We study the heat content on quantum graphs and investigate whether an analogon of the Rayleigh-Faber-Krahn inequality holds. This means that heat content at time $T$ among graphs of equal volume would be maximized by intervals (the graph analogon of balls as in the classic Rayleigh-Faber-Krahn inequality). We prove that this holds at extremal times, that is at small and at large times. For this, we employ two complementary approaches: In the large time regime, we rely on a spectral-theoretic approach, using Mercer's theorem whereas the small-time regime is dealt with by a random walk approach using the Feynman-Kac formula and Brownian motions on metric graphs. In particular, in proving the latter, we develop a new expression for the heat content as a positive linear combination of expected return times of (discrete) random walks - a formulation which seems to yield additional insights compared to previously available methods such as the celebrated Roth formula and which is crucial for our proof. The question whether a Rayleigh-Faber-Krahn inequality for the heat content on metric graphs holds at all times remains open.
The Faber-Krahn inequality for $p$-Hermite operators
College of informatics, Huazhong Agricultural University（华中农业大学信息学院）；School of Mathematical Sciences, Soochow University（苏州大学数学科学学院）；School of Mathematics and Statistics, Wuhan University（武汉大学数学与统计学院）
Reverse Faber-Krahn and Szego-Weinberger type inequalities for annular domains under Robin-Neumann boundary conditions
Indian Institute of Technology Madras（印度马德拉斯理工学院）；Institute of Mathematics, Ufa Federal Research Centre, RAS（俄罗斯科学院乌法联邦研究中心数学研究所）；Ufa University of Science and Technology（乌法科学技术大学）；Department of Mathematics and NTIS, Faculty of Applied Sciences, University of West Bohemia（西波希米亚大学应用科学学院数学与NTIS系）
