##### Department of Mathematics,

University of California San Diego

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### Math 278B - Mathematics of information, data, and signals

## Hrushikesh Mhaskar

#### Claremont Graduate University

## Revisiting the theory of machine learning

##### Abstract:

A central problem of machine learning is the following. Given data of the form $\{(y_i, f(y_i)+\epsilon_i)_{i=1}^M\}$, where $y_i$'s are drawn randomly from an unknown (marginal) distribution $\mu^*$ and $\epsilon_i$ are random noise variables from another unknown distribution, find an approximation to the unknown function $f$, and estimate the error in terms of $M$. The approximation is accomplished typically by neural/rbf/kernel networks, where the number of nonlinear units is determined on the basis of an estimate on the degree of approximation, but the actual approximation is computed using an optimization algorithm. Although this paradigm is obviously extremely successful, we point out a number of perceived theoretical shortcomings of this paradigm, the perception reinforced by some recent observations about deep learning. We describe our efforts to overcome these shortcomings and develop a more direct and elegant approach based on the principles of approximation theory and harmonic analysis.\\ %We demonstrate a duality between certain problems of function approximation and probability estimation in machine learning and problems of super-resolution in signal separation. In particular, we will explain how the same tools from harmonic analysis can be used for both purposes, leading to a unified theory. We will demonstrate our ideas with some numerical examples.

Host: Rayan Saab

### November 12, 2020

### 10:30 AM

### https://msu.zoom.us/j/96421373881 (Password: first prime number greater than 100)

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