Abstract
The fundamental vacuum state of quantum fields, related to Minkowski space, produces divergent fluctuations that must be suppressed in order to bring reality to the description of physical systems. As a consequence, negative vacuum expectation values of classically positive-defined quantities can appear. This has been addressed in the literature as subvacuum phenomenon. Here it is investigated how a scalar charged test particle is affected by the vacuum fluctuations of a massive scalar field in D + 1 spacetime when the background evolves from empty space to a thermal bath, and also when a perfectly reflecting boundary is included. It is shown that when the particle is brought into a thermal bath it gains an amount of energy by means of positive dispersions of its velocity components. The magnitude of this effect is dependent on the temperature and also on the field mass. However, when a reflecting wall is inserted, dispersions can be positive or negative, showing that subvacuum effect happens even in a finite temperature environment. Furthermore, a remarkable result is that temperature can even improve negative velocity fluctuations. The magnitude of the residual effects depends on the switching interval of time the system takes to evolve between two states.
Highlights
Notice that the above mentioned instances of vacuumrelated phenomena are linked to the transition between vacuum states of some field, driven by some external agent
Velocity fluctuations seems to diverge at the boundary and when τ = 2x, which corresponds to a round trip of a photon between the particle and the
We address the question of how to probe quantum fluctuations induced by an idealized boundary of a massive scalar field at finite temperature using velocity dispersions of test particles, following the smoothing measurement methodology
Summary
Notice that the above mentioned instances of vacuumrelated phenomena are linked to the transition between vacuum states of some field, driven by some external agent. There exists examples of more elusive phenomena like subvacuum effects, where classically positive-definite observables can assume negative values after renormalization In this regard, fingerprints of quantum field fluctuations were shown to be present on the motion of electric charged particles [8,9]. We address the question of how to probe quantum fluctuations induced by an idealized boundary of a massive scalar field at finite temperature using velocity dispersions of test particles, following the smoothing measurement methodology. The main results are given, where the behavior of the stochastic motion of the test particle is studied when it is immersed in a pure thermal bath (without a boundary), and when a reflecting boundary is added to the system In this later scenario it is shown that negative dispersions of the particle velocity occur.
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