In quantum field theory, virtual particles are mathematical entities that arise in perturbative calculations and do not correspond to particles in the same way as real particles. Virtual particles are used as a tool to describe interactions between particles and are not directly observable. They are an artifact of the mathematical framework used to calculate scattering amplitudes and other physical quantities.
Virtual particles do not have the same restrictions as real particles, and their properties, such as energy and momentum, can deviate from the usual conservation laws. They can briefly borrow energy from the vacuum and exist for a very short time before annihilating or transitioning into other particles.
However, it is important to note that virtual particles are not on-shell particles, meaning they do not obey the usual mass-shell relation (E² = m²c⁴ + p²c²) that real particles satisfy. They are not subject to the uncertainty principle in the same way as real particles and do not have definite positions or momenta.
Given their mathematical and conceptual nature, it is not meaningful to consider whether multiple virtual particles can occupy the same space at the same time. The concept of "occupying space" is not well-defined for virtual particles. Instead, virtual particles are part of a mathematical description of interactions in quantum field theory and should be understood as mathematical constructs used in calculations rather than as physical entities occupying space.