0 v 1 1 4 Ju l 1 99 5 Title : Critical curvature of large - N nonlinear O ( N ) sigma model on S 2 Short title
نویسندگان
چکیده
We study the nonlinear O(N) sigma model on S 2 with the gravitational coupling term, by evaluating the effective potential in the large-N limit. It is shown that there is a critical curvature R c of S 2 for any positive gravitational coupling constant ξ, and the dynamical mass generation takes place only when R < R c. The critical curvature is analytically found as a function of ξ (> 0), which leads us to define a function looking like a natural generalization of Euler-Mascheroni constant.
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