His contribution[1] to the memorial volume celebrating the 100th birthday of Lev Davidovich Landau earned him the Majorana Prize 2008 with Medal.

[9][10] Within the quantum field theories of quarks he found the origin[11] of the algebra of Regge residues conjectured by N. Cabibbo, L. Horwitz, and Y. Ne'eman (see p. 232 in reference[12]).

[19] This structure was discovered three years later in aluminum transition metal alloys by Dan Shechtman, which earned him the Nobel Prize 2011.

The Russian physicist A. Polyakov simultaneously proposed a similar extension, and so the model is now known as the Polyakov-Kleinert string Archived 11 June 2020 at the Wayback Machine.

This curvature reproduces all the effects of general relativity, but leads to different physics than string theory at the scale of the Planck length.

This theory inspired Italian artist Laura Pesce to create glass sculptures entitled "world crystal" (see also lower left on this page).

Kleinert's 60th birthday was honored by a Festschrift and a Festcolloquium with 65 contributions by international colleagues (for instance Y. Ne'eman, R. Jackiw, H. Fritzsch, R. Ruffini, C. DeWitt, L. Kauffman, J. Devreese, and K. Maki).