doped multilayer BP photo-transistors, and find that it is dominated by thermally driven thermoelectric and bolometric processes. The experimentally observed photocurrent polarities are consistent with ... More
Power dissipation and electrical breakdown in black phosphorusJul 02 2015We report operating temperatures and heating coefficients measured in a multi-layer black phosphorus device as a function of injected electrical power. By combining micro-Raman spectroscopy and electrical transport measurements, we have observed a linear ... More
Likelihood ratio tests and singularitiesMar 12 2007Apr 02 2009Many statistical hypotheses can be formulated in terms of polynomial equalities and inequalities in the unknown parameters and thus correspond to semi-algebraic subsets of the parameter space. We consider large sample asymptotics for the likelihood ratio ... More
Performance comparison between iSCSI and other hardware and software solutionsMay 30 2003We report on our investigations on some technologies that can be used to build disk servers and networks of disk servers using commodity hardware and software solutions. It focuses on the performance that can be achieved by these systems and gives measured ... More
Scalable and Quasi-Contractive Markov Coupling of Maxwell CollisionDec 08 2013Feb 21 2014This paper considers space homogenous Boltzmann kinetic equations in dimension $d$ with Maxwell collisions (and without Grad's cut-off). An explicit Markov coupling of the associated conservative (Nanbu) stochastic $N$-particle system is constructed, ... More
A $N$-uniform quantitative Tanaka's theorem for the conservative Kac's $N$-particle system with Maxwell moleculesJul 08 2014Aug 03 2014This paper considers the space homogenous Boltzmann equation with Maxwell molecules and arbitrary angular distribution. Following Kac's program, emphasis is laid on the the associated conservative Kac's stochastic $N$-particle system, a Markov process ... More
Statistical modeling of ground motion relations for seismic hazard analysisMay 14 2012Jul 13 2013We introduce a new approach for ground motion relations (GMR) in the probabilistic seismic hazard analysis (PSHA), being influenced by the extreme value theory of mathematical statistics. Therein, we understand a GMR as a random function. We derive mathematically ... More
Quantum Corrections in Quintessence ModelsJun 12 2006Sep 12 2006We investigate the impact of quantum fluctuations on a light rolling quintessence field from three different sources, namely, from a coupling to the standard model and dark matter, from its self-couplings and from its coupling to gravity. We derive bounds ... More
Sur la rigidité de polyèdres hyperboliques en dimension 3 : cas de volume fini, cas hyperidéal, cas fuchsienNov 18 2002A hyperbolic semi-ideal polyedron is a polyedron whose vertices lie inside the hyperbolic space $\mathbf{H}^{3}$ or at infinity. A hyperideal polyedron is, in the projective model, the intersection of $\mathbf{H}^{3}$ with a projective polyhedron whose ... More
Replica-deformation of the SU(2)-invariant Thirring model via solutions of the qKZ equationJul 17 1999The response of an integrable QFT under variation of the Unruh temperature has recently been shown to be computable from an S-matrix preserving (`replica') deformation of the form factor approach. We show that replica-deformed form factors of the SU(2)-invariant ... More
Polynomial Recursion Equations in Form Factors of ADE Toda Field TheoriesMay 20 1997It is shown that the problem of calculating form factors in ADE affine Toda field theories can be reduced to the nonperturbative recursive calculation of polynomials symmetric in each sort of variables. We determine these recursion equations explicitly ... More
Selfdual 2-form formulation of gravity and classification of energy-momentum tensorsApr 17 1995Dec 17 1996It is shown how the different irreducibility classes of the energy-momentum tensor allow for a Lagrangian formulation of the gravity-matter system using a selfdual 2-form as a basic variable. It is pointed out what kind of difficulties arise when attempting ... More
The Pólya sum kernel and Bayes estimationFeb 21 2012May 10 2012We consider a particular Cox process from a Bayesian viewpoint and show that the Bayes estimator of the intensity measure is the so-called P\'olya sum kernel, which occurred recently in the context of the construction of the so-called Papangelou processes. ... More
Optimal Hub Labeling is NP-completeJul 31 2014Distance labeling is a preprocessing technique introduced by Peleg [Journal of Graph Theory, 33(3)] to speed up distance queries in large networks. Herein, each vertex receives a (short) label and, the distance between two vertices can be inferred from ... More
A Multidimensional Central Sets TheoremJul 09 2008The Theorems of Hindman and van der Waerden belong to the classical theorems of partition Ramsey Theory. The Central Sets Theorem is a strong simultaneous extension of both theorems that applies to general commutative semigroups. We give a common extension ... More
On the cup product for Hilbert schemes of points in the planeJul 31 2014We revisit Ellingsrud and Str{\o} mme's cellular decomposition of the Hilbert scheme of points in the projective plane. We study the product of cohomology classes defined by the closures of cells, deriving necessary conditions for the non-vanishing of ... More
A Nekrasov-Okounkov Type formula for $\widetilde{C}$May 06 2015Sep 15 2015In 2008, Han rediscovered an expansion of powers of Dedekind $\eta$ function attributed to Nekrasov and Okounkov (which was actually first proved the same year by Westbury) by using a famous identity of Macdonald in the framework of type $\widetilde{A}$ ... More
A KMS-like state of Hadamard type on Robertson-Walker spacetimes and its time evolutionSep 09 1997In this work we define a new state on the Weyl algebra of the free massive scalar Klein-Gordon field on a Robertson-Walker spacetime and prove that it is a Hadamard state. The state is supposed to approximate a thermal equilibrium state on a Robertson-Walker ... More
Event-controlled constructions of random fields of maxima with non-max-stable dependenceJul 20 2014Max-stable random fields can be constructed according to Schlather (2002) with a random function or a stationary process and a kind of random event magnitude. These are applied for the modelling of natural hazards. We simply extend these event-controlled ... More
Modeling of magnitude distributions by the generalized truncated exponential distributionMay 22 2014Sep 08 2014The probability distribution of the magnitude can be modeled by an exponential distribution according to the Gutenberg-Richter relation. Two alternatives are the truncated exponential distribution (TED) and the cut-off exponential distribution (CED). ... More
Relation ideals and the Buchberger--Möller algorithmNov 11 2004We construct a Gr\"obner Basis of the relation ideal of a polynomial, give an interpolation formula for the basis elements and explain the connection of the interpolation formula to the Buchberger--M\"oller algorithm. We present a situation in which the ... More
$L_p$-theory for a Cahn-Hilliard-Gurtin systemMar 20 2012In this paper we study a generalized Cahn-Hilliard equation which was proposed by Gurtin. We prove the existence and uniqueness of a local-in-time solution for a quasilinear version, that is, if the coefficients depend on the solution and its gradient. ... More
Lattices of oscillator groupsMar 08 2013Aug 01 2013This paper is concerned with discrete, uniform subgroups (lattices) of oscillator groups, which are certain semidirect products of the Heisenberg group and the additive group of real numbers. The present paper rectifies the uncertainties in [1] of Medina ... More
Symplectic Lie algebras with degenerate centerSep 12 2016Every symplectic Lie algebra with degenerate (including non-abelian nilpotent symplectic Lie algebras) has the structure of a quadratic extension. We give a standard model and describe the equivalence classes on the level of corresponding quadratic cohomology ... More
Metric Symplectic Lie AlgebrasSep 12 2016Every metric symplectic Lie algebra has the structure of a quadratic extension. We give a standard model and describe the equivalence classes on the level of corresponding quadratic cohomology sets. Finally, we give a scheme to classify the isomorphism ... More
On contact tops and integrable topsJun 21 2007In this paper, we introduce a geometric structure called top, which is a trivialized bundle of plane pencils over a Riemannian 3-manifold, defined as the set of kernels of a circle of 1-forms (e.g. of contact and integrable forms) with particular properties ... More
On contact p-spheresApr 09 2005We study invariant contact p-spheres on principal circle-bundles and solve the corresponding existence problem in dimension 3. Moreover, we show that contact p-spheres can only exist on (4n-1)-dimensional manifolds and we construct examples of contact ... More
Cyclic Cohomology and Higher Rank LatticesDec 01 2006Jun 18 2007We give a new proof of the absence of non-trivial idempotents in the group ring of torsion-free cocompact lattices in SL(n,C). It is based on the following procedure. We lift the class of the trace in the cyclic cohomology of the group ring to the crossed ... More
Approximations for Decision Making in the Dempster-Shafer Theory of EvidenceFeb 13 2013The computational complexity of reasoning within the Dempster-Shafer theory of evidence is one of the main points of criticism this formalism has to face. To overcome this difficulty various approximation algorithms have been suggested that aim at reducing ... More
Extremal results for random discrete structuresMar 02 2016May 17 2016We study thresholds for extremal properties of random discrete structures. We determine the threshold for Szemer\'edi's theorem on arithmetic progressions in random subsets of the integers and its multidimensional extensions and we determine the threshold ... More
On Alternation and the Union TheoremFeb 15 2016Jun 03 2016Under the assumption $P=\Sigma_2^p$, we prove a new variant of the Union Theorem of McCreight and Meyer for the class $\Sigma_2^p$. This yields a union function $F$ which is computable in time $F(n)^c$ for some constant $c$ and satisfies $P=DTIME(F)=\Sigma_2(F)=\Sigma_2^p$ ... More
J/psi production in ep collisions at HERANov 16 2010This report is a short overview of experimental and theoretical results in J/psi production in electron-proton collisions at DESY HERA with special focus lying on recent developments in inelastic photoproduction.
Correlations of Quantum Fields on Robertson-Walker SpacetimesNov 09 1995It is a well known fact that quantum fields on Minkowski spacetime are correlated for each pair of spacetime regions. In Robertson-Walker spacetimes there are spacelike separated regions with disjoint past horizons but the absence of correlations in that ... More
On the deformability of Heisenberg algebrasAug 24 1995Based on the vanishing of the second Hochschild cohomology group of the enveloping algebra of the Heisenberg algebra it is shown that differential algebras coming from quantum groups do not provide a non-trivial deformation of quantum mechanics. For the ... More
Comment on Pisarenko et al. "Characterization of the Tail of the Distribution of Earthquake Magnitudes by Combining the GEV and GPD Descriptions of Extreme Value Theory"Jan 05 2015Jan 29 2015In this short note, I comment on the research of Pisarenko et al. (2014) regarding the extreme value theory and statistics in case of earthquake magnitudes. The link between the generalized extreme value distribution (GEVD) as an asymptotic model for ... More
B-L-symmetric Baryogenesis with Leptonic QuintessenceDec 12 2006We discuss a toy model where baryogenesis and cosmic acceleration are driven by a leptonic quintessence field coupled to the standard model sector via a massive mediating scalar field. It does not require the introduction of B-L-violating interactions ... More
The Lyddane-Sachs-Teller relationship for polar vibrations in materials with monoclinic and triclinic crystal systemsFeb 28 2016A generalization of the Lyddane-Sachs-Teller relation is presented for polar vibrations in materials with monoclinic and triclinic crystal systems. The generalization is derived from an eigen displacement vector summation approach, which is equivalent ... More
Charge Fluctuations as Thermometer for Heavy-Ion CollisionsNov 15 2013We present a determination of freeze-out conditions in heavy-ion collisions based on ratios of cu- mulants of net electric charge fluctuations obtained from lattice QCD. These ratios can reliably be calculated for a wide range of chemical potential values ... More
Computing all roots of the likelihood equations of seemingly unrelated regressionsAug 23 2005Seemingly unrelated regressions are statistical regression models based on the Gaussian distribution. They are popular in econometrics but also arise in graphical modeling of multivariate dependencies. In maximum likelihood estimation, the parameters ... More
The vanishing ideal of a finite set of closed points in affine spaceApr 06 2006Apr 07 2006Given a finite set of closed rational points of affine space over a field, we give a Gr\"obner basis for the lexicographic ordering of the ideal of polynomials which vanish at all given points. Our method is an alternative to the Buchberger--M\"oller ... More
Freeness and multirestriction of hyperplane arrangementsMar 03 2010Feb 16 2012Generalizing a result of Yoshinaga in dimension 3, we show that a central hyperplane arrangement in 4-space is free exactly if its restriction with multiplicities to a fixed hyperplane of the arrangement is free and its reduced characteristic polynomial ... More
Recent developments in quarkonium and open flavour production calculationsSep 08 2011This report reviews recent theory progress in the field of heavy quarkonium and open heavy flavour production calculations.
Discriminative Gaifman ModelsOct 28 2016We present discriminative Gaifman models, a novel family of relational machine learning models. Gaifman models learn feature representations bottom up from representations of locally connected and bounded-size regions of knowledge bases (KBs). Considering ... More
Symmetry-Aware Marginal Density EstimationApr 09 2013The Rao-Blackwell theorem is utilized to analyze and improve the scalability of inference in large probabilistic models that exhibit symmetries. A novel marginal density estimator is introduced and shown both analytically and empirically to outperform ... More
Markov Chains on Orbits of Permutation GroupsJun 23 2012Jun 28 2012We present a novel approach to detecting and utilizing symmetries in probabilistic graphical models with two main contributions. First, we present a scalable approach to computing generating sets of permutation groups representing the symmetries of graphical ... More
On infinitely divisible distributions with polynomially decaying characteristic functionsMay 14 2014Jul 09 2014We provide necessary and sufficient conditions on the characteristics of an infinitely divisible distribution under which its characteristic function $\phi$ decays polynomially. Under a mild regularity condition this polynomial decay is equivalent to ... More
Gröbner strata in the Hilbert scheme of pointsJul 02 2009Jan 22 2011The present paper shall provide a framework for working with Gr\"obner bases over arbitrary rings $k$ with a prescribed finite standard set $\Delta$. We show that the functor associating to a $k$-algebra $B$ the set of all reduced Gr\"obner bases with ... More
Arithmetic Progressions in Abundance by Combinatorial ToolsSep 10 2008Using the algebraic structure of the Stone-Cech compactification of the integers, Furstenberg and Glasner proved that for arbitrary k, every piecewise syndetic set contains a piecewise syndetic set of k-term arithmetic progressions. We present a purely ... More
Characterization of Cyclically Fully commutative elements in finite and affine Coxeter GroupsMar 05 2014Oct 02 2014An element of a Coxeter group W is fully commutative if any two of its reduced decompositions are related by a series of transpositions of adjacent commuting generators. An element of a Coxeter group W is cyclically fully commutative if any of its cyclic ... More
A novel model and estimation method for the individual random component of earthquake ground-motion relationsNov 06 2015Mar 15 2016In this paper, I introduce a novel approach to modelling the individual random component (also called the intra-event uncertainty) of a ground-motion relation (GMR), as well as a novel approach to estimating the corresponding parameters. In essence, I ... More
The Turing Test for TelepresenceNov 09 2015The quality of high-end videoconferencing systems has improved significantly over the last few years enabling a class of applications known as "telepresence" wherein the users engaged in a communication session experience a feeling of mutual presence ... More
Strong characterizing sequences of countable groupsJul 09 2008Andr\'as Bir\'o and Vera S\'os prove that for any subgroup $G$ of $\T$ generated freely by finitely many generators there is a sequence $A\subset \N$ such that for all $\beta \in \T$ we have ($\|.\|$ denotes the distance to the nearest integer) $$\beta\in ... More
Hoppe trees, random recursive sets and their barycentreJul 06 2012We consider a recursively defined random set of points and its barycenter, where the random set is constructed by the following inductive rule: Given a realization of $n-1$ points, one of them is picked at random and serves as a source the $n$-th point. ... More
Form Factors in $D_n^{(1)}$ Affine Toda Field TheoriesDec 12 1996May 02 1997We derive closed recursion equations for the symmetric polynomials occuring in the form factors of $D_n^{(1)}$ affine Toda field theories. These equations follow from kinematical- and bound state residue equations for the full form factor. We also discuss ... More
q-Deformed Relativistic Wave EquationsOct 15 1993Based on the representation theory of the $q$-deformed Lorentz and Poincar\'e symmeties $q$-deformed relativistic wave equation are constructed. The most important cases of the Dirac-, Proca-, Rarita-Schwinger- and Maxwell- equations are treated explicitly. ... More
Algebraic Techniques for Gaussian ModelsOct 23 2006Many statistical models are algebraic in that they are defined by polynomial constraints or by parameterizations that are polynomial or rational maps. This opens the door for tools from computational algebraic geometry. These tools can be employed to ... More
Probing Pauli Blocking Factors in Quantum Pumps with Broken Time-Reversal SymmetryJun 21 2000A recently demonstrated quantum electron pump is discussed within the framework of photon-assisted tunneling. Due to lack of time-reversal symmetry, different results are obtained for the pump current depending on whether or not final-state Pauli blocking ... More
Finite subsets of projective space, and their idealsNov 07 2007Nov 19 2007Let $\mathscr{A}$ be a finite set of closed rational points in projective space, let $\mathscr{I}$ be the vanishing ideal of $\mathscr{A}$, and let $\mathscr{D}(\mathscr{A})$ be the set of exponents of those monomials which do not occur as leading monomials ... More
Equivariant K-homology of Bianchi groups with non-trivial class groupJan 06 2013May 13 2013We compute the equivariant K-homology of the groups PSL_2 of imaginary quadratic integers with trivial and non-trivial class-group. This was done before only for cases of trivial class number. We rely on reduction theory in the form of the $\Gamma$-CW-complex ... More
Markov Chains on Orbits of Permutation GroupsAug 09 2014We present a novel approach to detecting and utilizing symmetries in probabilistic graphical models with two main contributions. First, we present a scalable approach to computing generating sets of permutation groups representing the symmetries of graphical ... More
A Delayed Column Generation Strategy for Exact k-Bounded MAP Inference in Markov Logic NetworksMar 15 2012The paper introduces k-bounded MAP inference, a parameterization of MAP inference in Markov logic networks. k-Bounded MAP states are MAP states with at most k active ground atoms of hidden (non-evidence) predicates. We present a novel delayed column generation ... More
Components of Gröbner strata in the Hilbert scheme of pointsJun 18 2010Jan 08 2013We fix the lexicographic order $\prec$ on the polynomial ring $S=k[x_{1},...,x_{n}]$ over a ring $k$. We define $\Hi^{\prec\Delta}_{S/k}$, the moduli space of reduced Gr\"obner bases with a given finite standard set $\Delta$, and its open subscheme $\Hi^{\prec\Delta,\et}_{S/k}$, ... More
An ultrafilter approach to Jin's TheoremAug 20 2009It is well known and not difficult to prove that if $C$ of integers has positive upper Banach density, the set of differences $C-C$ is syndetic, i.e. the length of gaps is uniformly bounded. More surprisingly, Renling Jin showed that whenever $A$ and ... More
A variant of the Hales-Jewett TheoremJul 09 2008It was shown by V. Bergelson that any set B with positive upper multiplicative density contains nicely intertwined arithmetic and geometric progressions: For each positive integer k there exist integers a,b,d such that $ {b(a+id)^j:i,j \in\nhat k}\subset ... More
Information bounds for inverse problems with application to deconvolution and Lévy modelsJul 24 2013May 06 2014If a functional in an inverse problem can be estimated with parametric rate, then the minimax rate gives no information about the ill-posedness of the problem. To have a more precise lower bound, we study semiparametric efficiency in the sense of H\'ajek-Le ... More
Quantile estimation for Lévy measuresMay 27 2014Jan 01 2015Generalizing the concept of quantiles to the jump measure of a L\'evy process, the generalized quantiles $q_{\tau}^{\pm}>0$, for $\tau>0$, are given by the smallest values such that a jump larger than $q_{\tau}^{+}$ or a negative jump smaller than $-q_{\tau}^{-}$, ... More
Mustafin degenerationsMar 08 2012Mar 07 2013A Mustafin degeneration is a degeneration of a flag variety induced by a vertex configuration in the Bruhat-Tits building of the projective linear group over a field with a non-archimedean discrete valuation. In the case where the flag type is projective ... More
Uniform bounds on sup-norms of holomorphic forms of real weightJun 11 2014We establish uniform bounds for the sup-norms of modular forms of arbitrary real weight $k$ with respect to a finite index subgroup $\Gamma$ of $\mathrm{SL}_2(\mathbb{Z})$. We also prove corresponding bounds for the supremum over a compact set. We achieve ... More
Beta-expansions of rational numbers in quadratic Pisot basesNov 10 2014We study rational numbers with purely periodic R\'enyi $\beta$-expansions. For bases $\beta$ satisfying $\beta^2=a\beta+b$ with $b$ dividing $a$, we give a necessary and sufficient condition for $\gamma(\beta)=1$, i.e., that all rational numbers $p/q\in[0,1)$ ... More
Tilings for Pisot beta numerationOct 04 2013For a (non-unit) Pisot number $\beta$, several collections of tiles are associated with $\beta$-numeration. This includes an aperiodic and a periodic one made of Rauzy fractals, a periodic one induced by the natural extension of the $\beta$-transformation ... More
Beta-expansions, natural extensions and multiple tilings associated with Pisot unitsJul 15 2009Jan 29 2010From the works of Rauzy and Thurston, we know how to construct (multiple) tilings of some Euclidean space using the conjugates of a Pisot unit $\beta$ and the greedy $\beta$-transformation. In this paper, we consider different transformations generating ... More
On the plasma flow inside magnetic tornadoes on the SunJun 27 2014High-resolution observations with the Swedish 1-m Solar Telescope (SST) and the Solar Dynamics Observatory (SDO) reveal rotating magnetic field structures that extend from the solar surface into the chromosphere and the corona. These so-called magnetic ... More
Recent Advances in the Exploration of the Small-Scale Structure of the Quiet Solar Atmosphere: Vortex Flows, the Horizontal Magnetic Field, and the Stokes-V Line-Ratio MethodFeb 17 2012We review (i) observations and numerical simulations of vortical flows in the solar atmosphere and (ii) measurements of the horizontal magnetic field in quiet Sun regions. First, we discuss various manifestations of vortical flows and emphasize the role ... More
Supnorm of Modular Forms of half-integral Weight in the Weight AspectApr 30 2015May 25 2015We bound the supnorm of half-integral weight Hecke eigenforms in the Kohnen plus space of level $4$ in the weight aspect, by combining bounds obtained from the Fourier expansion with the amplification method using a Bergman kernel.
Disaster Monitoring with Wikipedia and Online Social Networking Sites: Structured Data and Linked Data Fragments to the Rescue?Jan 26 2015In this paper, we present the first results of our ongoing early-stage research on a realtime disaster detection and monitoring tool. Based on Wikipedia, it is language-agnostic and leverages user-generated multimedia content shared on online social networking ... More
Effective Vinogradov's mean value theorem via efficient boxingMar 08 2016We combine Wooley's efficient congruencing method with earlier work of Vinogradov and Hua to get effective bounds on Vinogradov's mean value theorem.
Quantum Cosmology Close to the Classical Big Bang Singularity and in the Semiclassical LimitJan 28 2010We investigate a cosmological model whose energy content is described by a Chaplygin gas represented by a scalar field $\phi$ with an associated potential producing a big bang singularity such that for vanishing scale factor, $a\to 0$, one has $|\phi|\to ... More
The Cosmic Microwave Background for a Nearly Flat Compact Hyperbolic UniverseJul 18 2000Oct 06 2000The fluctuations of the cosmic microwave background (CMB) are investigated for a hyperbolic universe with finite volume. Four-component models with radiation, matter, vacuum energy, and an extra spatially constant dark energy X-component are considered. ... More
On the regularity of the generalised golden ratio functionNov 26 2015Sep 09 2016Given a finite set of real numbers $A$, the generalised golden ratio is the unique real number $\mathcal{G}(A) > 1$ for which we only have trivial unique expansions in smaller bases, and have non-trivial unique expansions in larger bases. We show that ... More
Near Counterexamples to Weil's Converse TheoremJun 22 2016We show that in Weil's converse theorem the functional equations of multiplicative twists for at least the first $\sqrt{\frac{p-24}{3}}$ moduli are needed in order to prove the modularity for $\Gamma_0(p)$.
Thermal infrared emission reveals the Dirac point movement in biased grapheneApr 02 2010Graphene is a 2-dimensional material with high carrier mobility and thermal conductivity, suitable for high-speed electronics. Conduction and valence bands touch at the Dirac point. The absorptivity of single-layer graphene is 2.3%, nearly independent ... More
Light-matter interaction in a microcavity-controlled graphene transistorDec 06 2011Jun 25 2012Graphene has extraordinary electronic and optical properties and holds great promise for applications in photonics and optoelectronics. Demonstrations including high-speed photodetectors, optical modulators, plasmonic devices, and ultrafast lasers have ... More
Energy dissipation in graphene field-effect transistorsDec 02 2009We measure the temperature distribution in a biased single-layer graphene transistor using Raman scattering microscopy of the 2D-phonon band. Peak operating temperatures of 1050 K are reached in the middle of the graphene sheet at 210 KW cm^(-2) of dissipated ... More
Time-resolved Scattering of a Single Photon by a Single AtomApr 27 2016Scattering of light by matter has been studied extensively in the past. Yet, the most fundamental process, the scattering of a single photon by a single atom, is largely unexplored [1-3]. One prominent prediction of quantum optics is the deterministic ... More
Efficient narrow-band light emission from a single carbon nanotube p-n diodeApr 30 2010Electrically-driven light emission from carbon nanotubes could be exploited in nano-scale lasers and single-photon sources, and has therefore been the focus of much research. However, to date, high electric fields and currents have been either required ... More
Ultimate RF Performance Potential of Carbon ElectronicsMay 05 2011Carbon electronics based on carbon nanotube array field-effect transistors (AFETs) and 2-dimensional graphene field-effect transistors (GFETs) have recently attracted significant attention for potential RF applications. Here, we explore the ultimate RF ... More
Electromagnetic Mach principleJun 28 2011We will introduce a gauge model which an electromagnetic coupling constant and local mass are related to all the charge in the universe. we will use the standard Dirac action, but where the mass and the electromagnetic coupling constant are a function ... More
Superfluid Response and the Neutrino Emissivity of Neutron MatterApr 03 2008{We calculate the neutrino emissivity of superfluid neutron matter in the inner crust of neutron stars. We find that neutrino emission due to fluctuations resulting from the formation of Cooper pairs at finite temperature is highly suppressed in non-relativistic ... More