91. A. V. Pokrovskii, S. J. Szybka, J. G. McInerney Topological Degree in Locating Homoclinic Structures for Discrete Dynamical Systems Izv. Ross. Akad. Estestv. Nauk Mat., vol. 5, pp. 152183 (2001). [abstract] [preprint] [journal] 
Abstract: A method of applying topological degree theory to analysis of chaotic behaviour of dynamical systems is described. The scheme combines one suggested by P. Zgliczynski with the method of topological shadowing. As an illustration a Henon mapping with a homoclinic tangency is considered. 
92. Jacek Guzik, Uros Seljak Galaxydark matter correlations applied to galaxygalaxy lensing: predictions from the semianalytic galaxy formation models MNRAS, vol. 321, p. 439 (2001). [preprint] [journal] 
Abstract:

93. Zdzislaw A. Golda, Andrzej Woszczyna Acoustics of early universe. I. Flat versus open universe models Class. Quant. Grav., vol. 18, pp. 543554 (2001). [abstract] [preprint] [journal] 
Abstract: A simple perturbation description unique for all signs of curvature, and based on the gaugeinvariant formalisms is proposed to demonstrate that:
(1) The density perturbations propagate in the flat radiationdominated universe in exactly the same way as electromagnetic or gravitational waves propagate in the epoch of the matter domination.
(2) In the open universe, sounds are dispersed by curvature. The space curvature defines the minimal frequency $\omega_{\rm c}$ below which the propagation of perturbations is forbidden.
Gaussian acoustic fields are considered and the curvature imprint in the perturbations spectrum is discussed 
94. Zdzislaw A. Golda, Andrzej Woszczyna Acoustics of early universe. II. Lifshitz vs. gaugeinvariant theories J. Math. Phys., vol. 42, pp. 856862 (2001). [abstract] [preprint] [journal] 
Abstract: Appealing to classical methods of order reduction, we reduce the Lifshitz system to a second order differential equation. We demonstrate its equivalence to well known gaugeinvariant results. For a radiation dominated universe we express the metric and density corrections in their exact forms and discuss their acoustic character.

95. Jacek Guzik, Uros Seljak, Matias Zaldarriaga Lensing effect on polarization in microwave background: extracting convergence power spectrum Phys.Rev. D, vol. 62, p. 043517 (2000). [preprint] [journal] 
Abstract:

96. Grazyna SiemieniecOzieblo, Andrzej Woszczyna Order reduction in semiclassical cosmology Phys. Rev. D, vol. 59, p. 083504 (1999). [abstract] [preprint] [journal] 
Abstract: We investigate the RobertsonWalker cosmology with Lagrangian $R+\alpha_1\hbar R^2+\alpha_2\hbar R^{\mu\nu}R_{\mu\nu} +L_{rad}$ where $L_{rad}$ means classical source with traceless energymomentum tensor. We weaken the selfconsistence condition (L. Parker, J. Z. Simon, Phys. Rev. {D47}(1993),{1339}). Quantum corrections are expressed as contributions to the effective equation of state. We show that the empty spacetime is stable within the class of radiationfilled expanding universes with no order reduction of the field equations.
