Vacuum Definition and 1000 Threads

Hi pf, i have been wondering what differentiates QED Vacuum from QCD Vacuum? How would u explain its implications? I mean, how can u define pure vacuum in 2 ways?

friction -- exists in a vacuum? Is it possible for friction to take place in a vaccum?

i have been pondering something. this is it: if a fellow had a tube with a plunger in it, like a syringe but without an opening for a needle or such. say the plunger is at the bottom of the tube. If you start to pull/raise it, it is my understanding that the force required to lift it would be...

Coulomb’s (electric force, electrostatic) constant (symbol κ (kC, ke)) is a proportionality constant, expressed as: κ ≡ kC ≡ ke = 1/(4πε0) = 8987551787.36818 N•m2/C2 (exactly) κ can also be derived from lightspeed squared divided by ten million (c2/107)... Can someone please help me...

I think I sort of know the answer but I'm still wondering how I can achieve what I want to achieve. I basically want to use the stored 'work' in the compressed air can to pressurize a different container and while doing so, taking in particulates from the ambient air to be contained into the...

Hello. Currently I am doing a test on a vacuum heat treatment machine and came up with an unsolved problem for the past 2 months. I am out of clue and I’m here to hear everyone's opinion. Below are the steps what I did. 1) Vacuum chamber pumped down to 4.5E-04 Pa (Rotary + Mechanical booster...

I am slightly confused on how do we calculate vacuum expectation values of product of creation and annihilation operators for bosons, e.g. ##\langle 0| a_{k_1} a^\dagger_{k_2} a_{k_3} a^\dagger_{k_4} |0 \rangle## If i commute ##k_3## and ##k_4##: $$\langle 0| a_{k_1} a^\dagger_{k_2}...

Let us assume there is a single atom in a vacuum chamber which is kept at near absolute zero. Now assume the system is closed and that the chamber is large enough such that the atom cannot diffuse far enough to reach the walls. Neglecting other stochastic effects, what do you think the atom's...

I'm a fresher in PF. If I'm posting indecently, please forgive.. Vacuum is something empty. It contains nothing. Then why should it have properties like permeability, permittivity etc.?

This isn't home work, just a curiosity question and I'm obviously under qualified to find the answer. Looking to approximate how the amount of of vacuum in inches of Hg negate the affects of atmospheric pressure in regards to acceleration. We all remember when David Scott let loose the...

Hello everyone! Just something I was thinking about today that I haven't been able to shake. I recently read that space is not actually a perfect vacuum, but that it contains low density particles, plasma, electromagnetic fields and so on. Is 'hard vacuum' the correct definition, or is it...

okay, here goes. Electron A moves through a vacuum. There are quantum fluctuations ocurring all the time, some generate electron positron pairs, which we'll call B. Electron A travels past these. Surely chared Electron A should interact with and lose energy to B electrostaticly in analoge to a...

Since Omega-lambda is very close to Omega-matter, what could it mean if we assume they are exactly equal to each other. Also, let's assume they were always equal since coincident problem is unnatural.

1.does antiparticles really travels backwards in time or is it just used to describe feynman diagrams and diracs negative energy states. 2.what does vacuum really means physically is it just a state in the fock space from which other particle states are created or it really means something...

Hi! I've seen it stated that because of Lorenz and translational invariance \langle 0| \phi(x) |0 \rangle has to be a constant and I wondered how to formally verify this?

Does the shape of the Higgs potential change if the energy of the vacuum changes? According to Wikipedia, If a more stable vacuum state were able to arise, then existing particles and forces would no longer arise as they presently do. Different particles or forces would arise from (and be...

I read that the mass of the Higgs boson is such that we may be living in an unstable vacuum state, and if a region of the universe tunnels to a lower energy vacuum state, and eventually the whole universe would be in that lower energy state (ending life on earth). Do physicists have guesses...

What do you think of the article published in the "European Physical Journal D" with the title: "The quantum vacuum as the origin of the speed of light" ? http://link.springer.com/article/10.1140%2Fepjd%2Fe2013-30578-7

hello, I have build a vacuum chamber out of an acrylic cylinder. I can get down to 50 micron but if I turn off the vacuum motor the chamber does not keep its atmosphere (air getting in) What i did is add a high quality valve between the chamber and motor. Sunk everything in an oil bath...

I am interesting in searching several options to catch big size wafer, 1 meter X 2 meter, the wide of this wafer is very thin, only 120 micro meter, the challenge is that it is forbidden to touch the wafer because we don't want to put some finger prints or scrap the wafer, and the mission is to...

I am curious to know if anyone knows if the following experiment has ever been conducted? If not, can anyone theorise what the result may be? 2 flasks A,B are of equal size. Flask A contains a vacuum. Flask B is entirely full of mercury, with no air present. To ensure that the effect of external...

I have some questions about the matrix <0|j^{\mu}_5|\pi(p)>=if_{\pi}p^{\mu} 1.Pi is a psuedoscalar particle, but the current between vacuum and pi state is an axial one, why not a psuedoscalar one? And how do we determine the current appearing in the similar matrix like <0|j|meson>...

Spontaneous symmetry breaking: 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 is spontaneously broken, that...

I am working on a computer simulation for an undergraduate capstone project. In the simulation I am trying to model an experiment done by Moseley and Harling in 1913 described in the paper The Attainment of High Potentials by the Use of Radium found in the Proceedings of the Royal Society of...

I have an anemometer that I bought that does not have the ability to put in the ID of the orifice I am trying to measure. In this case it is a 4.5 inch orifice-stays the same for me 95 percent of the time. Does anyone know how I convert the reading manually so that I can get an accurate...

Hello! The question refers to the supposed tachyons. Many experiments have been conducted based on cosmic ray studies with the following assumption: " If particles with u>c exist then they should emit Cherenkov radiation in vacuum. Thus... Let's detect it!" How can this argument stand...

The gravitational acceleration in vacuum varies with latitude, elevation, and local inhomogeneities in the Earth's crust. Use the following equation to find g in Lawrence based on a latitude of λ=38°57' ±3' and an elevation of H=259±10m. Calculate the uncertainty using the total difference.g =...

Various news outlets are reporting a AAAS talk by Joe Lykken which appears to be about vacuum instability based on the mass of the Higgs. Frustratingly, there appears to be no info on the web apart from these crap popularizations. Can anyone provide any insight? The best info I have is the...

Need to find out how much force would it take to pull up 650 gallons of water into a tank from the bottom by sucking out the air from the top of the tank? Also how much vacuum pressure would be inside tank once full? I am basing this off an upside down fish tank. Example on youtube or...

http://cosmiclog.nbcnews.com/_news/2013/02/18/17006552-will-our-universe-end-in-a-big-slurp-higgs-like-particle-suggests-it-might?lite There are several news sites saying the discovery of the higgs boson indicates that the universe is a 'false vacuum' but they're very light on the details...

New here and very much out of my element being on ANY physics forum but here it goes anyway. I am a beekeeper in S. E. NC. I sell honey from my hives and donate the proceeds through my NC Non-Profit. These proceeds go to chordomafoundation.org. Nearly all beekeepers feed their bees at some...

Homework Statement Two closed systems of the same size, temperature, and pressure. One is filled with pure nitrogen the other an atmospheric mix (nitrogen/oxygen/etc...throw in some moisture). I want to evacuate both systems to 500 microns using equally sized vacuum pumps. Why will the...

Homework Statement Condensed/simplified problem statement \vec{E} = f_{y}(x-ct)\hat{y} + f_{z}(x-ct)\hat{z} \\ \vec{B} = g_{y}(x-ct)\hat{y} + g_{z}(x-ct)\hat{z} \\ All the f and g functions go to zero as their parameters go to ±∞. Show that gy = fz and gz = -fy Homework Equations \nabla...

Hello everyone, Could someone help me with the following question: I'm trying to find out the equations that govern this process; why if you condense steam in a cylinder is a partial vacuum created (such as in early steam engines)? The pressure difference then causes the atmosphere to push...

Hey, I came across this idea a couple of years ago. It's been a long time since I took introductory physics. But I'm curious as to whether this is feasible. If I'm crazy, just say so! See attached image. 1. Intake tube, vacuum chamber and condenser are initially filled with water. Valve (A)...

I'm not exactly sure how a vacuum works. I understand that there are machines (motors?), as in a vacuum cleaner, that suck air. There are other vacuum designs though, if I am not mistaken. It is these that I am not sure about. So how do these work?

Homework Statement What is the likely main residual gas constituent of a high vacuum system (HV) (P~1x10-4 Pa) and where does it come from? Explain how the vacuum may be improved to give ultra-high vacuum (UHV) (P~1x10-8 Pa). What is the likely main residual gas constituent of ultra-high...

Hi what constitutes a vacuum? I mean it has to be made of something, since it it part of the space time continuum. In school you learn that a vacuum is empty space or area without matter, but it occurs to me that a vacuum must be made of something and there must be something there. What is it...

Assume you have a weightless constant volume container "filled with" vacuum. If you let it float in the atmosphere, how "high" would it go? I guess at some point Archimedes' principle should fail. What do you think?

I would like to try and set up a pressure control system in my lab using house vacuum and compressed air. Or otherwise using a compressed air source and vacuum pump. I want to be able to control the pressure in a reservoir (a syringe) within the range of -15 to +15psi. I was thinking...

Hi guys. I was wondering, what happens to the temperature of a object if it's put into vacuum? Say you have a box of steal (something that transfers thermal energy fast between the inside and outside). Inside the box you have a rock. The rock is held in the center of the box using...

Homework Statement I am trying to derive the line element for this geometry. But I am not sure how to show that ds can't contain any crossterms of d\theta and d\phi Homework Equations ds must be invariant under reflections \theta \rightarrow \theta'=\pi - \theta and \phi...

Homework Statement What is the de Broglie wavelength of a neutron that has fallen 0.60 in a vacuum chamber, starting from rest? Homework Equations Not entirely sure λ=h/mv The Attempt at a Solution I can't figure out what the velocity is, I think it would have to do with the change...

Homework Statement So, I was sitting in my algebra based college physics class and we were talking about buoyancy. According to Archimedes' Principal, "an object that is completely or partially submerged in a fluid experiences and upward force equal to the weight of the fluid displaced."...

hello, i have no bubbles in distillation of phenylacetone under vacuum, the heat is about 120c, and the vacuum pump produce around 20 torr. is that normal? please help me

Hi, I am using Hartle to study GR and at one point, there is a leap that I don't understand. He finds the result for the geodesic deviation equation and introduces the Riemann curvature tensor. Then, we are told that there is an object called the Ricci curvature tensor which is a...

Homework Statement An atom H has a charge +q (=proton) and -q(=electron). q = 1,6.10^-19. The electron is circeling around the proton at r distance r = 0,53.10^-10m. What is the force as a result of the electrostatic interaction between the proton and electron Homework Equations...

hi to everyone, i have the following question, see attached image. a vertical pipe containing water is exactly 28ft tall. at the top (A) the pipe is tight shut. at the bottom (B)the pipe is open and ends in a bowl of water. since no air can enter the pipe, the water remains within the pipe...

Hi We can derive equation \nabla.D=\rho_f from equation \nabla.E=\rho/\epsilon_0. But what about Ampere's law? I tried to derive \nabla\times{H}=J_f+\partial{D}/\partial{t} from \nabla\times{B}=\mu_0J+\epsilon_0\mu_0\partial{E}/\partial{t} but I could not. This is strange because I thought...

I always thought that the quantum vacuum was absolutely nothing. But I have heard that the quantum vacuum is not nothing and contains energy although it is the lowest state of energy. I am not talking about the fluctuations rather I am talking about the vacuum itself. Also do quantum...