Results for "Philippe Goldner"

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Counting tropical rational curves with cross-ratio constraintsApr 30 2018We enumerate rational curves in toric surfaces passing through points and satisfying cross-ratio constraints using tropical and combinatorial methods. Our starting point is arXiv:1509.07453, where a tropical-algebraic correspondence theorem was proved ... More
High-cooperativity coupling of a rare-earth spin ensemble to a superconducting resonator using yttrium orthosilicate as a substrateJan 10 2019Apr 25 2019Yttrium orthosilicate (Y$_2$SiO$_5$, or YSO) has proved to be a convenient host for rare-earth ions used in demonstrations of microwave quantum memories and optical memories with microwave interfaces, and shows promise for coherent microwave--optical ... More
High Resolution Optical Spectroscopy and Magnetic Properties of Yb3+ in Y2SiO5Jun 22 2016Rare earth doped crystals are promising systems for quantum information processing. In particular paramagnetic rare earths could be used to build coherent interfaces with optical and microwave photons. In addition, isotopes with non zero nuclear spins ... More
Faithful Solid State Optical Memory with Dynamically Decoupled Spin Wave StorageFeb 14 2013We report an optical memory in a rare earth doped crystal with long storage times, up to 20 ms, together with an optical bandwidth of 1.5 MHz. This is obtained by transferring optical coherences to nuclear spin coherences, which were then protected against ... More
Counts of (tropical) curves in $E\times \mathbb{P}^1$ and Feynman integralsDec 12 2018May 23 2019We study generating series of Gromov-Witten invariants of $E\times\mathbb{P}^1$ and their tropical counterparts. Using tropical degeneration and floor diagram techniques, we can express the generating series as sums of Feynman integrals, where each summand ... More
Tropical mirror symmetry in dimension oneSep 27 2018We prove a tropical mirror symmetry theorem for descendant Gromov-Witten invariants of the elliptic curve, generalizing a tropical mirror symmetry theorem for Hurwitz numbers of the elliptic curve. For the case of the elliptic curve, the tropical version ... More
Simultaneous coherence enhancement of optical and microwave transitions in solid-state electronic spinsDec 22 2017Solid-state electronic spins are extensively studied in quantum information science, both for quantum computation, sensing and communication. Electronic spins are highly interesting due to their large magnetic moments, which offer fast operations for ... More
Towards highly multimode optical quantum memory for quantum repeatersDec 09 2015Long-distance quantum communication through optical fibers is currently limited to a few hundreds of kilometres due to fiber losses. Quantum repeaters could extend this limit to continental distances. Most approaches to quantum repeaters require highly ... More
Efficient optical pumping using hyperfine levels in $^{145}$Nd$^{3+}$:Y$_2$SiO$_5$ and its application to optical storageDec 07 2017Jul 30 2018Efficient optical pumping is an important tool for state initialization in quantum technologies, such as optical quantum memories. In crystals doped with Kramers rare-earth ions, such as erbium and neodymium, efficient optical pumping is challenging due ... More
Diode-pumped Pr:BaY2F8 cw orange laserNov 04 2010We report the realization of the continuous wave laser emission in the orange at 607 nm from a Pr:BaY2F8 (Pr:BYF) crystal pumped by a blue GaN laser diode. A maximal output power of 78 mW is obtained in a quasi single transverse mode beam. The effect ... More
Coherent spin control at the quantum level in an ensemble-based optical memoryJan 16 2015Jun 17 2015Long-lived quantum memories are essential components of a long-standing goal of remote distribution of entanglement in quantum networks. These can be realized by storing the quantum states of light as single-spin excitations in atomic ensembles. However, ... More
Spectroscopic study of hyperfine properties in $^{171}$Yb$^{3+}$:Y$_2$SiO$_5$Dec 22 2017Nov 08 2018Rare-earth ion doped crystals are promising systems for quantum communication and quantum information processing. In particular, paramagnetic rare-earth centres can be utilized to realize quantum coherent interfaces simultaneously for optical and microwave ... More
Orange emission in Pr3+-doped fluoroindate glassesOct 23 2012We synthesize and study the properties of praseodymium doped fluoroindate glasses. Glass compositions with praseodymium molar concentrations up to 5% were obtained with good optical quality. Thermal, optical, and luminescence properties are investigated. ... More
Coherent spin dynamics of ytterbium ions in yttrium orthosilicateDec 01 2017We investigate the electron and nuclear spin coherence properties of ytterbium ($\mathrm{Yb}^{3+}$) ions with non-zero nuclear spin, within an yttrium orthosilicate (Y$_2$SiO$_5$) crystal, with a view to their potential application in quantum memories ... More
High precision measurement of the Dzyaloshinsky-Moriya interaction between two rare-earth ions in a solidMay 26 2016We report on a direct measurement of the pair-wise anti-symmetric exchange interaction, known as the Dzyaloshinsky-Moriya interaction (DMI), in a Nd3+-doped YVO4 crystal. To this end we introduce a broadband electron spin resonance technique coupled with ... More
Simultaneous coherence enhancement of optical and microwave transitions in solid-state electronic spinsDec 22 2017Jul 27 2018Solid-state electronic spins are extensively studied in quantum information science, as their large magnetic moments offer fast operations for computing and communication, and high sensitivity for sensing. However, electronic spins are more sensitive ... More
Hyperfine characterization and coherence lifetime extension in Pr3+:La2(WO4)3Jul 12 2011Rare-earth ions in dielectric crystals are interesting candidates for storing quantum states of photons. A limiting factor on the optical density and thus the conversion efficiency is the distortion introduced in the crystal by doping elements of one ... More
Electron Spin Coherences in Rare-Earth Optically Excited States for Microwave to Optical Quantum TransducersFeb 09 2018Efficient and reversible optical to microwave coherent transducers are required to enable entanglement transfer between superconducting qubits and light for quantum networks. Rare-earth-doped crystals that possess narrow optical and spin transitions are ... More
Coherent storage of microwave excitations in rare-earth nuclear spinsDec 23 2014Interfacing between various elements of a computer - from memory to processors to long range communication - will be as critical for quantum computers as it is for classical computers today. Paramagnetic rare earth doped crystals, such as Nd$^{3+}$:Y$_2$SiO$_5$ ... More
High resolution transient and permanent spectral hole burning in Ce$^{3+}$:Y$_2$SiO$_5$ at liquid helium temperaturesApr 08 2016We perform hole burning with a low drift stabilized laser within the zero phonon line of the 4f-5d transition in Ce$^{3+}$:Y$_2$SiO$_5$ at 2K. The narrowest spectral holes appear for small applied magnetic fields and are $6\pm4$ MHz wide (FWHM). This ... More
Characterization of the hyperfine interaction of the excited $^5$D$_0$ state of Eu$^{3+}$:Y$_2$SiO$_5$Oct 20 2017We characterize the Europium (Eu$^{3+}$) hyperfine interaction of the excited state ($^5$D$_0$) and determine its effective spin Hamiltonian parameters for the Zeeman and quadrupole tensors. An optical free induction decay method is used to measure all ... More
Experimental Tailoring of a Three-Level Lambda System in Tm3+:YAGSep 14 2005Quantum information transfer from light to atom ensembles and vice versa has both basic and practical importance. Among the relevant topics let us mention entanglement and decoherence of macroscopic systems, together with applications to quantum memory ... More
Electron Spin Coherences in Rare-Earth Optically Excited States for Microwave to Optical Quantum TransducersFeb 09 2018Feb 16 2018Efficient and reversible optical to microwave coherent transducers are required to enable entanglement transfer between superconducting qubits and light for quantum networks. Rare-earth-doped crystals that possess narrow optical and spin transitions are ... More
Characterization of the hyperfine interaction of the excited $^5$D$_0$ state of Eu$^{3+}$:Y$_2$SiO$_5$Oct 20 2017Mar 16 2018We characterize the Europium (Eu$^{3+}$) hyperfine interaction of the excited state ($^5$D$_0$) and determine its effective spin Hamiltonian parameters for the Zeeman and quadrupole tensors. An optical free induction decay method is used to measure all ... More
Spectral hole lifetimes and spin population relaxation dynamics in neodymium-doped yttrium orthosilicateNov 16 2016We present a detailed study of the lifetime of optical spectral holes due to population storage in Zeeman sublevels of Nd$^{3+}$:Y$_2$SiO$_5$. The lifetime is measured as a function of magnetic field strength and orientation, temperature and Nd$^{3+}$ ... More
Measurement of line widths and permanent electric dipole moment change of the Ce 4f-5d transition in Y_2SiO_5 for a qubit readout scheme in rare-earth ion based quantum computingMar 04 2013In this work the inhomogeneous (zero-phonon line) and homogeneous line widths, and one projection of the permanent electric dipole moment change for the Ce 4f-5d transition in Y_2SiO_5 were measured in order to investigate the possibility for using Ce ... More
Cavity-enhanced spectroscopy of a few-ion ensemble in Eu3+:Y2O3Feb 19 2018Sep 06 2018We report on the coupling of the emission from a single europium-doped nanocrystal to a fiber-based microcavity under cryogenic conditions. As a first step, we study the sample properties and observe a strong correlation between emission lifetime and ... More
Optical Excitation of Nuclear Spin Coherence in Tm3+:YAGOct 17 2007A thulium-doped crystal is experimentally shown to be an excellent candidate for broadband quantum storage in a solid-state medium. For the first time, nuclear spin coherence is optically excited, detected and characterized in such a crystal. The lifetime ... More
Mechanism Design for Social GoodOct 21 2018Across various domains--such as health, education, and housing--improving societal welfare involves allocating resources, setting policies, targeting interventions, and regulating activities. These solutions have an immense impact on the day-to-day lives ... More
Transferability of crystal-field parameters for rare-earth ions in Y$_2$SiO$_5$ tested by Zeeman spectroscopyOct 31 2018Zeeman spectroscopy is used to demonstrate that phenomenological crystal-field parameters determined for the two $C_1$ point-group sites in Er$^{3+}$:Y$_2$SiO$_5$ may be transferred to other ions. The two crystallographic six- and seven-coordinate substitutional ... More
A comprehensive understanding of ground and optically-excited hyperfine structure of $^{167}$Er$^{3+}$:Y$_2$SiO$_5$Sep 04 2018Using high-performance computing techniques and targeted experimental investigation we have developed a predictive crystal-field model of the complex hyperfine structure of $^{167}$Er$^{3+}$:Y$_2$SiO$_5$ We simultaneously match site-selective spectroscopic ... More
Branching ratio measurement of a "Lambda" system in Tm3+:YAG under magnetic fieldJun 06 2006Dec 21 2006A three-level Lambda system in Tm3+ doped YAG crystal is experimentally investigated in the prospect of quantum information processing. Zeeman effect is used to lift the nuclear spin degeneracy of this ion. In a previous paper [de Seze et al. Phys. Rev. ... More
High-cooperativity coupling of rare-earth spins using yttrium orthosilicate as a substrateJan 10 2019Yttrium orthosilicate (Y$_2$SiO$_5$, or YSO) has proved to be a convenient host for rare-earth ions used in demonstrations of microwave quantum memories and optical memories with microwave interfaces, and shows promise for coherent microwave-optical conversion ... More
Efficient optical pumping of Zeeman spin levels in Nd3+:YVO4Feb 15 2010We demonstrate that Zeeman ground-state spin levels in Nd3+:YVO4 provides the possibility to create an efficient lambda-system for optical pumping experiments. The branching ratio R in the lambda-system is measured experimentally via absorption spectroscopy ... More
A multiplicative property of quantum flag minorsDec 19 2001We study multiplicative properties of the (quantum) dual canonical basis B* associated to a semi-simple complex Lie group G. We provide a subset D of B* such that the following property holds : if two elements b, b' in B* q-commute and if one of these ... More
Gif Lectures on Cosmic AccelerationDec 18 2009Jan 06 2010These lecture notes cover some of the theoretical topics associated with cosmic acceleration. Plausible explanations to cosmic acceleration include dark energy, modified gravity and a violation of the Copernican principle. Each of these possibilities ... More
Harmonic functions on the real hyperbolic ball I : Boundary values and atomic decomposition of Hardy spacesFeb 08 1999We study harmonic functions for the Laplace-Beltrami operator on the real hyperbolic ball. We obtain necessary and sufficient conditions for this functions and their normal derivatives to have a boundary distribution.In doing so, we put forward different ... More
Disambiguating with Controlled DisjunctionsOct 14 1997In this paper, we propose a disambiguating technique called controlled disjunctions. This extension of the so-called named disjunctions relies on the relations existing between feature values (covariation, control, etc.). We show that controlled disjunctions ... More
Weighted Paley-Wiener spaces and mountain chain axioms: a detailed expositionMay 01 2013The present work reviews the second half of Lyubarskii and Seip's paper, Weighted Paley--Wiener Spaces. Axioms defining a larger class of de Branges spaces are abstracted, allowing us to state and prove their results at a higher level of generality.
Spin dynamics in Cuprates and its relation to superconductivitySep 25 2000The relevance of magnetism for the mechanism responsible for high-temperature superconductivity remains an open and still interesting issue. The observation by inelastic neutron scattering of strong antiferromagnetic dynamical correlations in superconducting ... More
SIMBOL-X, an X-ray telescope for the 0.5-70 keV rangeOct 10 2002SIMBOL-X is a high energy "mini" satellite class mission that is proposed by a European collaboration for a launch in 2009. SIMBOL-X is making use of a classical X-ray mirror, of ~600 cm2 maximum effective area, with a 30 m focal length in order to cover ... More
Spectroscopy of Gauge Theories Based on Exceptional Lie GroupsJul 18 2001Jul 25 2001We generate by computer a basis of invariants for the fundamental representations of the exceptional Lie groups E(6) and E(7), up to degree 18. We discuss the relevance of this calculation for the study of supersymmetric gauge theories, and revisit the ... More
Finite Number of States, de Sitter Space and Quantum Groups at Roots of UnityJun 26 2003Jul 20 2003This paper explores the use of a deformation by a root of unity as a tool to build models with a finite number of states for applications to quantum gravity. The initial motivation for this work was cosmological breaking of supersymmetry. We explain why ... More
Raman Spectrometry, a Unique Tool to Analyze and Classify Ancient Ceramics and GlassesJan 15 2007Raman micro/macro-spectroscopy allows for a non-destructive remote analysis: body and glaze, crystalline and amorphous phases can be identified, including the nanosized pigments colouring the glaze. Last generation instruments are portable which allows ... More
The quantum Poincare group from quantum group contractionSep 18 1994We propose a contraction of the de Sitter quantum group leading to the quantum Poincare group in any dimensions. The method relies on the coaction of the de Sitter quantum group on a non--commutative space, and the deformation parameter $q$ is sent to ... More
The Herschel View of Star FormationSep 30 2013Recent studies of the nearest star-forming clouds of the Galaxy at submillimeter wavelengths with the Herschel Space Observatory have provided us with unprecedented images of the initial conditions and early phases of the star formation process. The Herschel ... More
Improved energy extrapolation with infinite projected entangled-pair states applied to the 2D Hubbard modelAug 17 2015May 10 2016An infinite projected entangled-pair state (iPEPS) is a variational tensor network ansatz for 2D wave functions in the thermodynamic limit where the accuracy can be systematically controlled by the bond dimension $D$. We show that for the doped Hubbard ... More
Cuspidal RobotsOct 13 2016This chapter is dedicated to the so-called cuspidal robots, i.e. those robots that can move from one inverse geometric solution to another without meeting a singular confuguration. This feature was discovered quite recently and has then been fascinating ... More
Estimation of the shift parameter in regression models with unknown distribution of the observationsDec 20 2013This paper is devoted to the estimation of the shift parameter in a semiparametric regression model when the distribution of the observation times is unknown. Hence, we propose to use a stochastic algorithm which takes into account the estimation of the ... More
Against all odds? Forming the planet of the HD196885 binaryMar 20 2011HD196885Ab is the most "extreme" planet-in-a-binary discovered to date, whose orbit places it at the limit for orbital stability. The presence of a planet in such a highly perturbed region poses a clear challenge to planet-formation scenarios. We investigate ... More
Logarithmic conformal invariance in the Abelian sandpile modelMar 18 2013We review the status of the two-dimensional Abelian sandpile model as a strong candidate to provide a lattice realization of logarithmic conformal invariance with central charge c=-2. Evidence supporting this view is collected from various aspects of ... More
Wind on the boundary for the Abelian sandpile modelJul 25 2007Jul 25 2007We continue our investigation of the two-dimensional Abelian sandpile model in terms of a logarithmic conformal field theory with central charge c=-2, by introducing two new boundary conditions. These have two unusual features: they carry an intrinsic ... More
Symmetric boundary conditions in boundary critical phenomenaApr 14 1999Jun 30 1999Conformally invariant boundary conditions for minimal models on a cylinder are classified by pairs of Lie algebras $(A,G)$ of ADE type. For each model, we consider the action of its (discrete) symmetry group on the boundary conditions. We find that the ... More
Automorphisms of the affine SU(3) fusion rulesJan 29 1993We classify the automorphisms of the (chiral) level-k affine SU(3) fusion rules, for any value of k, by looking for all permutations that commute with the modular matrices S and T. This can be done by using the arithmetic of the cyclotomic extensions ... More
Spin-1/2 frustrated antiferromagnet on a spatially anisotopic square lattice: contribution of exact diagonalizationsJul 04 2003Apr 07 2004The phase diagram of a spin-1/2 $J-J'-J_2$ model is investigated by means of exact diagonalizations on finite samples. This model is a generalization of the $J_1-J_2$ model on the square lattice with two different nearest-neighbor couplings $J,J'$ and ... More
From entangled codipterous coalgebras to coassociative manifoldsJan 09 2003We construct from coassociative coalgebras, bialgebras, Hopf algebras, new objects such as Poisson algebras, Leibniz algebras defined by J-L Loday and M. Ronco and explore the notion of coassociative manifolds.
Maximal eigenvalue and norm of the product of Toeplitz matrices. Study of a particular caseOct 29 2012In this paper we describe the asymptotic behaviour of the spectral norm of the product of two finite Toeplitz matrices as the matrix dimension goes to the infinity. These Toeplitz matrices are generated by positive functions with Fisher-Hartwig singularities ... More
High temperature Sherrington-Kirkpatrick model for general spinsOct 09 2002Francesco Guerra and Fabio Toninelli have developped a very powerful technique to study the high temperature behaviour of the Sherrington-Kirkpatrick mean field spin glass model. They show that this model is asymptoticaly comparable to a linear model. ... More
A note on rational surfaces in projective four-spaceMay 24 1999It is proved that a smooth rational surface in projective four-space, which is ruled by cubics or quartics has degree at most 12. It is also proved that a smooth rational surface in projective four-space which is the image of Fn by a linear system with ... More
Group actions, $k$-derivations and finite morphismsApr 06 2006Let $G$ be an affine algebraic group over an algebraically closed field $k$ of characteristic zero. In this paper, we consider finite $G$-equivariant morphisms $F:X\to Y$ of irreducible affine $G$-varieties. First we determine under which conditions on ... More
Homotopy invariants of higher dimensional categories and concurrency in computer scienceFeb 26 1999Feb 27 2000The strict globular $\omega$-categories formalize the execution paths of a parallel automaton and the homotopies between them. One associates to such (and any) $\omega$-category $\C$ three homology theories. The first one is called the globular homology. ... More
A Bayesian Variational Framework for Stochastic OptimizationMay 05 2019This work proposes a theoretical framework for stochastic optimization algorithms, based on a continuous Bayesian variational model for algorithms. Using techniques from stochastic control with asymmetric information, the solution to this variational ... More
Towards a homotopy theory of process algebraJan 19 2007May 15 2008This paper proves that labelled flows are expressive enough to contain all process algebras which are a standard model for concurrency. More precisely, we construct the space of execution paths and of higher dimensional homotopies between them for every ... More
Concurrent Process up to Homotopy (II)Feb 24 2003One proves that the category of globular CW-complexes up to dihomotopy is equivalent to the category of flows up to weak dihomotopy. This theorem generalizes the classical theorem which states that the category of CW-complexes up to homotopy is equivalent ... More
A Convenient Category for The Homotopy Theory of ConcurrencyJan 25 2002May 03 2005Withdrawn paper because the results are published in math.AT/0308054 and math.AT/0308063.
Computations of Nambu-Poisson cohomologiesJul 17 2000Mar 01 2001We try to generalize the Poisson cohomology of a 2-dimensional Poisson manifold to the n-vectors on a n-dimensional manifold. We define several cohomologies and we compute locally some of them, in the case of germs at 0 of n-vectors on a real or complex ... More
On the Zeta Function of a Family of QuinticsJul 21 2009In this article, we give a proof of the link between the zeta function of two families of hypergeometric curves and the zeta function of a family of quintics that was observed numerically by Candelas, de la Ossa, and Rodriguez Villegas. The method we ... More
Isotypic Decomposition of the Cohomology and Factorization of the Zeta Functions of Dwork HypersurfacesDec 10 2009The aim of this article is to illustrate, on the example of Dwork hypersurfaces, how the study of the representation of a finite group of automorphisms of a hypersurface in its etale cohomology allows to factor its zeta function.
Sur le spectre des longueurs des groupes de trianglesJan 29 2009Feb 25 2009We describe in this report the beginning of the length spectra of fuchsian triangular groups
Expression asymptotique des valeurs propres d'une matrice de Toeplitz à symbole réelDec 14 2015Sep 20 2017This work provides two results obtained as a consequence of an inversion formula for Toeplitz matrices with real symbol. First we obtain an asymptotic expression for the minimal eigenvalues of a Toeplitz matrix with a symbolwhich is periodic, even and ... More
A characterization of Fourier transformsDec 16 2009The aim of this paper is to show that, in various situations, the only continuous linear map that transforms a convolution product into a pointwise product is a Fourier transform. We focus on the cyclic groups $\Z/nZ$, the integers $\Z$, the Torus $\T$ ... More
Zero-free regions of radar ambiguity functions and momentsJun 16 2006In this article, we give an estimate of the zero-free region around the origin of the ambiguity function of a signal $u$ in terms of the moments of $u$. This is done by proving an uncertainty relation between the first zero of the Fourier transform of ... More
Uncertainty principles for orthonormal basesJun 16 2006In this survey, we present various forms of the uncertainty principle (Hardy, Heisenberg, Benedicks). We further give a new interpretation of the uncertainty principles as a statement about the time-frequency localization of elements of an orthonormal ... More
L-algebras, triplicial-algebras, within an equivalence of categories motivated by graphsSep 21 2007Apr 16 2008In a previous work, we gave a coalgebraic framework of directed graphs equipped with weights (or probability vectors) in terms of (Markov) L-coalgebras. They are K-vector spaces equipped with two co-operations, \Delta_M, \tilde{\Delta}_M verifying, (\tilde{\Delta}_M ... More
Asymptotics of the solitary waves for the generalised Kadomtsev-Petviashvili equationsFeb 21 2009We investigate the asymptotic behaviour of the localised solitary waves for the generalised Kadomtsev-Petviashvili equations. In particular, we compute their first order asymptotics in any dimension $N \geq 2$.
Fedosov Star-Products and 1-Differentiable DeformationsSep 07 1998We show that every star product on a symplectic manifold defines uniquely a 1-differentiable deformation of the Poisson bracket. Explicit formulas are given. As a corollary we can identify the characteristic class of any star product as a part of its ... More
Invariant hypersurfaces for derivations in positive characteristicFeb 15 2006Let $A$ be an integral $k$-algebra of finite type over an algebraically closed field $k$ of characteristic $p>0$. Given a collection ${\cal{D}}$ of $k$-derivations on $A$, that we interpret as algebraic vector fields on $X=Spec(A)$, we study the group ... More
Generalised Mertens and Brauer-Siegel TheoremsMar 20 2007In this article, we prove a generalisation of the Mertens theorem for prime numbers to number fields and algebraic varieties over finite fields, paying attention to the genus of the field (or the Betti numbers of the variety), in order to make it tend ... More
A Bayesian Variational Framework for Stochastic OptimizationMay 05 2019May 08 2019This work proposes a theoretical framework for stochastic optimization algorithms, based on a continuous-time Bayesian variational model. Using techniques from stochastic control with asymmetric information, the solution to this variational problem is ... More
The geometry of cubical and regular transition systemsMay 20 2014Sep 29 2015There exist cubical transition systems containing cubes having an arbitrarily large number of faces. A regular transition system is a cubical transition system such that each cube has the good number of faces. The categorical and homotopical results of ... More
Towards a homotopy theory of higher dimensional transition systemsNov 03 2010Jan 30 2014We proved in a previous work that Cattani-Sassone's higher dimensional transition systems can be interpreted as a small-orthogonality class of a topological locally finitely presentable category of weak higher dimensional transition systems. In this paper, ... More
T-homotopy and refinement of observation (IV) : Invariance of the underlying homotopy typeMay 16 2005Jun 06 2006This series explores a new notion of T-homotopy equivalence of flows. The new definition involves embeddings of finite bounded posets preserving the bottom and the top elements and the associated cofibrations of flows. In this fourth part, it is proved ... More
Homotopical equivalence of combinatorial and categorical semantics of process algebraNov 08 2007Nov 12 2007It is possible to translate a modified version of K. Worytkiewicz's combinatorial semantics of CCS (Milner's Calculus of Communicating Systems) in terms of labelled precubical sets into a categorical semantics of CCS in terms of labelled flows using a ... More
T-homotopy and refinement of observation (III) : Invariance of the branching and merging homologiesMay 16 2005Sep 20 2006This series explores a new notion of T-homotopy equivalence of flows. The new definition involves embeddings of finite bounded posets preserving the bottom and the top elements and the associated cofibrations of flows. In this third part, it is proved ... More
T-homotopy and refinement of observation (II) : Adding new T-homotopy equivalencesMay 16 2005Mar 26 2007This paper is the second part of a series of papers about a new notion of T-homotopy of flows. It is proved that the old definition of T-homotopy equivalence does not allow the identification of the directed segment with the 3-dimensional cube. This contradicts ... More
Gradient estimates for a degenerate parabolic equation with gradient absorption and applicationsAug 10 2007Qualitative properties of non-negative solutions to a quasilinear degenerate parabolic equation with an absorption term depending solely on the gradient are shown, providing information on the competition between the nonlinear diffusion and the nonlinear ... More
Embedding Dark Energy in SupergravityNov 15 2007We give a brief overview of some of the constraints on the embedding of dark energy in supergravity.
Toric degenerations of Schubert varietiesDec 18 2000Let $G$ be a simply connected semi-simple complex algebraic group. Fix a maximal torus $T$ and a Borel subgroup $B$ such that $T\subset B\subset G$. Let $W$ the Weyl group of $G$ relative to $T$. For any $w$ in $W$, let $X_w=\bar {BwB/B}$ denote the Schubert ... More
On harmonic elements for semi-simple Lie algebraDec 12 2000Let ${\goth g}$ be a semi-simple complex Lie algebra, ${\goth g}={\goth n^-}\oplus{\goth h}\oplus{\goth n}$ its triangular decomposition. Let $U({\goth g})$, resp. $U_q({\goth g})$, be its enveloping algebra, resp. its quantized enveloping algebra. This ... More
Kadath: a spectral solver for theoretical physicsSep 07 2009Jan 16 2010Kadath is a library that implements spectral methods in a very modular manner. It is designed to solve a wide class of problems that arise in the context of theoretical physics. Several types of coordinates are implemented and additional geometries can ... More
Fully Packed Loop configurations in a Triangle and Littlewood-Richardson coefficientsDec 01 2011In this work we continue our study of Fully Packed Loop (FPL) configurations in a triangle. These are certain subgraphs on a triangular subset of the square lattice, which first arose in the study of the usual FPL configurations on a square grid. We show ... More
Fully Packed Loop configurations in a triangleNov 25 2011Fully Packed Loop configurations (FPLs) are certain configurations on the square grid, naturally refined according to certain link patterns. If $A_X$ is the number of FPLs with link pattern $X$, the Razumov--Stroganov correspondence provides relations ... More
Nanomechanics of Advanced Polymer FibresOct 23 2006The micro/nano-structural evolution before and after tensile/compressive loading, fatigue and ultimately, failure has been studied by Raman (and IR) microspectroscopy for PBO, PET, PA66, PP, silk and hair using three probes: low wavenumber collective ... More
Rectangular Young tableaux and the Jacobi ensembleOct 22 2015It has been shown by Pittel and Romik that the random surface associated with a large rectangular Young tableau converges to a deterministic limit. We study the fluctuations from this limit along the edges of the rectangle. We show that in the corner, ... More
An Environmental Variation of ConstantsOct 09 2013Jun 24 2014Models of modified gravity, whereby local tests of gravity are evaded thanks to a screening mechanism of the chameleon or Damour-Polyakov types, lead to a spatial variation of the particle masses and the fine structure constant. This is triggered by the ... More
Isoparametric functions and harmonic unit vector fields in K-contact geometrySep 16 2013We provide some examples of harmonic unit vector fields as normalized gradients of isoparametric functions from a K-contact geometry setting.
Sur l'uniformisation des orbifolds Kählériens compactsFeb 20 2013This article generalises to K\"ahler orbifolds general results on uniformisation of compact K\"ahler manifolds such as the Shafarevich conjecture for linear fundamental groups.
Contextual objectivity and the quantum formalismJul 03 2004Sep 18 2004The new orthodoxy of quantum mechanics (QM) based on the decoherence approach requires many-worlds as an essential ingredient for logical consistency, and one may wonder what status to give to all these "other worlds". Here we advocate that it is possible ... More
Reconstructing the formalism of quantum mechanics in the ``contextual objectivity" point of viewNov 29 2001In a previous preprint (quant-ph/0012122) we introduced a ``contextual objectivity" formulation of quantum mechanics (QM). A central feature of this approach is to define the quantum state in physical rather than in mathematical terms, in such a way that ... More