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. L

    Klein Gordon & spacelike/timelike virtual photon

    Homework Statement See attachment. Homework Equations The Attempt at a Solution So I have shown that the plane wave sol'n satisfies the Klein-Gordon equation by subbing in and reducing the equation to: E^2 = p^2c^2 + m^2c^4 which reduces to: E = pc for an m = 0...
  2. aleksbooker

    How do you calculate the location of the third virtual image?

    Homework Statement Two 3.0m wide mirrors meet at a corner. Taking the corner as the origin of the x/y axis, A red ball is placed at point A (-1m, -2m). 1) How many images are seen by an observer at point O? [Point O is not given coordinates, but looks to be at approximately (-3m, -3m)]...
  3. M

    Demonstrating Propagator is Virtual

    Hello, I've been given a problem which is asking me to flesh out a calculation. The calculation is word for word like this; So I am being asked to work this out in detail, fill in all the steps. I thought that maybe I should try and show that the four momentum squared is not conserved at...
  4. C

    Troubleshooting a Virtual Work Problem

    https://www.physicsforums.com/attachment.php?attachmentid=65907&stc=1&d=1390369310 I've been stuck on doing my revision on this problem. The equation of the virtual work, from what I deduce is [du = 0] -Pdx + mg dh However the answer given is...
  5. S

    Hamilton's Principle and the Principle of Virtual Work

    I understand that accepting Hamilton's principle will yield identical results as accepting Newton's laws. However, simply accepting that the integral of the difference between kinetic and potential energies is an extrema seems not intuitively obvious. The textbook that I used for my classical...
  6. G

    Momentum exchange of virtual pions

    I know that the strong force is viewed as the exchange of virtual pions between two nucleons, with the mass and range of them confirmed by the energy-time uncertainty principle. But if the momentum of the pion is transferred from one nucleon to the other in the interaction, wouldn't that give an...
  7. Q

    Optics question: converging lens with virtual object

    Hi everyone, I was thinking about an optics question in a physics textbook. I think the solutions I saw in the solution manual may be wrong. The question is: When you do the calculations using 1/p + 1/q = 1/f you find that the lens first creates an image 400 cm to the...
  8. P

    Virtual boxes mirror reflection

    Homework Statement Finding lightpaths with given starting and ending points via one or more mirrors. In those kind of problems you try image someone pointing a laser with a very narrow beam at a certain direction to the mirror, so it will reach point B. For example: You are seeing a square...
  9. P

    Which virtual cells look the same as the basic cell?

    Homework Statement Above is the basic cell drawn with an object inside of it. You look in top view of the basic cell and the space around it filled with virtual cells. You can see the top view of a basic cell (the square [that is marked blue] formed by the four real mirrors with a...
  10. P

    Virtual cells of mirror reflections

    Homework Statement Please note that this is an extension of this question here: https://www.physicsforums.com/showthread.php?p=4571995#post4571995**Questions** Mirrors A and B with the space between them, including the bird, are part of the real world. Those are all a part of a basic cell...
  11. P

    Virtual source at the back of the mirror

    Homework Statement What is meant by this: "When mirroring a source in a plane mirror, it looks like the rebounding light rays come from a virtual source at the back of the mirror." I will illustrate this with a question: The figure shows a light source A, from an ordinary light bulb, that...
  12. D

    Photons as virtual particles in High energy

    Hi, So i can accept that photons are virtual particles for the electromagnetic force but i have a question. Considering two stationary point charges. There are photon-like particles exchanged between them to produce the force? If so then placing a double slit between them should create some...
  13. M

    Virtual displacement vs. differential displacement

    So what exactly is the difference between these two things? I understand their individual uses perfectly well, I think (or perhaps hope), but I'm a little unclear on what exactly a virtual displacement is. is it just a sort of imagined displacement that can't really occur, while a differential...
  14. A

    Can Anyone Solve the Virtual Memory Issue in COMSOL?

    I have been asking for years how to fix the virtual memory issue in COMSOL. I have 32Gb of memory, and it will use more virtual memory than RAM when there are at least 25Gb of RAM unused. Does anyone have a fix for this? I'm using 64 bit COMSOL
  15. C

    What's with 'virtual' phonons in BCS pairing?

    Can someone explain why virtual phonons are necessary to explain BCS pairing in type I superconductors. I thought phonons originated with the lattice vibrations. I read that it s the 'virtual" phonons that explains the pairing; how so? what am I missing ?
  16. J

    When do I need to use virtual work in writing the equations of motion?

    I'm studying for our comprehensive exam . I just need to clarify something. So the equation of motion for lagrangian dynamics is \frac{d}{dt}\frac{\partial L}{\partial\dot{q}_{i}} = \frac{\partial L}{\partial {q}_{i}} However, in my notes there are example which uses the principle of virtual...
  17. M

    Destruction of virtual particles and virtual particle pairs

    I'm trying to understand the process that destroys particles very shortly after they "appear". I have read that they are usually annihilated by a virtual antiparticle, much in the same way as can happen to real particles. However, is this always the case? And if so, is it an intrinsic property...
  18. T

    Virtual work of constraint forces

    On a rigid body we usually use the formula δL=F*δP to calculate virtual work. My problem is about the force. This kind of force exists only before the contact. If I imagine a movement δP of the constrained body outside ,in the free space, I will have δL≥0 but as soon as P moves the force F...
  19. F

    What makes virtual particles separate and come together?

    So virtual particles are supposed to pop into and out of existence because the uncertainty principle dictates a non-zero ground state of energy. My question is what causes the virtual particles to separate from each other, presumably with some velocity with respect to each other. And then...
  20. medgalis

    Virtual particales and black holes.

    Hello, So i have heard that virtual particlees just pop-in and pop-out of existence, but if a black hole is near those particlee one of the pair of the virtual particlees gets sucked in. So what happens to the other particlee?
  21. T

    Calculating virtual temperature

    Homework Statement Problem: On a summer day, your classroom warms and becomes muggy with a vapor pressure of 20hPa and a temperature of 25C. a.) If the volume of the classroom is 40m^3, how much water is present in the room in vapor form?Assume density of liquid water is 1000 kg/m^3 b.) If...
  22. Crazymechanic

    Are DC circuits similar to AC circuits during switch on/off?

    Hello i have a little clarification to make for myself with the help of you:) So we know that electricity moves so fast through the wires because the charge is being "pushed" by the EM force which is mediated by the photon. Now AC systems no matter what the frequency have real photons...
  23. F

    Virtual photons and long range force carrier

    It is often said that the photon is the long range force carrier like the static force between electrons. Let's say we have two electrons galaxy apart, wouldn't the virtual particles have to travel long distances and "virtually" become real. And isn't the first sentence is wrong anyway since...
  24. B

    Is there such a thing as a virtual dimension

    Is there such a thing as a virtual dimension. for instance if you move on a two dimensional surface, say you take 4 steps in x dimension and then 3 steps in y dimension and then say in z 3 steps, and to move in z you step x+(some predefined formula) and y+(some predefined formula). The z...
  25. E

    Virtual Particles and Photons

    We know electric current travels around 200000 km/s.. Yet electrons are moving way much slower, just acting as a medium for the transportation of the energy. Can same principle apply for light? Although the energy flows at 300000 km/s the photons may actually not? Like, the energy traveling...
  26. C

    Imaginary momentum and virtual particles

    There is a type of exchange of particles which is generalised by a type of potential: \frac{e^{-\alpha\r}}{R} This potential is used to explain the exchange of bounded particles (e.g a poin between neutron and proton) between two possible configurations. The potential comes from the fact that...
  27. A

    Principal Virtual Work Theories - Cylindrical Pipe Application

    Dear All, I did post this issues in the physics forum, however there is somebody ask me to post it in the engineering forum. With this I re-post it here. Does anyone here familiar with a theory called Principal Virtual Work (Equilibrium theory) ? I read somewhere that with this theory, i...
  28. A

    Principal Virtual Work Theories - Cylindrical Pipe Application

    Dear All, Does anyone here familiar with a theory called Principal Virtual Work (Equilibrium theory) ? I read somewhere that with this theory, i could relate(for pipeline application - collapse & buckling) the components for ovalisation, external pressure and hoop strain. Appreciate if...
  29. Q

    Understanding Virtual Particles: An Introduction to the Concept and Properties

    Can somebody explain to me exactly what Virtual Particles are (Like the Higgs Boson) and their respective virtual fields, like what properties do they possesses compared to matter? Are there anti virtual particles? If Someone could give a basic introduction, that would be greatly appreciated...
  30. K

    Convex Mirror & Virtual images

    1. A spherical mirror is used to form an image 5 times as tall as an object, on a screen positioned 5.0m from the mirror. a) Describe the type of mirror required b) Where should the mirror be positioned relative to the object 2. M = (Di)/(Do) & 1/(Di) + 1/(Do) = 1/(F) 3. I have...
  31. V

    Calculate Vertical Displacement at Point C with Virtual Loads in Truss

    Hi I am trying to calculate the vertical displacement at point C for the following diagram https://www.physicsforums.com/attachments/57161 So far i have calculated the forces in each member and i now need to calculate the Virtual forces! I applied a virtual load at point c of 1 KN. I also...
  32. F

    Virtual differentials approach to Euler-Lagrange eqn - necessary?

    I'm currently teaching myself intermediate mechanics & am really struggling with the d'Alembert-based virtual differentials derivation for E-L. The whole notion of, and justification for, using 'pretend' differentials over a time interval of zero just isn't sinking in with me. And I notice...
  33. P

    What's the difference between a virtual and a real image

    I cannot seem to get the concept of real and virtual image. This is my understanding. If the light beams go to the reflecting surface(concave or convex mirror) then an image will be form assuming the reflecting beams meat at a point. If the image appears to be in front of the mirror(s' is...
  34. T

    Source of Virtual Particles in Space?

    I'm trying to understand the nature of the virtual particles that exists in empty space. I understand that they 'bubble' in and out of existence, but why do they exist in the vacuum of space? If all particles spend some of their time as virtual particles, does quantum mechanics suggest that some...
  35. A

    The Quantum field’s effect on Virtual Particles

    So many prominent physicists have argued that the universe may have formed within a vacuum from a virtual particle (either with no energy or without an opposite pair etc...). It’s the classical something from nothing argument. However, could it not be argued that a “vacuum” within our...
  36. M

    Why are only some photons virtual?

    Sorry it was hard to think of a good title. Essentially, why do only virtual photons carry the electromagnetic force? What stops 'normal' photons from carrying the EM force? Is it the fact that we can detect them? What decides whether a photon will be virtual and hence carry the EM force, or...
  37. M

    Why don't virtual particles cause decoherence?

    I was recently told virtual particles don't cause decoherence. Why not? Do they just never interact with their environment (apart from transferring energy/force) so they can never collapse a wavefunction?
  38. PerpStudent

    Virtual particles vs. real particles

    What distiguishes real and virtual particles? Virtual photons, virtual gluons and virtual W particles are often referred to in discussing the interactions they determine. Why and when are they virtual? Why and when are they real?
  39. J

    De Broglie Bohm interpretation & virtual particles

    I sincerely apologise if this has been asked previously, I searched via Google and have been unable to find an answer I understand. How does the de Broglie-Bohm, or Pilot Wave, interpretation, well interpret virtual particles. The beauty of the deBB interpretation seems to be the unity of the...
  40. A

    Virtual particle creation in black holes

    Hi, As I understand virtual particle pairs can be created outside of the event horizon of a black hole. I understand that they result from Vacuum Fluctuations. What creates these vacuum fluctuations? ***A side note: I hope I'm not violating any rules of the physics forums by creating two...
  41. X

    Calculating Bending Moment and Using Virtual Work Principle for Cantilever Beam

    Homework Statement see attachment Homework Equations The Attempt at a Solution I think #1 is to find the bending moment equation, then use the principle of virtual work. I have no idea how to find the bending moment equation and which principle of virtual work to use. Any...
  42. J

    Mass and velocity of virtual photon in Bhabha Scattering

    Homework Statement Determine the mass of the virtual photon in each of the lowest-order diagrams for Bhabha scattering (assume the electron and positron are at rest). What is its velocity? (Note that these answers would be impossible for real photons) Note: You can "just write down" the...
  43. H

    Why is virtual image not seen when a defective eye is corrected?

    Hello Everyone! I have a question related to the ACTUAL APPEARANCE of the virtual image/object formed when a person wears a lens. When a lens (spectacle) is used for correction of vision to make the rays meet at retina, my book says a virtual image seems to form before the lens. This takes...
  44. B

    Could Virtual Particles Explain the Acceleration of Galaxies?

    Hey guys, first post here. I'm just starting to learn physics at the college level, so keep that in mind. While doing some reading on dark energy and dark matter, something occurred to me that I'd never had answered before. Do virtual particles exist long enough to have even a slight...
  45. T

    Electrical Engineering: Build Your Own Virtual Reality

    Hi I just finished high school and want to study electrical engineering in college. My dream is to build a virtual reality machine of my own. Any advice on which area of electrical engineering that I should specialise?
  46. S

    Heisenberg's Uncertainty vs Virtual Particle Fluctuations

    I notice that many physicists say that virtual particle fluctuations occur in space "because Heisenberg's Uncertainty Principle allows them" Is this really the best form of reasoning? Isn't it actually the other way around - that because virtual particle fluctuations happen, then there is a...
  47. R

    Equation of Virtual Work VS Potential Energy

    For linear elastic materials (3D General)... The virtual work equation looks exactly like the equation for potential energy except that in the potential energy equation, the internal work term has a (1/2) coefficient. Why are these different?
  48. K

    Is a Flat Mirror Capable of Producing a Real Image?

    I am struggling on one concept that I can't find when doing a thorough search. System: You have a projector (known to project real images onto a screen). The projector expands light with a lens, the light propagates to a flat mirror on a wall and reflects onto a screen.Conclusion: Although the...
  49. T

    How does a virtual private network work (basics)

    is there anyway someone could explain basically how a vpn works (specifically "HotSpot Shield)? I am asking because i can't figured out if I am getting hacked or if the network is supposed to do this? Whenever I connect to a wireless network, hotspot shield secures the connection and then i...
  50. B

    What is a virtual photon and how is it used in quantum field theory?

    Hello all Does virtual photon have energy ? Does virtual photon travel same as speed of light ? That's energy how can calculate ? when a photon absorbed by electron , photon destroyed or changes to virtual photon ?
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