부산대학교 도서관

Summary: ``We construct boson star configurations in quantum fieldtheory using the semiclassical gravity approximation. Restricting ourattention to the static case, we show that the semiclassicalEinstein-Klein-Gordon system for a {\it single real quantum} scalarfield whose state describes the excitation of $N$ {\it identicalparticles}, each one corresponding to a given energy level, can bereduced to the Einstein-Klein-Gordon system for $N$ {\it complexclassical} scalar fields. Particular consideration is given to thespherically symmetric static scenario, where energy levels are labeledby quantum numbers $n, \ell$, and $m$. When all particles areaccommodated in the ground state $n = \ell = m = 0$, one recovers thestandard static boson star solutions, that can be excited if $n \neq0$. On the other hand, for the case where all particles have fixedradial and total angular momentum numbers $n$ and $\ell$, with $\ell\neq 0$, but are homogeneously distributed with respect to theirmagnetic number $m$, one obtains the $\ell$-boson stars, whereas when$\ell m = 0$ and n takes multiple values, the multistate boson starsolutions are obtained. Further generalizations of these configurationsare presented, including the multi-$\ell$ multistate boson stars, thatconstitute the most general solutions to the $N$-particle, static,spherically symmetric, semiclassical real Einstein-Klein-Gordon system,in which the total number of particles is definite. In spite of thefact that the same spacetime configurations also appear in multifieldclassical theories, in semiclassical gravity, they arise naturally asthe quantum fluctuations associated with the state of a single fielddescribing a many-body system. Our results could have potential impacton direct detection experiments in the context of ultralight scalarfield/fuzzy dark matter candidates.''