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STRINGY SPHALERONS AND GAUSS--BONNET TERM

The effect of the Gauss--Bonnet term on the SU(2) non--Abelian regular stringy sphaleron solutions is studied within the non--perturbative treatment. It is found that the existence of regular solutions depends crucially on the value of the numerical factor $β$ in front of the Gauss--Bonnet term in the four--dimensional effective action. Numerical solutions are constructed in the N=1, 2, 3 cases for different $β$ below certain critical values $β_N$ which decrease with growing N (N being the number of nodes of the Yang--Mills function). It is proved that for any static spherically symmetric asymptotically flat regular solution the ADM mass is exactly equal to the dilaton charge. No solutions were found for $β$ above critical values, in particular, for $β=1$.