https://repositorio.ufma.br/jspui/handle/123456789/857 2026-03-02T19:56:12Z https://repositorio.ufma.br/jspui/handle/123456789/862 Título: Trapping of spin-0 fields on tube-like topological defects Autor(es): CASANA, R.; GOMES, A. R.; MENEZES, R.; SIMAS, Fabiano de Carvalho Resumo: We have considered the localization of resonant bosonic states described by a scalar field Φ trapped in tube-like topological defects. The tubes are formed by radial symmetric defects in (2, 1) dimensions, constructed with two scalar fields φ and χ, and embedded in the (3, 1)-dimensional Minkowski spacetime. The general coupling between the topological defect and the scalar field Φ is given by the potential ηF (φ,χ)Φ2. After a convenient decomposition of the field Φ, we find that the amplitudes of the radial modes satisfy Schrödinger-like equations whose eigenvalues are the masses of the bosonic resonances. Specifically, we have analyzed two simple couplings: the first one is F (φ,χ) = χ2 for a fourth-order potential and, the second one is a sixth-order interaction characterized by F (φ,χ) = (φχ)2. In both cases the Schrödinger-like equations are numerically solved with appropriated boundary conditions. Several resonance peaks for both models are obtained and the numerical analysis showed that the fourth-order potential generates more resonances than the sixth-order one. 2014-01-01T00:00:00Z https://repositorio.ufma.br/jspui/handle/123456789/861 Título: Trapping Spin-0 particles on p-balls in (D, 1) dimensions Autor(es): CASANA, R.; GOMES, A. R.; SIMAS, Fabiano de Carvalho Resumo: p-Balls are topological defects in (D, 1) dimensions constructed with M≥1 scalar fields which depend radially on only 2 ≤ p ≤ D − 2 spatial dimensions. Such defects are characterized by an action that breaks translational invariance and are inspired on the physics of a brane with D − p extra dimensions. Here we consider the issue of localization of bosonic states described by a scalar field Φ sufficiently weak to not disturb sensibly the defect configuration. After describing the general formalism, we consider some specify examples with M = 1, 2 and 3, looking for some region of parameters where bound and resonant bosonic states can be found. We investigate the way the influence of the defect structure, number of radial dimensions and coupling between the fields are related to the occurrence of bound and resonant states. Descrição: CC BY 2015-01-01T00:00:00Z https://repositorio.ufma.br/jspui/handle/123456789/860 Título: Suppression of two-bounce windows in kink-antikink collisions Autor(es): SIMAS, Fabiano de Carvalho; GOMES, Adalto R.; NOBREGA, K. Z.; OLIVEIRA, J. C. R. E. Resumo: We consider a class of topological defects in (1, 1)-dimensions with a deformed ϕ 4 kink structure whose stability analysis leads to a Schrödinger-like equation with a zero-mode and at least one vibrational (shape) mode. We are interested in the dynamics of kink-antikink collisions, focusing on the structure of two-bounce windows. For small deformation and for one or two vibrational modes, the observed two-bounce windows are explained by the standard mechanism of a resonant effect between the first vibrational and the translational modes. With the increasing of the deformation, the effect of the appearance of more than one vibrational mode is the gradual disappearance of the initial two-bounce windows. The total suppression of two-bounce windows even with the presence of a vibrational mode offers a counterexample from what expected from the standard mechanism. For extremely large deformation the defect has a 2-kink structure with one translational and one vibrational mode, and the standard structure of two-bounce windows is recovered. Descrição: CC BY 2016-01-01T00:00:00Z https://repositorio.ufma.br/jspui/handle/123456789/859 Título: Degenerate vacua to vacuumless model and kink–antikink collisions Autor(es): SIMAS, Fabiano de Carvalho; GOMES, Adalto R.; NOBREGA, K. N. Resumo: In this work we investigate a Z2 symmetric model of one scalar field ϕ in (1,1) dimension. The model is characterized by a continuous transition from a potential V(ϕ) with two vacua to the vacuumless case. The model has kink and antikink solutions that minimize energy. Stability analysis is described by a Schrödinger-like equation with a potential that transits from a volcano-shape with no vibrational states (in the case of vacuumless limit) to a smooth valley with one vibrational state. We are interested in the structure of two-bounce windows present in kink–antikink scattering processes. The standard mechanism of Campbell–Schonfeld–Wingate (CSW) requires the presence of one vibrational state for the occurrence of two-bounce windows. We report that the effect of increasing the separation of vacua from the potential V(ϕ) has the consequence of trading some of the first two-bounce windows predicted by the CSW mechanism by false two-bounce windows. Another consequence is the appearance of false two-bounce windows of zero-order. Descrição: CC BY 2017-01-01T00:00:00Z