Questions tagged [vacuum]
A region of space devoid of any fluid molecules resulting in a zero pressure in ideal cases. In practice, even space has a small but finite number of molecules. In QFT, it signifies the ground state devoid of excitations/particles.
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Can vacuum shift to a higher energy level?
From this, I gather that a false vacuum can decay to a false vacuum of a lower energy. AFAIU vacuum decay is always local, propagating at the speed of light (whence the reference to the expanding ...
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How the vacuum expectation value of $\sigma$ is related to the tadpole diagram?
In Peskin & Schroeder's book, they introduce the linear sigma model with a Lagrangian (chapter 11.1,p349) $$ L = \frac{1}{2} (\partial_\mu \phi^i)^2 + \frac{1}{2} \mu^2 (\phi^i)^2 - \frac{\lambda}{...
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What do you think about linking vacuum energy to geometric entropy? [closed]
Lately I’ve been thinking about whether vacuum energy could be something that emerges from the geometry of spacetime, rather than being a fixed constant like in ΛCDM. What if, instead of treating it ...
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Implications of Reeh–Schlieder theorem for gravity
The Reeh-Schlieder theorem shows entanglement always happen in relativistic quantum theories even for vacuum states. The assumption it takes are existence of field operators and vacuum state ...
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Can there be no true vacuum and can we in principle do experiment about this?
I've searched a little bit on this site to find: (a) What does it mean for the Hamiltonian to not be bounded from below? (b) Why should energy have a lower bound but not an upper bound? (c) ...
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Does vacuum energy exist inside non-vacuums? (solids?)
I'm making a follow up version of this question because I agree with the author that [as of] 24 Feb 2022 [...] still not clear on the answer Does "vacuum" energy exist in regions of ...
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“Rock” chips in car paint [migrated]
i've been having an ongoing debate as to how and why some very, very small chips in the paint of a car are occurring. the person i disagree with is saying that they happen because the car is being ...
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Appearance of trace zero condition elsewhere in physics
I found it fascinating recently that under the general relativity equation, vacuum has zero Ricci curvature but nonzero general curvature tensor. Initially I was quite puzzled by the apparent ...
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How should we understand the vacuum in QFT?
In my understanding, the vacuum in quantum mechanics is discussed as $$|\Omega\rangle = \hat{S}|0\rangle,$$ where$ S $ modifies the vacuum state $ |0\rangle$ by applying all the disconnected Feynman ...
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Cooking ramen in a vacuum chamber
Water boils at a low temperature in a vacuum, if I put a bowl of ramen and water in a vacuum chamber, would it cook the ramen and result in cold, rehydrated ramen? Would it be as quick as boiling it ...
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Asymptotic in & out states in QFT
For any free scalar field, $\Phi(x) $, the creation operator $a^{\dagger}(p)$ is written without any time dependence or time label on it. So when it acts on the ground state $|0\rangle $, it creates a ...
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Supression of general field states in favour of the vacuum state at $T\rightarrow\infty(1-i\epsilon)$ in the derivation of the Gell-Mann & Low formula
When it comes to the computation of correlation functions from the path integral $Z$ usually the field states which the time evolution operator is sandwiched between are replaced by vacuum states. ...
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How could I model the Higgs effective potential with multiple minima?
In Higgs mass and vacuum stability in the Standard Model at NNLO, Eq. 52 gives the effective potential for the Higgs field as: $$\lambda_{\text{eff}}(h) = e^{4\Gamma(h)} \left\{ \lambda(h) + \frac{1}{(...
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Klein-Gordon-Maxwell equation
I am writing my Master's thesis on the semiclassical Klein-Gordon-Maxwell equations: $$ ((\partial_\mu + ieA_\mu) (\partial^\mu + ieA^\mu) + m^2)\phi = 0 \\ \partial_\mu F^{\mu\nu}= \partial_\...
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How does this analytic expression for the bounce action reduce to Coleman's in the thin-wall limit?
In the recent paper False Vacuum Decay Rate From Thin To Thick Walls , it is shown that in 4 dimensions, the bounce action is given by : $$S = \frac{2\pi^2 m^2}{4\eta^2}\frac{1}{6\epsilon_{\alpha}^3}\...
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