2. First Model: Oscillation of a Hubble scale Mass Particle in a Viscous Fluid
Consider any region of space in the Universe where a vacuum of space is defined by an oscillating Hubble scale mass particle (HSM) with mass,
in a fluid or vacuum of viscous damping coefficient
, where
, is the Planck mass [
3].
The damping coefficient given results from the presence of a residual Planck mass in the vacuum of space and the damping is therefore caused by a negative gravitational attraction of a HSM with the cosmic medium of a residual Planck mass.
The particle’s oscillating mass and the damping coefficient are therefore proportional to the Hubble angular frequency scale
(where
is the present Hubble constant parameter [
8],
is the density parameter [
8],
is the reduced Planck constant, and c is the constant speed of light).
Friction, or damping, slows the motion of the system and is always in a direction to oppose the motion. Due to frictional force, the velocity decreases in proportion to the acting frictional force as .
Consider the forces acting on the HSM particle; for a mass oscillating in a viscous fluid, the net force is equal to the restoring force
(where k is the force constant and
is the displacement from the initial equilibrium position) and the damping force
as,
Writing this as an equation in mass m, acceleration a, velocity v and displacement,
, we have
Using dimensional analysis, the force constant or spring constant k of a HSM particle is related to the current Hubble scale radius and the cosmological constant as, (where is the Gravitational constant).
Putting in the values of the viscous damping coefficient
and the force constant k we have,
Writing this as a differential equation [
23] in
, we obtain
This can be rewritten into the form [10, 21, 22,23]
From which the undamped angular frequency of the oscillator is given by an equation, , (Where , is the Schwarzschild radius of a HSM particle) .
The damping ratio is calculated to be, . This value of the damping ratio ζ determines the behavior of the system.
The exponential decay of the damped harmonic oscillator is given by,
The value obtained implies that space is vibrating at extremely high frequencies, potentially corresponding to the Planck time scale,, which is the smallest unit of time at any given point in space. Space-time therefore is an oscillation of tiny Planck length HSM particles.
This damped model might imply a universe that once oscillated more violently during the Big Bang and is now settling into a quieter state. In quantum gravity or string theory, the model might imply that space-time can also oscillate at tiny scales.
The concept of "space-time as a damped harmonic oscillator" is therefore a metaphorical analogy that attempts to describe the universe’s expansion and potential deceleration by comparing it to the behavior of a damped harmonic oscillator, where an oscillating system gradually loses energy over time due to friction-like forces, causing its amplitude to decrease exponentially; essentially suggesting that the universe’s expansion might be slowing down as time progresses due to some inherent "damping" mechanism.
2.1. Application of First Model to Cosmology
Let the frictional force be a repulsive gravitational force resulting from an interaction of a HSM particle with the Planck mass. Because friction or damping is always in a direction to oppose the motion, this leads to a large negative pressure within the interaction. Therefore the large negative pressure P has repulsive gravity and can lead to the observed accelerated expansion of the universe. If we consider a small area of the vacuum of space, the frictional force or repulsive gravity acting perpendicular on the area A is the negative pressure P and is given by a simple equation, .
Let the displacement of a HSM particle from its equilibrium position be given by, and its velocity by ( where , is the fine structure constant or electromagnetic coupling constant , is the Planck length and , is the angular frequency or natural frequency of a simple harmonic oscillator of a HSM particle). The displacement is known as the string length scale of a particle due to its extended nature.
The angular acceleration of a HSM particle is thus given as
, which then gives a net force on a HSM particle as
. Then Eq2 can be written as,
When the allowed calculable area for any region of space due to the foamy nature of space-time (space-time foam, [
15]) is
, we then have
Multiplying both sides by
, we obtain the modified Friedman equation as,
Where is the Schwarzschild radius of a HSM
For an accelerating expansion of the Universe, the R.H.S of the above model equation shows that, the Hubble length scale takes on a new length scale .
Still from our model, the minimum volume at the R.H.S of the equation denominator is given by . This volume is determined by the Planck area and the new Hubble scale length .
According to [
15] this is the allowed calculable volume for any region of space representing the foamy nature of space-time at small scales. The space-time foam is a result of quantum vacuum fluctuations represented by the oscillation of a HSM particle and its interaction with a Planck mass.
It is also worth noting that our model predicts cosmic acceleration at large cosmic length scales as,
Where;
, is the value of cosmic acceleration of the observable Universe. The cosmic acceleration, driven by an oscillating HSM and it’s gravitational attraction with a cosmic medium or Planck mass relics, manifests as the universe’s expansion accelerating over time, with a Hubble parameter (H) on the order of and a corresponding acceleration of roughly .
According to the equation given above,
is the acceleration due gravity or the gravitational field of an oscillating HSM particle at Planck length scales. This implies that these particles act as tiny black holes oscillating at great Planck frequencies creating space curvature and a constant gravitational field. If the cosmic medium was a residual Planck mass, then its interaction with the gravitational field would cause a repulsive force like friction which will lead to an accelerated expansion of the medium at a Hubble scale parameter
and a reduced velocity of the HSM particle of
due to damping. The acceleration of the cosmic medium is therefore given as
and is related to the gravitational field and the angular acceleration of a HSM by the equation,
This means that there is no difference between an accelerating HSM and the cosmic medium presented by a residual Planck mass. Therefore the friction force or repulsive gravity that derives an accelerated expansion of the Universe is,
This acceleration is also related to the Hubble parameter
and the Mond acceleration constant Milogram [
16,
17]
as
Where, , is the dimensionless reduced Hubble parameter. To be more precise,
It is also worth noting that the dimensionless parameter
can be expressed in terms of the physical baryon density today
and physical cold dark matter density today
as,
Notice here,
which gives a connection between cold dark matter
, dark energy
and baryon density
as,
This relation holds remarkably well for the values of , and obtained by the Planck(2018) collaborations.
Finally the dark gravity force can be expressed as,