Search results for "Invariant"

Rationally integrable vector fields and rational additive group actions

2016

International audience; We characterize rational actions of the additive group on algebraic varieties defined over a field of characteristic zero in terms of a suitable integrability property of their associated velocity vector fields. This extends the classical correspondence between regular actions of the additive group on affine algebraic varieties and the so-called locally nilpotent derivations of their coordinate rings. Our results lead in particular to a complete characterization of regular additive group actions on semi-affine varieties in terms of their associated vector fields. Among other applications, we review properties of the rational counterpart of the Makar-Limanov invariant…

Anisotropy Influences on the Drug Delivery Mechanisms by Means of Joint Invariant Functions

2017

In the frame of Higuchi’s type functionality, this paper presents the anisotropy influences on the drug delivery mechanisms through the joint invariant functions to the simultaneous actions of the two SL(2R) isomorphic groups. Then, a new equation for drug delivery mechanism, independent of the type of polymer matrix and/or drug, is proposed.

Some topological invariants for three-dimensional flows

2001

We deal here with vector fields on three manifolds. For a system with a homoclinic orbit to a saddle-focus point, we show that the imaginary part of the complex eigenvalues is a conjugacy invariant. We show also that the ratio of the real part of the complex eigenvalue over the real one is invariant under topological equivalence. For a system with two saddle-focus points and an orbit connecting the one-dimensional invariant manifold of those points, we compute a conjugacy invariant related to the eigenvalues of the vector field at the singularities. (c) 2001 American Institute of Physics.

Quel che resta del linguaggio. Diversità delle lingue e pratiche di significazione

2011

Invarianti topologici e grammatiche universali

2006

Le nozioni di "invariante linguistico" e "universale di linguaggio" sono all'origine di numerose tensioni irrisolte nella riflessione epistemologica di tanti linguisti e filosofi della linguistica. Le ragioni principali di queste tensioni sono principalmente riconducibili ad alcuni rilievi critici così formulabili: 1)la nozione di invariante linguistico non è automaticamente riducibile alla nozione di universale di linguaggio. Gli invarianti con cui il linguista lavora sono solitamente invarianti "locali" ossia schemi operativi esclusivamente generalizzabili a gruppi specifici di lingue storico-naturali; 2) vi sono senz'altro degli invarianti che sono universali, ma si tratta di identità pr…

Relation Between the State of a System as Isolated and as Open

2020

We discuss the differences in considering the description of a system as isolated or as a subsystem of a wider isolated system. In the latter case, a description in terms of a density operator directly arises without involving probability concepts, but as an orbit invariant. The non-probabilistic physical interpretation of the density operator is mathematically discussed.

Persistence of Asteroids After a Close Encounter

1999

We present here a first approximation to the planar circular restricted 2 + 2 problem. In this four body problem, we consider that the two secondaries do not affect the primaries but they do influence each other. It can be seen as a model for near collision orbits of two asteroids if the primaries are the Sun and Jupiter ([3], [5]). In particular, we analyze the values of the Jacobi constant of the two asteroids before and after the close approach.

Differential branching fraction and angular analysis of the decay $B^{0} \to K^{*0} \mu^{+}\mu^{-}$

2013

The angular distribution and differential branching fraction of the decay B-0 -> K*(0)mu(+)mu(-) are studied using a data sample, collected by the LHCb experiment in pp collisions at root s = 7 TeV, corresponding to an integrated luminosity of 1.0 fb(-1). Several angular observables are measured in bins of the dimuon invariant mass squared, q(2). A first measurement of the zero-crossing point of the forward-backward asymmetry of the dimuon system is also presented. The zero-crossing point is measured to be q(0)(2) = 4.9 +/- 0.9 GeV2/c(4), where the uncertainty is the sum of statistical and systematic uncertainties. The results are consistent with the Standard Model predictions.

Approximate renormalization-group transformation for Hamiltonian systems with three degrees of freedom

1999

We construct an approximate renormalization transformation that combines Kolmogorov-Arnold-Moser (KAM)and renormalization-group techniques, to analyze instabilities in Hamiltonian systems with three degrees of freedom. This scheme is implemented both for isoenergetically nondegenerate and for degenerate Hamiltonians. For the spiral mean frequency vector, we find numerically that the iterations of the transformation on nondegenerate Hamiltonians tend to degenerate ones on the critical surface. As a consequence, isoenergetically degenerate and nondegenerate Hamiltonians belong to the same universality class, and thus the corresponding critical invariant tori have the same type of scaling prop…

Extending the sGLOH descriptor

2015

This paper proposes an extension of the sGLOH keypoint descriptor [3] which improves its robustness and discriminability. The sGLOH descriptor can handle discrete rotations by a cyclic shift of its elements thanks to its circular structure, but its performance can decrease when the keypoint relative rotation is in between two sGLOH discrete rotations. The proposed extension couples together two sGLOH descriptors for the same patch with different rotations in order to cope with this issue and it can be also applied straightly to the sCOr and sGOr matching strategies of sGLOH. Experimental results show a consistent improvement of the descriptor discriminability, while different setups can be …