24 марта 2020 г. АннотацияIt is shown that in the polar phase of superfluid 3 He, stabilized by nematic aerogel, at the condition of specular reflection of quasiparticles from the strands of aerogel the temperature dependence of the gap in the spectrum of quasi-particles coincides with that in the bulk polar phase without impurities. The analogy with the Anderson theorem for conventional superconductors is discussed.

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Using liquid 3 He in aerogel as an example, it is shown that correlations in positions of impurities affect the temperature T c of transition of Fermi liquid in an unconventional superfluid or superconductive state. The effect is significant if the correlation length for impurities is greater than the coherence length in the superfluid or superconductive state ξ 0 . For 3 He in aerogel the suppression of T c is expressed in terms of the structure factor of aerogel. With the account of the fractal structure of aerogel a simple expression is obtained for the decrease of T c from its clean value. This expression is in a satisfactory agreement with the experimental data.