Yes. Arugula and Beet have a documented companion-planting benefit. Virginia Cooperative Extension lists beet as a companion for the cabbage-family crop arugula.
This is a practical yes, not a magic guarantee. Keep the normal spacing for Arugula and Beet, watch airflow and watering, and treat the companion note as one useful planning signal alongside sunlight, soil, and harvest timing.
Source basis: Virginia Cooperative Extension companion planting chart. The page does not add extra pest-control or yield claims beyond the sourced fact row.
Spacing tip: Sow in bands rather than one mixed clump, then thin promptly so roots and leaves have room.