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
85 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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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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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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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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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 ...
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1answer
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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
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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
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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 ...
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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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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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1answer
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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 ...
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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
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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
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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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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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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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1answer
130 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 ...
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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
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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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
155 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 ...
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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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5answers
575 views
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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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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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
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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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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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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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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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2answers
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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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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.
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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 ...
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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 ...
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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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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 ...
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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 ...
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2answers
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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 ...
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Is this a possible scenario for the teleportation of energy?
Ok, so I've been reading a paper (Here's the paper) published by a physicist named M. Hotta et al. recently and as far as I can tell with my limited understanding, the protocol for the teleportation ...
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1answer
138 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 ...
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2answers
108 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 ...
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Relating the deformation of Calabi-Yau metrics and the conformal quantum field theories
(v2)
As I read e.g. in this question, the nice holonomy group features of Calabi-Yau manifolds are valuable regarding supersymmetry (I suspect because it's a symmetry involving the target manifold, ...
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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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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 ...
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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). ...
