科研之友
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摘要
The field-theoretical model describing multicritical phenomena with two coupled order parameters with n(parallel to) and n(perpendicular to) components and of O(n(parallel to))circle plus O(n(perpendicular to)) symmetry is considered. Conditions for realization of different types of multicritical behaviour are studied within the field-theoretical renormalization group approach. Surfaces separating stability regions for certain types of multicritical behaviour in parametric space of order parameter dimensions and space dimension d are calculated using the two-loop renormalization group functions. Series for the order parameter marginal dimensions that control the crossover between different universality classes are extracted up to the fourth order in epsilon = 4 - d and to the fifth order in a pseudo-epsilon parameter using the known high-order perturbative expansions for isotropic and cubic models. Special attention is paid to a particular case of O(1)circle plus O(2) symmetric model relevant for description of anisotropic antiferromagnets in an external magnetic field.
- 出版日期2012
