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Vidyo Connection
Extension: 1010656363
Owner: Lorenzo Feligioni
Auto-join URL: https://vidyoportal.cern.ch/join/R8hWPzxNsly4
Abstract:
The naturalness principle has long been an influential guide to model-building in particle physics. It has been formulated variously as a prohibition on fine-tuned cancellations between bare parameters and quantum corrections in quantum field theory, as a prohibition on delicate sensitivity of the parameters characterizing low-energy physics on those characterizing physics at high energies, and as the requirement that all dimensionless couplings in the effective Lagrangian of a system be approximately of order one unless they are protected by a symmetry. The primary relevance of the naturalness principle for current high-energy particle physics is that, as a consequence of the 125Gev Higgs mass, the Standard Model will be found in violation of the naturalness principle if no new (i.e., beyond the Standard Model) physics is discovered at the LHC. This raises an important philosophical question: should the Standard Model's failure to abide by the naturalness principle be interpreted as a flaw in the Standard Model, and a signature of the physics that lies beyond it, or as a limitation of the naturalness principle itself?
In this talk, I aim to provide a few clarifying remarks concerning the status of two formulations of the naturalness principle: the fine-tuning naturalness principle, and the naturalness principle understood as a prohibition on delicate sensitivity between scales. I will argue that the status of the fine-tuning naturalness problem as a genuine flaw of the Standard Model depends on the particular physical interpretation of QFT that one adopts - in particular, on whether one assumes a Wilsonian picture in which the QFT in question is defined with a high-energy cutoff, or a continuum picture in which the QFT's amplitudes are mathematically defined up to arbitrarily high energies. Specifically, I will argue that the need for fine-tuning of bare parameters in the Standard Model can only be regarded as a flaw of the Standard Model on a Wilsonian parametrization of the theory's amplitudes. Concerning the understanding of naturalness as a prohibition on delicate sensitivity between scales, I will argue against one popular justification for prohibiting the particular sort of delicate sensitivity between scales that is brought into the Standard Model by the Higgs.
