According to our current understanding of physics, the expansion of a vacuum, also known as the expansion of space itself, can appear to be faster than the speed of light on large scales. This concept is known as the "inflationary period" in the early universe and is based on the theory of cosmic inflation.
During the very early moments after the Big Bang, the universe underwent a rapid expansion phase known as inflation. This inflationary period was proposed to explain some observed characteristics of the universe, such as its overall homogeneity and isotropy. The inflationary theory suggests that a brief period of exponential expansion caused the universe to rapidly increase in size by an enormous factor in a very short span of time.
During inflation, the expansion of space itself caused distant regions of the universe to move away from each other faster than the speed of light. However, it is important to note that this expansion does not violate the principle of relativity, which states that information or matter cannot travel faster than the speed of light through space. Inflation does not involve the motion of matter through space but rather the stretching of space itself.
The reason this expansion can appear faster than light is that the speed of light represents the maximum speed at which information or matter can propagate through space. However, during inflation, the fabric of spacetime itself expands, and it is not limited by the constraints that apply to matter or information. As a result, regions of space that were initially in close proximity can become vastly separated from each other due to the expansion.
It's worth noting that the expansion of the universe after the inflationary period, during the so-called "normal" expansion, does not exceed the speed of light. In fact, the expansion rate of the universe has been measured and is described by the Hubble constant, which is consistent with the speed of light being the cosmic speed limit.