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. H

    Joos's Treatment of Virtual Displacement

    I having a bit of trouble understanding Joos's treatment of virtual displacements. I am referring to pages 114 and 115 of Theoretical Physics, By Georg Joos, Ira M. Freeman http://books.google.com/books?id=vIw5m2XuvpIC&printsec=frontcover&source=gbs_ge_summary_r&cad=0#v=onepage&q&f=false...
  2. B

    Computing Virtual Work: Assumed Modes Method & Generalized Forces

    Hi all, I've been trying to understand the vibration of a cantilever beam subjected to a forcing function using Lagrange's equation, but have got stuck at the virtual work part. I would appreciate your inputs here. Using the assumed modes method, the transverse deformation is written as...
  3. B

    Do virtual particle pairs interact gravitationally?

    When two virtual particles appear through pair creation, does their brief presence present a gravitational influence on the surrounding universe? If so, then after they self annihilate, does that gravitational influence remain or disappear? The external gravitational influence of black holes...
  4. S

    Real and virtual images from mirrors

    Homework Statement When we look into a mirror, the image formed in virtual as it cannot be captured on a screen. However, If we shine a torchlight at an angle then the beam of light will reflect and form on a screen. But how are we so different from the torchlight's light? Since we simply...
  5. jaumzaum

    How Does Object Placement Affect Image Location in Convergent Lenses?

    I was solving the following problem, and I've got confused at the second question http://img407.imageshack.us/img407/7921/43545856.png 1) An object is put at the center of curvature C of a convergent lens. Where is the image? Calculate by gauss equation. It's obvious that the image is in...
  6. E

    Distinction between real and virtual photon

    a.) One electron emits one real photon and it hits another electron. b.) One electron emits one virtual photon and it hits another electron. (Repulsion because of charge repulsion) What is gradual transition between cases a. and b. ? Or maybe, does it not exist?
  7. Greg Bernhardt

    Fake Gun Used to Steal Man?s Virtual Currency

    Two men recently met in the Fordham University library for a simple currency exchange: $3,300 for 4.7 billion RuneScape coins. *When the deal looked shady, the seller of the coins wanted to back out. *That’s when the alleged buyer pulled … Continue reading...
  8. E

    Real vs. Virtual Photons: A Comparison

    What is the difference between real photons and virtual photons?
  9. J

    De Sitter Space and Virtual Particles

    So De Sitter Space has a constant scalar curvature in the absence of energy or mass where positive curvature corresponds to a repulsive force and negative curvature corresponds to an attractive force. My question is could "virtual particles" be replaced by De Sitter and Anti-De Sitter spaces? I...
  10. J

    Virtual Particles: Exploring Borrowing & Repaying

    So as I was taught in Modern Physics virtual particles are allowed to exist in virtue of "borrowing" energy from the vacuum as long as it is "re-paid" in a short enough time to satisfy the Heisenberg Uncertainty Principle. However after doing further research this doesn't seem to be the whole...
  11. J

    Extended Essay on Virtual Particles?

    I'm planning on doing my 4000-word extended essay for International Baccalaureate on virtual particles (theoretical and particle physics really interest me). I'm starting to get quite stressed, though, as summer is half over, and we were advised to have, at the least, our research done by...
  12. S

    Get the stress tensor using virtual displacement principle

    Homework Statement Using method of virtual displacement get the stress tensor for this problem. http://img32.imageshack.us/img32/7272/problemba.png The attempt at a solution The given system is 4-times tatically indeterminate. Since it is symetrical we can split it in half vertically...
  13. R

    Are Virtual Particles Always the Same or Do They Vary in Our Universe?

    Virtual particles or not only found spontaneously apearing in a vacuum, but also inside atoms via the strong force. My question is are these virtual particles always considered (as far as we know) the same, or do they come in documented/reasonably theorized variatys. Any other examples of...
  14. C

    Virtual Particles: Sources from Leading Universities

    Hello there, I have to do an essay for my university class, and want to use virtual particles (or virtual eletrons)... And i want to know if people here have good sources (good universities) about this issue. Thanks all
  15. D

    Virtual particles inside black holes

    First time poster, more of a nerd than an academic. So virtual particles, can they pop into and out of existence inside the event horizon of a black hole? What about in the black hole itself? If nothing can escape and matter is torn apart, what happens to those quantum particles? Or maybe...
  16. J

    How does a virtual image form in reflection?

    Homework Statement The diagram below shows rays come from object O are reflected by M1 and M2 in turn.Thus I2 can be seen by an eye. Homework Equations I am confused by I2,how does it form? My book said that I2 is the image of I1 However,I1 is a virtual image,no light rays reach I1...
  17. e2m2a

    Redundancy of Virtual Particles Borrowing Energy

    I often hear or read of virtual particles appearing because they borrow energy from the vacuum fluctuations, but they "return" the energy back to the vacuum so that there are no imbalances. Wait a minute. Doesn't the insights of relativity tell us there is no such thing as just energy or mass...
  18. N

    Images in a diverging lens are always virtual. when an objectis placed

    images in a diverging lens are always virtual. when an objectis placed betweenthe focus and optical centre of a converging lens, the image is also virtual. what are the differences between these virtual images? explain by studying the 4 characteristics of each image. i have no idea of...
  19. B

    Optics problems - real vs, virtual / thin film

    Homework Statement 33. This experiment projects a red laser light beam of wavelength λ through a diffraction grating labeled 750 lines/mm onto a screen that is positioned a distance l from the diffraction grating. The diffraction grating has a distance d between adjacent lines. The...
  20. R

    Constrain forces and virtual displacements

    I've read conflicting descriptions of the relationship between constraint forces and virtual displacements that I'd like to clarify. Suppose \vec{C}_i is the constraint force on the ith particle, and \delta \vec{r}_i is its virtual displacement. Is it the case that \vec{C}_i\cdot\vec{r}_i=0...
  21. A

    Do fermions produce virtual bosons when they interact?

    Dear Physics Forum, I understand that forces between fermions are mediated by virtual bosons. My "sense" of it is that a fermion produces virtual bosons (quarks would produce photons, gluons, and W/Z bosons; electrons photons and W/Z; neutrinos W/Z) within the confines of the uncertainty...
  22. G

    Virtual displacement and generalised forces

    I am unsure about the virtual displacement and work definition even after looking through the definition and seeming to understand it. If we have ## \delta W = \displaystyle \sum_{i} \vec{F}_i \cdot \delta \vec{r}_i ##, I can use, ## \delta \vec{r}_i = \sum_{i} \frac{\partial...
  23. C

    Virtual particle production beyond the event horizon.

    Good morning. I am wondering what is the nature of virtual particle production beyond the event horizon of a black hole. When a particle-antiparticle pair is created from the vacuum, it takes time for them to attract electromagnetically and annihilate; but since the event horizon separates...
  24. J

    Could very low energy virtual particles last a very long time?

    By looking at layman's books on physics I have picked up the idea that "virtual" particle-antiparticle pairs continually pop out of the vacuum and then back into it again. Apparently according to the Heisenberg Uncertainty Principle the time that the particle pair can exist, \Delta t, is...
  25. D

    Virtual work and kinetic energy

    Question about analytical mechanics. Suppose we have a system with N degrees of freedom, and hence N generalized coordinates {q_i}, \ i=1...N. A virtual displacement is defined as an infinitesimal change in a generalized coordinate without producing a change in the generalized velocities...
  26. J

    Virtual photon-antiphoton pairs?

    I have heard of the phenomenon of virtual particle-antiparticle pairs popping out of the vacuum and then back into it within a time \Delta t \approx \hbar / \Delta E. Do virtual photon-antiphoton pairs pop out of the vacuum in a similar way? I understand that antiphotons are the "same" as...
  27. T

    Virtual Particle Creation Rate Near an Event Horizon

    In class, our instructor talked about a pecularity of black holes. When virtual particles come into existence for an instant at the event horizon, sometimes one is trapped by the black hole, while the other is able to escape. My question is, what determines the rate at which particles are...
  28. S

    Can the Big Rip affect virtual particles' annihilation process?

    Layman here. Two questions on Virtual Particles. I am not trying to make some claim to spontaneous generation, just curious about how to expand the holes in my knowledge... which is about the level of a post grad engineer who likes to buy the popular physics books in stores to read. 1)...
  29. G

    Time-energy uncertainty and virtual particles

    I have seen an argument that the time-energy uncertainty relation allows heavy particles to exist for short periods of time as virtual particles: (ΔE Δt)>h Δt>h/ΔE However, shouldn't the inequality be the other way: Δt<h/ΔE to suggest that a heavy particle with large ΔE can exist...
  30. L

    Do virtual particles interact?

    (First off, I'm not sure that I'm asking this question in the right area, but there does seem to be other questions associated with the topic, so hopefully I'm ok, but if I'm wrong, apologies.) I understand that virtual particles are... virtual, a mathematical construct that is used to describe...
  31. mishima

    Misc Questions: Virtual work, RMS, Friction on incline, and Virtual Displacement

    I have a few questions I thought I'd post together instead of making separate threads, hope that's ok. They are more or less unrelated... 1. Are there 2 conceptual ideas that use the term "virtual work"? I am familiar with the one from intro level physics, but I read there is also one from...
  32. Greg Bernhardt

    Move Over Sudoku; Studies Show Virtual Worlds Can Be Good for Your Health

    A recent story on Forbes.com reported on a new study about the effects of playing massively-multiplayer online games on one’s cognitive abilities. Conducted on a small sample group of 39 adults between the ages of 60 and 77, the study … Continue reading...
  33. L

    Virtual particles in interactions

    Hi, so we have just started doing some physics of fundamental particles etc at school. i am reading a lot about the exchange of 'virtual' photons etc. i am confused about whether these particles actually exist in a physical sense or whether they just have to be there to conserve...
  34. P

    Unruh Effect: Virtual Particles Become Real in Accelerated Frames

    Would it be fair to describe the Unruh effect by saying that from the perspective of an accelerated observer, some virtual particles in an inertial frame become real particles in the accelerated frame? Wald talks about how the appropriate transformations between inertial and accelerated...
  35. P

    Do virtual gnomes play a role in black hole physics?

    Hello. On the "Ask an Astrophysicist" page on the NASA site, one can read the following: This raises three questions for a layman such as me: 1. Do the scientific community agrees with this answer? 2. Can the virtual gnomes break any rule and fulfill any wish as long as we don't detect...
  36. Z

    Exploring the World of Virtual Images

    Virtual image?? Nvm I got it. Thank you anyways virtual image is not the actual distance kk.
  37. M

    Do have virtual particles gravity?

    First I would like to apalogize if this is not right thread for my question, but I am not sure where to put it. If I understand it right, vacuum is actually full of virtual particles and antiparticles popping into existence and anihilating again and that always particle and antiparticle are...
  38. F

    Hypothetical Question of Virtual Particles and Magnets

    I wasn't sure where to put this question, since it didn't seem to fit any category. However, because it brings up the topic of virtual particles, I'll ask here. From what I understand, virtual particles can travel faster than light, and it is virtual photons that are responsible for the...
  39. B

    Virtual Particles: What is Known & Effects on Spacetime, Matter, Light

    All I ever hear about Feynman’s virtual particles is that they are created then destroy each other in a short period of time. I was wondering what else we know about these particles? How often is this occurring? How big are these particles? What if any affects do these particles have on...
  40. H

    Method of virtual displacement

    http://img267.imageshack.us/img267/9636/qw5e64a2d1sda54.png Hi guys. i have a question that needs verification. Referring to the above diagram, Please determine the Moment, M (Nm) needed in order to hold the mechanism in equilibrium state as shown above by using "Method of Virtual...
  41. C

    Does Rope Position Affect Acceleration in Rotational Movement?

    I refer to the figure: Is it true that affixing the rope at the point A isn't the same of affixing it at the point B? (I consider the rotation movement around O since the disk is rolling, and so the radius of rotation is different in the two cases) I'm sorry because my english is not very...
  42. J

    A question on virtual antiparticles and Hawking Radiation

    I know that Hawking Radiation is caused by the separation of virtual particles on the event horizon of a black hole, but I do not understand why the antiparticle is always the particle from the pair that falls into the black hole. It seems to me that the gravitational effects of the black hole...
  43. edpell

    Can Virtual Particle Lifetimes Be Calculated?

    Is it possible to calculate the lifetime of a virtual particle? For example is an electron and a proton form a virtual neutron that is off shell by 0.8Mev how long will it last? Is this something we can calculate? At first I would think it would be short lived because of the 0.8MeV energy...
  44. S

    Antiparticles vs virtual particles

    Im a grade 12 student and I just started reading black holes aint so black in the brief history of time. However, I'm having a hard time distinguishing a difference between these two particles. What is a difference? thanks!
  45. C

    Can a virtual particle create another virtual particle?

    I can see the answer being no for large particles, but what about strings? What stops them from expanding to make up the universe as we know it?
  46. D

    Virtual Work-very confused about the sign conventions

    The problem statement is "each of the four uniform links has a mass m. determine the horizontal force P required to hold them in place in the vertical plane as shown." I attached the solution, but I don't get when a force causes a +/- virtual work.
  47. R

    Active Force Diagrams/ Virtual Work

    Homework Statement Homework Equations ? The Attempt at a Solution a) y=2Lcos(θ) x=2Lsin(θ) b) I haven't started the next question as I want to make sure the active force diagram is correct first.. If somebody could just check the diagram and help me with where I'm going...
  48. T

    Is the following correct about virtual particles

    On yahoo I asked if "since virtual particles cone to existence out of nothing. Is it possible that anything else ( discovered or not yet discovered in any universe) would be able to do the same, besides other virtual particles " And I got this answer Is it correct? "No. Virtual...
  49. D

    New (apparent) confirmation of virtual particles.

    Using a simulated rapid-moving mirror, scientists provided evidence the existence of virtual photons by coaxing them out of a vacuum by means of the dynamical Casimir effect: http://www.world-science.net/othernews/111117_casimir.htm As a layman, I will reserve judgement until the experts...
  50. R

    Hawking Radiation's Virtual Particles?

    Not sure if this is the right forum but hey ho.. I have been reading about Hawking radiation in Black Holes, whereby virtual particles are created at the event horizon and of the particle and anti particle pair 1 can escape before it is annihilated. Why are the particles which make up the...
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