The characters of the holomorphic discrete series

A power series represents a function as an infinite sum of terms involving powers of a variable, typically expressed relative to a central value. This center, denoted as a, shifts the powers to terms of (x − a)n, where n is a non-negative integer and the coefficients define the behavior of the function. When the center is zero, the power series becomes a straightforward expansion in powers of x, closely resembling an infinite polynomial. This structure allows power series to model complex...

The Discrete-Time Fourier Series (DTFS) is a fundamental concept in signal processing, serving as the discrete-time counterpart to the continuous-time Fourier series. It allows for the representation and analysis of discrete-time periodic signals in terms of their frequency components. Unlike its continuous counterpart, which utilizes integrals, the calculation of DTFS expansion coefficients involves summations due to the discrete nature of the signal.
For a discrete-time periodic signal x[n]...

An infinite series is the sum of an infinite sequence of terms. Instead of adding only a fixed number of values, the addition continues without end. To make sense of this process, mathematicians examine partial sums, which are running totals formed by adding the first few terms of the series. If these partial sums approach a fixed number, the infinite series is said to converge. If they do not approach a finite value, the series diverges.The water tank example illustrates convergence through...

The Fourier series is a powerful mathematical tool for representing periodic signals as an infinite sum of complex exponentials. In practice, this infinite series is truncated to a finite number of terms, yielding a partial sum. This truncation makes the approximation of the signal feasible but introduces certain challenges, particularly near discontinuities, known as the Gibbs phenomenon.
The Gibbs phenomenon refers to the persistent oscillations and overshoots that occur near discontinuities...

A mass attached to a vertical spring can exhibit oscillatory motion as it moves above and below a central equilibrium point. In an ideal spring, the oscillations would continue indefinitely with constant amplitude. In a damped spring, however, resistive forces such as air resistance or internal friction gradually reduce the size of each swing. This behavior is often modeled by combining a sinusoidal function, which represents the repeated motion, with an exponential decay factor, which reduces...

The Taylor series provides a systematic method for approximating a smooth function by a polynomial that closely matches the function near a chosen point. This approach is particularly valuable in scientific and engineering contexts where functions may be difficult to evaluate directly, such as oscillatory voltages in alternating current (AC) circuits. Replacing complex functions with polynomial expressions simplifies computation while preserving essential local behavior. Taylor’s Theorem...