  Theoretical light curves of four recurrent novae in outburst are modeled to
obtain various physical parameters. They are those with a red giant companion,
T CrB, RS Oph, V745 Sco, and V3890 Sgr. Our model includes irradiations of the
companion star and the accretion disk together with a shadowing effect on the
companion by the accretion disk. The early visual light curves are well
reproduced with a thermonuclear runaway model on a very massive white dwarf of
1.37 Mo for T CrB, 1.37 Mo for RS Oph with low metallicity (Z=0.004), 1.35 Mo
for V745 Sco, and 1.35 Mo for V3890 Sgr. Each envelope mass at the optical
maximum is also estimated to be 3 x 10^{-6}, 2 x 10^{-6}, 5 x 10^{-6}, and 3 x
10^{-6} Mo, indicating an average mass accretion rate of 0.4 x 10^{-7}, 1.2 x
10^{-7}, 0.9 x 10^{-7}, and 1.1 x 10^{-7} Mo/yr during the quiescent phase.
Although a large part of the envelope mass is blown in the wind, each WD can
retain a substantial part of the envelope mass after hydrogen burning ends.
Thus, we have obtained net mass-increasing rates of the WDs as 0.1 x 10^{-7},
0.12 x 10^{-7}, 0.05 x 10^{-7}, and 0.11 x 10^{-7} Mo/yr. These results
strongly indicate that the WDs in the recurrent novae have now grown up to near
the Chandrasekhar mass limit and will soon explode as a Type Ia supernova if
the WDs consist of carbon and oxygen. We also include a radiation-induced
warping instability of the accretion disk to reproduce the second peak of T CrB
outbursts. Thus, we have clarified the reason why only T CrB shows a secondary
maximum but the other three systems do not.
