arXiv:2611.07906v1 Announce Type: new Abstract: In this paper, spatial reuse in a multi-cell pinching-antenna system (PASS) is investigated, where each cell employs a dielectric waveguide with one activated pinching antenna (PA) to serve a single user. Spatial reuse refers to the simultaneous use of the same time-frequency resource block (RB) by multiple spatially separated cells. Due to inter-cell interference (ICI), simultaneous transmission by all cells on the same RB may be infeasible, and multiple RBs may be required to serve all users. The spatial-reuse capability is thus characterized by the minimum number of RBs required to satisfy all users' signal-to-interference-plus-noise ratio (SINR) targets under per-cell power budgets. Flexible PA placement can enhance the desired-link gain of each user and reduce the required transmit power of its serving cell, which in turn mitigates ICI and allows more cells to share the same RB. To exploit these benefits, a joint optimization problem of RB allocation, PA placement, and power control is formulated. For the two-cell case, the globally optimal PA placement is determined by minimizing the peak transmit power required by the two cells. A one-dimensional special case is further analyzed to derive analytical expressions for the average RB requirement and its scaling laws with respect to cell length under different PA-placement strategies. For the general multi-cell case, the optimal two-cell solution is exploited to construct a weighted compatibility graph, whose edge weights represent the minimum peak transmit powers required for feasible pairwise RB reuse. Based on this graph, a greedy RB allocation algorithm with minimum-weight pair initialization and element-wise PA-placement optimization is developed. Numerical results validate the analytical findings and demonstrate that PASS significantly reduces the required RBs compared with conventional fixed-antenna systems.