I am sorry. I apologize for my poor English.
Below explanation is answer for Marcoen's questions. Please refer to below answer.
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Question1: For example, if one would apply contact forces to a body with negative inertial mass (assuming there is such a thing in a world where also positive inertial mass exists). If I would push such a body away from me, it would accelerate towards me, or not? Doesn't this sound so implausible that we can dismiss the idea of negative inertial mass? I would be interested in your thoughts about this.
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Answer: For gravity, there is the influence of attractive force between objects with the same signs, but it does not come into existence, when applying this to electromagnetic force as it is. Charges with the same signs exchange repulsive force with each other, although this phenomenon is very weird, considering the case of gravity.
Most of people have strong aversion of negative mass, but no law of physics says there is only positive mass in nature.
I think that implausible phenomena in nature are phenomena against physical laws such as the law of conservation of energy or momentum, not our thoughts.
We are necessary to watch carefully the fact that sort of physical laws such as law of energy conservation or law of conservation of momentum do not deny negative mass.
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Question2 : In your essay you write that "negative mass has repulsive effects towards each other so it cannot form any structure". However, two bodies with negative inertial mass and like electrical charges would attract each other: the Coulomb force on the first charged particle, exerted by the second equally charged particle, is directed away from the second particle, so the first particle would accelerate towards the second because of its negative inertial mass. So why would atomic structures (e.g. hydrogen-like) be impossible in a universe?
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Answer : As examined the equation of motion for negative mass, it is marked in form of F = -ma(m > 0), when attraction is applied together with nuclear force(when usually nuclear force is attraction, but has the form of repulsive core), and assuming nuclear force has the form of F = -Q(r) r^, Q(r) is the function of distance r, thus nuclear force is in the form of attraction worked in the direction of -r^. Because they form a binding structure together, regardless of the form of force~
Here, for the force worked on negative mass m,
F = - ma = - Q(r) r^
a = (Q(r)/m) r^
The term of acceleration is positive, so the effect of increasing distance r, namely repulsive effect appears. This means that negative mass hard to form the structure like atom(massive nucleon, baryon, particle consists of multi elementary particle), because nuclear force has not binding negative mass when it is applied to negative mass. Also, gravity has not binding negative mass (repulsive).
We have to open up a lot of possibilities about negative mass(energy) and also, consider the possibility that negative mass does not make electromagnetic interaction.
In a particular case, negative mass can form the structure such as atoms, but in general, it seems it is difficult for it to form a large-scale structure like stars or galaxies.
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Question3 : If small particles with negative inertial mass would exist everywhere in the universe, would not we then observe a constant incoming flow of these particles on earth?
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Answer : In my article,
If negative mass and positive mass were came into being together at the beginning of universe, since positive mass has attractive effects with each other, so it forms stars and galaxy. In addition, negative mass has repulsive effects towards each other so it cannot form any structure and may spread out almost uniformly across the whole area of universe.
Therefore, positive masses and negative masses are completely offset in the whole universe, but there is a local area where positive masses exist more than negative masses.
Owing to the effect of negative mass and positive mass, negative mass disappears near massive positive mass structures (such as the galaxy and galaxy clusters, etc.) after meeting positive mass. However, negative mass, which came into existence at the beginning of universe, can still exist in a vacuum state outside of general galaxy.
The current structure of the galaxy is a structure that survived in the pair-annihilation of positive mass and negative mass and, since negative mass existed outside of this galaxy structure, therefore it has not been observed at the Earth.