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.

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2
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0answers
251 views

Vacuum to vacuum transition amplitude

I have two questions about Vacuum to vacuum transition amplitude. Can any particle stay in $|0\rangle$? I was studying this topic from Srednicki's QFT book. He writes in eq.$(6.22)$ $$\langle0|0 ...
1
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1answer
205 views

Multiple vacua vs. vev's in qft

Take a (possibly supersymmetric) relativistic quantum field theory: when we construct it, we suppose that there is a unique vacuum state $|0\rangle$ which is Lorentz invariant, vector of some Hilbert ...
4
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1answer
509 views

Can electrons move through vacuum?

I studied that electronics is the branch of physics which deals with the practical applications of moving electrons through vacuum, semi-conductors and gasses. Can electrons move through vacuum?
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1answer
274 views

maybe the universe has already 'ended'? [closed]

I aks you if this reasoning has a base in what we know of universe. There are many articles about so called "vacuum metastability event". As I understand this happens (can happen) with an enormous low ...
5
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1answer
260 views

Spontaneous symmetry breaking: How can the vacuum be infinitly degenerate?

In classical field theories, it is with no difficulty to imagine a system to have a continuum of ground states, but how can this be in the quantum case? Suppose a continuous symmetry with charge $Q$ ...
0
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1answer
111 views

Difference between $|0\rangle$ and $0$ in the context of isospin

I know this has been asked before, but I am confused having read it in the context of isospin, where the creation operators act on the "vacuum" state (representing no particles) $$a^\dagger_m|0\rangle ...
3
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1answer
241 views

Influence of air resistance in space

Consider the following situation: You are locked inside a cylindric container allowing you to move around freely without being in contact with any of the items or surfaces aboard. The container is ...
3
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3answers
91 views

What's in my box?

Let's say that I have a box which is 100% empty. I fly into the vacuum of space, open the box and close it after a certain time. Then I go back to earth and my question is.. What's in my box? ...
11
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1answer
190 views

How long will our artifacts last in moon & space?

Given all the different space probes and equipment that have been either launched into space or lying on the moon. How long will they last before they get decayed into dust or some unrecognizable ...
0
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1answer
116 views

The equilibrium temperature distribution of a pan in vacuum

If a rectangular pan has a constant and uniform temperature $T$ first, then put it in a vacuum. Considering the effect of thermal radiation, the temperature distribution of the rectangular blackbody ...
10
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6answers
3k views

Does anything exist in the intergalactic space?

I am a part time physics enthusiast and I seldom wonder about the intergalactic space. First, it is my perception that all(almost all) the objects in the universe are organized in the forms of ...
4
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0answers
283 views

Stability of the vacuum state of interacting quantum fields

"Stability" is generally taken to be the justification for requiring that the spectrum of the Hamiltonian should be bounded below. The spectrum of the Hamiltonian is not bounded below for thermal ...
6
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1answer
389 views

Defining the ground state energy of a QFT

I would like to hear of some general discussion on how is the ground state and its energy defined in QFT and how does one go about finding it. (..at least in some simple cases I have seen the use of ...
12
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1answer
1k views

How to interpret vacuum instability of Higgs potential

If the Higgs mass is in a certain range, the quartic self-coupling of the Higgs field becomes negative after renormalization group flow to a high energy scale, signalling an instability of the vacuum ...
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3answers
989 views

Can one heat up a vacuum?

I've got a question about heating a vacuum. If there were, say, a container in space, at 2.7 degrees kelvin (the typical temperature of space, if I'm not mistaken) and as empty as space (as close to ...
2
votes
2answers
461 views

Speed of light in a vacuum

I see many references to the speed of light in a vacuum implying that it is only truly a constant measurement in a vacuum. I can live with that, but what kind of vacuum? Are we still talking about ...
6
votes
1answer
322 views

Why does the echo for soundwaves hitting a vacuum come back out of phase? [duplicate]

Possible Duplicate: Phase shift of 180 degrees on reflection from optically denser medium I've read in a physics book for musicians that, when a soundwave hits a near-solid object, it ...
0
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4answers
1k views

Atoms pop out of nothing/vacuum/pre-big-bang?

I saw a great documentary last night about 'nothing'. It's about vacuums, and how if you have a total vacuum atoms will pop out of nowhere! Pretty crazy stuff. Atoms literally coming out of ...
1
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2answers
520 views

What is the expectation value of the number operator when the vacuum has a VEV?

The number operator N applied to a field whose vacuum has zero VEV gives $N|0>=0$. What if we apply it to the Higgs field? The background of this question is that in popular scientific accounts, ...
2
votes
1answer
828 views

Can traditional steam (water vapour) exist in a vacuum?

Can steam (water vapour) exist in a vacuum, and if so does it look and behave the same as in air? Let's assume the actual case is a kettle boiling in a vacuum. Note that I'm talking about a gas-less ...
2
votes
1answer
294 views

Why dynamic Casimir effect does not appear in static gravity field?

Dynamic Casimir effect tells us that a constantly-accelerated mirror should emit radiation due to interaction with vacuum. Following principle of equivalence, a similar mirror placed in static ...
12
votes
2answers
706 views

Does string theory have a notion of vacuum?

Does string theory have a notion of vacuum? If yes, what is known about it?
1
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2answers
2k views

What causes the vacuum in my bento box?

I can't think of a good title for my post, sorry about that. I've got a lunch box (called a bento box) Basically it's a plastic box with a plastic lid with a rubber rim around the lid to create an ...
1
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2answers
181 views

How can thrust be generated in space which is a vacuum?

Since thrusters have no matter to push off of, how can a spacecraft generate thrust in the vacuum of space?
3
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1answer
682 views

How to properly bake a ultra high vacuum chamber?

I need to get rid of water excess in my vacuum chamber, and for that there is the procedure of baking. In order to do that there are several things that one needs to consider, the power, heat load, ...
2
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1answer
214 views

Asynchronous generator run in vacuum chamber

what will be happen if we put asynchronous generator in vacuum chamber & run it above its synchronous speed. After reaching its over synchronous speed we will cut off electrical supply. Can it run ...
2
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2answers
958 views

can sound travel is space?

Everybody knows that sound cant travel through space, but is really valid? Here is my scenerio: Given the size of a football field's length cubed, there are two objects at two opposing sides. the ...
0
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1answer
74 views

Does reactive force require the two force involved have to have two different medium for reactive force to occur?

Does reactive force require the two force involved have to have two medium for reactive force to occur? I know the fuel-thruster is working on vacuum space, but we human could not use arm to swim in ...
2
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2answers
583 views

Why $\lambda\phi^4$ theory, where $\lambda>0$, is not bounded from below?

Why the following interaction, in QFT, $$\displaystyle{\cal L}_{\rm int} ~=~\frac{\lambda}{4!}\phi^4$$ where $\lambda$ is positive, represents a theory that is unstable (or unbounded from below as it ...
2
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0answers
140 views

How long must two surfaces be in contact for vacuum weld/cementing to occur?

Vacuum cementing apparently is far more likely in space than on a planetary surface in atmosphere. How long must two surfaces be kept in contact with each other in a vacuum for vacuum weld/cementing ...
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4answers
1k views

Is there an intuitive description of vacuum entanglement?

People often refer to the fact that the vacuum is an entangled state (It's even described as a maximally entangled state). I was trying to get a feeling for what that really means. The problem is ...
8
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1answer
1k views

Measured Higgs mass and vacuum stability

There is such a thing, called "stability bound" on mass of the Higgs boson. The basic idea (as I understand it) is that we take Higgs self-coupling, and calculate its renormalization running. And it ...
2
votes
2answers
100 views

Is there any correlation between the energy density fluctuations of two separate systems in a vacuum state?

I think the title says it all. What I am curious to find out is if there are any observable changes in the fluctuations of zero-point energy in a vacuum state system that are the consequence of ...
1
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1answer
575 views

If a container is in a vacuum state, what will inside the container?

Let say I can make the container or a bottle vacuum inside, what will actually inside? If this is not vacuum, we can say that it is fill with air, but if we make it vacuum... Will the bottle or ...
2
votes
2answers
213 views

If I lift a submerged hose over 35 feet above the water's surface, what's in the top foot?

I've been arguing with a friend about the whole "perfect vacuum" concept. He and I agree that the most powerful vacuum pump in the world couldn't pump water more than ~34 feet above the surface of a ...
4
votes
1answer
420 views

Does the vacuum energy problem of quantum field theory only occur in the Hamiltonian approach, or also in the path integral approach and in AQFT?

In a standard QFT class, you're being indoctrinated that there is the "infinite vacuum energy density problem". (This is sometimes paraphrased as the "cosmological constant problem", which is in my ...
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1answer
519 views

Resonance and Natural Vibrations in Vacuum

In my Physics textbook, it says that if two pendulums of the same natural frequency are placed next to each other and if one is set into vibration, the other starts resonating and when the first one ...
2
votes
1answer
194 views

Amount/flow rate of N2 needed to cool substrate

I'm trying to cool a substrate inside a vacuum chamber with liquid nitrogen. The substrate holder is a block of copper suspended from the top of the chamber via nylon screws (for thermal insulation). ...
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1answer
284 views

String theory landscape and false vacua

What is the multiverse of string theory? I always thought it would be from brane cosmology where there's chances for multiple collisions of the branes that can make a universe. So this "multiverse" ...
4
votes
1answer
298 views

What are the current (popular(ish)) approaches to modelling the quantum nature of spacetime at the Planck scale?

My guess at a list of them would be: spin foams, casual sets, non-commutative geometry, Machian theories, twistor theory or strings and membranes existing in some higher-dimensional geometry... ...
0
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1answer
172 views

Understanding particle's space travel

Before the discovery of dark matter, the prevailing popular understanding of Space content is that of celestial bodies (planets, stars..etc) floating in 'void' and emitting particles and waves ...
12
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2answers
2k views

Are we living in a false vacuum? Is there any way to tell?

I was thinking of the noted 1980 paper by Sidney Coleman and Frank de Luccia--"Gravitational effects of and on vacuum decay"-- about metastable vacuum states that could tunnel to a lower energy "true ...
2
votes
1answer
363 views

Calculating spacecraft water leak flow rate

A large container of heated water is floating in space. How can I calculate leak rate if a small puncture is opened? I'm assuming the water is kept at 298K and in the liquid state inside the chamber. ...
3
votes
5answers
180 views

Will a warm body naturally slowdown?

Suppose a warm body moving in an empty space with high speed. The body emits radiation based on its temperature. The protons emitted forwards of the body will have higher energy due to Doppler shift ...
0
votes
2answers
476 views

Effect of coarse vacuum on consumer electronics?

What is the long-term effects of storing materials in consumer electronics in a vacuum? Ie, plastics, electronic circuits and optical glasses?
2
votes
5answers
436 views

Can computers survive bubble nucleations?

According to string landscape theory, our vacua with a cosmological constant of $10^{-123}$ is a metastable vacua which can decay to a supersymmetric vacua with either a zero or negative cosmological ...
0
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1answer
2k views

Would a generator in vacuum/space provide electricity endlessly?

At it's simplest, electricity generation is achieved by induced voltage due to a changing magnetic field. In a vacuum in the absence of friction, would the initial spin imparted to the rotor of a ...
2
votes
1answer
1k views

Would a high-explosive in a vacuum be less harmful?

Putting aside shrapnel effects, I believe that high-explosives cause damage by producing a shockwave. How do shockwaves work in space? I've managed to convince myself that a high-explosive shockwave ...
3
votes
2answers
812 views

Who first realized the uncertainty principle allows for virtual particle pair production?

For all I've read about Quantum Field Theory I've never seen the concept of the living vacuum accredited to someone in particular. Given the importance of this very application of the uncertainty ...
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6answers
6k views

Does vacuum (empty space) exist? [closed]

Added: 5 times down vote for now! Down voter is this religion or physics, please try to explain your decision. I'm confused about this. In physics we know for a vacuum, but I think that there is a ...