Most particle physicists now believe that protons, neutrons, and other strongly interacting particles are built from more basic constituents known as “quarks” and “gluons,” which interact according to the rules of a relativistic quantum field theory known as “quantum chromodynamics.”

## REFERENCES

1.

**The 1/N expansion**developed from the spherical model of

T. H.

Berlin

and M.

Kac

, Phys. Rev.

86

, 821

(1952

),and was formulated in a more modern version by

H. E.

Stanley

, Phys. Rev.

176

, 718

(1968

).2.

**QCD:**The first application to QCD was by

G.

't Hooft

, Nucl. Phys.

B72

, 461

(1974

);G.

't Hooft

, B75

, 461

(1974

).Some recent reviews of the $1/N$ expansion in QCD, from different points of view, are:

G.

Rossi

and G.

Veneziano

, Nucl. Phys.

B123

, 507

(1977

);G. F.

Chew

and C.

Rosenzweig

, Phys. Reports

41C

, No. 5

(1978

);A. de Rujula, talk at the 1979 European Physical Society Conference (CERN preprint);

S. Coleman, Erice Lectures, 1979 (to appear);

E.

Witten

, Nucl. Phys.

B160

, 57

(1979

).3.

**Planar diagrams:**There is a certain amount of literature by now on the problem of trying to sum planar diagrams. One particularly interesting paper is

E.

Brezin

, C.

Itzykson

, G.

Parisi

, and J. B.

Zuber

, Comm. Math. Phys.

59

, 35

(1978

).4.

**Atomic physics:**A recent study of the $1/N$ expansion in atomic physics is L. D. Mlodinow and N. Papanicolaou, “SO(2,1) Algebra and the Large

*N*Expansion in Quantum Mechanics,” Berkeley preprint, November 1979.

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© 1980 American Institute of Physics.

1980

American Institute of Physics

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