Could null branes hold the key to understanding quantum horizons? This paper explores a new class of D-branes with a single null direction, constructed by adding a specific boundary term to the Polyakov action. The system is described by a single quantized left-mode sector of a conformal field theory on the string world sheet. By employing a Wick rotation of space-time, the authors map open strings attached to null branes into chiral closed strings. These so-called H-branes are proposed as a description of quantum horizons, such as black holes and cosmological de-Sitter spaces. The research investigates how one can obtain a space/phase space transmutation near the horizon and discusses the new features of boundary states, which become squeezed states. This work presents a novel perspective on quantum horizons and their relationship to string theory. The introduction of H-branes and the analysis of their properties contribute to a deeper understanding of the fundamental nature of space-time and the behavior of strings near extreme gravitational environments. The findings could potentially impact research in black hole physics and cosmology.
Published in the International Journal of Modern Physics A, this paper aligns with the journal's focus on nuclear and particle physics, atomic physics, and the constitution and properties of matter. The research on H-branes and chiral strings contributes to theoretical advancements in these areas, pushing the boundaries of our understanding of fundamental physics.