Publications by Tudor Ratiu | EPFL Graph Search

Related publications (105)

Clebsch Optimal Control Formulation In Mechanics

This paper introduces and studies a class of optimal control problems based on the Clebsch approach to Euler-Poincare dynamics. This approach unifies and generalizes a wide range of examples appearing in the literature: the symmetric formulation of N-dimen ...

2011

Flexible beam in R3 under large overall motions and Asynchronous Variational Integrators

Tudor Ratiu, Yves Weinand, François Gay-Balmaz, François Marie Alain Demoures

The theory of discrete variational mechanics has its roots in the optimal control literature of the 1960's. The past ten years have seen a major development of discrete variational mechanics and corresponding numerical integrators, due largely to pioneerin ...

IABSE ETH Zurich2011

The geometric structure of complex fluids

Tudor Ratiu, François Gay-Balmaz

This paper develops the theory of affine Euler-Poincare and affine Lie-Poisson reductions and applies these processes to various examples of complex fluids, including Yang-Mills and Hall magnetohydrodynamics for fluids and superfluids, spin glasses, microf ...

Elsevier2009

Symmetry Reduced Dynamics of Charged Molecular Strands

Tudor Ratiu, François Gay-Balmaz

The equations of motion are derived for the dynamical folding of charged molecular strands (such as DNA) modeled as flexible continuous filamentary distributions of interacting rigid charge conformations. The new feature is that these equations are nonloca ...

Springer-Verlag2010

Simultaneous local normal forms of dynamical systems with singular underlying geometric structures

Tudor Ratiu

The aim of this paper is to develop, for the first time, a general theory of simultaneous local normalisation of couples (X,G), where X is a dynamical system (vector field) and G is an underlying geometric structure preserved by X, even if both have singul ...

IOP Publishing Ltd2024

Bi-Jacobi Fields And Riemannian Cubics For Left-Invariant SO(3)

Tudor Ratiu

Bi-Jacobi fields are generalized Jacobi fields, and are used to efficiently compute approximations to Riemannian cubic splines in a Riemannian manifold M. Calculating bi-Jacobi fields is straightforward when M is a symmetric space such as bi-invariant SO(3 ...

Int Press Boston, Inc2016

On the coupling between an ideal fluid and immersed particles

Tudor Ratiu

In this paper, we present finite-dimensional particle-based models for fluids which respect a number of geometric properties of the Euler equations of motion. Specifically, we use Lagrange-Poincare reduction to understand the coupling between a fluid and a ...

Elsevier2013

Extensions of Lie-Rinehart algebras and cotangent bundle reduction

Tudor Ratiu

Let Q denote a smooth manifold acted upon smoothly by a Lie group G. The G-action lifts to an action on the total space TQ of the cotangent bundle of Q and hence on the standard symplectic Poisson algebra of smooth functions on TQ. The Poisson algebra of ...

Oxford University Press2013

Lagrange-Poincare field equations

Tudor Ratiu, François Gay-Balmaz

The Lagrange-Poincare equations of classical mechanics are cast into a field theoretic context together with their associated constrained variational principle. An integrability/reconstruction condition is established that relates solutions of the original ...

2011

Noether's theorem for dissipative quantum dynamical semi-groups

Tudor Ratiu

Noether's theorem on constants of the motion of dynamical systems has recently been extended to classical dissipative systems (Markovian semi-groups) by Baez and Fong [J. Math. Phys. 54, 013301 (2013)]. We show how to extend these results to the fully quan ...

Amer Inst Physics2015

A New Lagrangian Dynamic Reduction In Field Theory

Tudor Ratiu, François Gay-Balmaz

For symmetric classical field theories on principal bundles there are two methods of symmetry reduction: covariant and dynamic. Assume that the classical field theory is given by a symmetric covariant Lagrangian density defined on the first jet bundle of a ...

2010

Invariant frames for vector bundles and applications

Tudor Ratiu, Madeleine Jotz

This paper completes a proof of the Dirac reduction theorem by involutive tangent subbundles. As a consequence, Dirac reduction by a proper Lie group action having one isotropy type is carried out. The main technical tool in the proof is the notion of part ...

Springer Verlag2012

Geometry of non-holonomic diffusion

Tudor Ratiu, Simon Hochgerner

We study stochastically perturbed non-holonomic systems from a geometric point of view. In this setting, it turns out that the probabilistic properties of the perturbed system are intimately linked to the geometry of the constraint distribution. For G-Chap ...

European Mathematical Soc2015

Singular Reduction Of Dirac Structures

Tudor Ratiu, Madeleine Jotz

The regular reduction of a Dirac manifold acted upon freely and properly by a Lie group is generalized to a nonfree action. For this, several facts about G-invariant vector fields and one-forms are shown. ...

2011

A Class of Integrable Flows on the Space of Symmetric Matrices

Tudor Ratiu

For a given skew symmetric real n x n matrix N, the bracket X, Y = XNY - YNX defines a Lie algebra structure on the space Sym(n, N) of symmetric n x n real matrices and hence a corresponding Lie-Poisson structure. The purpose of this paper is to inves ...

Springer Verlag2009

Quantum Anomalies via Differential Properties of Lebesgue-Feynman Generalized Measures

Tudor Ratiu

We address the problem concerning the origin of quantum anomalies, which has been the source of disagreement in the literature. Our approach is novel as it is based on the differentiability properties of families of generalized measures. To this end, we in ...

MAIK NAUKA/INTERPERIODICA/SPRINGER2020

Integrable G-strands on semisimple Lie groups

Tudor Ratiu, François Gay-Balmaz

The present paper derives systems of partial differential equations that admit a quadratic zero curvature representation for an arbitrary real semisimple Lie algebra. It also determines the general form of Hamilton's principles and Hamiltonians for these s ...

Iop Publishing Ltd2014

Symmetry and Symplectic Reduction

Tudor Ratiu

The use of symmetries in the quantitative and qualitative study of dynamical systems has a long history that goes back to the founders of mechanics. In most cases, the symmetries of a system are used to implement a procedure generically known under the nam ...

Elsevier2006

A multisymplectic integrator for elastodynamic frictionless impact problems

Tudor Ratiu, François Gay-Balmaz, François Marie Alain Demoures

We present a structure preserving numerical algorithm for the collision of elastic bodies. Our integrator is derived from a discrete version of the field-theoretic (multisymplectic) variational description of nonsmooth Lagrangian continuum mechanics, combi ...

Elsevier2017

Induced and coinduced Banach Lie-Poisson spaces and integrability

Tudor Ratiu

The Poisson induction and coinduction procedures are used to construct Banach Lie-Poisson spaces as well as related systems of integrals in involution. This general method applied to the Banach Lie-Poisson space of trace class operators leads to infinite H ...

2008