New Solutions to the Gauge Hierarchy Problem

Applying dimensional analysis to the Higgs mass leads one to predict new physics interactions that generate this mass at a scale of the order of 1 TeV. The question of what these interactions could be is known as the gauge hierarchy problem. Resolving this question has been a central aim of particle physics for the past few decades. Traditional solutions introduce new particles with masses below 1 TeV, but that prediction is now challenged by experiment. In this article, I review recent new approaches to the problem that do not require new particles at the TeV mass scale. I first discuss the relaxation approach, whereby the Higgs mass is made dynamical and is small at the absolute minimum of its potential. I then discuss the historical approach, whereby details about inflation and/or reheating after inflation cause the Higgs mass to be smaller than otherwise expected. Finally, I discuss solutions that use conditional probability, whereby conditioning on the fact that the cosmological constant is small automatically leads one to select vacua where the Higgs mass is also small.