The conservation of parity and time reversal

The fact that the multiplication rule is still valid for improper Lorentz transformations does not necessarily mean that P and T are conserved, but rather that the mathematical structure of the group still holds. In summary, while studying Ch 2.6 of Weinberg QFT vol I, the conversation discussed the conservation of parity and time reversal. It was noted that while the fundamental multiplication rule of the Poincare group is still valid for improper Lorentz transformations, this does not necessarily mean that P and T are conserved in real physics. This is due to the fact that the multiplication rule is a mathematical statement and does not always hold in physical reality.
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While I was studying Ch 2.6 of Weinberg QFT vol I, I came to have some question about the conservation of parity and time reversal.

In page 74 and 75 of Weinberg vol I, it says the fact that fundamental multiplication rule of the Poincare group is still valid even when we concerns improper Lorentz transformations(such as P and T in the beginning of page 75) incorporate that P or T are conserved.

However, we know that Parity and Time Reversal are not conserved in real physics, so fundamental multiplication rule of the Poincare group is not valid when we concerns improper Lorentz transformations.

But, I don't know why.. fundamental multiplication rule is from pure group theoretical approach. isn't it?

Please point out what I am missing.
 
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  • #2
The fundamental multiplication rule of the Poincare group is a pure mathematical statement which assumes that the elements of the group (which includes P and T) obey certain properties. In reality, however, these elements do not always obey those properties, so the fundamental multiplication rule can be violated. This is why parity and time reversal are not conserved in real physics.
 

FAQ: The conservation of parity and time reversal

What is the conservation of parity and time reversal?

The conservation of parity and time reversal, also known as the CPT symmetry, is a fundamental principle in physics that states that the laws of physics should remain the same if the direction of time is reversed, and if the positions of particles are swapped with their antiparticles. It is a crucial concept in understanding the symmetry of the universe.

Why is the conservation of parity and time reversal important?

The conservation of parity and time reversal is important because it helps explain the fundamental laws and principles of the universe. It also plays a critical role in various fields of physics, including particle physics, quantum mechanics, and cosmology. This principle has been extensively tested and confirmed through various experiments and observations.

Can the conservation of parity and time reversal be violated?

While the conservation of parity and time reversal has been extensively tested and found to hold true, there have been a few rare cases where it has been observed to be violated. These occurrences are usually in high-energy particle interactions and are still being studied by physicists to better understand the underlying principles of the universe.

How does the conservation of parity and time reversal relate to the conservation of energy and momentum?

The conservation of parity and time reversal is closely related to the conservation of energy and momentum. These principles all stem from the idea of symmetry in the universe. Just as energy and momentum are conserved, the CPT symmetry dictates that the laws of physics should also be conserved when certain transformations are made to the system.

How does the violation of the conservation of parity and time reversal impact our understanding of the universe?

The rare occurrences of the violation of the conservation of parity and time reversal have led to significant advancements in our understanding of the universe. They have challenged our current understanding of the fundamental laws of physics and have opened up new avenues for research. By studying these violations, scientists hope to gain a deeper understanding of the underlying principles that govern our universe.

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