Context :

Aims : We present synthetic bolometric and broad-band UBVRI light curves of SNe Ia , for four selected 3-D deflagration models of thermonuclear supernovae .

Methods : The light curves are computed with the 1-D hydro code stella , which models ( multi-group time-dependent ) non-equilibrium radiative transfer inside SN ejecta .
Angle-averaged results from 3-D hydrodynamical explosion simulations with the composition determined in a nucleosynthetic postprocessing step served as the input to the radiative transfer model .

Results : The predicted model UBV light curves do agree reasonably well with the observed ones for SNe Ia in the range of low to normal luminosities , although the underlying hydrodynamical explosion models produced only a modest amount of radioactive ^ { 56 } Ni ( i.e . \sim 0.24 - 0.42 M _ { \sun } ) and relatively low kinetic energy in the explosion ( less than 0.7 \times 10 ^ { 51 } erg ) .
The evolution of predicted B and V fluxes in the model with a ^ { 56 } Ni mass of 0.42 M _ { \sun } follows the observed decline rate after the maximum very well , although the behavior of fluxes in other filters somewhat deviates from observations , and the bolometric decline rate is a bit slow .
The material velocity at the photospheric level is of the order of 10 ^ { 4 } km s ^ { -1 } for all models .
Using our models , we check the validity of Arnett ’ s rule , relating the peak luminosity to the power of the deposited radioactive heating , and we also check the accuracy of the procedure for extracting the ^ { 56 } Ni mass from the observed light curves .

Conclusions : We find that the comparison between theoretical light curves and observations provides a useful tool to validate SN Ia models .
The steps necessary to improve the agreement between theory and observations are set out .