Dirichlet dynamical zeta function for billiard flow
Vesselin Petkov
TL;DR
The paper investigates the Dirichlet dynamical zeta η_D(s) for billiard flows around multiple strictly convex obstacles, formulating η_D(s) as η_D(s)=∑ a_n e^{−λ_n s} with increasing frequencies {λ_n}. It develops a local trace formula and applies Hardy–Riesz summability to show that, under σ_c<0, if η_D(s) were entire, the Dirichlet series would be (λ,k)-summable for all k, forcing strong tail-sum constraints on the coefficients {a_n}. The main result (Theorem 1.1) provides concrete conditions on frequency gaps λ_{m_j}−λ_{m_j−1} and tail sums |∑_{n≥m_j} a_n| that preclude entireness, and Section 4 builds abundant intervals with clustering frequencies to produce these conditions. Collectively, the work links analytic continuation properties of η_D to the distribution of resonances and supports the non-entireness conjecture under verifiable spectral-data assumptions, with implications for the MLPC in scattering theory.
Abstract
We study the Dirichlet dynamical zeta function $η_D(s)$ for billiard flow corresponding to several strictly convex disjoint obstacles. For large ${\rm Re}\: s$ we have $η_D(s) =\sum_{n= 1}^{\infty} a_n e^{-λ_n s}, \: a_n \in \mathbb R$ and $η_D$ admits a meromorphic continuation to $\mathbb C$. We obtain some conditions of the frequencies $λ_n$ and some sums of coefficients $a_n$ which imply that $η_D$ cannot be prolonged as entire function.
