Section: New Results
Algebraic representations for geometric modeling
Fitting ideals and multiple-points of surface parameterizations
Participants : Nicolàs Botbol, Laurent Busé.
Given a birational parameterization
This work is done in collaboration with Marc Chardin (University Pierre et Marie Curie).
Algebraic geometry tools for the study of entanglement: an application to spin squeezed states
Participant : Alessandra Bernardi.
In [18] a short review of Algebraic Geometry tools for the decomposition of tensors and polynomials is given from the point of view of applications to quantum and atomic physics. Examples of application to assemblies of indistinguishable two-level bosonic atoms are discussed using modern formulations of the classical Sylvester's algorithm for the decomposition of homogeneous polynomials in two variables. In particular, the symmetric rank and symmetric border rank of spin squeezed states is calculated as well as their Schrödinger-cat-like decomposition as the sum of macroscopically different coherent spin states; Fock states provide an example of states for which the symmetric rank and the symmetric border rank are different.
This is a joint work with I. Carusotto (University of Trento, Italy).
A partial stratification of secant varieties of Veronese varieties via curvilinear subschemes.
Participant : Alessandra Bernardi.
In [11] we give a partial quasi-stratification of the secant varieties of the order
This is a joint work with E. Ballico (University of Trento, Italy).
Decomposition of homogeneous polynomials with low rank.
Participant : Alessandra Bernardi.
Let
This is a joint work with E. Ballico (University of Trento, Italy).
Higher secant varieties of embedded in bi-degree
Participant : Alessandra Bernardi.
In [15] , we compute the dimension of all the higher secant varieties to the Segre-Veronese embedding of
This is a joint work with E. Ballico, M. V. Catalisano (University of Trento, Italy).
Symmetric tensor rank with a tangent vector: a generic uniqueness theorem
Participant : Alessandra Bernardi.
Let
with
This is a joint work with E. Ballico (University of Trento, Italy).
General tensor decomposition, moment matrices and applications.
Participants : Alessandra Bernardi, Bernard Mourrain.
In [17] the tensor decomposition addressed may be seen as a generalisation of Singular Value Decomposition of matrices. We consider general multilinear and multihomogeneous tensors. We show how to reduce the problem to a truncated moment matrix problem and give a new criterion for flat extension of Quasi-Hankel matrices. We connect this criterion to the commutation characterisation of border bases. A new algorithm is described. It applies for general multihomogeneous tensors, extending the approach of J.J. Sylvester to binary forms. An example illustrates the algebraic operations involved in this approach and how the decomposition can be recovered from eigenvector computation.
This is a joint work with J. Brachat and P. Comon (i3S, CNRS).
On the cactus rank of cubic forms
Participant : Alessandra Bernardi.
In this work, we prove that the smallest degree of an apolar 0-dimensional scheme of a general cubic form in
This is a joint work with K. Ranestad (University of Oslo, Norway) that will be published in 2013 in the Journal of Symbolic Computation. The preprint is available at http://hal.inria.fr/inria-00630456 .
Tensor ranks on tangent developable of Segre varieties
Participant : Alessandra Bernardi.
In [14] we describe the stratification by tensor rank of the points belonging to the tangent developable of any Segre variety. We give algorithms to compute the rank and a decomposition of a tensor belonging to the secant variety of lines of any Segre variety. We prove Comon's conjecture on the rank of symmetric tensors for those tensors belonging to tangential varieties to Veronese varieties.
This is a joint work with E. Ballico (University of Trento, Italy).
On the dimension of spline spaces on planar T-meshes
Participant : Bernard Mourrain.
In [33] , we analyze the space of bivariate
functions that are piecewise polynomial of bi-degree
On the problem of instability in the dimension of a spline space over a T-mesh
Participant : Bernard Mourrain.
In [23] , we discuss the problem of instability in the dimension of
a spline space over a T-mesh. For bivariate spline spaces
This is a joint work with Berdinsky Dmitry, Oh Min-Jae and Kim Taewan (Department of Naval Architecture and Ocean Engineering Seoul National University, South Korea).
Homological techniques for the analysis of the dimension of triangular spline spaces
Participant : Bernard Mourrain.
The spline space
This is a joint work with Nelly Villamizar (CMA, University of Oslo, Norway).
Analysis-suitable volume parameterization of multi-block computational domain in isogeometric applications
Participants : Bernard Mourrain, André Galligo.
Parameterization of computational domain is a key step in isogeometric analysis just as mesh generation is in finite element analysis. In [36] , we study the volume parameterization problem of multi-block computational domain in isogeometric version, i.e., how to generate analysis-suitable parameterization of the multi-block computational domain bounded by B-spline surfaces. Firstly, we show how to find good volume parameterization of single-block computational domain by solving a constraint optimization problem, in which the constraint condition is the injectivity sufficient conditions of B-spline volume parametrization, and the optimization term is the minimization of quadratic energy functions related to the first and second derivatives of B-spline volume parameterization. By using this method, the resulted volume parameterization has no self-intersections, and the isoparametric structure has good uniformity and orthogonality. Then we extend this method to the multi-block case, in which the continuity condition between the neighbor B-spline volume should be added to the constraint term. The effectiveness of the proposed method is illustrated by several examples based on three-dimensional heat conduction problem.
This is a joint work with Régis Duvigneau (Inria, EPI OPALE) and Xu Gang (College of computer - Hangzhou Dianzi University, China).
A new error assessment method in isogeometric analysis of 2D heat conduction problems
Participants : Bernard Mourrain, André Galligo.
In [35] , we propose a new error assessment method
for isogeometric analysis of 2D heat conduction problems. A
posteriori error estimation is obtained by resolving the isogeometric
analysis problem with several
This is a joint work with Régis Duvigneau (Inria, EPI OPALE) and Xu Gang (College of computer - Hangzhou Dianzi University, China).
On the cut-off phenomenon for the transitivity of randomly generated subgroups
Participant : André Galligo.
Consider
This is a joint work with Laurent Miclo (University of Toulouse).