Flavor-changing neutral interactions in the Higgs sector 

One of the most serious constraints on models with one or more extra Higgs scalars come from the presence of flavor-changing neutral-currents at tree-level. For generic couplings, these can be orders of magnitude above experimental bounds. The most popular solutions involve discrete or global symmetries which eliminate these interactions. An alternative suggestion suppresses, but doesn’t eliminate these couplings, and has been coined (not by me) the “Cheng-Sher ansatz”. Although this ansatz has been used extensively over the past 25 years, it is finally being laid to rest (sadly) by recent experimental data and theoretical analyses. Other suggestions involve Minimal Flavor Violation and a “muon-specific” model. These will all be discussed in the talk. It will be assumed that the audience is familiar with the Standard Model, 
but not with extensions of the Higgs sector.