Our intuition for how quantum field theories behave is guided by the principle of naturalness. This principle, which relies merely on the zero-point energy of quantum systems, states that generic quantum field theories are well-characterized by dimensional analysis, unless contraints from symmetries intervene. But current null results from the Large Hadron Collider seem to suggest that particle physics (without gravity) is described by the Standard Model, a highly unnatural quantum field theory. The new question in particle physics is ''what is the question?'' Are there experimental violations of the Standard Model at the LHC that we have missed, or that we will find eventually using advanced methods? Or is the LHC's result truly null? If so, why has the principle of naturalness failed? Are we dealing with a theoretical subtlety, a selection bias, or some other consequence of cosmological history?

Harvard University