What is Gravitons: Definition and 173 Discussions

In theories of quantum gravity, the graviton is the hypothetical quantum of gravity, an elementary particle that mediates the force of gravity. There is no complete quantum field theory of gravitons due to an outstanding mathematical problem with renormalization in general relativity. In string theory, believed to be a consistent theory of quantum gravity, the graviton is a massless state of a fundamental string.
If it exists, the graviton is expected to be massless because the gravitational force is very long range and appears to propagate at the speed of light. The graviton must be a spin-2 boson because the source of gravitation is the stress–energy tensor, a second-order tensor (compared with electromagnetism's spin-1 photon, the source of which is the four-current, a first-order tensor). Additionally, it can be shown that any massless spin-2 field would give rise to a force indistinguishable from gravitation, because a massless spin-2 field would couple to the stress–energy tensor in the same way that gravitational interactions do. This result suggests that, if a massless spin-2 particle is discovered, it must be the graviton.

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  1. W

    B Cosmic Graviton Background and Primordial Gravitational Waves

    I understand inflation is thought to predict primordial gravitational waves although their strength is undetermined by the theory with some models of inflation predicting them to be strong and others so weak they can never be detected. However , this paper claims that if we detect a background...
  2. J

    I What effect do gravitons have on electrons?

    Hi, what effect do gravitons have on electrons. I know with photons the electrons absorb the photons and leave the atom. Would gravitons have the same effect?
  3. A

    B Gravitrons vs Photons: how come light and gravity exist?

    if matter and anti-matter meet, they annihilate each other. Gravitons are anti-photons and photons are anti-gravitons. They MUST meet in immesurable quantities in our universe. Yet gravity exists, and light exists in our known universe. This denies the annihilation necessity. And annihilation...
  4. jaketodd

    I The speed of forces, and applying relativity to force carriers

    Are there any limits to how fast forces can exert influence... or are they all instantaneous? How fast are the forces of a collision? I think frame dragging, with gravity, shows that at least gravity is not instantaneous, because if it is instantaneous, then how would it produce drag - it...
  5. BadgerBadger92

    I How can gravitons have anti particles?

    https://physics.stackexchange.com/questions/273918/is-there-a-possibility-for-discovery-of-anti-graviton-i-e-the-graviton-antipar How can a graviton have an anti particle even though they are essentially the same thing? Same thing with the photon. Any help would be great [Mentor Note: The PSE...
  6. L

    B Why are gravitons needed to explain gravitational attraction?

    Hi! Isn't gravity just a smaller object moving toward the lower energy state created by a larger object (time slows down the closer you are to a massive object)? Why do we need a force carrying particle for gravity?
  7. ohwilleke

    I Is the Continuum Limit of Spin Foam Dynamics Equivalent to Massless Gravitons?

    The spin-foam approach to quantum gravity is part of the class of approaches, that also include loop quantum gravity and a variety of other methods, that sets out to quantize space-time rather than the gravitational force itself. But, according to a new paper, it turns out that "the continuum...
  8. Kairos

    B Gravitons: Relationship to Space-Time & Black Holes

    1) What is the relationship between gravitons and the curvature of space-time? 2) As gravitons move at speed c, the curvature of space-time is not instantaneous either, so how the curvature sets in or disappears gradually (for theoretical example if mass disappears suddenly upon collision of...
  9. thegroundhog

    I Why are gravitons expected to exist when gravity is just warped spacetime?

    As per the summary I don't understand why physicists talk as if gravitons are inevitable, when gravity is just curved spacetime? Why would curved spacetime have a particle?
  10. K

    I Do gravitons interact with gravitons?

    Specifically, how would graviton-graviton interactions increase the gravitational binding of matter? I visualize that the beam of spacetime between two stars is very ordered, in that streams of gravitons from each star flow in very nearly anti-parallel paths. Will these gravitons interact? Light...
  11. CallMeDirac

    B Theory about gravitons and space warping

    We know about the Higg's field and boson, so what if gravity is the same. There has long been a dispute as to weather gravity is a field or a particle. Why can't it be like the Higg's boson.
  12. SamRoss

    I Gravitons Replacing General Relativity: Can it Work?

    Einstein's theory describes gravity as a curvature of spacetime. As such, everything is affected by it. This includes light, which has no mass, as was made clear for the first time during the famous 1919 solar eclipse. In the standard model, the cause of gravity is supposed to be gravitons...
  13. J

    I Could gravitons be dimensionless?

    If the metric ##g_{\mu\nu}## is dimensionless and gravitons are quantum excitations of the metric does that mean that gravitons themselves are dimensionless? I say this as locally the metric is just the flat metric ##\eta_{\mu\nu}=\hbox{diag}(-1,1,1,1)## with the dimensions in the co-ordinates...
  14. Physics4Eva

    I Could the Discovery of the Graviton Connect Quantum and Classical Physics?

    W and Z bosons, gluons, and photons are all gauge bosons that have been found. Since the graviton can be connnected to atoms and mass in certain ways, I think that CERN may eventually prove the graviton(if real) through smashing atoms that, supposedly, have a graviton orbiting them. Could...
  15. ohwilleke

    I QFT of Gravitons in Minkowski Space vs GR

    A central feature of classical GR that it is background independent and operates via a curvature in space-time. As I understand it, this is not true of the other Standard Model forces which are consistent with special relativity and operate in Minkowski space, in which forces are transmitted via...
  16. Raffaele

    B Black Holes, Gravitational Waves & Gravitons Explained

    I wonder why electromagnetic waves don't escape from a black hole while gravitational waves (obviously) do. What is the difference between the two kind of waves? And between gravitons and photons? thank you for your attention
  17. N

    I Would these (unrealistic) conditions imply gravitons existed?

    So quantum states collapse when observed, ie they are interacted with, if one had an uncharged massive particle, in a true vacuum (yes, this assumption is egregious, not your usual "ignore air resistance"), and the state of the aforementioned particle collapsed, would that imply gravitons did...
  18. S

    If photons can't escape a black hole, how come gravitons can?

    It would seem that they both must observe the laws of General Relativity.
  19. S

    A A question about graviton self-interaction

    Would making the graviton self-interaction easily calculable solve most of the problems of quantum gravity?
  20. C

    Aliens with Control over Gravitons in the KHz Range

    See my previous post! https://www.physicsforums.com/threads/do-gravitons-have-frequency-like-photons.957146/ Let's say we had some aliens that had the ability to emit/interact with gravitons with frequency roughly in the range corresponding to human hearing (20Hz-20KHz), and that they had an...
  21. P

    I How do we calculate galactic gravitation?

    <Moderator's note: Several threads merged and moved to cosmology.> So I’m wondering about gravity. I was under the impression that gravity was created due to the curvature of 4d spacetime and whatnot. Can someone explain to me what gravitons are in relation to that? Are the gravitons making...
  22. S

    I How Many Gravitons Were Detected in Recent Gravity Wave Observations?

    Gravity waves are very weakly absorbed. The gravity wave detectors have so far detected 3 events of gravity wave emission: 2 from black hole pairs and 1 from neutron star pair. The absorption is weak but the detectors are very sensitive. How much energy did the gravity wave detectors actually...
  23. C

    I Do gravitons have frequency, like photons?

    Something I've been thinking about lately. If so, how'd we detect high frequency gravitons? I have Bachelors in physics so you may get a little technical ;)
  24. Islam Hassan

    I Gravitational Waves vs Gravitons

    Are gravitons postulated to be excitations of gravitational waves? If so, and since gravitational waves have been unambiguously observed, then gravitons must exist, no? If not, then what is the postulated relationship between gravitational waves and gravitons? Are both deemed/postulated to...
  25. N

    B Is Gravity a Force or Effect? Exploring the Theories Behind Gravity's Nature

    If what we perceive as the force of gravity is really just the effect of curvature of spacetime, why do theorists hypothesize the graviton as the force carrier for gravity? I thought that GR does away with the notion that gravity is a "force." So, is gravity a force or is it merely an effect?
  26. Fig Neutron

    B Why Do We Need Gravitons for Understanding Gravity?

    I understand, for example, the photon for electromagnetic force, but I don't see the need for graviton. From my understanding of general relativity, gravity is caused by the warping of space-time. If I am right, why do we need a force carrier particle for a feature of space? From what I can...
  27. S

    B Learning Gravity: Gravitons nor mass of a particle

    Hi everyone, today, I have a question about quantum gravity, good to begin with. I used Newton's formula to calculate gravity for nêutron , the result exceeded Planck's radius, the question is: could it be that gravity is not necessarily connected to the mass of a particle, nor with graviton...
  28. Sophrosyne

    B Relationship between Higgs particles and gravitons?

    In trying to understand the relationship between Higgs particles and gravitons, I would like to pose a question on hypothetical question: What would happen if you increase the Higgs field around a planet? It seems it would mean its mass increases, which would mean its gravitation increases...
  29. N

    B What is the theory of gravitons

    Gravitons are particles believed to be the cause of gravity but can anyone tell me their principle and how they work
  30. P

    B Are inflatons the same as fewer gravitons?

    I'm not very conversant in the subject. But it is my impression that the acceleration of the expansion of the observable universe has generated a theory that there might be a new particle (field?) call the inflaton. On the other hand, I thought I'd heard that scientists were trying to find...
  31. K

    I Clarification of Higgs field, Higgs boson and gravitons

    since gravity under GR has unlimited range the graviton must be massless. since the graviton is massless, the higgs field does not couple to the graviton. If the higgs field did couple to gravitons, it would cause gravitons to have mass, contradicting observation. but the higgs field carries...
  32. K

    B Are massive gravitons what ripple when galaxies collide?

    Is a sea of massive gravitons what ripples when galaxy clusters collide? Accepted at APS Physical Review D: https://journals.aps.org/prd/accepted/8b07dQ8dFbd1051b06704364802ee6ba42eea6f5e Precursor: Bigravitons as dark matter and gravitational waves We consider the possibility that the...
  33. twistor

    A What would happen if only gravitons existed?

    This is a somewhat weird question, but here it goes: What would happen if there were only gravitons? Would some other kind of particle appear in the Universe sooner or later? Would there be any chance for mass to appear in such a Universe (assuming that the graviton is a massless particle)...
  34. P

    I If there are gravitons, is space not curved?

    If gravitons are proven to exist, would that mean space is not curved?
  35. J

    Gravitational Wave Discovery & Einsteinian Gravity: What's the Connection?

    Hi Everyone, my first post here. I'm really confused by the comments around the recent LIGO gravitational waves discovery and how it connects to Einsteins gravitational model. My understanding is that he said a body warped spacetime around it forming a gravitational well into which other bodies...
  36. S

    Gravitational Waves, Gravitons: Does Discovery Change Odds?

    Now that we have confirmed the existence of gravitational waves, have the odds of discovering a force carrying particle changed? With my limited knowledge it kind of seems like if gravity is caused by the warping of space-time, which was confirmed by gravitational waves, would mean that there is...
  37. DuckAmuck

    Are gravitons the quanta of spacetime?

    In QFT, an ultraviolet cutoff is imposed to avoid singularities. One physical reason for why this works may be that there actually is an ultraviolet cutoff from spacetime being quantized. Since in GR spacetime is responsible for the force of gravity, and gravitons are the hypothesized quanta of...
  38. SuperGadger

    B Gravitational Waves and Gravitons

    Does the discovery/confirmation of the existence of Gravitational Waves change or add to current theory in regard to Gravitons?
  39. P

    Gravity Wave Discovery and Gravitons

    Does the discovery of gravity waves imply the existence of gravitons?
  40. P

    Does E in E=mc^2 Include Gravity?

    Does the E in E=MC^2 include the gravitons?
  41. DaniV

    Gravitons Energy: Range & Dependence on Scientists

    There is theory that masses like charges are transfering force gague bosons. According to charges they transfering the boson called photon between the charges and responsible for the electromagnetic force. Photones qualities are that it doesn't have mass and behave like a particlee and also as a...
  42. G

    Gravity Waves & Gravitons: Exploring the Distortion of Space-Time

    If a mass bends space-time somehow and then I nudge it, the bend changes. This distortion of space-time bend is supposedly expanding at the speed of light and could be called a "gravity wave" that carries energy. Why is this wave not the distortion that creates a "graviton" like EM and photons?
  43. Ryan Reed

    How Can Gravitons Escape A Black Hole?

    Past the event horizon of a black hole, gravity is so immense that even light can't escape. Wouldn't this cause the the gravitons, which travel the speed of light, to be trapped, making a singularity?
  44. Einstein's Cat

    Whether gravitons can exist or not

    Is the change in the effect of gravity when a mass moves towards or away from another instantaneous?
  45. AaromTheBritt

    I Anti-gravitons effect on spacetime

    So, I'm still a bit new to the realm of physics but I was discussing theorized particles with my professor the other day and came to the conclusion, if gravitons do exist, could anti-gravitons be an explanation for why the universe is expanding? I was reading around and came across a similar...
  46. K

    In LQG, do objects attract via gravitons or curved spacetime

    planet Earth and the sun. in GR, gravity is not a force but simply a manifestation of spacetime curvature. the sun curves spacetime and the Earth is simply traveling through geodesic motion through curved spacetime. in string theory, the sun and Earth exchange virtual gravitons through a...
  47. Wallis

    Let's Sort Out This Gravity Thing - c And All That

    "General relativity predicts that disturbances in the gravitational field propagate as gravitational waves, and that low-amplitude gravitational waves travel at the speed of light." It seems high energy waves may travel slower, but certainly not faster. So, a large star whilst going supernova...
  48. S

    Gravitons and other subatomic particles

    Hi everyone. Am trying to find out how many gravitons are in a quark, or in a proton. Anyone here know, or can point to a reference that might have the answer? Thanks!
  49. A

    Why do gravitons remain undetected?

    Gravitons are hypothetical, I know. But, unlike other force carriers, gravity is simple ruled out by gravitational field theory. If gravitons are real, why can't we detect them?
  50. nuclearhead

    Explaining Universe Expansion with Gravitons in String Theory/Supergravity

    In a theory like string theory or supergravity, gravity is described by gravitons on (usually) Minkowski background. But I don't see how this works in terms of the expansion of the Universe. For example, two galaxies far apart can be moving away from each other at more than the speed of light...