高能暂现源 · 每日文献综述

Detecting gravitational waves above 100 kHz would constitute a major discovery, as any observable signal would have to arise from new physics within the late universe. Although many technologies have been identified to explore this high-frequency regime, the known landscape of promising sources remains extremely sparse. In this work, we aim to rectify this issue by providing model-independent arguments that highlight the most interesting parts of theory space, while remaining agnostic of the specific signal mechanism. For example, energy-conservation implies that gravitational waves detectable by future experiments well above a MHz would most likely have to originate from within the Solar System. Based on these arguments, we also constrain the physical properties of such sources.

We fully classify the phenomenology of gravitational wave emission from scaling cosmic string networks with varying tension and compute the spectral indices of the resulting stochastic backgrounds. In string compactifications, periods of varying tension occur when moduli acquire a time dependence. We present concrete examples in type IIB string theory as D3- and NS5-branes wrapping internal cycles, which become dynamical due to the effect of moduli potentials. Moreover, we use swampland constraints to derive general bounds on the allowed time variation of the effective string tension in Friedmann-Lemaitre-Robertson-Walker backgrounds and on the resulting spectral indices.