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From quadratic Hamiltonians of polymomenta to abstract geometrical Maxwell-like and Einstein-like equations  [PDF]
Alexandru Oana,Mircea Neagu
Mathematics , 2012,
Abstract: The aim of this paper is to create a large geometrical background on the dual 1-jet space J^{1*}(T,M) for a multi-time Hamiltonian approach of the electromagnetic and gravitational physical fields. Our geometric-physical construction is achieved starting only from a given quadratic Hamiltonian function of polymomenta H, which naturally produces a canonical nonlinear connection N, a canonical Cartan N-linear connection C\Gamma(N) and their corresponding local distinguished (d-) torsions and curvatures. In such a context, we construct some geometrical electromagnetic-like and gravitational-like field theories which are characterized by some natural geometrical Maxwell-like and Einstein-like equations. Some abstract and geometrical conservation laws for the multi-time Hamiltonian gravitational physical field are also given.
Distinguished dimensions for special Riemannian geometries  [PDF]
Pawel Nurowski
Mathematics , 2006,
Abstract: The paper is based on relations between a ternary symmetric form defining the SO(3) geometry in dimension five and Cartan's works on isoparametric hypersurfaces in spheres. As observed by Bryant such a ternary form exists only in dimensions n_k=3k+2, where k=1,2,4,8. In these dimensions it reduces the orthogonal group to the subgroups H_k\subset SO(n_k), with H_1=SO(3), H_2=SU(3), H_4=Sp(3) and H_8=F_4. This enables studies of special Riemannian geometries with structure groups H_k in dimensions n_k. The neccessary and sufficient conditions for the H_k geometries to admit the characteristic connection are given. As an illustration nontrivial examples of SU(3) geometries in dimension 8 admitting characteristic connection are provided. Among them there are examples having nonvanishing torsion and satisfying Einstein equations with respect to either the Levi-Civita or the characteristic connections.
Special Riemannian geometries modeled on distinguished symmetric spaces  [PDF]
Pawel Nurowski
Mathematics , 2006,
Abstract: We propose studies of special Riemannian geometries with structure groups $H_1=SO(3)\subset SO(5)$, $H_2=SU(3)\subset SO(8)$, $H_3=Sp(3)\subset SO(14)$ and $H_4=F_4\subset SO(26)$ in respective dimensions 5, 8, 14 and 26. These geometries, have torsionless models with symmetry groups $G_1=SU(3)$, $G_2=SU(3)\times SU(3)$, $G_3=SU(6)$ and $G_4=E_6$. The groups $H_k$ and $G_k$ constitute a part of the `magic square' for Lie groups. Apart from the $H_k$ geometries in dimensions $n_k$, the `magic square' Lie groups suggest studies of a finite number of other special Riemannian geometries. Among them the smallest dimensional are U(3) geometries in dimension 12. The other structure groups for these Riemannian geometries are: $S(U(3)\times U(3))$, U(6), $E_6\times SO(2)$, $Sp(3)\times SU(2)$, $SU(6)\times SU(2)$, $SO(12)\times SU(2)$ and $E_7\times SU(2)$. The respective dimensions are: 18, 30, 54, 28, 40, 64 and 112. This list is supplemented by the two `exceptional' cases of $SU(2)\times SU(2)$ geometries in dimension 8 and $SO(10)\times SO(2)$ geometries in dimension 32.
Counterexamples of the Geometrization Conjecture  [PDF]
Sze Kui Ng
Mathematics , 2003,
Abstract: In this paper we propose counterexamples to the Geometrization Conjecture and the Elliptization Conjecture.
Splitting homomorphisms and the Geometrization Conjecture  [PDF]
Robert Myers
Mathematics , 1999, DOI: 10.1017/S0305004100004631
Abstract: This paper gives an algebraic conjecture which is shown to be equivalent to Thurston's Geometrization Conjecture for closed, orientable 3-manifolds. It generalizes the Stallings-Jaco theorem which established a similar result for the Poincare Conjecture. The paper also gives two other algebraic conjectures; one is equivalent to the finite fundamental group case of the Geometrization Conjecture, and the other is equivalent to the union of the Geometrization Conjecture and Thurston's Virtual Bundle Conjecture.
On Distinguished Curves in Parabolic Geometries  [PDF]
Andreas Cap,Jan Slovak,Vojtech Zadnik
Mathematics , 2003,
Abstract: All parabolic geometries, i.e. Cartan geometries with homogeneous model a real generalized flag manifold, admit highly interesting classes of distinguished curves. The geodesics of a projective class of connections on a manifold, conformal circles on conformal Riemannian manifolds, and Chern--Moser chains on CR--manifolds of hypersurface type are typical examples. We show that such distinguished curves are always determined by a finite jet in one point, and study the properties of such jets. We also discuss the question when distinguished curves agree up to reparametrization and discuss the distinguished parametrizations in this case. We give a complete description of all distinguished curves for some examples of parabolic geometries.
Distinguished Varieties  [PDF]
Jim Agler,John McCarthy
Mathematics , 2005,
Abstract: A distinguished variety is a variety that exits the bidisk through the distinguished boundary. We show that Ando's inequality for commuting matrix contractions can be sharpened to looking at the maximum modulus on a distinguished variety, not the whole bidisk. We show that uniqueness sets for extremal Pick problems on the bidisk always contain a distinguished variety.
Completion of the Proof of the Geometrization Conjecture  [PDF]
John Morgan,Gang Tian
Mathematics , 2008,
Abstract: This article is a sequel to the book `Ricci Flow and the Poincare Conjecture' by the same authors. Using the main results of that book we establish the Geometrization Conjecture for all compact, orientable three-manifolds following the approach indicated by Perelman in his preprints on the subject. This approach is to study the collapsed part of the manifold as time goes to infinity in a Ricci flow with surgery. The main technique for this study is the theory of Alexandrov spaces. This theory gives local models for the collapsed part of the manifold. These local models can be glued together to prove that the collapsed part of the manifold is a graph manifold with incompressible boundary. From this and previous results, geometrization follows easily.
Diffeomorphism-invariant Covariant Hamiltonians of a pseudo-Riemannian Metric and a Linear Connection  [PDF]
J. Mu?oz Masqué,M. Eugenia Rosado María
Physics , 2011,
Abstract: \noindent Let $M\to N$ (resp.\ $C\to N$) be the fibre bundle of pseudo-Riemannian metrics of a given signature (resp.\ the bundle of linear connections) on an orientable connected manifold $N$. A geometrically defined class of first-order Ehresmann connections on the product fibre bundle $M\times_NC$ is determined such that, for every connection $\gamma $ belonging to this class and every $\mathrm{Diff}N$-invariant Lagrangian density $\Lambda $ on $J^1(M\times_NC)$, the corresponding covariant Hamiltonian $\Lambda ^\gamma $ is also $\mathrm{Diff}N$-invariant. The case of $\mathrm{Diff}N$-invariant second-order Lagrangian densities on $J^2M$ is also studied and the results obtained are then applied to Palatini and Einstein-Hilbert Lagrangians.
Parametrizing distinguished varieties  [PDF]
Jim Agler,JOhn E. McCarthy
Mathematics , 2005,
Abstract: A distinguished variety is a variety that exits the bidisk through the distinguished boundary. We look at the moduli space for distinguished varieties of rank (2,2).
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