An update on supersymmetry and competitors to string theory

About 12 years ago, I read Lee Smolin's The Trouble with Physics:  The Rise of String Theory, the Fall of a Science, and What Comes Next (Houghton Mifflin, 2007).  Like a few other physicists, Smolin was not pleased with the lack of evidential basis for string and M-theory, and the desire of some physicists to abandon the need for such empirical support.  Part III of the book looks at alternatives to string theory.  Though I am a physicist, I am as good as a layperson in this particular arena, and Smolin's book gave me a nontechnical discussion of string theory's competitors.

At the time Smolin wrote, the Large Hadron Collider at CERN was still under construction.  Smolin predicted that the LHC would find the Higgs boson (it did) and that its biggest task would be to find evidence for supersymmetry.  Last month, The Economist featured an article that essentially gives an update on all this ("Bye, bye, little Susy", Aug. 28, 2021).  It's a refreshing look at the situation as it stands today.

First, hopes of finding evidence for supersymmetry ("SUSY") are slipping quickly.  While SUSY hasn't been ruled out entirely, evidence has been lacking so far.  Without SUSY, string theory is also near a dead end.  Meanwhile, experimental anomalies with the standard model are beginning to accumulate.  

The article describes a number of competing "theories of everything" to string theory.  In some, the very notions of space, time, and causality are emergent phenomena.  I find it exhilarating to read that statistical physics and information theory may play a fundamental role in the standard model's successor. When I audited an undergraduate thermal physics class while in grad school, the professor introduced the topic by saying that thermodynamics was more general than either mechanics or electromagnetism.  From the Economist article, perhaps thermodynamics may be more general than we ever had a right to expect!

Experimental physicists discovered the Top Quark not long after I began studying physics; the discovery of the Higgs boson and gravitational waves have been more recent experimental breakthroughs.  However I remember in grad school seeing the high energy theory professors publishing about SUSY.  Theoretical physics may have indeed been in a rut, as Smolin would have you believe, during much of my professional lifetime.  The competitors to string theory discussed in the Economist article may be the first steps to a renaissance of theoretical physics.  If so, theoretical physics might get exciting again!