What is Graviton: Definition and 158 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. S

    Why graviton particle theory concept is not accepted?

    is graviton does really exist?
  2. X

    Relation between graviton and space curvature

    Hi, i read a few books (pop ones) and one thing that left me thoroughly confused was the relation between graviton and space curvature, is there any relation between the two... if we find a graviton then does it mean that space is not curved? regards Monty
  3. menniandscience

    Can a graviton pull another graviton?

    thanks
  4. C

    Is the Higgs Boson Really the Graviton?

    Hello there. I have a question, or better yet, a proposition on the higgs boson/graviton: would it be possible for these to be one in the same? What I mean by this is that under the assumption that higgs boson does exist (which I agree with) that gravity is then propagated from the boson...
  5. C

    What Is the Explanation for the Graviton's Wave Length and Mass?

    Hello PF community! While reciently reading another thread this paper was posted as a link: http://arxiv.org/ftp/cond-mat/papers/0602/0602591.pdf now about 5 pages in it stated that the authors found a wave length and mass for a graviton? I did not even know they were proven to be...
  6. R

    Dep inelastic scattering with graviton as propogater

    consider deep inelastic scattering of e-p.assuming that a graviton acts as a propogater in this interaction how would it effect the structure functions of the proton.now we have a spin 2(graviton) instead of the usual spin 1(photon).basically what is the effect of this spin change on the...
  7. N

    Graviton and Photon Emission

    Based on the following excerpt, I'd appreciate any general comments/observations and then follow with a specific question. Leonard Susskind says in THE BLACK HOLE WAR, 2008, PG 347 : #: my parenthetical comment I knew physics was crazy, but that just seems "over the horizon" crazy...
  8. H

    Graviton Scatter: Exploring Implications

    Hi, Does graviton scatter and what is the implication? Thanks!
  9. A

    Question about graviton polarization tensor

    Hi I’m a student, and I started reading Zwiebach’s First Course in String Theory, but I still haven’t learned general relativity, only special relativity, and so I’m having some difficulties in understanding the polarization tensor for the perturbation of the Minkowski metric leading to the...
  10. T

    Spin 2 graviton will appear to us as spin 0,1 or 2

    Is it true that spin 2 graviton will appear to us as spin 0,1 or 2, since it has a momentum component in the bulk? How about fermions and other spin bosons ?
  11. N

    Graviton bosonic degrees of freedom

    Hi, Could you pls advise me why in on-shell case graviton has two degrees of freedom? and in general how do I calculate bosonic or fermionic degrees of freedom of any particle? I was reading some books about supersummetry and stuck when they said gravitopn has two degrees of freedom and...
  12. T

    What is a Graviton? Reconciling Gravity and Quantum

    is a graviton some kind of energy quantum? how does that reconcile with gravity as the geometry of curved spacetime? Is it energy with little quantum packets? or is it geometry? or is it somehow both? or is it neither and that's just the way we describe it's effects?
  13. A

    Reconciling graviton exchange with a black hole

    Perhaps this is a bit of a naive question, but I'm having trouble with the following issue. It is easy to describe the motion of a test particle near a black hole using classical general relativity. The underlying assumption is that gravity is a geometric manifestation, and the orbits are...
  14. D

    What is the difference between the God Particle and the Graviton?

    What is the difference between the "God Particle" and the Graviton? I understand that they are looking for, and are hopefully close to finding the Higgs Boson, either with the Tevatron or with the LHC, whichever finds evidence for it first, and that the Higgs supposedly generates a field which...
  15. L

    GR and the role of the graviton

    If I understand things correctly, GR says that gravity isn't really a force at all, gravity is just particles moving in the geometry of spacetime. Given this, I don't understand the role of the graviton. I thought that gauge bosons were force mediators, that they somehow communicated and...
  16. L

    Graviton and photon point particles in reality

    Suppose you have a fine layer of dust facing perpendicular to a strong gravitational body. If gravitons are point particles then could you expect to observe the gravitons pulling at the dust particles one by one as they come into contact with the dust or would the dust move uniformly closer to...
  17. C

    How can people predict that the graviton is a particle of spin 2?

    how can people predict that the graviton is a particle of spin 2?
  18. D

    Graviton energy and frequency/wavelength?

    Hopefully I can get some knowledgeable help on this question. I'm not a physicist but I am an electrical engineer (by education anyway) and a database architect by avocation. I'm a bit of a physics junkie and some of my self study leads to this problem. I see a lot of mention of searching...
  19. shintashi

    Graviton amusement ride as generator?

    Hi, I was thinking about the graviton ride at amusement parks - the one that sort of simulates the feeling of gravity by spinning. I was wondering if the pressure between two objects (such as your head and the surface when spinning around) is potentially useful in terms of power generation, via...
  20. G

    Graviton vs Gluon Ball: Can Graviton Replace Gluon?

    Can graviton possible act like gluon ball? Why not?
  21. D

    Why do people insist on the graviton

    When Einstein specifically showed there was no gravitational 'force', rather a repulsion of curved space. Is there something wrong with his theory that we must throw it all out the window and replace it with another meaningless hypothetical particle scenario?
  22. scupydog

    Can the LHC Detect Gravitons and Reveal New Physics?

    Does anyone know if the LHC could detect the graviton thx
  23. E

    Could the quanta of gravity be something other than a spin-2 graviton?

    GR predicts gravitational waves, and QM says all waves are also particles. But does the particle of gravity have to be a spin-2 graviton? could the particle of gravity be, for example, a quanta of space-time curvature?
  24. J

    Finding Graviton Propagator from QFT in a Nutshell- Zee's Exercise

    On page 36 of QFT in a nutshell, Zee sets an exercise to find the propagator for a massive spin 2 particle by assuming that it is a linear combination of terms such as G_{\mu\nu}G_{\lambda\sigma}. The only method I can think up for doing this is to write down all 36 products of...
  25. C

    Is the Graviton Fundamental in Quantum Gravity Theories?

    From the Not Even Wrong thread on Garrett Lisi's E8 theory: I had some questions in response to this; Woit complained (quite correctly) that my post didn't have anything to do with E8 or Woit's blog and requested the discussion not continue there. So I'm posting it here instead. My response...
  26. M

    What is the graviton propagator in the first order formalism?

    With the help of harmonic gauge condition, graviton propagator can be obtained by weak field expansion around the flat Minkowski metric (assuming cosmological constant is zero). Gravitation theory can also be written in the first order (Palatini) formalism. In stead of the metric, the basic...
  27. H

    Uncovering the Mystery of the Graviton: Evidence and Implications

    What proof do we have that the graviton actually exists? Quote from http://hyperphysics.phy-astr.gsu.edu/hbase/particles/expar.html" "The graviton is the exchange particle for the gravity force. Although it has not been directly observed, a number of its properties can be implied from the...
  28. U

    Can Photons Emit Gravitons in the Absence of Black Holes?

    They say that light cannot escape gravitational pull of black holes, and also that gravitation is due to exchange of graviton particles, how can thy photons give out thy graviton, black holes don't exist
  29. K

    The graviton pisses me off.. .

    Well, not really, but I am really struggling with understanding the motivation for its inclusion in the Standard Model; I'm hoping someone here might provide some guidance. My understanding of General Relativity is that gravitation is a purely local phenomenon; i.e. two massive entities in...
  30. Pythagorean

    Higgs & Graviton: Interaction or Separate Particles?

    Are the Higgs and the Graviton supposed to interact or are they two different particles from two different theories?
  31. S

    Second-Order Graviton Propagator in Rovelli-Smolin's Loop Quantum Gravity

    I have finished a quick first reading of the rovelli at all paper ingraviton propagator http://arxiv.org/gr-qc/0604044 I couldn´t dive too much into the details because spin foams was a prerequisite and i only could do an equally fast reading of the alejandro perez review of the subjecto...
  32. C

    Graviton Spin: What is Moment of Inertia x Angular Frequency?

    If Spin is 'moment of inertia' (I) x 'angular frequency' (w), what does it mean when we say a particle has spin = 1 or spin =2 like in the theoretical Graviton's case?
  33. C

    Graviton Properties, best guesses?

    Hey, Do physicists have any idea about any of the theorized 'graviton's' properties? spin charge rest mass wave length anything? As far I know (which is very little) the only thing we know is Gravity's strength relative to the other 3 forces. P.S. Why was LISA's three arms set...
  34. T

    Why Can't Photons Have a Spin of 0 Like Gravitons?

    The graviton has a spin of 2. So, that means the graviton can take possible spins: -2, -1, 0, 1, 2 ? Just want to make sure since, for a photon, even if it's spin 1, it can only take two possibilities, i.e. -1 and +1. 0 is not allowed.
  35. Orion1

    Is the Yukawa Strong Nuclear Flux dependent on both gauge and radius?

    What is the solution for a static graviton flux monopole through a closed surface? :rolleyes: Sphere surface area: dA = 4 \pi r^2 \Phi_G = \oint G_g \cdot dA = \oint G_g \cdot (4 \pi r^2)
  36. E

    Can a Functional Equation Solve the Problem of Time in Quantum Gravity?

    We have for Quantum gravity the equation: H|\Psi>=0 as you can see this is time-independent partial differential equation, my question is if we could construct a functional differential equation in the form: \alpha{d\Psi/dt}+\Beta{H_1}=0 where the H1 would have the derivatives respect to...
  37. R

    Understanding Graviton Spin: Unveiling the Mystery of Spin 2

    How do we know that a graviton has to be spin 2?
  38. Ε

    Gravitons & GR: Does Curved Space-Time Exist?

    Would a graviton theory replace the curved geometry of general relativity? If gravitons are the cause of the gravitational force, does that mean space and time aren't really curved as Einstein thought?.. :confused: And maybe an unrelated question, is it better to think of curved space-time...
  39. R

    Graviton and general relativity

    Is the idea of a graviton reconcilable with general relativity? Is that already quantum gravity or something that works perfectly with existing gr?
  40. R

    What is the difference between the Higgs Boson and Graviton?

    Hi. I hope I'm posting in the right place. I was just wondering, what is the difference between the graviton and the higgs boson. I'm not quite sure, I think I sort of understand it... but not really. Also, since I don't want to make a new thread for such a small question, is there...
  41. W

    Graviton Theory: Inertial vs Gravitational Mass

    gravitons ?? is the inertial mass proportinal to the gravitational mass in the graviton theory of gravitation ? I ask this because I can see easily how GR imply that the two masses must be equal since spacetime curvature acts at everypoint in the body. But with gravitons I can't understand how...
  42. A

    The higgs boson=the graviton= the speed of light

    an underlying fabric that permeates even a vacuum space and displays liquid like characteristics (most evident on a macro and micro cosmic scale ie wave particle duality, dark energy) the energy of this fabric is known as c, the speed of light which is the manifestation of the expansion...
  43. J

    What Are the Degrees of Freedom for a Massive Spin 1 Particle?

    I was wondering if anyone has any insights or can guide me to some decent literature of the coupling of the graviton to mass. I became intrigued about this when thinking about presenting the gravitational interaction in a Feynman diagram. If anyone has any ideas or knows I would greatly...
  44. S

    Graviton and the equivalence principle

    I posted this in general physics, but I didn't get an answer, so I'll try again here: Einstein's theory of general relativity was motivated by his equivalence principle, that no experiment can distinguish between an accelerated frame and a still frame under the influence of gravity. But if...
  45. O

    Graviton Effects in Different Media: Investigating the Variations

    Hello everyone! How does the effects of gravitons work in different media? I know it expands with the speed of light, but since light has different speeds in different media, does gravitons aswell? I'd appreciate any answers.
  46. marcus

    What is Alejandro's take on strings, gauge theory, and gravity?

    Alejandro recently submitted a post at SPS which engaged the active attention of Lubos Motl. So much so that unless one has sharp eyes one cannot see Alejandro's original post-----there are so many "moderator notes" inserted by Lubos. this means Alejandro's original post probably has some...
  47. N

    How Are Gravitons Related to Closed Strings in String Theory?

    I don't know the relation of graviton and closed string. Why the graviton is closed string? And what conditions need that? :confused: I really want to know about it in detail.(of course including formula)
  48. J

    Gravity: Warped Space-Time or Graviton?

    if common theory states that gravity exists due to a warping of space-time, then that really doesn't leave any room for the graviton, right? or wrong?
  49. S

    What is the graviton? Please place your definitions

    1. A quantizied gravitational wave... 2. They travel at the speed of light 3. They have never been experimentally proven to exist. 4. They have been theoretically proven? 5. They permeate all dimensions. I have some ideas fixed in my head that need to be corrected. In another thread...
  50. T

    Why Does Quantum Mechanics Treat Gravity as a Force?

    Gravity is seen as an effect of spacetime curvature in GR. Why is it that QM sees gravity as a force like the other three fundamentals: Strong, weak and EM. If this is so, why bother envisaging on the graviton, when gravity is due to spacetime curvature and not force via virtual particles.
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