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We construct the Wess-Zumino-Witten (WZW) term in lattice gauge theory by using a Dirac operator which obeys the Ginsparg-Wilson relation. Topological properties of the WZW term known in the continuum are reproduced on the lattice as a consequence of a non-trivial topological structure of the space of admissible lattice gauge fields. In the course of this analysis, we observe that the gauge anomaly generally implies that there is no basis of a Weyl fermion which leads to a single-valued expectation value in the fermion sector. The lattice Witten term, which carries information of a gauge path along which the gauge anomaly is integrated, is separated from the WZW term and the multivaluedness of the Witten term is shown to be related to the homotopy group π 2n+1 (G). We also discuss the global SU(2) anomaly on the basis of the WZW term.

Numerical model of subsonic CO discharge laser is formulated. System of two-dimensional narrow channel equations or onedimensional gasdynamic equations is used. The peculiarities of the spatial distribution of gain for laser with longitudinal discharge are analysed. The computations for various experimental installations are made. The recommendations concerning the modernisation ofthese lasers are given. The lasers with line selecting on are analysed.

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