So the real particle does not propagate and the real particle becomes again virtual.

The pair is composed of virtual one partiple and virtual one anti-particle.

However, the kinetic energy of virtual particles may be negative.

it's possible for the energy of a particle to become negative,

However, the kinetic energy of virtual particles may be negative.

However, the kinetic energy of virtual particles may be negative.

their antiparticles, then the transmission of a virtual F particle

Virtual particles do not violate the conservation of energy.

An instant later, the particle disappears, but it's place is immediately taken by another virtual particle.

So we must, of course, immediately reabsorb the virtual

If the field is strong enough, the virtual particles can become real.

Virtual particles are in virtual state where the probability amplitude is not conserved.

Apparently you’re unfamiliar with the concept of virtual particles.

By the way, I wanted to know what virtual friends were.

The default search didn’t yield any information that I didn’t already have.