Response Of A Particle Detector Interacting With Spin-3/2Fields

In quantum field theory, concept of a particle is ambiguous without speci-fying observer’s state of movement, that it is, definition of a particle is observer dependent. Response of the accelerated Unruh-DeWitt detector to vacuum scalar fields in Minkowski spacetime verified this characteristic of particles’ concept. Re-sponses of accelerated particle detectors to other vacuum fields also embody the characteristic:Boyer and two physicists Iyer and Kumer studied the cases of accel-erated detectors coupled to vacuum electromagnetic and Dirac field fluctuations, respectively, and they all found nonvanished responses of these accelerated particle detectors.Audretsch and Miiller adopted the method of DDC to study the spontaneous excitation of a uniformly accelerated atom coupled to fluctuating vacuum scalar fields, which gave a clear physical mechanism to Unruh effect. Subsequently, DDC formalism was applied to study spontaneous excitation of the accelerated detectors linearly and nonlinearly coupled to fluctuating vacuum electromagnetic and Dirac fields, respectively. By comparing the outcomes of these work, one finds that there are some terms related to atomic acceleration in excitation rate, but they are not same completely in different cases:the excitation rate of accelerated atom coupled to vacuum electromagnetic field fluctuations has one more term proportional to quadratic acceleration, compared the case of scalar fields; the excitation rate of accelerated atom coupled to vacuum Dirac field fluctuations has one more term proportional to quadruplicate acceleration, compared the case of electromagnetic fields. This paper has taken a two-level atom nonlinearly coupled to massless spin-3/2fields as a particle detector, and calculated the even rate of change of the energy of it, i.e. the excitation rate of it, in which DDC formalism is generalized to study interaction between Rarita-Schwinger fields and the atom. In this paper, we have considered all the possible ways of coupling between a particle detector and spin-3/2fields and between a particle detector and the first order derivative of spin-3/2fields, and found only two modes of coupling are nonvanished, i.e.μR2ψμψu and μR2(?)αψμ(?)αψμ. In these two ways of coupling, we have found that the particle detector can spontaneously excite, i.e. its responses are not nonvanished. What is more, we have found the contribution from a cross term of vacuum fluctuation and rediation of reaction apart from the term of pure vacuum fluctuations and the term of pure rediation reaction in the even rate of change of the atomic energy, and the term of pure rediation reaction could be negligible due to it is a small quantity by comparison with the other two terms. When atomic acceleration approaches to zero, for ground-state atom, the even rate of change of atomic energy contributed by the term of vacuum fluctuations and cross term cancel each other thereby rendering it stable. In the first mode of coupling, we have found that the excitation rate of accelerated atom coupled to spin-3/2field is two times of that coupled to Dirac fields. In second mode of coupling, we have found that there are two corrections proportional to a6and a8respectively in excitation rate which have never appeared in the cases of scalar, Dirac and electromagnetic fields.