The vacuum tag has no wiki summary.
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de Sitter versus Minkowski QFT and cosmological constant
WMAP/Planck results confirm than we live in a de Sitter-like phase, i.e., a Universe with positive acceleration or positive cosmological constant! Therefore, I believe that a way to solve the ...
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3answers
83 views
What causes the permittivity and permeability of vacuum?
When light travels through a material, it gets "slowed down" (at least its net speed decreases). The atoms in the material "disturb" the light in some way which causes it to make stops on its path. ...
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1answer
44 views
How does a pierced vacuum move?
If a can of compressed air is pierced on the right, air pushes out, and the can moves to the left.
If a vacuum container is pierced on the right, which way does it move? Right? Left? Not at all? ...
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1answer
143 views
What happens when a piezo crystal is exposed to a vacuum?
Application of mechanical stress to a piezo crystal generates a charge.
Quoting from wikipedia, a 1 cm3 cube of quartz with 2 kN (500 lbf) of correctly applied force can produce a voltage of 12500 ...
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1answer
89 views
How important is it, really, to clean vacuum parts?
In every lab I've seen, people are quite meticulous about cleaning parts that are to be used in ultrahigh vacuum, as well as the components of the chamber itself. The parts may be put in an ultrasonic ...
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How to find out the reduction of air flow rate when the air goes to 'Y' and 'T' joints? [closed]
If I have same radius in all junctions
case I) I have 100 CFM air go to the one end of Y (120 degrees between each leg)
case II) I have 100 CFM air go to the one end of T
Since air is compressible, ...
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0answers
154 views
How is it possible the speed of light is not constant?
I was reading this article recently, which summarizes a couple of new studies into the speed of light.
In one paper, Marcel Urban from the University of Paris-Sud, located in Orsay, France and his ...
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0answers
31 views
How to find the inflow pressure and outflow pressure of blower and vacuum?
To find the outflow pressure of blower and inflow pressure of vacuum is not too difficult. Does any reference information (do not need to be too accurate) of how inflow pressure of blower relate to ...
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1answer
41 views
How does the radius and length of a pipe affect vacuum performance?
Can I use Poiseuille's equation?
Also
If I have a vacuum pump which says that its performance is 30 cubic feet per minutes and I have two pipes (one is radius R1 and L1, the other one is 2*R1 and ...
3
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1answer
47 views
What would happen if a piece of matter, in our atmosphere, were to suddenly vanish?
What would happen if an object were to suddenly disappear? I mean actually disappear, as in, the space occupied by that object were now completely empty- and a vacuum was left.
If I was holding a ...
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1answer
85 views
A water balloon in vacuum: does it boil?
If I put water in a vacuum it will boil. But what if I put this water inside a balloon ?
I searched for answers and fount this video: http://www.youtube.com/watch?v=9q8F3ClUuV0
It seams that the ...
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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 ...
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1answer
84 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
332 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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2answers
2k views
How does space affect the human body (no space suit, no space craft)
How does "outer space" affect the human body? Some movies show it as the body exploding, imploding or even freezing solid.
I know space is essentially a vacuum with 0 pressure and the dispersion of ...
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1answer
106 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 ...
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1answer
94 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$ ...
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2answers
448 views
What exists in the Space between atoms
Apologies to all if this has been asked before, I searched but was unable to find one similar.
This is a question that has been bugging me for a while that i haven't really been able to find a ...
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1answer
95 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 ...
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3answers
580 views
Anti-laser: How sure we are that energy is transported?
Reading this PE question
can-we-transport-energy-over-infinite-distances-through-vacuum-using-light, a related question arises naturally:
Is energy transported (by light)? -- (I did believed in this ...
3
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1answer
78 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
69 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? ...
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1answer
134 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 ...
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1answer
69 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 ...
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2answers
198 views
A hot object exposed to low temperature in a vacuum doesn't lose heat?
I heard somewhere that if the human body were exposed to outer space where the temperature is extremely low, the human won't actually feel cold because in a vacuum, the heat energy doesn't have ...
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5answers
309 views
Have we managed to make a perfect vacuum?
Have we managed to make a device with no ANY atom inside it on earth ?
I was reading about vacuum here : http://en.wikipedia.org/wiki/Free_space, and I found in the Examples part here : ...
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6answers
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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 ...
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0answers
125 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 ...
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1answer
216 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 ...
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1answer
796 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
195 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 ...
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2answers
196 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 ...
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1answer
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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 ...
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1answer
320 views
What is the best tool for simulating Vacuum and Fluids together?
I require a software to simulate Fluid simulation with the capability of supporting vacuum simulation. My requirements are that all numbers must reflect their real counterparts almost exactly. For ...
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4answers
519 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 ...
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2answers
180 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, ...
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1answer
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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 ...
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1answer
237 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 ...
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2answers
540 views
Does string theory have a notion of vacuum?
Does string theory have a notion of vacuum? If yes, what is known about it?
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5answers
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Is there perfect vacuum 10000 billion lightyears away?
Is there perfect vacuum about some 10,000 billion light years away?
With perfect vacuum, I mean that there are no particles, not even virtual photons!
I had this idea by assuming that all particle ...
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2answers
342 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 ...
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2answers
316 views
Creation of particle anti-particle pairs
I was reading some QFT notes and there is one point that I don't understand, they are justifying why we need QFT saying that the number of particles is not preserved once we consider special ...
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2answers
98 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?
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1answer
160 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, ...
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58 views
Refractive index outside a vacuum [closed]
Refractive index is defined as n = c/v where c is the speed of light in the vacuum and v is the velocity of the light in a given material. Therefore refractive index outside of vacuum can be any ...
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3answers
275 views
How can there be heat in a vacuum?
I keep reading in the Physics World focus issue on vacuum technology about scientists creating high temperatures in the vacuums etc.
If heat is caused by thermal energy being radiated from particles ...
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4answers
181 views
Direct exposure to the vacuum of space
I was watching a few sci-fi movies and was wondering the real science explaining what would happen if you were to be subject to the conditions of outerspace.
I read the wikipedia article on space ...
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1answer
162 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 ...
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2answers
757 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 ...
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3answers
447 views
What really goes on in a vacuum?
I've been told that a vacuum isn't actually empty space, rather that it consists of antiparticle pairs spontaneously materialising then quickly annihilating, which leads me to a few questions.
...
