Some musings on theta eta and zeta : from E8 to cold plasma to an inhomogeneous universe This book continues the applications of mathematics more specifically of theta eta and zeta functions and modular forms to various areas of theoretical physics. It is a follow up and extension in some sense of the author’s earlier book entitled A window into zeta and modular physics. Some of the main topics are 1. A new approach to logarithmic corrections to black hole entropy 2. My recent work that provides for an explicit cold plasma black hole connection 3. Generalization of work of physicists on certain asymptotic problems relating to string theory for example by way of the general theory of modular forms of non positive weight 4. A construction of the E8 root lattice its theta function and its relevance for heterotic string theory 5. Applications of elliptic functions to KdV nonlinear Schrödinger and Duffing equations for example including a discussion of Lax pairs and the Miura transformation 6. Finite temperature zeta functions and partition functions for quantum fields in thermal equilibrium on various curved background spacetimes 7. Exact solutions of the Einstein gravitational field equations for Lemaitre and inhomogeneous cosmological models with a special focus on the Szekeres–Szafron exact solutions by way of the Weierstrass elliptic function 8. Elementary particles and my zeta function formula for higher spin fermionic particles; this covers in particular the gravitino particle (of spin 3 2) and bosons with integral spin s = 2 3 4 5. These are some sample topics. Others include the continuous Heisenberg model reaction diffusion systems Dirichlet and Hecke L functions the modular j invariant the computation of the one loop effective potential for non compact symmetric spaces the BTZ black hole Jacobi inversion formulas etc. Thus there is a very large range of material with the first 9 chapters of preliminary expositional background for mathematicians and physicists.