arXiv subjects

Lino Grama

Publications and source records attributed to Lino Grama.

44 records · Page 3Linked to original sources

arXiv2016

A numerical treatment to the problem of the quantity of Einstein metrics on flag manifolds

In this paper we employ numerical methods to study the Einstein equation \[ Ric(g)=λ\, g, \] where $Ric$ is the Ricci tensor and $λ$ is the Einstein constant, restricted to a class of full flag manifolds. These metrics describe the gravitational field of a vacuum with cosmological constant (vacuum is the case $λ=0$). In particular, we give estimates to the number of such metrics on the full flag manifolds $SU(n+1)/T^n$ for $n=4,5$, improving some classical estimatives. We also examine the isometric problem for these Einstein metrics. Our method can be applied for any fixed $n$.

math.DG↗

arXiv2016

Variational aspects of homogeneous geodesics on generalized flag manifolds and applications

We study conjugate points along homogeneous geodesics in generalized flag manifolds. This is done by analyzing the second variation of the energy of such geodesics. We also give an example of how the homogeneous Ricci flow can evolve in such way to produce conjugate points in the complex projective space $\mathbb{C} P^{2n+1} = Sp(n+1)/({U}(1)\times{Sp}(n))$.

math.DG↗

arXiv2015

A remark about mirror symmetry of elliptic curves and generalized complex geometry

In this short note we prove that in the case of elliptic curves, the isomorphism of generalized complex structure between $T$-dual manifolds described by Cavalcanti-Gualtieri coincides with the mirror map for elliptic curves described by Polishchuk and Zaslow.

math.DG↗

arXiv2014

Adjoint orbits of semi-simple Lie groups and Lagrangean submanifolds

We give various realizations of the adjoint orbits of a semi-simple Lie group and describe their symplectic geometry. We then use these realizations to identify a family of Lagrangean submanifolds of the orbits.

math.SG↗

arXiv2011

Equigeodesics on full, $G_2$ and a rank-three condition on flag manifolds

This paper provides a characterization and examples of homogeneous geodesics on full $G/T$ and $G_{2}$ flag manifolds. We discuss for generalized root systems the property of sum-zero triple of $T$-roots and give several applications of this result.

math.DG↗

arXiv2009

Global behavior of the Ricci flow on homogeneous manifolds with two isotropy summands

In this paper we study the global behavior of the Ricci flow equation for two classes of homogeneous manifolds with two isotropy summands. Using methods of the qualitative theory of differential equations, we present the global phase portrait of such systems and derive some geometrical consequences on the structure of such manifolds under the action of the Ricci flow.

math.DG↗

arXiv2009

Equigeodesics on flag manifolds

This paper provides a characterization of homogeneous curves on a geometric flag manifold which are geodesic with respect to any invariant metric. We call such curves homogeneous equigeodesics. We also characterize homogeneous equigeodesics whose associated Killing field is closed, hence, the corresponding geodesics is closed.

math.DG↗

arXiv2009

The Ricci flow of left invariant metrics on full flag manifold SU(3)/T from a dynamical systems point of view

In this paper we study the behavior of the Ricci flow at infinity for the full flag manifold $SU(3)/T$ using techniques of the qualitative theory of differential equations, in special the Poincaré Compactification and Lyapunov exponents. We prove that there are four invariant lines for the Ricci flow equation, each one associated with a singularity corresponding to a Einstein metric. In such manifold, the bi-invariant normal metric is Einstein. Moreover, around each invariant line there is a cylinder of initial conditions such that the limit metric under the Ricci flow is the corresponding Einstein metric; in particular we obtain the convergence of left-invariant metrics to a bi-invariant metric under the Ricci flow.

math.DG↗