ABSTRACT
Semilocal strings-a particular limit of electroweak strings-are an interesting example of a stable non-topological defect whose properties resemble those of their topological cousins, the Abrikosov-Nielsen-Olesen vortices. There is, however, one important difference: a network of semilocal strings will contain segments. These are 'dumbbells' whose ends behave almost like global monopoles that are strongly attracted to one another. While closed loops of string will eventually shrink and disappear, the segments can either shrink or grow, and a cosmological network of semilocal strings will reach a scaling regime. We discuss attempts to find a 'thermodynamic' description of the cosmological evolution and scaling of a network of semilocal strings, by analogy with well-known descriptions for cosmic strings and for monopoles. We propose a model for the time evolution of an overall length scale and typical velocity for the network as well as for its segments, and some supporting (preliminary) numerical evidence. This article is part of a discussion meeting issue 'Topological avatars of new physics'.
Subject(s)
Bird Diseases/diagnosis , Cystadenocarcinoma/veterinary , Falconiformes , Leiomyoma/veterinary , Uterine Neoplasms/veterinary , Animals , Bird Diseases/pathology , Cystadenocarcinoma/diagnosis , Cystadenocarcinoma/pathology , Fatal Outcome , Female , Leiomyoma/diagnosis , Leiomyoma/pathology , Uterine Neoplasms/diagnosis , Uterine Neoplasms/pathologyABSTRACT
We present a first principle study of the electron-phonon (e-p) interaction at the Be(0001) surface. The real and imaginary parts of the e-p self-energy (Sigma) are calculated for the Gamma; surface state in the binding energy range from the Gamma; point to the Fermi level. Our calculation shows an overall good agreement with several photoemission data measured at high and low temperatures. Additionally, we show that the energy derivative of Re Sigma presents a strong temperature and energy variation close to E(F), making it difficult to measure its value just at E(F).
ABSTRACT
We present a comprehensive theoretical investigation of the electron-phonon contribution to the lifetime broadening of the surface states on Cu(111) and Ag(111), in comparison with high-resolution photoemission results. The calculations, including electron and phonon states of the bulk and the surface, resolve the relative importance of the Rayleigh mode, being dominant for the lifetime at small hole binding energies. Including the electron-electron interaction, the theoretical results are in excellent agreement with the measured binding energy and temperature dependent lifetime broadening.
