What is Virtual: Definition and 565 Discussions

In computing, a virtual machine (VM) is the virtualization/emulation of a computer system. Virtual machines are based on computer architectures and provide functionality of a physical computer. Their implementations may involve specialized hardware, software, or a combination.
Virtual machines differ and are organized by their function, shown here:

System virtual machines (also termed full virtualization VMs) provide a substitute for a real machine. They provide functionality needed to execute entire operating systems. A hypervisor uses native execution to share and manage hardware, allowing for multiple environments which are isolated from one another, yet exist on the same physical machine. Modern hypervisors use hardware-assisted virtualization, virtualization-specific hardware, primarily from the host CPUs.
Process virtual machines are designed to execute computer programs in a platform-independent environment.Some virtual machine emulators, such as QEMU and video game console emulators, are designed to also emulate (or "virtually imitate") different system architectures thus allowing execution of software applications and operating systems written for another CPU or architecture. Operating-system-level virtualization allows the resources of a computer to be partitioned via the kernel. The terms are not universally interchangeable.

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  1. A. Neumaier

    I Exploring the Differences Between Virtual and Ordinary Statistical Ensembles

    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...
  2. A

    Calculating weights on a slope using virtual work.

    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...
  3. muimerp

    On the proof of the Principle of Virtual Work

    I'm having some trouble understanding the proof of the Principle of Virtual Work for deformable bodies. I'll give below the proof that I've read, and, next, I'll remark what I'm not understanding. The first thing to remember before going through the proof is that the virtual work done by a...
  4. D

    I Virtual Particles and Charge Screening

    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...
  5. W

    In X-ray diffraction, what is the virtual source?

    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?
  6. M

    B How long can a virtual particles exist in a vacuum state?

    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...
  7. G

    Ansoft Maxwell virtual vs Lorentz force

    Hello people, I am trying to model a motor in maxwell that has an array of magnets in it , the thing is that I get the non zero forces for the magnets even when there are no excitations if I choose virtual forces , I am selecting the whole array of magnets so the computation should be for the...
  8. M

    Help with Drawing Momentum with Virtual Method

    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?
  9. Thomas Eaton

    B Virtual Particles; Making the Universe an Open System?

    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.
  10. G

    I don't know -> how does the virtual world work?

    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
  11. W

    Ref: Safe Site Request:Anaconda and Virtual Box, Please

    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...
  12. A

    I Clarification virtual photons, real photons

    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...
  13. J

    I Loop Quantum Gravity and Virtual Particles....

    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...
  14. O

    Virtual Intertia in Power Systems

    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...
  15. KT KIM

    I Study Lagrangian Mechanics: D'Alembert's Principle

    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'?
  16. A

    I 'Real particle and virtual particle interactions' Part 2....

    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...
  17. LarryS

    I Why must force-carrying particles be virtual?

    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.
  18. K

    I Virtual photons [in electrostatic interactions]

    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?
  19. RabbitWho

    Virtual image on the perpendicular

    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...
  20. Jlister

    Absolute Relativity (who needs virtual photons anyhow?)

    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...
  21. A

    I Clarify interaction between real and virtual particles....

    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...
  22. P

    Image of a virtual object by a plane mirror

    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...
  23. M

    B Virtual Particle Speed: Is It Measurable?

    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...
  24. A

    I The Higgs and virtual particles

    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...
  25. KarminValso1724

    B Could dark energy just be caused by virtual particles

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

    B What causes recombination of virtual particles?

    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...
  27. CrackerMcGinger

    How would virtual reality devices really work?

    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...
  28. Ranku

    I Virtual Particles: Inflation vs Present Universe

    Are virtual particles of the false vacuum during inflation indistinguishable from virtual particles of the true vacuum of the present universe?
  29. A. Neumaier

    Insights Misconceptions about Virtual Particles - Comments

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

    Insights The Physics of Virtual Particles - Comments

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

    I Virtual particles in Feynman diagrams and not

    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)...
  32. H

    Prove forces of semiholonomic constraints do no virtual work

    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...
  33. S

    Virtual work principle: equilibrium state of a system

    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...
  34. H

    Why is there no virtual work done by a rolling friction?

    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...
  35. J

    How does a virtual particle becomes a point interaction?

    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}=...
  36. S

    How Do Resonances Differ from Virtual States in Quantum Physics?

    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...
  37. S

    Perturbation theory, Intermediate states, Virtual particles

    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...
  38. N

    I Why teleportation, time travel, virtual reality haven't happened yet?

    (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...
  39. R

    Virtual Work to find equilibrium condition

    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)...
  40. J

    Can virtual particles exist without their counterparts?

    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 Casimir effect (i may have...
  41. T

    Displacement of virtual image problem

    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...
  42. J

    I Are virtual particles real or just math filler

    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?
  43. N

    Howto set Microsoft Virtual Wifi Miniport Adapter as default

    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...
  44. F

    A Do virtual particles interact with each other?

    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...
  45. Ryan Reed

    Do Electrons Excite the EMF or do the Virtual Photons?

    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?
  46. Ryan Reed

    Are there Virtual Particles for Every Field?

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

    De Broglie Bohm interpretation with virtual particles....

    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...
  48. CivilSigma

    Virtual Work - Determining Relations

    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.
  49. amjad-sh

    Prerequisites needed to grasp virtual displacement

    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...
  50. ComaBerenices

    Virtual Particles & the Casimir Force: Exploring the Link to Universe Expansion

    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...
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