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

    I Are all photons virtual?

    My understanding is (was) that "virtual particles" is a computational concept used in perturbation calculations in QFT e.g. in Feynman diagrams. This understanding is in conflict with the following note in Quantum Field Theory for the Gifted Amateur by Tom Lancaster and Stephen J. Blundell: and...
  2. Ahmed1029

    I Virtual work and constraint forces

    Suppose I'm considering a system of N particles that are constrained in their possible motions and so there are less that 3N generalized coordinates. Suppose now I perform a virtual displacement on one particle, which due to some constraints might force some other particles to more virtually...
  3. T

    A Principle of Virtual Work and the forces that DO NOT do work

    In this 2D figure below, I can place: a motor at O a motor at J gravity on each link I can use Hamilton's principle, modified to the principle of virtual work and I can compute the motion of the linkage system. I do not have to account for these force FOUR forces (in this planar problem)...
  4. NovatoOfPhysica

    Virtual Work and Static Equilibrium

    Hi there, this question has already been discussed in this forum, however I do not know how to proceed further and if my reasoning is correct. I start by imagining a downard displacement of the 1kg weight. As a consequence of this, block A moves upward and to the right. Also, block B moves...
  5. rishurboi

    I Applications of Virtual objects

    I've heard virtual objects are used in cinema halls I'm not sure of what that means, can someone explain this to me please? And btw by virtual object i mean when diverging rays from real object passes through a convex lens, the rays will converging and if you'll place a plane mirror infront of...
  6. T

    Principle of Virtual Work to the FE method

    (I do understand there are many ways to formulate the FE method, but I wish to understand this one.) I understand that Hamilton's Principle is just that: a principle ( a law the recapitulates the equations of motion) I also understand that the Principle of Virtual Work (PVW) is a reformulation...
  7. E

    B Virtual photons as force carriers

    (My multipart question is from a very naive perspective, so sorry if it is rife with misunderstandings. Please answer conceptually, with as few & as simple equations as possible. I think that all of the answers to these questions should be understandable to a high schooler, though maybe the...
  8. A

    Troubleshooting Game Issues on Virtual Machine

    Game on VM won't work. It did work before i re-created machine, but I don't remember what did i do to get game working. I'm using windows 10 64 bit on machine and host is the same. When i launch the game it's just black screen and music, when I tried to play in window mode it showed the window...
  9. Q

    Real Virtual Reality: Join the Discussion

    Does anyone know of any groups who discuss this from a scientific or even experimental standpoint? Yes I am talking about a Matrix type virtual world. I have many ideas and with the state of the world in the way it is, from my perspective - could perhaps be a very important thing to consider.
  10. Green dwarf

    I Virtual Photons: The Long-Distance Repulsion of Electrons

    My understanding is that the repulsion between two electrons is mediated by the exchange of virtual photons – virtual meaning not lasting long enough to be detected. But suppose one of the electrons is in the sun and the other on Earth. There should still be a repulsion because the...
  11. R

    B Why exactly do Virtual Particles not violate Conservation of energy?

    Recently I've read more about virtual particles and at first I tought that there were only doubts that virtual particles are not interpretable with the help of uncertainty principle. Furthermore it can't be used an an "excuse" for the temporary violation of the conservation of energy. Can...
  12. K

    A Hamilton's principle and virtual work by constraint forces

    Found a question on another website, I have the exact same question. Please help me Goldstein says : I do not understand how (2.34) shows that the virtual work done by forces of constraint is zero. How does the fact that "the same Hamilton's principle holds for both holonomic and...
  13. K

    I Virtual displacement is not consistent with constraints

    Goldstein 3rd ed says "First consider holonomic constraints. When we derive Lagrange's equation from either Hamilton's or D'Alembert's principle, the holonomic constraint appear in the last step when the variations in the ##q_i## were considered independent of each other. However, the virtual...
  14. K

    Virtual displacement for a block sliding down a wedge

    A block slides on a frictionless wedge which rests on a smooth horizontal plane. There are two constraints in this system. One that the wedge can only move horizontally and another that the block must remain in contact with the wedge. We want to find the virtual displacements for the two block...
  15. Ranku

    I Energy of virtual particles

    Are the typical energies of virtual particles lower than real particles?
  16. F

    Virtual Machine and Images

    Hello, I am about to create (should I say install?) a virtual machine (VM) on my Windows pc to experiment with Linux. My understanding is that a VM is a "software" (or is it more properly a file? Or is it an image? I guess an image is just a big file?) that is run/managed by a hypervisor...
  17. T

    Using virtual work to find the angle of a bar supported by two planes

    I imagined the bar slipping along a virtual displacement, with the top and the bottom slipping by equal amounts. Since the planes are orthogonal, I took the components of these displacements: the lower end is displaced Lsinα in the direction of the right plane and by Lcosα in the direction of...
  18. e2m2a

    B Virtual Particles Momentum Transfer

    My understanding is that virtual particles don't really exist. However, they somehow come into existence under certain circumstances. For example, in the Casimir Effect the virtual particles on the outside of the plate now have the capacity to transfer momentum and kinetic energy to the...
  19. D

    Determine the forces using virtual work(unit force method)

    Summary:: Require to determine the designated forces using principle of virtual work ( unit force method ) I have no idea how to determine the multispan beam using virtual work, if I start to analyse the subsidiary portion BC member, the Yc can be calculated and following by the Ma... it seems...
  20. kyphysics

    Virtual Doctor's Visits - Do/Would You Use Them?

    My insurance plan allows these, but I've never used one. I'm wondering if anyone has considered (or maybe already has) partaking in telehealth? If so, I have some questions: a.) Are there particular types of doctor's visits you would tend to use tele-visits for vs. in-person...
  21. docnet

    I Can an electron in a magnetic field radiate a virtual photon?

    In Theoretical Minimum: Quantum mechanics, Leonard Susskind describes an electron in the higher energy spin state in a magnetic field radiates a photon of energy ##\hbarγ|B_0|## and flips into the lower energy spin state. I am wondering if this photon is related to the "virutal photon" that...
  22. N

    Virtual and real image with concave mirror at 45 degrees

    I have a spherical concave mirror with focal length of 65cm, radius of curvature of 130cm. I hold the mirror close to the eye at approximate 45 degrees and I reflect an object below it as shown in the image. The distance between the object and the mirror is 90cm, that is more than the focal...
  23. Ander99

    Comp Sci What are the differences between a virtual node and a physical one

    Hi everyone! Can someone explain which are the differences between a physical node and a virtual one and which one is potentially better . I've been looking for information but I haven't found anything. Thank you a lot.
  24. Macoleco

    How long until Full Dive Virtual Reality?

    I am obsessed with the development of the Full Dive Virtual Reality (transporting your consciousness to a virtual world, such as Sword Art Online). I believe this technology may be available at around 200 to 300 years. How long do you think it will take us, if at all?
  25. LuisBabboni

    I Virtual particles and Heisenberg

    Hi people. Having as uncertainty principle that ΔE Δt≥ h/4Pi, why Δt≤ h/4PiΔE to allow the existence of a virtual particle? How ≥ becomes ≤ ? I think... real particles must obey ≥ so any particle that do not obey that is a virtual particle and thus why virtual particle needs to obey Δt≤...
  26. DarkMattrHole

    I Virtual Tidal Effect in Accelerating Ship - Does it Exist?

    Does a sort of virtual tidal effect exist inside an accelerating body (space ship) similar to the way the tidal effect is present while rest on a massive body? Or could an accurate enough 'thought experiment' measuring device figure out if it's in an accelerating ship or resting on a planet, by...
  27. robphy

    AAPT Virtual 2020 Summer Meeting

    https://www.aapt.org/Conferences/SM2020/index.cfm I wasn't originally planning to attend the meeting in Grand Rapids. But when it went virtual, I submitted an abstract before the original abstract deadline in March. They extended the deadline for abstract submission to June 3. Unfortunately...
  28. HexHammer

    B Virtual Particles are not Dark Matter?

    So far as I understand it, a photon can split up and create particles with matter, even though the photon is massless, yes? So if a photon can be more places at the same time, it should be able to create multiple particles all at once? So how is this not Dark Matter?
  29. robphy

    AAPT 2020 Summer Meeting (now Virtual)

    https://www.aapt.org/Conferences/SM2020/ Hopefully, it will be free to register, like the recent APS Virtual April Meeting. In that APS meeting, you had to register to view the presentations, whether live or pre-recorded. Registrants could also watch a recording of a live session. During live...
  30. T

    Virtual Physics Labs - giving some resources and asking for some

    Hi all! Like everyone else, our university physics department is prepping for online labs. We are utilizing great simulations from several sites, check them out below if you haven't already. We are able to rewrite many of our labs 1:1 conversion to online! Colorado PhETs...of course ...
  31. new90

    Virtual work in a pulley system

    If 1kg make a displacement of 1unit upward then A make a 1/2unit down because 1/sin 30.after that i have no idea what do I will really need help. Thanks!
  32. A

    I Virtual particle content of the vacuum state....

    Hi all, One more virtual particle question (sorry all!): for individuals who would take virtual particles as being 'real' (but unobservable), what is their understanding then of the content of the vacuum? For example, if I place a electron all by itself in the vacuum (thus making it no longer...
  33. A

    I Frank Wilczek on Virtual Particles and Summing diagrams....

    Hi all, - an initial apology - there are a large number of threads on virtual particles on the site, and I apologize for adding another one. I had two questions - on a related note, the guidance provided by @A. Neumaier's FAW on virtual particles has been highly valuable for a novice . 1) Upon...
  34. Z

    Paging, Virtual Address Space and Physical Memory and Page Frames

    Hi, The following is not a homework question. My question is: My answer is: Total pages required = 2^32/2^7 = 2^25 pages Thus page table has 2^25 entries PM = 2^16 Total page frames in PM = 2^16/2^ 7= 9 page frames Somebody please guide me what is the correct solution for the above. Zulfi.
  35. F

    B Where do virtual particles come from?

    I watched a Youtube! video on black holes, and it said that black holes evaporate via Hawking radiation. If I understood the video correctly a virtual particle can pop into existence just outside the event horizon, and that one of the resulting pair can subsequently fall back into the black hole...
  36. A

    I On-shell virtual particles and 'physical' Hilbert spaces....

    Hi all, Just a clarification question as I'm learning. It's possible to have Feynman diagrams where the internal lines (virtual particles) are in fact on shell. 'On shell' would imply 'observable,' (maybe?) but as noted in @A. Neumaier's great FAQ, only sets of Feynman diagrams have predictive...
  37. Sophrosyne

    B The nature of virtual photons in quantum electrodynamics

    In quantum electrodynamics, the energy exchange between two charged particles is called a virtual photon, allowing the exchange of quanta of energy between the two charged particles. But these are not the traditional photons of electromagnetic waves. They apparently just arise from the equations...
  38. D

    Quantum Quantum Fluctuations & Virtual Bosons: A Guide for Amateur Physicists

    I am searching for anything on quantum fluctuations and virtual bosons for someone who is a serious but amateur physicist ie. I have completed undergrad physics/math and some graduate level math at university. I am having a hard time finding anything that isn't beyond pop science. Not really...
  39. Nonametheone

    Can a virtual particle from a maget accelerate another particle on a linear path?

    Summary: Can a particle accelerator accelerate gaseous fuel? Does space-time differ for detonating ionized fuel moving near the speed of light within a magnetic field such as a particle accelerator?
  40. L

    A Timescale of virtual photon interaction in particle scattering

    I'm studying the electron-proton deep inelastic scattering. In the notes that I'm studying from the author states that the time-scale for a virtual photon to interact with a proton is ##τ\sim\frac{1}{Q}##, where ##Q## is the momentum transfer with ##Q\gg M##, which is the mass of the proton. I...
  41. Ranku

    B Virtual particles motion

    Do virtual particles travel at the speed of light, or do they have 'virtual rest mass'?
  42. T

    Principle of Virtual Work

    Hello May I ask: "What is the guiding philosophy of the Principle of Virtual Work?" I do understand it an how to use it, in classical mechanics. (And I will openly admit that I do not entirely understand what I am looking for, or what I am asking.) But what is happening at this moment in...
  43. Michael Price

    A Massive gauge bosons in QFT in/out states

    Because massive gauge bosons have a finite half life, are they excluded from the (infinitely, asymptotically remote?) in and out states of QFT? Or, to put it another way, are they restricted to the internal legs of Feynman diagrams, i.e. to being virtual only? We can see W and Z tracks in...
  44. Lunct

    B Can virtual particles have an imaginary mass?

    I was talking to a physicist who said to me that virtual particles can have a mass of a constant times by i ,as in the root of -1. I have been thinking about this more and it intrigues me. I have done some research into this and can't find further details. If they have an imaginary mass does...
  45. K

    I Confused about virtual particles

    Hello! I am a bit confused about the distinction between virtual and real particles. For example a Z boson, which has a very short lifetime, in all experiments will decay to some other stable particles (i.e. it is detected through its decay). This means that it will always appear as a...
  46. almostvoid

    Virtual Revolution Sci Fi Movie [2016]

    for once not a Hollywood ending. Looks like Blade Runner at first, the plot is not unfamiliar but the ending is.
  47. navneet9431

    B Can we get a real image of virtual objects?

    Is it possible to get a real image of virtual objects, If so please explain with examples and some real life situations? Look at my assertion "rays will not pass through virtual objects so how it can form real image", is this possible, please help.
  48. K

    Virtual work in Atwood's machine

    The first chapter in Goldstein's Classical Mechanics ends with 3 examples about how to apply Lagrange's eqs. to simple problems. The second example is about the Atwood's machine. The book says that the tension of the rope can be ignored, but I don't understand why. The two masses can move...
  49. A

    B The Gain of the Inverting Amplifier and Virtual Earth....

    This is an inverting amplifier incorporating an ideal op-amp with infinite open loop gain. I have a simple question concerning the derivation of its gain (-R2/R1). The point I circled is at 0V (Virtual Earth) but then, if V+=V-, Shouldn't Vout=0 regardless of what R2 and R1 are?? What's wrong in...
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