Comments on the D-instanton calculus in (p,p+1) minimal string theory

The FZZT and ZZ branes in (p,p+1) minimal string theory are studied in terms of continuum loop equations. We show that systems in the presence of ZZ branes (D-instantons) can be easily investigated within the framework of the continuum string field theory developed by Yahikozawa and one of the present authors [M. Fukuma, S. Yahikozawa, Phys. Lett. B 396 (1997) 97, hep-th/9609210]. We explicitly calculate the partition function of a single ZZ brane for arbitrary p. We also show that the annulus amplitudes of ZZ branes are correctly reproduced.