Results for "Mattias Beck"

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Pulses from a mid-infrared quantum cascade laser frequency comb using an external compressorMay 14 2019A Martinez-type stretcher-compressor is used to modify the spectral phases of a high-power (~1 W) QCL comb emitted at 8.2 {\mu}m with more than 100 cm-1 spectral bandwidth. Using this scheme, we demonstrate a compression of the QCL output from a 134 ps ... More
Measuring intensity correlations of a THz quantum cascade laser around its threshold at sub-cycle timescalesNov 29 2016The quantum nature of photonic systems is reflected in the photon statistics of the light they emit. Therefore, the development of quantum optics tools with single photon sensitivity and excellent temporal resolution is paramount to the development of ... More
THz ultrastrong light-matter couplingNov 28 2016Cavity photon resonators with ultrastrong light-matter interactions are attracting interest both in semiconductor and superconducting systems displaying the capability to manipulate the cavity quantum electrodynamic ground state with controllable physical ... More
Observation of Zone-Folded Acoustic Phonons in Terahertz Quantum Cascade Lasers using Picosecond UltrasonicsDec 06 2010We have investigated the time-resolved vibrational properties of terahertz quantum cascade lasers by means of ultra-fast laser spectroscopy. By the observation of the acoustic folded branches, and by analyzing the involved phonon modes it is possible ... More
On Bohr's equivalence theoremJan 20 2016Nov 30 2016In this note we prove a converse of Bohr's equivalence theorem for Dirichlet series under some natural assumptions.
A note on the universality of Hurwitz-Lerch zeta functionsDec 02 2016Jan 03 2017A failed attempt to prove the universality of Lerch zeta function $L(\lambda,\alpha,s)$ when $\lambda$ is irrational and $\alpha$ is rational, and for any $\lambda$ when $\alpha$ is irrational algebraic.
Isomorphisms between complements of projective plane curvesFeb 17 2019In this article, we study isomorphisms between complements of irreducible curves in the projective plane $\mathbb{P}^2$, over an arbitrary algebraically closed field. Of particular interest are rational unicuspidal curves. We prove that if there exists ... More
A preconditioning strategy for linear systems arising from nonsymmetric schemes in isogeometric analysisMay 11 2017In the context of isogeometric analysis, we consider two discretization approaches that make the resulting stiffness matrix nonsymmetric even if the differential operator is self-adjoint. These are the collocation method and the recently-developed weighted ... More
Matrix biorthogonal polynomials on the unit circle and non-Abelian Ablowitz-Ladik hierarchyApr 22 2008Aug 24 2009Adler and van Moerbeke \cite{AVM} described a reduction of 2D-Toda hierarchy called Toeplitz lattice. This hierarchy turns out to be equivalent to the one originally described by Ablowitz and Ladik \cite{AL} using semidiscrete zero-curvature equations. ... More
Prescribing eigenvalues of the Dirac operatorNov 11 2003Aug 05 2005In this note we show that every compact spin manifold of dimension $\geq 3$ can be given a Riemannian metric for which a finite part of the spectrum of the Dirac operator consists of arbitrarily prescribed eigenvalues with multiplicity 1.
Dynamics on Berkovich spaces in low dimensionsJan 10 2012Oct 13 2014These are expanded lecture notes for the summer school on Berkovich spaces that took place at the Institut de Math\'ematiques de Jussieu, Paris in 2010. They serve to illustrate some techniques and results from the dynamics on low-dimensional Berkovich ... More
A comparison between pretriangulated $\mbox{A}_{\infty}$-categories and $\infty$-Stable categoriesSep 02 2016In this paper we will prove that the $\mbox{A}_{\infty}$-nerve of two quasi-equivalent $\mbox{A}_{\infty}$-categories are weak-equivalent in the Joyal model structure, a consequence of this fact is that the $\mbox{A}_{\infty}$-nerve of a pretriangulated ... More
Finite groups acting on hyperelliptic 3-manifoldsMay 16 2018We consider 3-manifolds admitting the action of an involution such that its space of orbits is homeomorphic to $S^3.$ Such involutions are called hyperelliptic as the manifolds admitting such an action. We consider finite groups acting on 3-manifolds ... More
On Bohr's equivalence theoremJan 20 2016Jan 21 2016In this note we show a converse of Bohr's equivalence theorem.
The Spitzer Data Fusion: Contents, Construction and Applications to Galaxy Evolution StudiesApr 08 2016Jun 21 2016We present the Spitzer Data Fusion, a database incorporating far-ultraviolet to far-infrared flux measurements as well as photometric and spectroscopic redshifts for 4.4 million IRAC-selected sources detected over 8 extragalactic fields covering 65 deg$^2$ ... More
Singularities of moduli of curves with a universal rootApr 02 2015Oct 03 2017In a series of recent papers, Chiodo, Farkas and Ludwig carry out a deep analysis of the singular locus of the moduli space of stable (twisted) curves with an $\ell$-torsion line bundle. They show that for $\ell\leq 6$ and $\ell\neq 5$ pluricanonical ... More
Existence and extinction in finite time for Stratonovich gradient noise porous media equationsNov 26 2018We study existence and uniqueness of distributional solutions to the stochastic partial differential equation $dX - ( \nu \Delta X + \Delta \psi (X) ) dt = \sum_{i=1}^N \langle b_i, \nabla X \rangle \circ d\beta_i$ in $]0,T[ \times \mathcal{O}$, with ... More
The Forward Euler Scheme for Nonconvex Lipschitz Differential Inclusions Converges with Rate OneJan 30 2009In a previous paper it was shown that the Forward Euler method applied to differential inclusions where the right-hand side is a Lipschitz continuous set-valued function with uniformly bounded, compact values, converges with rate one. The convergence, ... More
Extended Applicability of the Symplectic Pontryagin MethodJan 29 2009The Symplectic Pontryagin method was introduced in a previous paper. This work shows that this method is applicable under less restrictive assumptions. Existence of solutions to the Symplectic Pontryagin scheme are shown to exist without the previous ... More
On the density of zeros of linear combinations of Euler products for $σ>1$Jun 18 2015Jan 20 2016It has been conjectured that the real parts of the zeros of a linear combination of two or more $L$-functions are dense in the interval $[1,\sigma^*]$, where $\sigma^*$ is the least upper bound of the real parts of such zeros. In this paper we show that ... More
Expanding solitons to the Hermitian curvature flow on complex Lie groupsOct 11 2018Mar 05 2019We investigate the algebraic structure of complex Lie groups equipped with left-invariant metrics which are expanding semi-algebraic solitons to the Hermitian curvature flow (HCF). We show that the Lie algebras of such Lie groups decompose in the semidirect ... More
Evidence of Linear Chirp in Mid-Infrared Quantum Cascade LasersApr 11 2018We measure the inter-modal phase relation of a quantum cascade laser frequency comb operating at 8 um using a coherent beatnote spectroscopy. We find these phases to be reproducible after cycling the power of the device, and to be smoothly varying with ... More
Retrieval of phase relation and emission profile of quantum cascade laser frequency combsMay 02 2019The major development recently undergone by quantum cascade lasers has effectively extended frequency comb emission to longer-wavelength spectral regions, i.e. the mid and far infrared. Unlike classical pulsed frequency combs, their mode-locking mechanism ... More
Octave-spanning semiconductor laserJul 11 2014We present here a semiconductor injection laser operating in continuous wave with an emission covering more than one octave in frequency, and displaying homogeneous power distribution among the lasing modes. The gain medium is based on a heterogeneous ... More
Room temperature terahertz polariton emitterJan 09 2012The strong-coupling regime between an electronic transition and the photonic mode of a optical resonator manifests itself in the lifting of the degeneracy between the two modes and the creation of two polariton states with mixed optical and electronic ... More
Coupled-waveguides for dispersion compensation in semiconductor lasersNov 24 2017The generation of optical frequency combs via direct electrical pumping of semiconductor lasers is an attractive alternative to the well-established mode-locked laser sources in terms of compactness, robustness and integrability. However, the high chromatic ... More
InGaAs/AlInGaAs THz Quantum Cascade Lasers operating up to 195 K in strong magnetic fieldNov 06 2014Feb 20 2015Terahertz quantum cascade lasers based on InGaAs wells and quaternary AlInGaAs barriers were measured in magnetic field. This study was carried out on a four quantum well active region design with photon energy of 14.3 meV processed both with Au and Cu ... 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
Every Runner is Sometimes LonelyJun 06 2016Jun 07 2016We describe a geometric attack to the \emph{Lonely Runner Conjecture}, conceived by J\"org Wills in the 1960's: Given positive integers $r_1, r_2, \dots, r_k$, there exists a positive real number $t$ such that for all $1 \le j \le k$ the distance of $t ... More
Estimating grouped data models with a binary dependent variable and fixed effects: What are the issuesSep 18 2018This article deals with asimple issue: if we have grouped data with a binary dependent variable and want to include fixed effects (group specific intercepts) in the specification, is Ordinary Least Squares (OLS) in any way superior to a (conditional) ... More
Stable Parabolic Higgs Bundles as Asymptotically Stable Decorated SwampsOct 28 2014Parabolic Higgs bundles can be described in terms of decorated swamps, which we studied in a recent paper. This description induces a notion of stability of parabolic Higgs bundles depending on a parameter, and we construct their moduli space inside the ... More
Moduli of Decorated Swamps on a Smooth Projective CurveAug 07 2014In order to unify the construction of the moduli space of vector bundles with different types of global decorations, such as Higgs bundles, framed vector bundles and conic bundles, A. Schmitt introduced the concept of a swamp. In this work, we consider ... More
A Generalization of Principal Bundles With a Parabolic or Level StructureJul 10 2015We define a parameter dependent notion of stability for principal bundles with a certain local decoration, which generalizes both parabolic and level structures, and construct their coarse moduli space. A necessary technical step is the construction of ... More
An attempt to prove an effective Siegel theorem--Part OneNov 06 2013Nov 09 2013We describe a plan how to prove an effective Siegel theorem (about the exceptional Dirichlet character). We give a brief outline in Section 0. We give a more detailed plan in Sections 1-5. The missing details (mostly routine elementary estimations) are ... More
Abelianization of Subgroups of Reflection Group and their Braid Group; an Application to CohomologyMar 03 2010Aug 31 2010The final result of this article gives the order of the extension $$\xymatrix{1\ar[r] & P/[P,P] \ar^{j}[r] & B/[P,P] \ar^-{p}[r] & W \ar[r] & 1}$$ as an element of the cohomology group $H^2(W,P/[P,P])$ (where $B$ and $P$ stands for the braid group and ... More
Aspects of Calabi-Yau Integrable and Hitchin SystemsSep 15 2018Jan 02 2019In the present notes we explain the relationship between Calabi-Yau integrable systems and Hitchin systems based on work by Diaconescu-Donagi-Pantev and the author. Besides a review of these integrable systems, we highlight related topics, for example ... More
Elements of reality in quantum mechanicsJul 17 2018Oct 08 2018The notion of the Einstein-Podolsky-Rosen (EPR) "element of reality" is much discussed in the literature on the foundations of quantum mechanics. Recently, it has become particularly relevant due to a proposed criterion of the physical reality of a given ... More
Causation, Information, and PhysicsJul 27 2017Dec 03 2018This work outlines the novel application of the empirical analysis of causation, presented by Kutach, to the study of information theory and its role in physics. The central thesis of this paper is that causation and information are identical functional ... More
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
Determination of the E2/M1 Ratio in the γN \to Δ(1232) Transition from a Simultaneous Measurement of p(\vecγ,p)π^0 and p(\vecγ,π^+)nAug 26 1999Tagged linearly polarized photons have been used at the Mainz Microtron MAMI for simultaneous measurements of the p(\vec{\gamma},p)\pi^0 and p(\vec{\gamma},\pi^+)n reaction channels to study the \gamma N \to \Delta(1232) transition. The energy dependence ... 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
Regularity versus singularities for elliptic problems in two dimensionsOct 30 2009Aug 30 2010In two dimensions every weak solution to a nonlinear elliptic system $\rm{div} a(x,u,Du)=0$ has H\"older continuous first derivatives provided that standard continuity, ellipticity and growth assumptions hold with a growth exponent $p \geq 2$. We give ... More
Estimating grouped data models with a binary dependent variable and fixed effect via logit vs OLS: the impact of dropped unitsOct 26 2018This letter deals with a very simple issue: if we have grouped data with a binary dependent variable and want to include fixed effects (group specific intercepts) in the specification, is Ordinary Least Squares (OLS) in any way superior to a logit form ... More
Calabi-Yau orbifolds over Hitchin basesJul 13 2018Any irreducible Dynkin diagram $\Delta$ is obtained from an irreducible Dynkin diagram $\Delta_h$ of type $\mathrm{ADE}$ by folding via graph automorphisms. For any simple complex Lie group $G$ with Dynkin diagram $\Delta$ and compact Riemann surface ... More
Boundary regularity for elliptic systems under a natural growth conditionFeb 09 2010Jul 28 2010We consider weak solutions $u \in u_0 + W^{1,2}_0(\Omega,R^N) \cap L^{\infty}(\Omega,R^N)$ of second order nonlinear elliptic systems of the type $- div a (\cdot, u, Du) = b(\cdot,u,Du)$ in $\Omega$ with an inhomogeneity satisfying a natural growth condition. ... More
Braid Group Action and Quantum Affine AlgebrasApr 27 1994We lift the lattice of translations in the extended affine Weyl group to a braid group action on the quantum affine algebra. This action fixes the Heisenberg subalgebra pointwise. Loop like generators are found for the algebra which satisfy the relations ... More
Magnetism in Nearby Galaxies, Prospects with the SKA, and Synergies with the E-ELTAug 23 2010Radio synchrotron emission, its polarization and its Faraday rotation are powerful tools to study the strength and structure of interstellar magnetic fields. In the Milky Way, Faraday rotation of the polarized emission from pulsars and background sources ... More
Measuring interstellar magnetic fields by radio synchrotron emissionDec 29 2008Radio synchrotron emission, its polarization and its Faraday rotation are powerful tools to study the strength and structure of interstellar magnetic fields. The total intensity traces the strength and distribution of total magnetic fields. Total fields ... More
The Origin of Magnetic Fields in Galaxies: Observational Tests with the Square Kilometre ArrayDec 20 2005Apr 07 2006The all-sky survey of Faraday rotation, a Key Science Project of the planned Square Kilometre Array, will accumulate tens of millions of rotation measure measurements toward background radio sources and will provide a unique database for characterizing ... More
Stanley's Major Contributions to Ehrhart TheoryJul 01 2014Oct 08 2015This expository paper features a few highlights of Richard Stanley's extensive work in Ehrhart theory, the study of integer-point enumeration in rational polyhedra. We include results from the recent literature building on Stanley's work, as well as several ... More
Outermost apparent horizons diffeomorphic to unit normal bundlesJun 27 2016For $p \geq 1$, $q \geq 2$ with $n = p + q \leq 7$ and a compact, embedded submanifold $S \subset \mathbb R^p$ of dimension at most $p - 1$ we construct an $n$-dimensional asymptotically Euclidean Riemannian manifold with zero scalar curvature having ... More
Isogeometric preconditioners based on fast solvers for the Sylvester equationFeb 04 2016Jul 21 2016We consider large linear systems arising from the isogeometric discretization of the Poisson problem on a single-patch domain. The numerical solution of such systems is considered a challenging task, particularly when the degree of the splines employed ... More
AR Identification of Latent-variable Graphical ModelsApr 30 2014Dec 01 2014The paper proposes an identification procedure for autoregressive gaussian stationary stochastic processes wherein the manifest (or observed) variables are mostly related through a limited number of latent (or hidden) variables. The method exploits the ... More
Thresholds, valuations, and K-stabilityJun 14 2017Let X be a normal complex projective variety with at worst klt singularities, and L a big line bundle on X. We use valuations to study the log canonical threshold of L, as well as another invariant, the stability threshold. The latter generalizes a notion ... More
An isoperimetric constant associated to horizons in $S^3$ blown-up at two pointsOct 31 2009Let $g$ be a metric on $S^3$ with positive Yamabe constant. When blowing up $g$ at two points, a scalar flat manifold with two asymptotically flat ends is produced and this manifold will have compact minimal surfaces. We introduce the $\Th$-invariant ... More
The effect of rotation on the thermal instability of stratified galactic atmospheres - II. The formation of High Velocity CloudsMar 14 2019Whether High Velocity Clouds (HVCs) can form by condensation of the hot ($T \sim 10^6 \, {\rm K}$) Galactic corona as a consequence of thermal instabilities has been controversial. Here we re-examine this problem and we suggest that rotation of the corona ... More
Convergence of p-adic pluricanonical measures to Lebesgue measures on skeleta in Berkovich spacesMay 07 2019Let $K$ be a non-archimedean local field, $X$ a smooth and proper $K$-scheme, and fix a pluricanonical form on $X$. For every finite extension $K'$ of $K$, the pluricanonical form induces a measure on the $K'$-analytic manifold $X(K')$. We prove that, ... More
The motivic class of the classifying stack of the special orthogonal groupSep 26 2016Jul 05 2017We compute the class of the classifying stack of the special orthogonal group in the Grothendieck ring of stacks, and check that it is equal to the multiplicative inverse of the class of the group.
Dynamical compactifications of C^2Nov 19 2007Sep 02 2009We find good dynamical compactifications for arbitrary polynomial mappings of C^2 and use them to show that the degree growth sequence satisfies a linear integral recursion formula. For maps of low topological degree we prove that the Green function is ... More
Boltzmann-type models with uncertain binary interactionsSep 07 2017In this paper we study binary interaction schemes with uncertain parameters for a general class of Boltzmann-type equations with applications in classical gas and aggregation dynamics. We consider deterministic (i.e., a priori averaged) and stochastic ... More
Kinetic-controlled hydrodynamics for traffic models with driver-assist vehiclesJul 28 2018Feb 13 2019We develop a hierarchical description of traffic flow control by means of driver-assist vehicles aimed at the mitigation of speed-dependent road risk factors. Microscopic feedback control strategies are designed at the level of vehicle-to-vehicle interactions ... More
Weighted sub-Laplacians on Métivier Groups: Essential Self-Adjointness and SpectrumOct 31 2016Let $G$ be a M\'etivier group and let $N$ be any homogeneous norm on $G$. For $\alpha>0$ denote by $w_\alpha$ the function $e^{-N^\alpha}$ and consider the weighted sub-Laplacian $\mathcal{L}^{w_\alpha}$ associated with the Dirichlet form $\phi \mapsto ... More
Darboux transformations and random point processesJan 19 2014Feb 03 2014In this paper we describe a general method to derive formulas relating the gap probability of some classical determinantal random point process (Airy, Pearcey and Hermite) with the gap probability of the processes related to the same kernels with "wanderers", ... More
Crossover between integer and fractional vortex lattices in coherently coupled two-component Bose-Einstein condensatesMar 11 2013Nov 01 2013We study effects of the internal coherent (Rabi) coupling in vortex lattices in two-component BECs under rotation. We find how the vortex lattices without the Rabi coupling known before are connected to the Abrikosov lattice of integer vortices with increasing ... More
Isometry groups and mapping class groups of spherical 3-orbifoldsJul 21 2016We study the isometry group of compact spherical orientable $3$-orbifolds $S^3/G$, where $G$ is a finite subgroup of $\mathrm{SO}(4)$, by determining its isomorphism type and, when $S^3/G$ is a Seifert fibrered orbifold, by describing the action on the ... More
A finiteness property of graded sequences of idealsNov 17 2010Jul 04 2011Given a graded sequence of ideals (a_m) on a smooth variety $X$ having finite log canonical threshold, suppose that for every m we have a divisor E_m over X that computes the log canonical threshold of a_m, and such that the log discrepancies of the divisors ... More
Valuations and asymptotic invariants for sequences of idealsNov 16 2010Oct 20 2011We study asymptotic jumping numbers for graded sequences of ideals, and show that every such invariant is computed by a suitable real valuation of the function field. We conjecture that every valuation that computes an asymptotic jumping number is necessarily ... More
The effect of rotation on the thermal instability of stratified galactic atmospheres - I. Local analysisMar 14 2019Observations show that (i) multiple gas phases can coexist in the atmospheres of galaxies and clusters; (ii) these atmospheres may be significantly rotating in the inner parts, with typical velocities that approach or even exceed the local sound speed. ... More
Moduli spaces of abstract and embedded Kummer varietiesJun 01 2018In this paper, we investigate the construction of two moduli stacks of Kummer varieties. The first one is the stack $\mathcal K^{\text{abs}}_g$ of abstract Kummer varieties and the second one is the stack $\mathcal K^{\text{em}}_g$ of embedded Kummer ... More
Vortex lattices in three-component Bose-Einstein condensates under rotation: simulating colorful vortex lattices in a color superconductorApr 16 2013Aug 14 2013We study vortex lattices in three-component BECs under rotation, where three kinds of fractional vortices winding one of three components are present. Unlike the cases of two-component BECs where the phases of square and triangular lattices are present ... More
Efficient Computation of Null-Geodesic with Applications to Coherent Vortex DetectionOct 29 2016Recent results suggest that boundaries of coherent fluid vortices (elliptic coherent structures) can be identified as closed null-geodesics of appropriate Lorentzian metrics defined on the flow domain. Here we derive an automated method for computing ... More
Endomorphisms of the plane preserving a pencil of curvesMar 02 2007We classify endomorphisms of the plane that preserve a pencil of curves.
Stable manifolds of holomorphic diffeomorphismsJan 29 2001Mar 18 2002We consider stable manifolds of a holomorphic diffeomorphism of a complex manifold. Using a conjugation of the dynamics to a (non-stationary) polynomial normal form, we show that typical stable manifolds are biholomorphic to complex Euclidean space.
Valuative analysis of planar plurisubharmonic functionsJan 12 2004Feb 09 2005We show that valuations on the ring R of holomorphic germs in dimension 2 may be naturally evaluated on plurisubharmonic functions, giving rise to generalized Lelong numbers in the sense of Demailly. Any plurisubharmonic function thus defines a real-valued ... More
The valuative treeOct 17 2002Nov 26 2003We describe the set V of all real valued valuations v on the ring C[[x,y]] normalized by min{v(x),v(y)}=1. It has a natural structure of an R-tree, induced by the order relation v is less than v' iff v(f) is less than v'(f) for all f. It can also be metrized, ... More
Valid parameter space of a bivariate Gaussian Markov random field with a generalized block-Toeplitz precision matrixApr 19 2016Gaussian Markov random fields (GMRFs) are extensively used in statistics to model area-based data and usually depend on several parameters in order to capture complex spatial correlations. In this context, it is important to determine the valid parameter ... More
Asymptotics for the Heat Kernel on H-Type GroupsSep 30 2017We give sharp asymptotic estimates at infinity of all radial partial derivatives of the heat kernel on H-type groups. As an application, we give a new proof of the discreteness of the spectrum of some natural sub-Riemannian Ornstein-Uhlenbeck operators ... More
Community structure and interaction dynamics through the lens of quotesApr 15 2016This is the first work investigating community structure and interaction dynamics through the lens of quotes in online discussion forums. We examine four forums of different size, language, and topic. Quote usage, which is surprisingly consistent over ... More
Forecasting Long-Lived Lagrangian Vortices from their Objective Eulerian FootprintsMay 15 2016We derive a non-dimensional metric to quantify the expected Lagrangian persistence of objectively defined Eulerian vortices in two-dimensional unsteady flows. This persistence metric is the averaged deviation of the vorticity from its spatial mean over ... More
The Kato-Nakayama space as a transcendental root stackNov 12 2016We give a functorial description of the Kato-Nakayama space of a fine saturated log analytic space that is similar in spirit to the functorial description of root stacks. As a consequence we get a global description of the comparison map constructed in ... More
Infinite root stacks and quasi-coherent sheaves on logarithmic schemesOct 05 2014We define and study infinite root stacks of fine and saturated logarithmic schemes, a limit version of the root stacks introduced by Niels Borne and the second author. We show in particular that the infinite root stack determines the logarithmic structure, ... More
The motivic class of the classifying stack of the special orthogonal groupSep 26 2016We compute the class of the classifying stack of the special orthogonal group in the Grothendieck ring of stacks, and check that it is equal to the multiplicative inverse of the class of the group.
Effective Action of Non-Abelian Monopole-Vortex ComplexJul 09 2012We construct effective actions for non-Abelian 1/4 Bogomol'nyi-Prasad-Sommerfield (BPS) monopole-vortex complexes in 4d N = 2 supersymmetric gauge theories with gauge groups U(N), U(1) \times SO(2n) and U(1) \times USp(2n). In the color-flavor locked ... More
Fibered spherical 3-orbifoldsJul 02 2013Jul 21 2016In early 1930s Seifert and Threlfall classified up to conjugacy the finite subgroups of $\mathrm{SO}(4)$, this gives an algebraic classification of orientable spherical 3-orbifolds. For the most part, spherical 3-orbifolds are Seifert fibered. The underlying ... More
Estimating the dimensionality of neural responses with fMRI Repetition SuppressionMay 12 2016We propose a novel method that exploits fMRI Repetition Suppression (RS-fMRI) to measure the dimensionality of the set response vectors, i.e. the dimension of the space of linear combinations of neural population activity patterns in response to specific ... More
Algebraic webs invariant under endomorphismsJul 22 2009We classify noninvertible, holomorphic selfmaps of the projective plane that preserve an algebraic web. In doing so, we obtain interesting examples of critically finite maps.
The First Dirac Eigenvalue on Manifolds with Positive Scalar CurvatureMay 19 2003We show that on every compact spin manifold admitting a Riemannian metric of positive scalar curvature Friedrich's eigenvalue estimate for the Dirac operator can be made sharp up to an arbitrarily small given error by choosing the metric suitably.
On the motivic class of the classifying stack of $G_2$ and the spin groupsFeb 08 2017Aug 17 2017We compute the class of the classifying stack of the exceptional algebraic group $G_2$ and of the spin groups $\mathrm{Spin}_7$ and $\mathrm{Spin}_8$ in the Grothendieck ring of stacks, and show that they are equal to the inverse of the class of the corresponding ... More
Infinite root stacks and quasi-coherent sheaves on logarithmic schemesOct 05 2014Dec 12 2017We define and study infinite root stacks of fine and saturated logarithmic schemes, a limit version of the root stacks introduced by Niels Borne and the second author. We show in particular that the infinite root stack determines the logarithmic structure, ... More
Uncertainty damping in kinetic traffic models by driver-assist controlsMar 30 2019In this paper, we propose a kinetic model of traffic flow with uncertain binary interactions, which explains the scattering of the fundamental diagram in terms of the macroscopic variability of aggregate quantities, such as the mean speed and the flux ... More
Dispersion engineering of Quantum Cascade Lasers frequency combsSep 29 2015Quantum cascade lasers are compact sources capable of generating frequency combs. Yet key characteristics - such as optical bandwidth and power-per-mode distribution - have to be improved for better addressing spectroscopy applications. Group delay dispersion ... More
Intensity autocorrelation measurements of quantum cascade laser frequency combs in the Terahertz rangeFeb 10 2017We report on the first direct measurement of the emission character of quantum cascade laser based frequency combs, using intensity autocorrelation. The correlation technique is based on fast electro-optic sampling, with a bandwidth optimized to match ... More
Ultra strong coupling regime and plasmon-polaritons in parabolic semiconductor quantum wellsNov 30 2011Dec 13 2011Ultra strong coupling is studied in a modulation-doped parabolic potential well coupled to an inductance-capacitance resonant circuit. In this system, in accordance to Kohn's theorem, strong reduction of the energy level separation caused by the electron-electron ... More
An electrically pumped phonon-polariton laserAug 29 2018We report a device that provides coherent emission of phonon polaritons, a mixed state between photons and optical phonons in an ionic crystal. An electrically pumped GaInAs/AlInAs quantum cascade structure provides intersubband gain into the polariton ... More
Room temperature surface emission on large-area photonic crystal quantum cascade lasersNov 21 2018We design and fabricate large-area (1.1 mm $\times$ 1.1 mm) photonic crystal quantum cascade lasers, enabling single-mode (wavelength $\sim$ 8.5 $\mu$m) surface emission at room temperature, with a maximum peak power up to 176 mW. The beam divergence ... More
On-chip, self-detected THz dual-comb spectrometerFeb 01 2016We present a directly generated on-chip dual-comb source at THz frequencies. The multi-heterodyne beating signal of two free-running THz quantum cascade laser frequency combs is measured electrically using one of the combs as a detector, fully exploiting ... More
Ultra-broadband quantum cascade laser operating from 1.88 to 3.82 THzDec 22 2016Dec 23 2016We report on a heterogeneous active region design for terahertz quantum cascade laser based frequency combs. Dynamic range, spectral bandwidth as well as output power have been significantly improved with respect to previous designs. When operating individually ... More