Understanding Spin 2 Particles: Exploring the Possibility of Gravitons

In summary, two spin 1 photons put together will create a particle that looks the same when rotated through 180 degrees. This particle is called a spin 2 particle and is supposed to have the spin of a graviton. While we're here, it is possible to create single particle states from other single particle states by going between massless and massive representations.
  • #1
kurious
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If two spin 1 photons are put together so that the tips of their magnetic field vectors just touch one another ( the vector lines are all in the same plane), a particle results which looks the same when it is rotated through 180 degrees - a spin 2 particle.This is the spin a graviton is supposed to have.
Is this a graviton?
 
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  • #2
You can construct systems of n photons in which the total spin angular momentum is any integer between -n and +n. This does not mean that single particle states with helicity n and -n are formed. A single particle state is defined as an irreducible representation of the little group of the Poincare group in whatever spacetime dimension you're considering. In 4 dimensions, the little group is ISO(2). A helicty +/- 1 states form an irreducible representation. A helicty +/- 2 states form an irreducible representation. Etc. Therefore, two photons together do not a graviton make.
The n photon system forms a reducible representation under ISO(2): n copies of helicty 1 states.

While we're here, a situation where we can construct single particle states from other single particle states can occur when you go between massless and massive representations. For example, the little group for massive states in 4D is SO(3). A massive spin 1 particle forms the 3 dimensional (irreducible) representation of that group. Under the little group for the massless states, ISO(2), the 3 rep breaks into a 2 and a 1. These are interpreted as a massless spin 1 particle and a scalar particle. This type of decomposition (in reverse) happens when we say a massless vector particle "eats" a scalar particle to become massive.
 
  • #3
What do you think a graviton would be like then - I think we should be able to visualise what it is - we can visualise photons and atoms - so why should a graviton be so different? I agree that two photons do not a graviton make because two photons in a beam of light would then be a graviton! If the photons traveled faster than light, that would make them different - perhaps gravitons.
 

1. What are spin 2 particles?

Spin 2 particles are subatomic particles that have a spin quantum number of 2. This means that they have two units of intrinsic angular momentum, and are classified as bosons. They are fundamental particles that make up the fabric of the universe.

2. How are spin 2 particles different from other particles?

Spin 2 particles are different from other particles because they have a higher spin quantum number. This means they have more intrinsic angular momentum and behave differently in certain interactions. They also follow different rules when it comes to quantum mechanics and have unique properties.

3. What is the significance of spin 2 particles in physics?

Spin 2 particles are significant in physics because they are crucial in explaining fundamental forces and interactions in the universe. For example, the graviton, which is a spin 2 particle, is responsible for the force of gravity. Understanding the properties of spin 2 particles helps us understand the fundamental laws of nature.

4. How are spin 2 particles detected and studied?

Spin 2 particles are detected and studied using particle accelerators and detectors. Scientists accelerate particles to high energies and collide them, producing new particles, including spin 2 particles. These particles are then analyzed using detectors that can measure their properties and behavior.

5. Can spin 2 particles be observed in everyday life?

No, spin 2 particles cannot be observed in everyday life. They are only observed in high-energy experiments, such as particle accelerators. In everyday life, we interact with particles that have lower spin quantum numbers, such as electrons and protons.

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