Gravitational induction is a property of gravitational
field to cause rotation of matter in a changing flux, of gravitomagnetic field
in general relativity, and of gravitational torsion field in Lorentz-invariant
theory of gravitation
and covariant theory of gravitation.
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One of the four equations of Lorentz-invariant theory of
gravitation (see also gravitomagnetism
and Maxwell-like gravitational equations)
has the following form: [1]
where:
According to (1), after a
change in time of there appear circular field (rotor) of
, having the opportunity to lead matter in rotation.
If the vector of torsion
crosses a certain surface
, then we can calculate the flux of this
field through this surface:
where –
the vector normal to the element of surface
.
Let’s take the partial derivative in equation (2) with respect to time
with the minus sign and integrate over the surface, taking into account the
equation (1):
In the integration was used Stokes' theorem, replacing
the integration over a surface of the curl of vector on the integration of this
vector over the boundary of the surface. In the right side of (3) is a term, equal to the work on transfer of a unit
mass of matter on closed path , bounding the surface
. By analogy with electromagnetism, this
work could be called gravitomotive force.
In the middle of (3) is time derivative of the
flux
. According to (3),
gravitational induction occurs when the flux of field through a certain surface changes and is expressed in occurrence of
rotational forces acting on particles of matter.
Gravitational induction can be regarded as gravitational
analogue of the law of electromagnetic induction. [2]
[3] [4]
Just as in electromagnetism, there are two different cases
of gravitational induction. In the first case the flux is
changed due to variable
with a constant flow surface, bounded by a loop.
In the second case, the torsion remains constant, but the flux
changes due to changes in the area occupied
by the matter of the loop. For example, consider rubber hose filled with liquid
and arranged in a closed rectangular loop in the torsion field
. Let the three sides of the loop are
fixed, while the fourth side extends with speed
, increasing the area of the loop. Since
the flux
through the loop changes, the liquid in the
hose begins to circulate. The direction of motion of the fluid will be such
that torsion field
of the fluid will be sent in the
same direction as initial torsion field created the circulation of fluid (this
is contrary to the Lenz's_law in electromagnetism).
The second case, with expanding of the loop, can also be
considered using the expression for full gravitational force:
where:
From (4) for the unit mass,
located only in torsion field , should:
The integral of field strength (5) around the contour of the loop gives gravitomotive force, as the work of
gravitational force on the displacement of unit mass. This integral will be:
where is
the vector describing change in the area of the loop during time
, arises due to the movement of one side
of the loop
in the direction of velocity
.
Expression (6) is the rate of change of the flux of
torsion field when the contour of the area changes. Comparing (3), (5) and (6) we find for the induced field strength: . Thus, during of changing the flux
liquid inside the hose comes in motion and
begins to circulate in the direction specified by the vector of induced field strength
. Gravitational induction regards to the matter of the hose too, so that if
the hose is not attached, it will rotate synchronously together with its
contents.
At first glance, it is unclear
why the effect of gravitational induction in the form of rotation of matter is caused
by two different phenomena - either a change in amplitude of torsion field, or
a change in area of the circuit through which the torsion field passes. The
answer can be found in the article, [5] where the integral equations
of electromagnetic field in curved space-time were considered. In this article,
it is shown that electromotive force in the circuit is determined by the
strength of vortex electric field, which occurs when magnetic flux through the
circuit changes. With regard to the electric field strength, it is known that
it can arise when vector potential of electromagnetic field changes over time,
which is what happens when magnetic field in the circuit changes over time. If
any part of the circuit begins to move and cross the magnetic field lines, then
an electric field strength arises in this part of the circuit, regardless of
whether there are electric charges in the circuit matter or not. This follows
from transformation of electromagnetic field tensor components from a
stationary reference frame to a moving reference frame associated with the
moving part of the circuit. Thus, in a conducting circuit that changes its area
due to compression or stretching, an electromotive force of electromagnetic
induction arises, and an explanation with the Lorentz force is not required.
Hence, in view of similarity of electromagnetic and gravitational phenomena,
the effect of gravitational induction becomes clear.
The theory of phenomena of gravitational induction can be
explained also by means of differential quantities. [6]
If we assume that the flux of torsion field instead of (2) is determined by the
expression , where
is the vector of a certain small
area, and torsion
is homogeneous in this area, then the rate of change of the flux of torsion
field can be written:
Substituting (1) and (6):
From this, taking into account (3) in the general case
follows:
so in the case of changing of field
torsion , or in the case of changing of vector of
area
when contour is intersecting the torsion
field, the flux of torsion field is changing and gravitomotive force is
creating. When the vector of area is changing gravitomotive force arises in the
sides of the loop, which move at the speed
crossing lines of torsion field. The direction
of the force acting on matter of the loop is determined by vector product
.
In covariant theory
of gravitation (CTG) gravitational stress-energy tensor has the form: [6] [7]
,
where –
speed of light,
– gravitational
constant,
– metric tensor, and gravitational tensor is calculated through
gravitational
four-potential
as
follows:
.
In weak field approximation, when the curvature of
spacetime can be set almost equal to zero, the equations of CTG become close to
equations of Lorentz-invariant theory of
gravitation. This causes the wave equations [8] [9] for potentials of gravitational field ( –
scalar potential,
–
vector potential), and for field strength
and torsion (gravitomagnetic) field
. In stationary case, the wave equations
of gravitational field become Poisson's equations of classical physics. In this
approximation time-like components of gravitational stress-energy tensor can be written explicitly:
– energy density of gravitational
field,
, where index
and
is the vector of energy flux density of gravitational field or Heaviside vector.
Negative energy density and energy flux lead to unique
property inherent to gravitational field. This property lies in the fact that
the gravitational effect of induction between two masses under certain
conditions is not damped, and may increase in amplitude, as in systems with
positive feedback. For example, if two bodies are attracted by gravitation and
rotate in the same direction, then the change of potential energy of
gravitational field will transform into
rotational energy of the bodies through gravitational induction. Thus, the
bodies will rotate each other, increasing torsion field around them.
Described mechanism is proposed to explain the nuclear
forces between nucleons in atomic nuclei in gravitational
model of strong interaction. [6] With proper arrangement of nucleons
in nucleus due to the gravitational induction nucleons spin up to a maximum
angular velocity. The result is a repulsive force of nucleons spins (in gravitoelectromagnetism these forces are
called gravitomagnetic forces) of such magnitude that are enough to compensate
the force of attraction of the nucleons from the field of strong gravitation. In such evaluating of
the forces acting in atomic nuclei, is used strong
gravitational constant.[10]