Does Antimatter Repel Matter Due to CPT Symmetry?

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Discussion Overview

The discussion centers around the implications of CPT symmetry on the interaction between matter and antimatter, specifically whether antimatter repels matter. Participants explore the definitions and consequences of CPT symmetry, including its effects on gravity and the nature of attraction and repulsion between matter and antimatter.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants assert that CPT symmetry implies antimatter would repel matter, while matter attracts matter and antimatter attracts antimatter.
  • Others argue that matter and antimatter attract each other due to gravity, as both possess positive energy, and gravity does not differentiate between them.
  • Participants discuss the components of CPT symmetry: charge conjugation, parity, and time reversal, and their implications for the behavior of particles.
  • One participant requests clarification on the meaning of spatial coordinates being reversed and the implications of time direction being reversed in the context of CPT symmetry.
  • There is mention of annihilation events, such as positrons being attracted to electrons, as part of the discussion on interactions between matter and antimatter.

Areas of Agreement / Disagreement

Participants express conflicting views on whether antimatter repels matter or if they attract each other through gravity. The discussion remains unresolved with multiple competing perspectives presented.

Contextual Notes

Some assumptions about the nature of gravity and energy in relation to matter and antimatter interactions are not fully explored. The discussion also lacks a consensus on the interpretation of CPT symmetry and its implications.

Johnleprekan
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According to CPT Symmetry matter has reversed charge, spatial coordinates, and time. This includes gravity. So this means that antimatter would attract other antimatter and matter would attract other matter. The difference is when antimatter gets near matter. They repel each other.

First, can someone explain what CPT is in layman's terms? What does it mean to have spatial coordinates reversed? For time, it does not mean time is reversed but direction is. Can someone explain this one anyway?

If the cpt is reversed, why does antimatter repel matter? What is happening on a quantum level that causes it to repel?
 
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Johnleprekan said:
According to CPT Symmetry matter has reversed charge, spatial coordinates, and time. This includes gravity. So this means that antimatter would attract other antimatter and matter would attract other matter. The difference is when antimatter gets near matter. They repel each other.

No. Matter and antimatter attract each other via gravity. Gravity only cares about energy, and matter and antimatter both have positive energy.

CPT has three parts:

Slightly simplified, these are:
C - Charge conjugation. This is flipping positive and negative charges.
P - Parity. This is just reflection in a mirror.
T - Time reversal. This is just reversing the direction of motion of all particles.

CPT symmetry means that if you do all of these things at once--reflect the universe in a mirror, flip all positive charges with negative ones, and reverse the direction of motion of all particles--you get a universe that looks and acts exactly like the original one. The laws of physics will not notice if you perform C, P, and T all at once.
 
Last edited:
Thank you.
 
The_Duck said:
No. Matter and antimatter attract each other via gravity. Gravity only cares about energy, and matter and antimatter both have positive energy.
Matter and antimatter are attracted by charge difference, e.g., a positron is attracted to an electron, and both are annihilated.

Matter and antimatter have rest mass, and a mass (e.g., kg) of antimatter would behave the same in a gravity field as would the same quantity of mass of matter, i.e., gravity does not distinguish between matter and antimatter, as far as we know.
 

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