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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How would the vacuum look like if no mass/energy is present in it?

The observable universe is thought to inflate faster and faster towards infinity. The energy will be diluted to zero in the far future. The influence of attractive gravity is getting smaller and ...
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How (if) is the metric of the quantum vacuum different from the metric of the classical vacuum?

The classical vacuum, with no matter or energy in it, has a flat metric. Meanwhile we know that the classical vacuum is a chimera. There are lots of things going on, eventhough its called virtual. ...
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Are the particles in the zero-energy Higgs field real or virtual?

We all know that in particle physics the vacuum state is the state with no real particles. Unless the vacuum has the least energy with particles, because the degenerate vacuum, lowest energy state ...
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Does spacetime exist without matter? [closed]

A citation of Einstein is: “It was formerly believed that if all material things disappeared out of the universe, time and space would be left. According to relativity theory, however, time and space ...
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Vacuum capillary to sample pressure at 1 atm

I've been trying to design a system to measure pressure at 1 atm using an RGA (Residual Gas Analyzer) from a vacuum. However, this is higher pressure than the RGA is used to (it likes to measure at ...
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Does the vacuum really have infinite energy density?

I said: As far as I understand it quantum field theory says that the vacuum has an infinite energy density. r/AskPhysics RedditorAbstractAlgebruh said: But wouldn't that be due to the way we do the ...
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References to superpositions of vacua states, for SSB

I would like to read more about this subject, about having an unbroken symmetric superposition of the vaccua (minimum energy state), instead of directly chosing one, for computing SSB as my teachers ...
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Is it possible the Black Holes to be pure deformations in the fabric of spacetime and not an effect of super-dense matter?

Is there any theory in the literature that supports this hypothesis that BHs in their center do not have a super-dense matter singularity but are pure deformations in the fabric of spacetime itself or ...
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Buoyancy versus viscosity

A common problem in casting is removing the air bubbles that might might be in the mold material, like plaster or resin. This is typically done by degassing--putting the mold material under vacuum to ...
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How can I model basic heat transfer in a partial vacuum?

If we imagine an object in a vacuum chamber being heated, how can this be modelled? There would be three heat flows to the object: (1) by convection/conduction of the air, (2) by radiant heat from the ...
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Free energy from the vacuum?

An electric field with an intensity of the Schwinger limit $$E=\frac{m_e^2c^3}{e\hbar} \approx 10^{18} \hbox{ V/m}$$ is strong enough to create electron-positron pairs out of the vacuum by separating ...
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Vacuum Transitions and Lorentz Symmetry Breaking

There are many "bumblebee" models 1, 2 where Lorentz invariance is violated usually resulting from a local vector or tensor field acquiring a nonzero vacuum expectation value We do not know ...
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Electromagnetic wave in vacuum - Do we have always ${\bf E}\cdot {\bf B} = 0$ and $E = cB$?

In vacuum, but not necessarily into free space, e.g. inside a waveguide, does a EM wave always fulfill the relations $${\bf E}\cdot {\bf B} = 0, \quad E = cB,$$ with $\bf E$ and $\bf B$ the electric ...
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Does the vacuum have a heat capacity ratio? Since there is nothing to 'warm' up

So the heat capacity ratio is the ratio of the heat capacity at constant pressure to heat capacity at constant volume. Since there is no pressure in the vacuum, the heat capacity ratio of the vacuum ...
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Is it true there is no dynamic pressure/impact pressure in vacuum?

If I understand correctly dynamic pressure is a kind of 'drag force' produced by a fluid on an object. Since space is empty/vaccuum this means that there is no drag force and thus no dynamic pressure. ...
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Even if the Standard Model was found to be complete and in a stable vacuum, could a transition into a false vacua and then decaying change it?

In theory (please correct me if I am wrong in any point), if our vacuum were metastable (i.e. in a "false vacuum" state), it could go through a phase transition into a stable state (a "...
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Wave function of a real scalar field in interacting quantum field theory

In interacting real scalar field theory, if I intuitively define the "wave function" of a state as $$\Psi(x)\equiv\langle\Omega|\hat{\phi}(x)|\Psi\rangle.$$ Does this wave function satisfy ...
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Could the Lorentz symmetry be theoretically broken in vacuum?

In this paper 1 which considers the possibility that the Lorentz symmetry could be broken, at page 4-5 the author says: "We now introduce a Higgs sector into the Lagrangian density such that the ...
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At what velocity and pressure will water enter a Vacuum chamber?

Assuming we have a chamber with a near-perfect vacuum, and we are at sea level. If the chamber is 4 feet long and 2 feet wide, we forced it underwater and opened a valve that was 1 inch in diameter to ...
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In QFTCS, is the indeterminacy in the local energy density due to vacuum particle-antiparticle creation?

In QFT in curved spacetime, there is an indeterminacy in the local energy density (because of the indeterminacy in defining annihilation/creation operator) if the spacetime is not stationary. Is it ...
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What is the probability distribution of the density of a random part of vaccuum?

If I understand correctly the vaccuum fluctuates and has a zero point energy. Because of Heisenberg Uncertainty principle the density of a random part of vaccuum cannot be zero. So imagine if you have ...
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Can oil "boil" in vacuum ? (Is it usable to make absolute (low) pressure measurement ?)

In order to measure vacuum absolute pressure, I thought about making a water column barometer, however, water will boil under high vacuum. Can I use oil instead ? On one side, I would expect any ...
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Does longer straw has its advantage with suction force than shorter straw?

After the pandemic, I've gotten chances to use various types of hand sanitizers with different design of bottles. Among them, I've found that the bottles with longer straws (I couldn't find the exact ...
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Defining Temperature [duplicate]

I have learnt the definition of Temperature as Temperature is defined as the average of Kinetic energy of the particles in the Object. My doubt is can't we measure the temperature near the sun as ...
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How does the wringing of gauge blocks make them stick together?

I was surprised to learn about gauge blocks and how you stick them together. The blocks have very smooth surfaces and still they stick by wringing ( https://youtu.be/2lOOl3VxOtE ). One speaks of ...
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Is it a fact that vacuum energy exists?

I have always read that vacuum energy and zero point energy are established facts of physics supported by various observations of their effects both indirectly and even directly. But I have also read ...
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Is it possible to fill the ballon or a bottle with vacuum?

Is it possible to fill the ballon or a bottle with vacuum? If so how do they do it? With a vacuum machine that sucks all the air inside the substance?
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Simple explanation on 'How vacuum is treated in the different quantum gravity theories?' And is there a theory where there is NO space without matter?

Could you please make an easy-to-understand synopsis on how the different quantum gravity theories (loop quantum gravity, causal dynamic triangulation, and the many other) treat empty space? That ...
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Can false vacuum decay (temporarily) to a new more stable false vacuum state rather than going straight to a true vacuum state?

I want to know if theoretically a false vacuum collapse/decay could lead to a new false vacuum state - a state that is (presumably more) metastable but not a true vacuum state. I assume that if this ...
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(Coleman QFT notes) Physical vacuum has no one-meson content?

I'm looking at Lecture 14 in Coleman's QFT notes. In defining the renormalized field $\phi'(x)$ corresponding to the meson field $\phi(x)$, Coleman notes first that \begin{equation*} \langle k | \phi(...
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Does time exist in vacuum? [duplicate]

The universe is known as 4D universe (3 space dims, 1 time dim). Does time exist in vacuum? coz no material there to experience time. And if not existing, the universe is just 3D in vacuum?
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What is the most massive single piece of matter created with 50% chance in the lifetime of the visible universe due to quantum vacuum fluctuations?

Quantum vacuum fluctuations are said to be able to spontaneously generate matter at a very low probability. Wikipedia (https://en.wikipedia.org/wiki/Timeline_of_the_far_future) reports a Boltzman ...
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Which of these 2 ideas is correct about a "bubble" of false vacuum decay?

The whole volume of the bubble is true vacuum. Only the surface layer of the bubble is true vacuum while the interior has turned back to false vacuum.
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Magnet spindown in a vacuum

How long will it take for a strong neodymium magnet with a mass of 1kg to spindown in free space (vacuum) due to the radiation energy loss and hence the loss of angular momentum?
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Will a body start to deform if it is accelerating very fast? [closed]

I had a question in my mind that when a body will start accelerating in outer space where there is vacuum and no other object to hit the accelerating one, then will that body start to deform? I mean ...
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Relationship between expanding space and dark energy [duplicate]

The excerpt below has been taken from a pop-science article. Dark energy is thought to be different, though. Rather than being a type of particle, it appears to behave as though it were a type of ...
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Vacuum energy and my little brother's question: "can it be used?"

I'm studying Cosmology Lectures of Prof. Leonard Susskind (no GR involved at the moment). Vacuum energy density was introduced as $\rho_0$ and related to the Cosmological Constant $\Lambda$. I know ...
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Would the Casimir effect make this perpetually rotating engine possible?

If I understand the Casimir effect right, two microscopic plates approach each other in a vacuum because the space between them is limited allowing only shorter wavelengths to arise from quantum ...
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Why are vacuum tubes in vacuum and how high vacuum has to be so that electrons can flow through it freely?

As in the title, I'm curious about electron movement through vacuum, how high vacuum has to be to make vacuum tubes work and how to calculate friction caused by air when electrons are moving through ...
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Does negative energy in Casimir effect cause repulsive gravity?

In the Casimir effect a negative vacuum energy exists between two plates. Does this cause repulsive gravity? Can this have consequences for the situation near the big bang, in relation to inflation?
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Vacuum pen manipulation of dies in viscous media [duplicate]

I'm using a vacuum pen to lift a die and manipulate it in an epoxy pool. The die is slipping off the tool as the viscosity of the epoxy may be too large. I need to design a new vacuum tool and I like ...
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Convection from rapidly evaporating liquid inside vacuum chamber?

If we have a liquid that is is being actively heated and is rapidly evaporating (let's say around 1g/s for Ag at 1500K) inside a vacuum chamber, can convection around the liquid/vapor interface occur ...
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Momentum of a gas expanding into a vacuum chamber in outer space

Consider a gas expanding adiabatically from a gas chamber through an orifice into a vacuum chamber as shown in the schematic figure. In order for significant number of gas molecules (which we refer to ...
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In a photoelectric cell, how come the electrons don't move to the higher potential through the vacuum without the need of an incident light?

I have been reading about the photoelectric effect and I have arrived at the photoelectric cell. Knowing that the air is removed from inside the cell, and assuming there's no incident light. How come ...
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How do you mathematically describe the quantum bubble?

The vacuum is filled with quantum bubbles. In a Feynman diagram this would correspond to a closed one particle propagator line, a circle, or a bubble. I'm curious how this is described mathematically. ...
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Pressure required to create enough suction to pull water up height h

I am trying to find out how much pressure needs to be added to a system to draw up water. The system is essentially a 5-gallon water bottle with a manual hand pump, like this: https://www.terapump.net/...
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How is synthesized Vacuum different from the one in the Universe?

This question is with reference to Torricelli's Vacuum Barometer which was one of the first experiments involving vacuum creation in Laboratories. The Atmospheric pressure causes a rise in the mercury ...
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QFT vacuum and the zero point energy

In a general QFT we say that the vacuum state $| \Omega \rangle$ is a state that is invariant under the poincare action, that is $U(\Lambda , a) | \Omega \rangle = |\Omega \rangle$ (wightmann axioms)....
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Is a vacuum-energy smaller than zero forbidden? Why?

Einstein's Field Equations allow for the derivation of Newton's law and this, together with the velocity profile of the stars within the galaxies and the galaxies within the galaxy clusters, leads to ...
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What is the difference between a perturbative and a non-perturbative vacuum?

What is the difference between a perturbative and a non-perturbative vacuum in quantum field theory? Is there an analog of these ideas in non-relativistic quantum mechanics?
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