In this paper, we introduce a vector model to describe gravitational field. The model is based on the assumption that the gravitational mass is Lorentz invariant . We introduce a non- relativistic equation system to describe the gravitational field, then we generalize it to obtain a relativistic equation system . dent | TẠP CHÍ PHÁT TRIÉN KH CN TẬP 9 Số 4-2006 A VECTOR MODEL FOR GRAVITATION FIELD Vo Van On Department of physics University of Natural Sciences VNU- HCM Manuscript Received on December 01st 2005 Manuscript Revised March 2 th 2006 ABSTRACT In this paper we introduce a vector model to describe gravitational field. The model is based on the assumption that the gravitational mass is Lorentz invariant. We introduce a non- relativistic equation system to describe the gravitational field then we generalize it to obtain a relativistic equation system . 1. INTRODUCTION It is known that free fall acceleration gravitation acceleration is the same for all bodies at the same observation point. This is the Galileo s law of free fall and its generalization is the proportion between inertial mass mi and gravitational mass mg of a body. We also know that inertial mass mi is dependen -t on each inertial frame of reference in which it is measured. Is gravitational mass dependent on the frame of reference The weak equivalent principle identifies mg with mi so mg is also dependent on each inertial frame of reference. In fact all experiments confirming proportion between inertial and gravitational mass were realized only for macro objects at rest and micro particles which slowly moved. There are not any experiments which confirm that gravitational mass is dependent on velocity. In this model we recognize that gravitational mass is Lorentz invariant and also has two signs as electrical charge. A question is arisen that whether inertial mass of a particle with negative gravitational mass is positive or negative . The weak equivalent principle affirms that it is negative. But if there were some form of matter with a negative inertial mass how would it behave The first insight is that it would move in a direction opposite to that in which it is pushed. So if we have a body with the negative inertial mass and we push it . apply a force to the right it will move . accelerate to the left. .
