Virtual Definition and 547 Threads

Please translate to English, so that it can be discussed here! I am primarily interested in how the virtual ensemble differs from an ordinary statistical ensemble, i.e., a large collection of actually identically prepared systems. The latter is the usual ensemble on which one can make...

Homework Statement A cart on an inclined plane is balanced by the weight w. All parts have negligible friction. Find the weight W of the cart using the principle of virtual work. Picture of set-up is attached.Homework Equations ∫Fdh = 0 for virtual displacement dh in statics F_p = W cos...

The following article says virtual particles don't exist or are just book keeping device. https://www.physicsforums.com/insights/physics-virtual-particles If that's the case, then how do you explain charge screening? We observe the charge of an electron to be less than the bare charge, or what...

In X-ray diffraction, during the experiment a X-ray beam will create an incident and diffracted beam, but what exactly is the virtual source? I may be mistaken but isn't the source the incident beam, in the attached image, it seems to suggest otherwise?

As much as I have understood, virtual particles keep appearing and disappearing in a vacuum state. This leads to zero-point energy, Casimir effect etc. Now, I want to know if there is a lifetime (i.e. a time limit) for which these virtual particles can exist before disappearing. Also can there...

Hello guys I'm struggling a bit with drawing momen/[M_o], to this "frame". I will be using virtual Method. So, could you you have corrected me if it's wrong?

The question here is simple; would the existence of virtual particles make the universe an open system? And if not, why? I thank all who consider this question for their time and would love to hear an answer.

Hello! How does computer download files and send files(from physical perspective, electrical engineering perspective)? Electrons, binary code, photons, electromagnetic waves... Sorry, my english knowledge is not good :D

Hi All, After three days cleaning up my computer, having downloaded a funky copy of Anaconda Python, I was hoping to get addresses for Anaconda that are known to be legit and or legit downloads for virtual boxes, so that I can install Anaconda in the box and just shut it down if there is a...

I need clarification on the difference between a virtual photon of a transmitted force and “radiated photons” of accelerated charges. Imagine two electric charges separated by a distance “d” but not moving. They exchange virtual photons which tell the electric charges to attract/repel. How are...

Hi all, Following up on another post - for a layman, can someone describe the status of virtual particles in Loop Quantum Gravity models? Since LQG avoid UV divergences, and has a different structure from field-based theories, are virtual particles still talked about? (in the context of closed...

Hi again PF. I recently came across the term "virtual inertia" when reading about photovoltaics and power converters (DC/DC, DC/AC etc.). Article: http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=6953370, not sure if people are able to view the article, I have access via university library...

Studying Lagrangian mechanics starting from D'Alembert's principle. I just ran into this. Why virtual displacement doesn't contain time t for it's coordinates What does that mean 'take place at a fixed time'?

Hi folks, I number of years ago, I asked a question about real particles interacting with virtual particles - since then, I've learned a little bit (maybe not too much :-), but I'm still curious about one thing. Original thread here...

Why must photons, for example, that carry the EM force be virtual? Is it because they are tied to gauge invariance and that is not observable? Thanks in advance.

I've been looking through the internet and I haven't found anything too clear on this: is it correct to assume a electrostatic interaction, say, between two stationary electrons as an exchange of virtual photons?

Homework Statement The book ("Real World Physics") says A virtual image in a plane mirror is on the perpendicular from the object to the mirror Homework Equations I know that the normal line is perpendicular to the surface of the mirror And I know that the angle of the incidence and reflection...

I've seen, in the description of a black hole's photon sphere, a mention of a "light-like ds." I was happy to see it because I've been thinking about a photon's physical environment; at the speed of light, it would experience no radial dimension & no time dimension. Might it make more sense to...

Hi all, I've read a number of posts on virtual particles (including one of my own), but I'm still confused about one aspect - the interaction between real and virtual particles. Say we have an electron moving from position A to position B. As the electron moves, there should be virtual...

A plane mirror forms a virtual image of a real object placed in front of it and a real image of a virtual object placed in front of it. I can't picture the second case. Please show me a ray diagram showing real image formation by a plane mirror or just explain the case of real image formation by...

I'm reading up on relativity, but it confuses me. If I observe a virtual particle pop up in empty space, what sort of average speed would that particle have? It cannot depend on my reference frame, because the particle doesn't know about that. Or perhaps it does, as my observation ties it into...

I have been reading the Quantum Diaries here http://www.quantumdiaries.org/2011/03/25/an-idiosyncratic-introduction-to-the-higgs/ and in discussing the Higgs and the LHC experiment he says "The general problem is this: at the LHC, we’re smashing protons into one another. The protons are each...

The tital pretty much explains it all? Why would this be impossible or not explain everything?

In a situation like this: What causes the particle/antiparticle pair to recombine? They obviously will have opposite charge, is there a virtual photon being exchanged between them that's omitted from Feynman diagrams? That would imply that it's mathematically irrelevant, I know than these...

I have thought about virtual reality headsets and other futuristic devices for a month now, but now I it has peaked my interest enough to ask about it on the forum. My idea for a safe virtual reality headset would be a device that is able to use a method similar to that of dreams. I thought of...

Are virtual particles of the false vacuum during inflation indistinguishable from virtual particles of the true vacuum of the present universe?

A. Neumaier submitted a new PF Insights post Misconceptions about Virtual Particles Continue reading the Original PF Insights Post.

A. Neumaier submitted a new PF Insights post The Physics of Virtual Particles Continue reading the Original PF Insights Post.

I know some people here hate the subject of virtual particles. So I will try to narrow my questions. Granted, virtual particles are just attempts to describe the math and are not real in and of themselves. But there seem to be a couple of different kinds of virtual particles (in the math)...

I do not see how (2.34) shows that forces of semi-holonomic constraints do no work in the displacements ##\delta q_k## between the varied path and the actual path. Starting from (2.31), I seem to be able to prove that such forces do do work, in contrary to what is claimed in the paragraph...

Homework Statement We have a system (see attached graphics) of two rods with length ##l## and mass ##m## and some external force ##F##. The coefficients ##k## of the two springs are given. The springs have no deformation when ##\varphi =0##. a) Find generalized force of the system. b) Determine...

Why is there no virtual work done by a rolling friction? In pure rolling, is the virtual displacement parallel or perpendicular to the surface? I believe it can't be perpendicular because the object is not allowed to lose contact with the surface. But if it's parallel, then there must be a...

If you want to show that a propagator of a heavy particle reduces to a point interaction at distances large compared to the inverse mass of the particle by Taylor expanding the propagator (for simplicity take 1-dimension): $$G(x)=\int^\infty_{-\infty} \frac{dk}{2\pi} \frac{e^{-ikx}}{k^2+M^2}=...

What´s the difference between a resonance and a virtual state? For comparison, a standard moderately lived state, hydrogen 2p state, has energy of 10,2 eV above ground, and width 4*10ˇ-7 eV. An example of resonance is Delta - with mass 1232 MeV, it´s energy is about 290 MeV above ground...

The following is taken from page 13 of Peskin and Schroeder. Any relativistic process cannot be assumed to be explained in terms of a single particle, since ##E=mc^{2}## allows for the creation of particle-antiparticle pairs. Even when there is not enough energy for pair creation, multiparticle...

(I apologize beforehand if I'm asking such an 'amateur' question , I admit that I'm not a physics student / physicist nor scientist / science student ,.. but , as just a 'normal ordinary' person, at least I am very interested in these things ,. and how I deeply wish Humanity / Mankind can 'leap...

Homework Statement Find the tension T needed to hold the cart shown (pic included) in equilibrium, no friction. Using virtual work, and force components. (I don't care about signs, just looking for the magnitude of tension with quick reasoning) (not homework, just studying virtual work)...

[FONT=UICTFontTextStyleBody]Hello, I was curiose as to if it is possible for a virtual particle to appear without its anti-mater/matter counter part. I posted a thread before asking about the existence and untimatly the "realness" of virtual particles. I concluded that they are real from the...

An object is within a glass sphere of radius R with a refractive index of 1.5 . I'm trying to calculate the displacement of the virtual object relative to the actual when viewed from the side, such that the refracted ray emanating from the object becomes horizontal. I would like to know S (the...

Hello, My question on virtual particles is quite simple but I cannot find an answer. Are virtual particles just a filler for math or do they actually come into existence?

Dear Group, I just set up a Microsoft Virtual Wifi Miniport Adapter using administration command prompt, its function as wifi hot spot, so the other devices could use this hot spot for the internet. ( ) But whenever I shutdown the computer and turn it on, I can not find it, I have to...

Do separate instances of virtual pair production interact with each other. Say you have a virtual pair production of an electron and a positron; they separate and then come back together. What happens in the event that there is another occurrence of a virtual electron/positron pair production...

Do electrons excite the EM field or do they just create virtual photons that do? If you could only see EMF excitations, would you see the electrons or virtual photons coming from the electrons?

Just as there are virtual photons, which are in the EM field, are there virtual particles in fields such as the Higgs and Strong?

Hi all, This question is similar to a question asked previously, but slightly different. I understand that there have now been attempts to extend the Broglie-Bohm, or Pilot Wave, interpretation of QM to QFT. I'm a layman, but if I understand correctly, the standard method for computing the...

Homework Statement Hello, I'm having problems determining the relationships between delta a and delta c . I don't see how how delta C = 4/9 delta A [/B] http://imgur.com/a/B6eTx Thank you.

In most of classical mechanics textbooks,the concept of virtual displacement and virtual work is not represented deeply.They just focus in how the method should be used without explaining from where this principle came and why scientists created it in the first place. So to grasp this concept...

This is just a short question, it might have been asked already but I couldn't find anything. I read that we have attempted to reconcile the Casimir force with the observed expansion of the universe, doing this, we get a number 10^120 times too big. This is obviously a bad number to say the...

Homework Statement The system shown in Fig. 2-6 is in static equilibrium. Use the principle of virtual work to find the weights A and B. Neglect the weight of the strings and the friction in the pulleys. Quick aside: This is straight out of the Exercises for the Feynman Lectures on Physics, in...

It's easy to find references which explain that the photon is the force carrying particle for the electromagnetic force (ie https://en.wikipedia.org/wiki/Force_carrier). Similarly there are force carrying particles for other forces, like W and Z bosons carry the weak force. This has always...