All possible models to explain the hierarchy problem?

In summary, the hierarchy problem refers to the discrepancy between the gravitational scale and the electroweak scale in particle physics, leading to questions about the stability of the Higgs boson mass. Various models have been proposed to address this issue, including supersymmetry, which introduces partner particles to cancel out radiative corrections; extra dimensions, where the effects of gravity are diluted; and composite Higgs models, suggesting the Higgs boson is not fundamental but a composite particle. Other approaches include the use of anthropic principles in a multiverse scenario and models involving new symmetries or dynamics. Each model presents its own implications and challenges, contributing to ongoing debates in theoretical physics.
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All possible models to explain the hierarchy problem?
There is an interesting paper by Arkani-Hamed and collaborators (https://arxiv.org/abs/1607.06821) to address the hierarchy problem.

There, they consider many possible models of fundamental particle physics where they all have an exact copy of the Standard Model but with different Higgs masses.

However, they indicate that this assumption is done for simplicity, but that we could relax these assumptions and consider models with greater differences

At the beginning, they say:

The first step is to introduce N sectors which are mutually non-interacting. The detailed particle content of these sectors is unimportant, with the exception that the Standard Model (SM) should not be atypical; many sectors should contain scalars, chiral fermions, unbroken gauge groups, etc. For simplicity, we imagine that they are exact copies of the SM, with the same gauge and Yukawa structure.

And at the end:

However, it is easy to imagine a broader class of theories that realizes the same mechanism. We can relax the assumption that the Higgs masses are uniformly spaced (or even pulled from a uniformly distribution) or that all the new sectors are exact copies of the SM. It is also possible to construct different models of reheating, with new physics near the weak scale to modify the UV behavior of the theory.All of this made me wonder: Are they saying that we could relax the assumptions of the model so that it would even include all possible UV theories (meaning all possible "microscopic" or "high-energy" physics, such as the different theories of quantum gravity and theories of everything proposed so far)?
 

FAQ: All possible models to explain the hierarchy problem?

What is the hierarchy problem in particle physics?

The hierarchy problem in particle physics refers to the question of why the Higgs boson mass is so much lighter than the Planck scale, despite quantum corrections that should drive it to much higher values. This discrepancy suggests that there might be some underlying principle or new physics that stabilizes the Higgs mass at the observed value.

What are supersymmetry (SUSY) models?

Supersymmetry (SUSY) models propose a symmetry between fermions and bosons, predicting the existence of superpartners for all Standard Model particles. These superpartners can cancel out the large quantum corrections to the Higgs mass, thereby addressing the hierarchy problem. Despite extensive searches, no direct evidence for SUSY particles has been found yet.

How do extra dimensions explain the hierarchy problem?

Extra-dimensional models, such as those proposed by Arkani-Hamed, Dimopoulos, and Dvali (ADD) or Randall-Sundrum (RS), suggest that additional spatial dimensions could dilute the strength of gravity, making it appear weaker in our 4-dimensional spacetime. This can help explain why the Higgs mass remains small compared to the Planck scale, offering a potential solution to the hierarchy problem.

What is the concept of "Technicolor" in addressing the hierarchy problem?

Technicolor theories propose that the Higgs boson is not a fundamental particle but a composite one made up of new, strongly interacting particles. This strong interaction dynamically generates the Higgs mass, naturally resolving the hierarchy problem without requiring fine-tuning. However, these models face challenges in matching experimental data, particularly in flavor physics.

Can the "Relaxion" mechanism solve the hierarchy problem?

The Relaxion mechanism is a more recent proposal that introduces a new scalar field, the relaxion, which dynamically adjusts the Higgs mass during the early universe. This process allows the Higgs mass to settle at a naturally small value, providing an elegant solution to the hierarchy problem. While promising, this idea is still under theoretical investigation and requires further validation.

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