The analysis of the spin wave excitations in two-dimensional isotropic Heisenberg ferromagnet is performed with a single skyrmion in the ground state. We employ the ideas of semiclassical quantization method, duly modified for the use of the lattice model and Maleyev-Dyson boson representation of spin operators. The resulting Schrödinger equation for magnons describes the dispersion and wave functions of spin-wave excitations with strictly non-negative spectrum. In contrast to usual ferromagnet, we demonstrate the existence of three zero modes, corresponding to conformal symmetries spontaneously violated by the skyrmion configuration.1. Topological defects play an important role in condensed matter physics. The first and the most famous example is vortex lines, defining critical properties of type II superconductors in the external magnetic field [1]. In two dimensions, the role of defects is even more noticeable. So an interaction of vortices in the O(2) model leads to emergence of a quasi-long-range order and a Berezinskii-Kosterlitz-Thouless (BKT) transition [2]. In O(2) symmetric systems with the additional twofold degeneracy of the ground state, such as Josephson junction arrays in the magnetic field or XY helimagnets, vortex excitations with fractional charges lead to a phase transition on domain walls, and as a consequence to separation of a BKT and Ising (chiral) transitions [3,4]. The appearance of so-called Z 2 -vortices corresponds to exceptional thermal properties of twodimensional frustrated magnets with isotropic spins (see [5] and Refs. therein). The superlattice structure observed in magnets [6,7,8,9, 10] and multiferroics [11] with the Dzyaloshinskii-Moria (DM) spin-orbit interaction in the magnetic field is believed to be related to vortex-like excitations, called skyrmions. The similar skyrmion structures appear in the quantum Hall systems [12,13,14,15].In this paper we discuss topological defects in twodimensional quantum ferromagnets. It is known that the usual O(N ) model, describing ferromagnets, has different types of topological defects. The case N = 1 corresponds to the Ising model, where line-like defects are domain walls. The case N = 2 has been mentioned above in a context of point-like vortices and a BKT transition. At N = 3, defects of another type are present. They can be obtained as static classical solution of the O(3) sigma model [16], describing lowtemperature properties of ferromagnets,Taking into account the isotropic condition at spatial infinity ϕ(∞) = ϕ 0 , the field ϕ becomes a map ϕ : R 2 ∪ {∞} S 2 → S 2 , which is characterized by an integer number Q, the topological degree of the map ϕ.The families of solutions consist of configurations related to each other by global field-rotations and coordinate transformations. The latter symmetry includes rescalings (dilatations), that is specific to the two-dimensional sigma model, which is conformal invariant. As a consequence, a size of defects is not defined by the energy minimum conditions, in accordance with the Derrick the...
This review paper presents the results of the recent studies designed to elucidate the etiopathogenetic role ofhuman papilloma virus infection in the development of respiratory papillomatosis in the children. Special attention is given to the possible pathways and mechanisms of the mother-to-child transmission of papilloma virus, its frequency and risk factors during pregnancy and in the postnatal period. The results of investigations into the frequency of papilloma virus infection in the children are presented along withrisk factors contributing to its persistence and the development ofjuvenile respiratory papillomatosis. The possible approaches to the management of this condition are proposed.
Objective : to define the features of the course of pregnancy, delivery, postpartum period and state of newborns in female patients with genital HPV infection, depending on its form and viral load; to assess the factors of the course of gestation and delivery in the vertical transmission of neonatal persistence of HPV infection. Material and methods. The study involved 132 pregnant women with genital HPV infection, their babies immediately after birth (n = 107) and at the age of 6 months (n = 106). The comparison group included pregnant patients, women in delivery and postpartum period who were under supervision and who gave childbirth in Gomel region over 2011-2012 (30087 pregnancies, 33477 births). Results. Pregnancy in women with HPV infection is frequently complicated by the threat of miscarriage (p = 0.0016). The clinical manifestations of HPV infection showed no effect on the gestation. Patients with high HPV load (5 lg GE per 100,000 cells) had birth canal injuries (p = 0.029) 3 times more often. Pregnancy complicated by gestosis and anemia, as well as vaginal childbirth were risk factors for perinatal transmission of HPV. The course of pregnancy and delivery were not determining factors in the persistence of HPV in the baby`s upper airways. Conclusion. We have defined the features of the course of pregnancy and delivery in women with genital HPV infection (the threat of miscarriage, birth canal injury with high viral load of HPV), the factors of perinatal transmission (gestosis and anemia during pregnancy, vaginal delivery).
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