The first by James Wells in June 2003 in a more modest form that mildly relaxed the assumption about naturalness in the Higgs potential.
In May 2004 Nima Arkani-Hamed and Savas Dimopoulos argued that naturalness in the Higgs sector may not be an accurate guide to propose new physics beyond the Standard Model and argued that supersymmetry may be realized in a different fashion that preserved gauge coupling unification and has a dark matter candidate.
In June 2004 Gian Giudice and Andrea Romanino argued from a general point of view that if one wants gauge coupling unification and a dark matter candidate, that split supersymmetry is one amongst a few theories that exists.
The striking feature of split supersymmetry is that the gluino becomes a quasi-stable particle with a lifetime that could be up to 100 seconds long.
A gluino that lived longer than this would disrupt Big Bang nucleosynthesis or would have been observed as an additional source of cosmic gamma rays.
The upper bounds on proton decay rate can also be satisfied because the squarks are very heavy as well.
One proposal is that the hierarchy problem is "solved" by assuming fine-tuning due to anthropic reasons.
After the supersymmetric Standard Model was proposed, Sheldon Glashow quipped that 'half of the particles have already been discovered.'
Kenneth Wilson originally advocated for it, but has recently called it one of his biggest mistakes during his career.
[citation needed] Steven Weinberg relaxed the notion of naturalness in the cosmological constant and argued for an environmental explanation for it in 1987.
Leonard Susskind, who initially proposed technicolor, is a firm advocate of the notion of a landscape and non-naturalness.