In my attached work, I have come to the conclusion that space-time are equivalent to oscillating energy. One cannot talk about space-time alone. For example, when you talk about wavelength and period, you must have the energy wave in background. In this sense space-time are imaginary. What people call empty space is really a state of energy without any oscillation or motion which does not interact with any matter. This state cannot be called energy. So I call this the unmanifest. When the unmanifest begins to move it gives out elemantary particles which we call energy. In my opinion, the speed and spontaneous symmetry breaking are related to Bose-Einstein condensate theory. As the particles from hot big bang cool, their speeds drop due to collision and one form of particle condense into another form which acquire mass due to conversion of their kinetic energy into potential energy. This is how all particles acquire their mass. Not by swimming in Higgs field. This is discussed in my another article "Periodic quantum gravity and cosmology."

Article Periodic relativity: Basic framework of the theory

Please read the paper, may be helpful for you.  A new approach to the correction of

Galilean transformation.

Dear Sheng

I think there is more considerable relationship between mass and energy in relation E=mc^2. For example, in pair production, properties of electron and positron (also their interaction) transfers of photon structure to fermions.

E= mc2 only applies to systems where momentum is not significant. Einstein knew this.

Since about 1911 the more complete form was predicted and later verified in every experiment for 5 decades. Albert Einstein and Max Planck created it, but Paul Dirac proved it Is relativisticly invariant. A great many accelerator experiments confirmed it to be exact, and relativisticly invariant, but only one equation of an incomplete set..

E2= (mc2)2 + (pc)2

Also the companion equation was found.

pc = E (v./c)

There is the fundamental equation derived from definitions when vectors v and p are in the same direction.

dE =  v dp

Still there is at least one missing equation which I try to provide in my articles.

The energy momentum equation is familiar and widely accepted for high speed particles. I cover some aspects of it in my articles. Paul Dirac used it to predict positron with negative energy. Later positron was discovered but with positive energy. In fact the equation has more than two solutions which lead to speculation of negative mass and negative energy which are not found anywhere.

Another form of same energy momentum equation can be used to infer the additional results you asked about.

E2= [ (mc2) + (pc) ]2   -  2  (mc2) (pc)2 

First momentum energy increases faster than total energy does. It implies the unpopular truth that mass energy {mc2} decreases under acceleration.

Second when combined with the companion equations, mass will decrease if light speed increases and conversely.

Third the mass energy applies to creation of particle interactions and creation of particle pairs, as well as induced mass equivalents in dynamic systems and electromagnetic fields. This area needs original research with experiments to sort out which predictions can occur and which are false answers originating in the math.

Dear Jerry

Thank you for interesting comment.

Motion is an intrinsic property of physical existence. But there is a problem about concept of acceleration in theoretical physics.

Newton and Einstein define the acceleration regardless of the structure of particles (in classical mechanics and relativity). This definition belongs to Newton era or macroscopic level era. It should be noted that the interaction between large objects (e.g. collision of two bodies) under the action of the quantum layer (in fact sub quantum level) has been done. Thus, according to quantum mechanics and mass–energy equivalence E=mc^2, we must redefine acceleration. It means we should review the relativistic Newton's second law.

https://www.researchgate.net/publication/280491440_Reconsidering_relativistic_Newton%27s_second_law_and_its_results?ev=prf_pub

https://www.researchgate.net/publication/279185909_Graviton_and_Newton%27s_second_law?ev=prf_pub

Article Reconsidering relativistic Newton's second law and its results

Article Graviton and Newton's second law

There was a problem with the concept of velocity and acceleration in theoretical physics concerning reference frame for relative measurement. Problems have been resolved  in reference to the Doppler shifting of cosmic background microwaves clearly defining an unambiguous frame to measure velocity and acceleration.

Einstein argued against a preferred reference for velocity and acceleration. He died in 1955 before background microwaves were discovered in 1964. Some scientists still hold to the Einstein point of view. Others accept the proof from quantum mechanics, entanglement, and cosmology that sometimes he was wrong.

I have published several articles about high speed and acceleration with no reluctance to claim microwave reference, and no objections from readers. Velocity and acceleration are essential to complete the set of equations for energy and momentum.

Dear Jerry

You mean cosmic background microwaves is an absolute inertia reference frame?