A Matrix Model of Four-Dimensional Noncommutative Gravity (original) (raw)

Noncommutative gravity in two dimensions

Classical and Quantum Gravity, 2002

We deform two-dimensional topological gravity by making use of its gauge theory formulation. The obtained noncommutative gravity model is shown to be invariant under a class of transformations that reduce to standard diffeomorphisms once the noncommutativity parameter is set to zero. Some solutions of the deformed model, like fuzzy AdS_2, are obtained. Furthermore, the transformation properties of the model under

Some Remarks on Gravity in Noncommutative Spacetime and a New Solution to the Structure Equations

2003

In this paper, starting from the common foundation of Connes' noncommutative geometry (NCG) [1,2,3,4], various possible alternatives in the formulation of a theory of gravity in noncommutative spacetime are discussed in detail. The diversity in the final physical content of the theory is shown to the the consequence of the arbitrariness in each construction steps. As an alternative in the last step, when the staructure equations are to be solved, a minimal set of constraints on the torsion and connection is found to determine all the geometric notions in terms of metric. In the Connes-Lott model of noncommutative spacetime, in order to keep the full spectrum of the discretized Kaluza-Klein theory [5], it is necessary to include the torsion in the generalized Einstein-Hilbert-Cartan action.

Three-dimensional Noncommutative Gravity

Physical Review D, 2001

We formulate noncommutative three-dimensional (3d) gravity by making use of its connection with 3d Chern-Simons theory. In the Euclidean sector, we consider the particular example of topology T2timesRT^2 \times RT2timesR and show that the 3d black hole solves the noncommutative equations. We then consider the black hole on a constant U(1) background and show that the black hole charges (mass and angular momentum) are modified by the presence of this background.

Massive particles coupled with 2+1 dimensional gravity and noncommutative field theory

2009

Recently, it has been shown that the effective field theory of the Ponzano-Regge model with which spinless massive particles are coupled is given by three dimensional Euclidean noncommutative scalar field theory in the Lie algebraic noncommutative space [x^i, x^j]=2i kappa epsilon^{ijk}x_k (i,j,k=1,2,3) with kappa=4 pi G, where G is a gravitational constant. We examine whether there exists the relation between spinless massive particles coupled with 2+1 dimensional Einstein gravity and the Lorentzian version of the noncommutative field theory. Then, we point out that the momentum space of the spinless massive particles in 2+1 dimensional Einstein gravity is generally different from that of the noncommutative field theory, which is given by SL(2,R)/Z_2 group space.

A Noncommutative Extension of Gravity

International Journal of Modern Physics D, 1994

The commutative algebra of functions on a manifold is extended to a noncommutative algebra by considering its tensor product with the algebra of n×n complex matrices. Noncommutative geometry is used to formulate an extension of the Einstein-Hilbert action. The result is shown to be equivalent to the usual Kaluza-Klein theory with the manifold SUn as an internal space, in a truncated approximation.

Towards a noncommutative version of Gravitation

2010

Alain Connes' noncommutative theory led to an interesting model including both Standard Model of particle physics and Euclidean Gravity. Nevertheless, an hyperbolic version of the gravitational part would be necessary to make physical predictions, but it is still under research. We shall present the difficulties to generalize the model from Riemannian to Lorentzian Geometry and discuss key ideas and current attempts.

Noncommutative Geometry and Modified Gravity

2008

Using noncommutative deformed canonical commutation relations, a model of gravity is constructed and a schwarchild like static solutions are obtained. As a consequence, the Newtonian potential is modified and it is shown to have a form similar to the one postulated by Fishbach et al. to explain the proposed fifth force. More interesting is the form of the gravitational acceleration expression proposed in the modified Newtonian dynamics theories (MOND) which is obtained explicitly in our model without any ad hoc asymptions.

Introducing matter fields in model of noncommutative gravity

Facta universitatis - series: Physics, Chemistry and Technology, 2019

Theory founded on SO(2,3)* gauge symmetry. One significant feature of this approach is that gravitational field, given by the vierbein, becomes manifest only after a suitable gauge fixing and it is formally united with other gauge fields. Starting from a model of pure noncommutative gravity, we extend it by introducing fermions and Yang-Mills gauge field. Using the enveloping algebra approach and the Seiberg-Witten map we construct corresponding actions and expand them perturbatively in powers of the canonical noncommutativity parameter ???. Unlike in the case of pure noncommutative gravity, first non-vanishing noncommutative corrections are linear in the noncommutativity parameter and they describe the coupling of matter and gauge fields with gravity due to spacetime noncommutativity. This is augmented by the fact that some of these corrections pertain even in flat spacetime where they induce potentially observable noncommutative deformations. We discuss the effects of noncommutati...

Noncommutative Spacetime and Emergent Gravity

Bulg.J.Phys.35 (2008) 323-328, 2007

We argue that a field theory defined on noncommutative (NC) spacetime should be regarded as a theory of gravity, which we refer to as the emergent gravity. A whole point of the emergent gravity is essentially originated from the basic property: A NC spacetime is a (NC) phase space. This fact leads to two important consequences: (I) A NC field theory can basically be identified with a matrix model or a large N field theory where NC fields can be regarded as master fields of large N matrices. (II) NC fields essentially define vector (tetrad) fields. So they define a gravitational metric of some manifold as an emergent geometry from NC gauge fields. Of course, the pictures (I) and (II) should refer to the same physics, which should be familiar with the large N duality in string theory. The 1/N corrections in the picture (I) correspond to the derivative corrections in terms of the noncommutativity \theta for the picture (II).