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Register a new userMagnetic Field Effect on Charged Scalar Pair Creation at Finite Temperature
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In this work we explore the effects of a weak magnetic field and a thermal bath on the decay process of a neutral scalar boson into two charged scalar bosons. Our findings indicate that magnetic field inhibits while temperature enhances the pair production. The employed formalism allows us to isolate the contribution of magnetic fields in vacuum, leading to a separate analysis of the effects of different ingredients. This is essential since the analytical computation of the decay width necessarily needs of some approximation and the results that can be found in the literature are not always coincident. We perform the calculation in vacuum by two different weak field approximations. The particle pair production in vacuum was found to coincide with finite temperature behavior, which is opposite to results obtained by other authors in scenarios that involve neutral particles decaying into a pair of charged fermions. Among other differences between these scenarios, we traced that the analytical structure of the self-energy imposed by the spin of particles involved in the process is determinant in the behavior of the decay rate with the magnetic field.
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We use the evolution operator method to find the Schwinger pair-production rate at finite temperature in scalar and spinor QED by counting the vacuum production, the induced production and the stimulated annihilation from the initial ensemble. It is shown that the pair-production rate for each state is factorized into the mean number at zero temperature and the initial thermal distribution for bosons and fermions.
In this work we investigate the dynamical Casimir effect in a nonideal cavity by deriving an effective Hamiltonian. We first compute a general expression for the average number of particle creation, applicable for any law of motion of the cavity boundary. We also compute a general expression for the linear entropy of an arbitrary state prepared in a selected mode, also applicable for any law of motion of the cavity boundary. As an application of our results we have analyzed both the average number of particle creation and linear entropy within a particular oscillatory motion of the cavity boundary. On the basis of these expressions we develop a comprehensive analysis of the resonances in the number of particle creation in the nonideal dynamical Casimir effect. We also demonstrate the occurrence of resonances in the loss of purity of the initial state and estimate the decoherence times associated with these resonances.
We discuss equilibrium relativistic fermionic systems in lattice regularization, and extend the consideration of chiral magnetic effect to systems with spatial inhomogeneity and finite temperature. Besides, we take into account interactions due to exchange by gauge bosons. We find that the equilibrium chiral magnetic conductivity remains equal to zero.
Radical pair recombination reactions are known to be sensitive to the application of both low and high magnetic fields. The application of a weak magnetic field reduces the singlet yield of a singlet-born radical pair, whereas the application of a strong magnetic field increases the singlet yield. The high field effect arises from energy conservation: when the magnetic field is stronger than the sum of the hyperfine fields in the two radicals, ${rm S}to {rm T}_{pm}$ transitions become energetically forbidden, thereby reducing the number of pathways for singlet to triplet interconversion. The low field effect arises from symmetry breaking: the application of a weak magnetic field lifts degeneracies among the zero field eigenstates and increases the number of pathways for singlet to triplet interconversion. However, the details of this effect are more subtle, and have not previously been properly explained. Here we present a complete analysis of the low field effect in a radical pair containing a single proton, and in a radical pair in which one of the radicals contains a large number of hyperfine-coupled nuclear spins. We find that the new transitions that occur when the field is switched on are between ${rm S}$ and ${rm T}_0$ in both cases, and not between ${rm S}$ and ${rm T}_{pm}$ as has previously been claimed. We then illustrate this result by using it in conjunction with semiclassical spin dynamics simulations to account for the observation of a biphasic--triphasic--biphasic transition with increasing magnetic field strength in the magnetic field effect on the time-dependent survival probability of a photoexcited carotenoid-porphyrin-fullerene radical pair.
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