Vacuum energy and momentum

In summary, quantum field theory predicts that the vacuum should have energy and momentum, and this can be seen in the non-zero vacuum energy value due to the Heisenberg Uncertainty Principle. These fluctuations in energy are a result of virtual particles, which correspond to internal Feynman lines and violate the Einstein energy relationship. However, total energy and momentum conservation is always respected in all states. Current research and theories focus on understanding these virtual particles and their role in interactions.
  • #1
touqra
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I read that quantum field theory predicts that the vacuum should have some sort of energy and momentum.

I could this be when the concept of energy is not absolute? All we measure in the lab is the difference in energy.

In addition, I also read that the cosmological constant in Einstein equation can be interpreted as the energy density of the vacuum. What are the current research and theories on these?
 
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  • #2
touqra said:
I read that quantum field theory predicts that the vacuum should have some sort of energy and momentum.

Are you referring to the fact that in QM/QFT, the vacuum energy value is NON ZERO because of HUP ? If so, you are asking about vacuum fluctuations, right ?

such fluctuations are a manifestation of
1) HUP (vacuum energy value is non zero)
2) HUP (short timed violation of energy conservation)
3) the transistion from QM to QFT (virtual particles)
4) Appropriate conservation laws that are valid for the appropriate interaction (like charge conservation for EM-interaction)

Point 3 means that in quantummechanical perturbation theory the interaction goes from the initial state to the final state by passing over the "virtual transition states". These states have a short lifetime because of the HUP for time and energy.

Due to the fact that energy is uncertain, such states can (and will) violate total energy conservation. Beware that if you compare initial and final state, total energyconservation is ALWAYS respected. Momentum conservation is always respected in ALL states. In QFT, these transition states correspond to virtual particles (ie fluctuations of fields).

Virtual particles correspond to internal Feyman lines. They are always off mass shell (ie they don't respect the Einstein energy relationship). The bigger the difference between the particle's four momentum and it's mass (thus the bigger the violation of E=mc^2) the smaller the probability for such an interaction (mediated by the virtual particles) to occur. Hence, there is a price to pay for being virtual...isn't that nice ? :)


regards
marlon
 
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  • #3


I can confirm that quantum field theory does indeed predict the existence of vacuum energy and momentum. This concept arises from the idea that even in empty space, there are constantly fluctuations and interactions of quantum fields that give rise to energy and momentum.

The idea of energy not being absolute is a fundamental concept in physics, as energy is always measured relative to a reference point. In the case of vacuum energy, it is the lowest possible energy state that can exist in a given space.

Regarding the cosmological constant, it is indeed interpreted as the energy density of the vacuum in Einstein's equation. This is a topic of ongoing research and there are various theories and models attempting to explain the nature and origin of this energy. Some theories propose that it is a fundamental property of space, while others suggest that it could be linked to the existence of dark energy.

Further research and experiments are needed to fully understand the nature of vacuum energy and its implications for our understanding of the universe. The concept of vacuum energy and momentum is a fascinating area of study that continues to challenge our understanding of the fundamental laws of physics.
 

What is vacuum energy and momentum?

Vacuum energy and momentum are concepts in quantum mechanics that refer to the energy and momentum associated with the vacuum or empty space. In classical physics, vacuum is considered to be completely empty, but in quantum mechanics, it is filled with virtual particles that constantly pop in and out of existence. These particles contribute to the overall energy and momentum of the vacuum.

How does vacuum energy and momentum affect the universe?

Vacuum energy and momentum play a crucial role in the dynamics of the universe. They are responsible for the expansion of the universe, as well as the formation of structures such as galaxies and clusters of galaxies. The amount of vacuum energy and momentum also affects the overall curvature of the universe.

Can vacuum energy and momentum be measured?

While vacuum energy and momentum cannot be directly measured, their effects can be observed through various phenomena such as the Casimir effect and the expansion of the universe. Scientists also use mathematical models and calculations to estimate the amount of vacuum energy and momentum in the universe.

What is the relationship between vacuum energy and dark energy?

Vacuum energy is often equated with dark energy, which is a hypothetical form of energy that is believed to be responsible for the accelerated expansion of the universe. However, there is still much debate and research being done on the exact nature of dark energy and its relationship to vacuum energy.

Is vacuum energy and momentum a limitless source of energy?

No, vacuum energy and momentum cannot be harnessed as a source of energy. While they do contribute to the overall energy of the universe, the amount is incredibly small and cannot be extracted or utilized for human purposes. Additionally, the laws of thermodynamics state that energy cannot be created or destroyed, only transformed, so the idea of using vacuum energy and momentum as an unlimited energy source is not possible.

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