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. Quarlep

    Graviton and other particle interections

    We know that graviton spin is 2 so other lepton and quarks spin is 1/2 I am confused because If Graviton and a quark or maybe a lepton make an interaction than the last spin must be 3/2 or 5/2 but there's no particle exist in this spin quantity.It means there's no particle called graviton or I...
  2. J

    Is the Graviton Too Elusive for Particle Physicists to Find at the LHC?

    Why is there seemingly so little interest among particle physicists about discovering the graviton? Is it because it is believed to be too difficult, even hopeless, to find, or some other reason?
  3. sujoykroy

    Does Einstein's General Theory of Relativity imply graviton?

    I was reading Einstein's paper "The Foundation of the General Theory of Relativity" and as i understood, he tried to establish that gravitation arises due to different kind of motions of objects. As per his opinion, in infinitesimally small space-time region special theory of relativity is still...
  4. K

    What Is Graviton? Understanding Gravity & Matter

    i read an article about graviton. but i still don't understand what graviton is. I think gravity is force not matter .
  5. P

    Why Do Physicists Postulate the Existence of a Graviton?

    We know that there are force carrying particles for the strong and weak nuclear force, and the electromagnetism force. But in Einsteins theory of relativity, he states that gravity is the bending of space time, not a force. So if there is no force, why do we say there must be a graviton? Ps I'm...
  6. craigi

    How do gravitational fields and waves interact with black holes and FTL travel?

    How fast do we expect the hypothetical graviton to travel? It seems that if the graviton were to mediate the gravitational force then it wouldn't be subject to the normal FTL rules otherwise black holes would have no gravitational effect on the rest of the universe. What's the current...
  7. S

    Why is a massless spin-2 automatically a graviton

    The Wikipedia page on the graviton http://en.wikipedia.org/wiki/Graviton contains the following sentence: "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 must couple to (interact...
  8. H

    Regarding graviton and negative energy

    Hi. I recently listened to a lecture by Alan Guth, speaking about cosmological inflation. He made the statement that the energy of a gravitational field is negative (followed by a great thought experiment with a collapsing shell of matter to demonstrate this). I am curious; does this mean that...
  9. K

    How is the effective Lagrangian for the Graviton coupling to matter derived?

    Could someone point to me where they derive the follow effective Lagrangian for the Graviton coupling to matter L = \frac{1}{M_{pl{}}}h^{\mu \nu}T_{\mu \nu}
  10. R

    Why are we looking for graviton particles

    General relativity shows that gravity is a culture of space time. Suppose that we are in a gravitational field. This can be caused by the presence of matter or being in an accelerating frame of reference. In either case, it is possible to select another accelerating frame of reference for which...
  11. T

    Exploring the Debate: Graviton vs Higgs Boson and the Origin of Gravity

    How can we propose the existence of a massless graviton when the recent discovery of the higgs boson means that there is a Higgs field that endows everything with mass? Doesn't the higgs field disprove the graviton? In that case, we would now have no idea where gravity fundamentally comes from...
  12. L

    What is a Graviton? Exploring Origin & Properties

    I tried looking it up but I can't understand it. Is the graviton some kind of theoretical particle that gives of gravitational waves? I read that it has a 2 spin and is also a boson. And where did this idea originate from? Thanks in advance.
  13. Mordred

    Is the Graviton Necessary for Gravity in Light of Higgs Field Discoveries?

    After the Cern discovery supporting the Higgs field Which is something I have little familiarity with. Due mainly to fourm opinions not necessarily this one that had discounted anything Higgs related. I started wondering if we do need a graviton to be the force carrier of gravity in the...
  14. U

    Electron and graviton degrees of freedom

    Hi dear all Please explain to a stupid dummy a very simple thing. Take an a photon in 1+3 dimensions. How DOF it has? We all know that 2. How we calculate it? a) 1) We have a spin 1 particle that should have 2s+1=3 spin state. So DOF=3. 2) We have 4 Aμ guys. One is out because of gauge...
  15. S

    Is the Graviton the Key to Understanding Gravity?

    Why? As I understand it General Relativity states that gravity is the warping of space-time, so it seems a reasonable assumption that as a consequence of this that gravity does not require a force carrying particle as the strong and electroweak forces do. Are there theories being explored...
  16. bcrowell

    Angular momentum coupling with graviton exchange?

    I know there are many deep issues that come up in attempts to do quantum gravity, but I suspect that the following is not deep but easily explained by someone who knows more about this than I do. Suppose two neutrons are interacting gravitationally. The Feynman diagram that I would naively draw...
  17. L

    Interaction Between the Higgs and the Graviton

    Recently, I was surfing Youtube looking for scientific videos, and I came across one on black holes. Naturally, I figured I'd already heard it all before, but decided i might as well watch it anyways. At one point, it talked about black holes making "dents" in space-time due to its its gigantic...
  18. S

    Could the new particle @ CERN be a massive graviton?

    Hi PF. I was wondering, if the newly observed particle @ CERN, could be a massive tensor boson, like a massive graviton. I have not been able to find out, whether ATLAS or CMS have determined if the new particle is a scalar, vector or tensor boson, so I thought it would be intersting, if the...
  19. A

    Higgs boson and graviton relationship?

    F=GM1M2/r^2 The force of gravity without mass is 0. Wouldn't this imply that gravitons and higgs bosons come in pairs? Is there any evidence of gravitons and higgs bosons existing only in pairs?
  20. D

    What is Graviton-Graviton Scattering in Quantum Theory of Gravity?

    Hi Everyone, :shy: I read in some paper about the significance of Graviton-Graviton Scattering as a theoretical tool in Quantum Theory of Gravity. Would someone bother to explain in detail what phenomena it is and how it is useful in Quantum Theory of Gravity.:confused: And I might not have...
  21. N

    Graviton Propagator and energy-momentum tensor

    Dear PF, I am a little bit confused could you pls help me ... Suppose I a have a scatering or conversion of two particles via graviton propagator. Graviton propagator couples with energy-momentum tensor of matter fields. So can i assume that vertex to which graviton propagator is coupled...
  22. R

    How could a graviton mediate gravity at places such as a black hole?

    Is there some type of exception to the singularity for gravitons? And if not gravitons then what? I understand the spacetime curvature except why does a sun not collapse in on itself right now when it does after fusion has stopped? I'm told it's from energy creating pressure outwards...
  23. M

    Energy release from Graviton / Higgs Boson

    With so much coverage in the press over the seemingly imminent discovery of the Higgs particle, there's one question that never seems to get raised - which more than likely means I've missed something fundamentally simple; so this may be a very short thread! Higgs Boson / Graviton - it may be...
  24. A

    Hypothetical graviton : Why a spin of 2 ?

    Hi, Why have the hypothetical gauge boson of gravitation, the so-called graviton, a spin of 2 ? What about his chirality ? (projection of spin on his propagation direction) I mean, does it mean that the graviton can have a polarisation like a photon, but that this polarisation is two...
  25. E

    Are there Spin-2 bosons other than graviton?

    Are there Spin-2 bosons other than graviton? Does QFT allow for this? Spin-1 bosons not only includes photons, but W Z bosons and gluons could there be spin-2 bosons that have mass or have other types of charges?
  26. M

    Graviton: Energy, Impulse, Frequency & Quantum

    Graviton is an analogy or an exact object in he framework of classical GR? What bout the energy and impulse of a graviton with frequency nu? What is the quantum?
  27. G

    Higgs Boson & Graviton: Same or Different?

    Is the Higgs boson and the Graviton two descriptions of the same thing?
  28. D

    Relation between Higgs boson and graviton

    The graviton (spin 2) and the Higgs boson (spin 0) are both involved in gravity. The Higgs carrying mass, and the graviton carrying the gravitational interaction. On the internet I red that a lot of people wonder if there is a connection. In electroweak interaction the forces are carried by...
  29. michael879

    Deriving Graviton Propagator from Linearized Lagrangian

    Hi, I'm working with the free space linearized gravitation lagrangian and trying to derive the proper propagator for it. I have no problem doing this, the only problem is that my QFT makes a quick note of what form this should take and I'm off by a factor of 4. The flatspace metric terms...
  30. Q

    Who is the top physicist skeptical of gravitons?

    Who would you say is the leading physicist, if any, who does not believe in gravitons?
  31. R

    Write a report into what graviton is

    So, I have to write a report into what the graviton is and how we are searching for it. However after reading around a fair bit,I really don't know what to do.I know what it is but I don't know how we are looking for it/theories relating to it. So what I am asking is if anyone can help me...
  32. R

    What the graviton is and how we are searching for it

    So, I have to write a report into what the graviton is and how we are searching for it. However after reading around a fair bit,I really don't know what to do.I know what it is but I don't know how we are looking for it/theories relating to it. So what I am asking is if anyone can help me...
  33. E

    A question about graviton self-interactions in QFT

    Gravity when expressed as QFT suffers from renormalization problems. From the point of view of the techniques of (four-dimensional) quantum field theory, and as the numerous and heroic efforts to formulate a consistent quantum gravity theory by some very able minds attests, gravitational...
  34. D

    Solving the Mystery of Graviton & Einstein's Accelerating Frame Model

    Hi. I'm a sophomore level undergrad trying to understand General Relativity (and all of physics for that matter) with the currently insufficient tools I possess. I was reading Einstein's book, "Relativity", and when I came to the section that describes gravity as the apparent force that arises...
  35. U

    Gravity and Mass: What's the Need for a Graviton?

    Hello, Please help an amateur understand. I don't see the need for a Graviton. I thought gravity was explained by: "Mass causes the curvature of space time". Hence objects "fall" toward each other in a sense; along the curved space time caused by their respective masses. So why the need...
  36. N

    Gravity curvature and graviton

    Hello all, I'm new to GR and trying to understand everything in general now... I was looking at pictures like this one http://upload.wikimedia.org/wikipedia/commons/2/22/Spacetime_curvature.png for a very long time. I made two major "experimental" conclusions here: 1. A meter near planet...
  37. D

    Gauge Boson: Higgs vs Graviton

    Forgive my lack of particle physics undestanding, I'm still trying to teach myself! I've been looking into gauge bosons and I'm trying to distinguish between the Higgs and the graviton. From what I know, the Higgs is the particle postulated by the standard model to give all others mass...
  38. R

    Graviton: Is It Possible That It Does Not Exist?

    hi, is it possible that the graviton does not exist?. except the success of quantum field theory, and the usefulness of graviton in string theory, are there other good reasons to hypothesize the graviton? thank you in string theory, gravitons are different because they can travel outside...
  39. Z

    General Relativity and a Force Mediating Graviton?

    This may be a naive question as I am only still working on my undergrad in physics and while I am quite familiar with special relativity it will be another year or two before I formally study general relativity. On top of that my knowledge of the modern work to explain gravity alongside quantum...
  40. F

    Is the graviton a different particle from the higgs boson

    I was reading this book that separated the graviton from the higgs boson. Can I get some help anything works for me.
  41. C

    Why is the graviton non-renormalizable?

    Okay, I've taken relativistic E&M and the first semester of quantum mech. Why is the graviton non-renormalizable? As I understand it, renormalization means that you can apply a "weight" to the feynman diagrams of an interaction to make it come out right (is that correct?) Why can you not do...
  42. jaketodd

    Graviton & Conservation of Energy etc.

    If an object absorbs a graviton, can it emit the same graviton? I would think that the gravitational energy would have to be transmitted to the object and if the object emitted the graviton again, it would lose the effect the graviton had on it. But I read somewhere that gravitons are not...
  43. jaketodd

    Does the graviton move at the speed of light in any reference frame?

    Does the graviton move at the speed of light in any reference frame? Thanks, Jake
  44. jaketodd

    Spacetime proven or is the Graviton still alive?

    Has the interlinking of space and time been proven? If so, how? Is there any hope left for the graviton?
  45. V

    Could Gravitons Be the Missing Link to Understanding Dark Matter?

    Hey guys, I was just pondering the idea of dark matter and a thought crossed my mind. I may be entirely off, but a few connections can be made between gravitons and dark matter. Neither can be detected directly with any classical methods (EM, pressure, etc..), and dark matter has no apparent...
  46. B

    Would a graviton follow the geodesic?

    A graviton, if massless, is generally expected to travel at c. If so, we would not expect it to follow the geodesic, which is the path a hypothetical particle with infinite speed. Therefore I would think for example that a massless graviton that was gravitationally lensed around a galaxy would...
  47. N

    Feynman rules (vertecies) for graviton

    Hi, Could u advise me please some references where the Feynman rules for graviton are derived I mean graviton-scalar graviton-graviton scattering ... in general graviton vertecies ... Thank you
  48. C

    How is it also a graviton particle as in string theory

    if gravity is a a sheet of space and time how is it also a graviton particle as in string theory
  49. A

    Exploring the Possibility of the LSP as the Graviton

    Hey, guys. I'm going to start off by saying I know near nothing regarding physics and don't claim to be more than completely ignorant in anything passed the fields considered pre-calculus. I have a huge interest in particle physics, though—and have decided to take a more academically rigerous...
  50. K

    New to Graviton & Doppler Shift: Need Help Understanding

    I am new at this so I hope you all will excuse me if I am stupid. But I got this idea about the graviton. If it is a wave then it should display some sort of doppler shift when it moves with respect to the observer. So there it is , somebody tell me why I am dumb.
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