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Prog. Theor. Phys. Vol. 81 No. 2 (1989) pp. 482-497

A Detailed Renormalization Group Analysis in Superstring Inspired Models

Nobuhiro Nakamura, Isao Umemura and Katsuji Yamamoto

Department of Nuclear Engineering, Kyoto University, Kyoto 606

(Received October 6, 1988)

Abstract:

A renormalization group analysis is performed for a class of superstring inspired models, where the effects on the estimate of the low-energy parameters, sin²θ_W, α and α₃, at M_W are examined which are due to (i) the two-loop contributions to the RGEs, (ii) the extra U(1)_E coupling and (iii) the threshold effects at M_C and M_I. The two-loop effects are significant if somewhat large α_i(M_C) \gtrsim0.1 are required at the one-loop level to reproduce the right values of the low-energy parameters. The effects of the U(1)_E coupling, however, turn to be rather negligible. The threshold effects at M_I are not so significant either, and actually hidden by the ambiguity of M_I. If small α_i(M_C) \lesssim0.1 are taken, the low-energy parameters are rather sinsitive against the deviation from some specific values of α_i(M_C) = α_U. On the other hand, in some models with M_I ∼10¹⁰ GeV and certain matter contents, the right values of the low-energy parameters are obtained for a somewhat large region α_i(M_C) > 0.1.

URL : http://ptp.ipap.jp/link?PTP/81/482/
DOI : 10.1143/PTP.81.482

[ Full Text PDF : FREE ACCESS (811K) ] Citation: Plain Text BiBTeX EndNote(RIS) RSS

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