Graviton vs Einstein's Curvature of Spacetime

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Discussion Overview

The discussion centers on the compatibility of the graviton concept with Einstein's theory of gravity as the curvature of spacetime caused by matter and energy. It explores the theoretical implications of viewing gravity through both classical and quantum lenses, addressing the nature of gravitons and their relationship to gravitational fields.

Discussion Character

  • Debate/contested
  • Conceptual clarification
  • Technical explanation

Main Points Raised

  • Some participants question whether the existence of gravitons can coexist with the idea of gravity as spacetime curvature, suggesting a potential conflict between quantum and classical views.
  • Others argue that there is no contradiction, proposing that spacetime can appear smooth at large scales while being composed of gravitons at smaller scales.
  • One participant notes that while conventional wisdom suggests a massless spin-2 graviton replicates Einstein's field equations, there are qualitative differences, particularly regarding the localization of energy in gravitational fields.
  • Another viewpoint emphasizes that gravitons, like other force carriers, are better understood as excitations of fields rather than traditional particles, challenging the notion of calling them particles.
  • Some participants propose alternative terminology, such as "quantum particle" or "quanticle," to better describe these entities.
  • There is a discussion about the properties of particles and fields, with some arguing that the historical classification of particles may be misleading, particularly in light of quantum field theory.

Areas of Agreement / Disagreement

Participants express differing views on the relationship between gravitons and classical gravity, with no consensus reached on whether the two concepts can be reconciled. There is also disagreement regarding the terminology and conceptualization of particles versus fields.

Contextual Notes

Limitations in the discussion include unresolved definitions of "particle" and "field," as well as the implications of quantum mechanics on classical theories. The debate reflects ongoing uncertainties in the interpretation of gravitational phenomena.

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As far as I understand it, Einstein theorized that gravity was the result of the curvature of space created by the presence of mater/energy, but that idea seems like it does not meld well with the idea that gravity is the result of a specific force carrying particle, as with the other fundamental forces. So my question is this: is the idea of the existence of gravitons compatible with the idea that gravity is the manifestation of spaced being warped by matter and/or energy?
 
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The graviton is a quantummechanical concept, while GR is classical. You could say that just as a laserbeam is a coherent state of photons but classically looks like a wave, spacetime might look smooth at large distances but a coherent bunch of gravitons at smaller scales.

So no, there is no contradiction.
 
Conventional wisdom holds that the physics of a massless spin-2 graviton exactly replicate Einstein's field equations in the classical limit, although there are certainly important qualitative differences between a graviton theory and classical GR, and I am not convinced that the conventional wisdom is correct. For example, in classical GR it is impossible to localize the energy in a gravitational field, while in a graviton theory, the energy of a gravitational field is by definition, localized.
 
The graviton (photon, gluon) is not really a particle but an elementary excitation of the gravitational (electromagnetic, chromodynamic) field. To call gravitons, photons, or gluons particles is just a historical accident. They have hardly any particle properties in an intuitive particle sense and are best pictured as little wavelets, though even this is more an illustration than a correct picture of what they are.
 
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Let's call it a 'quantum particle',then.
 
or a 'quanticle'.
 
Last edited:
haushofer said:
Let's call it a 'quantum particle',then.
I think the word "particle" is best left in the classic domain and "quantum object" is better for photons, etc.
 
A. Neumaier said:
The graviton (photon, gluon) is not really a particle but an elementary excitation of the gravitational (electromagnetic, chromodynamic) field. To call gravitons, photons, or gluons particles is just a historical accident. They have hardly any particle properties in an intuitive particle sense and are best pictured as little wavelets, though even this is more an illustration than a correct picture of what they are.

Not sure that I would agree with this point, particularly given the fact that the W and Z bosons that transmit the weak force have mass, that gluons, while the lack rest mass, appear to acquire mass dynamically in QCD, and that all Standard Model bosons (except the Higgs, of course) have a well defined spin-1. Moreover, particles aptly capture the observation of Planck, that at any given frequency, the energy of a photon comes in discrete chunks. Arguably, it is the fields, and not the particles, that are historical accidents.
 

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