“…Research in ToDL attempts to demystify the various hidden transformations of deep architectures to provide a theoretical guarantee and understanding on the learning, approximation, optimization, and generalization capability of deep networks-and their variants-such as FNNs, convolutional neural networks (CNNs) [26], [27], recurrent neural networks (RNNs) [28], [29], autoencoders (AEs) [30]- [32], generative adversarial networks (GANs) [33]- [35], ResNet [36], and DenseNet [37], [38]. To interpret/explain learning [39], approximation [40], optimization [41], [42], and generalization [43] in these deep networks employed for classification [44], [45] and regression problems [46], advancements in ToDL have been made via numerous frameworks such as mean field theory [47]- [49], random matrix theory [50], [51], tensor factorization [52], [53], optimization theory [54]- [57], kernel learning [58]- [60], linear algebra [61], [62], spline theory [63], [64], theoretical neuroscience [65]- [67], highdimensional probability and statistics [68]- [70], manifold theory [48], [71], Fourier analysis [72], and scattering networks (vis-à-vis a wavelet transform)…”