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In field theory, there are two vacua. The non-perturbative vacuum $|\Omega\rangle$ and the vacuum of the free theory $|0\rangle$. The wikipedia article makes reference to $|\Omega\rangle$ in terms of $|0\rangle$ and its excitations. The true vacuum is annihilated by the (dressed) annihilation operators, and can be thought of perturbatively in terms ...

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This is how brake boosters on cars work. The check valve will obviously leak slowly over time, but it can last several minutes, perhaps hours, and a better-designed system could likely last longer depending on your application. There's no such thing as "vacuum" in some tangible sense. Vacuum is just a relatively lower pressure, and pressure tends to go from ...

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Smoothed particle hydrodynamics (SPH) is a fluid simulation approach that has been initially developed for astrophysics fluids (galaxies, nebula, exploding stars...), showing huge range of possible "densities", and embedded in ambient vacuum. see https://en.wikipedia.org/wiki/Smoothed-particle_hydrodynamics

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A vacuum cleaner motor is a fan that spins very fast and has vanes on it. The vanes spin the air and the air is thrown to the outside by centrifugal force. This creates a large flow of air but the pressure is limited. Since the centrifugal action requires air to be flowing through the fan, this type of pump will stall if the airflow drop below a certain ...

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If the valve is totally effective, then yes, the pressure will remain low. The pressure of a gas is a measure of how much force its particles exert on the container it's in, over a given area. The pump removes many of the particles, so the force they collectively exert goes down; it stays down as long as no new particles enter.

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