In general relativity, the pressure term can also be defined in terms of mass.
Physicists and astronomers have a sense of rejection of negative mass (energy), so they use a trick to introduce negative pressure, but if you look at the essence ~
P = - ρ, the pressure term of the vacuum energy, suggests that the pressure P is the energy density -ρ, and its dimension is the energy density. That is, the mass term. Though scholars use the word negative pressure to make it seem like this is not a negative energy, but the essence of negative pressure is the energy(mass) density of the negative.
Dimensional analysis reveals its essence.
Energy and mass are equivalent except for the proportional constant. The same relationship holds for negative energy and negative mass.
As exchemist already explained ~
$$
{E^2} = {({m_0}{c^2})^2} + {(pc)^2}
$$
Solution is ~
$$
{E_ + } = + \sqrt {{{({m_0}{c^2})}^2} + {{(pc)}^2}} = + m{c^2}
$$
$$
{E_ - } = - \sqrt {{{({m_0}{c^2})}^2} + {{(pc)}^2}} = - m{c^2}
$$
1. The solution of the negative mass was abandoned because physicists had the wrong stereotype.
All this time, the field of Physics did not seriously consider the possibility of existence of negative mass (energy) in a general state. The standard explanation of negative mass is that the state of low energy is stable when a negative energy level exists and that the lowest state of energy is minus infinity. Thus, this means that all positive mass emits energy and it will transit to the energy level of minus infinity and the universe will collapse.
However, at the present, our universe exists without collapsing, so the explanation for this has become strong proof of the nonexistence of the negative mass and negative energy level of.
However, this logic is wrong.
One of physics' fundamental principles, "lower energy state is associated with stability" can be only applied to positive mass. However, both negative mass and negative energy level have been denied, as it has been wrongly applied to negative mass.
Figure 1. When there is negative mass in potential which has a point of maximum value and a point of minimum value.
$$
\begin{array}{l}
\vec F = - {m_ - }\vec a\\
({m_ - } > 0)
\end{array}
$$
$$
\vec a = - \frac{{\vec F}}{{{m_ - }}}
$$
When negative mass exists within potential with maximal and minimal points, different directions of force and acceleration should be considered for negative mass.
The acceleration of negative mass is opposite to the direction of force. Therefore, the negative mass has harmonic oscillation at the maximum point and it is also stable at the maximum point.
In the case of positive mass, it was stable at the minimum point at which energy is the low. However, in case of negative mass, stable equilibrium is a point of maximum value, not a point of minimum value.
It is stable at a low energy state in the case of positive mass. However, it is stable at a high energy state in the case of negative mass.
Due to this, "the problem of transition to minus infinite energy level" does not occur, therefore negative mass(energy) and positive mass(energy) can exist stably in our universe.
2. In the discovery of accelerated expansion of universe in 1998, negative mass and negative energy were the first result of the field equation.
From the discovery of the accelerating expansion of the universe, people generally claim the existence of cosmological constants or vacuum energy. However, by borrowing their logic, the accelerating expansion of the universe can be interpreted as evidence for the existence of negative mass.
However, since those who received the first result had the wrong stereotype of negative mass and negative energy, so they rather modified the field equation to their taste. They resurrected the cosmological constant and modified the equation.
Nobel lecture by Adam Riess
https://www.nobelprize.org/mediaplay...ex.php?id=1729
Refer to 10m : 50s ~
Negative Mass?
Actually the first indication of the discovery!
Days later… What does this mean?
There cannot be negative mass, but would Einstein’s Cosmological Constant explain this acceleration?
Removing his prejudice and looking at the facts, the universe is accelerating expansion, this suggesting that negative mass (density) exists or a positive cosmological constant exists.
But what if they had a problem because they had the wrong knowledge of negative mass or negative energy levels?
From the observance of the HSS team and SCP team in 1998, they gained the mass density of the negative, using field equation (and Friedman eq. and acceleration eq. ) which do not have the cosmological constant.
The first findings were as follows:
HSS(The High-z Supernova Search) team :
SCP(Supernova Cosmology Project) team :
This is the originally value they got. They were surprised at the results, and thus revived the cosmological constant.
Anyway, negative mass (negative energy) is a valid solution for accelerating expansion of the universe.
However, the two teams concluded that negative mass could not exist in our universe. So they revised the field equation by inserting the cosmological constant.
We have to know that not the field equation has disposed the value, but our stereotype disposed that value.
What if he was a P.A.M. Dirac, who trusted more of the results from the formula than he himself? Did he just throw the result of the equation?
And
we have to know that negative logic of negative energy(mass), which is the root of stereotype, is wrong.
Moreover, we considered vacuum energy as the source of cosmological constant
, but the current result of calculation shows difference of
times between the two(observation value and calculation value), which is unprecedented even in the history of Physics.