# All the vacuums in physics

• B
We live in an atmosphere with pressure of 14.7 psi. People never thought of it in ancient times. We don't live in vacuum.

The higgs field is non zero too. What are the other vacuums in physics that is also none zero? Is there none where we are exposed to raw vacuum?

jedishrfu
Mentor
A classical vacuum is simply a space where there are few to no molecules floating about. There is no perfect vacuum not even in outer space.

https://en.wikipedia.org/wiki/Vacuum

The Higgs field is something altogether different from a classical vacuum. It refers to a quantum vacuum state which means the particle is in its lowest possible energy state.

In quantum field theory, the quantum vacuum state (also called the quantum vacuum or vacuum state) is the quantum state with the lowest possible energy. Generally, it contains no physical particles. Zero-point field is sometimes used as a synonym for the vacuum state of an individual quantized field.

According to present-day understanding of what is called the vacuum state or the quantum vacuum, it is "by no means a simple empty space".[1][2] According to quantum mechanics, the vacuum state is not truly empty but instead contains fleeting electromagnetic waves and particles that pop into and out of existence.[3][4][5]
https://en.wikipedia.org/wiki/Quantum_vacuum_state

So while both concepts use the term vacuums, they are very much different ideas.

A classical vacuum is simply a space where there are few to no molecules floating about. There is no perfect vacuum not even in outer space.

https://en.wikipedia.org/wiki/Vacuum

The Higgs field is something altogether different from a classical vacuum. It refers to a quantum vacuum state which means the particle is in its lowest possible energy state.

https://en.wikipedia.org/wiki/Quantum_vacuum_state

So while both concepts use the term vacuums, they are very much different ideas.
In quantum field theory, how many vacuums are there? I have thought of the following:

1. Higgs vacuum
2. Electroweak vacuum
3. QCD vacuum

Are these the only vacuums in qft? I wasn't asking about the classical vacuum.

What equations in quantum field theory prove the vacuum is Lorentz invariant?

There are many articles now such as by Gell-Mann that say Lorentz invariance is just an effective theory. If this were true, that means it is still possible for the vacuum to be like the ocean which is not Lorentz Invariant? So the equations proving Lorentz invariant could only be a temporary lower limit?