| 1. |
- Andreasson, Håkan, 1966
(författare)
-
On gravitational collapse and cosmic censorship for collisionless matter
- 2014
-
Ingår i: International Journal of Geometric Methods in Modern Physics. - : World Scientific Pub Co Pte Lt. - 0219-8878 .- 1793-6977. ; 11:2
-
Tidskriftsartikel (refereegranskat)abstract
- The weak cosmic censorship conjecture is a central open problem in classical general relativity. Under the assumption of spherical symmetry, Christodoulou has investigated the conjecture for two different matter models; a scalar field and dust. He has shown that the conjecture holds true for a scalar field but that it is violated in the case of dust. The outcome of the conjecture is thus sensitive to which model is chosen to describe matter. Neither a scalar field nor dust are realistic matter models. Collisionless matter, or Vlasov matter, is a simple matter model but can be considered to be realistic in the sense that it is used by astrophysicists. The present status on the weak cosmic censorship conjecture for the Einstein-Vlasov system is reviewed here.
|
|
| 2. |
- Arnlind, Joakim
(författare)
-
Levi-Civita connections for a class of noncommutative minimal surfaces
- 2021
-
Ingår i: International Journal of Geometric Methods in Modern Physics (IJGMMP). - : WORLD SCIENTIFIC PUBL CO PTE LTD. - 0219-8878. ; 18:12
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, we study connections on hermitian modules, and show that metric connections exist on regular hermitian modules; i.e. finitely generated projective modules together with a non-singular hermitian form. In addition, we develop an index calculus for such modules, and provide a characterization in terms of the existence of a pseudo-inverse of the matrix representing the hermitian form with respect to a set of generators. As a first illustration of the above concepts, we find metric connections on the fuzzy sphere. Finally, the framework is applied to a class of noncommutative minimal surfaces, for which there is a natural concept of torsion, and we prove that there exist metric and torsion free connections for every minimal surface in this class.
|
|
| 3. |
- Bergman Ärlebäck, Jonas, 1972-, et al.
(författare)
-
The Bach tensor and other divergence-free tensors
- 2005
-
Ingår i: International Journal of Geometric Methods in Modern Physics (IJGMMP). - 0219-8878. ; 2:1, s. 13-21
-
Tidskriftsartikel (refereegranskat)abstract
- In four dimensions, we prove that the Bach tensor is the only symmetric divergence-free 2-tensor which is also quadratic in Riemann and has good conformal behavior. In n > 4 dimensions, we prove that there are no symmetric divergence-free 2-tensors which are also quadratic in Riemann and have good conformal behavior, nor are there any symmetric divergence-free 2-tensors which are concomitants of the metric tensor gab together with its first two derivatives, and have good conformal behavior.
|
|
| 4. |
- Bette, Andreas
(författare)
-
Twistors, special relativity, conformal symmetry and minimal coupling - A review
- 2005
-
Ingår i: International Journal of Geometric Methods in Modern Physics (IJGMMP). - 0219-8878. ; 2:2, s. 265-304
-
Forskningsöversikt (refereegranskat)abstract
- An approach to special relativistic dynamics using the language of spinors and twistors is presented. Exploiting the natural conformally invariant symplectic structure of the twistor space, a model is constructed which describes a relativistic massive, spinning and charged particle, minimally coupled to an external electro-magnetic field. On the two-twistor phase space the relativistic Hamiltonian dynamics is generated by a Poincare scalar function obtained from the classical limit (appropriately defined by us) of the second order, to an external electro-magnetic field minimally coupled Dirac operator. In the so defined relativistic classical limit there are no Grassman variables. Besides, the arising equation that describes dynamics of the relativistic spin differs significantly from the so-called Thomas Bergman Michel Telegdi equation.
|
|
| 5. |
- Harrathi, F., et al.
(författare)
-
Kupershmidt operators on Hom-Malcev algebras and their deformation
- 2022
-
Ingår i: International Journal of Geometric Methods in Modern Physics (IJGMMP). - : World Scientific. - 0219-8878.
-
Tidskriftsartikel (refereegranskat)abstract
- The main feature of Hom-algebras is that the identities defining the structures are twisted by linear maps. The purpose of this paper is to introduce and study a Hom-type generalization of pre-Malcev algebras, called Hom-pre-Malcev algebras. We also introduce the notion of Kupershmidt operators of Hom-Malcev and Hom-pre-Malcev algebras and show the connections between Hom-Malcev and Hom-pre-Malcev algebras using Kupershmidt operators. Hom-pre-Malcev algebras generalize Hom-pre-Lie algebras to the Hom-alternative setting and fit into a bigger framework with a close relationship with Hom-pre-alternative algebras. Finally, we establish a deformation theory of Kupershmidt operators on a Hom-Malcev algebra in consistence with the general principles of deformation theories and introduce the notion of Nijenhuis elements.
|
|
| 6. |
- Koivisto, Tomi S.
(författare)
-
An integrable geometrical foundation of gravity
- 2018
-
Ingår i: International Journal of Geometric Methods in Modern Physics (IJGMMP). - : World Scientific Publishing Co. Pte Ltd. - 0219-8878. ; 15
-
Tidskriftsartikel (refereegranskat)abstract
- In a talk at the conference Geometrical Foundations of Gravity at Tartu, 2017, it was suggested that the affine spacetime connection could be associated with purely fictitious forces. This leads to gravitation in a flat and smooth geometry. Fermions are found to nevertheless couple with the metrical connection and a phase gauge field. The theory is reviewed in this proceeding in a Palatini, and in a metric-affine gauge formulation.
|
|
| 7. |
- Roknizadeh, Rasoul, et al.
(författare)
-
COMPLEXIFIER VERSUS FACTORIZATION AND DEFORMATION METHODS FOR GENERATION OF COHERENT STATES OF A 1D NLHO I. MATHEMATICAL CONSTRUCTION
- 2013
-
Ingår i: International Journal of Geometric Methods in Modern Physics (IJGMMP). - 0219-8878. ; 10:10, s. 1350056-
-
Tidskriftsartikel (refereegranskat)abstract
- Three methods: complexifier, factorization and deformation, for construction of coherent states are presented for one-dimensional nonlinear harmonic oscillator (1D NLHO). Since by exploring the Jacobi polynomials P-n(a, b)' s, bridging the difference between them is possible, we give here also the exact solution of Schrodinger equation of 1D NLHO in terms of Jacobi polynomials.
|
|
| 8. |
- Zheltukhin, Aleksandr A.
(författare)
-
ON NONLINEARITY OF p-BRANE DYNAMICS
- 2012
-
Ingår i: International Journal of Geometric Methods in Modern Physics (IJGMMP). - 0219-8878. ; 9:6
-
Tidskriftsartikel (refereegranskat)abstract
- Nonlinear equations of p-branes in D = (2p + 1)-dimensional Minkowski space are discussed. Presented are new exact solutions for a set of spinning p-branes with the Abelian symmetries U(1) x U(1) x ... x U(1) of their shapes.
|
|
