Volume 16, № 1, 1964

The author considers the matrix linear groups described in 13], namely partition groups. The problem was to distinguish in the complete linear group, given as invariant, the subgroups which, with proper choice of basis, become partition groups. Three solutions of the problem are given.

For a system of $n + m$ equations $$\frac{dx}{dt} = X(y)x + \varepsilon X*(t, x, y),$$ $$\frac{dy}{dt} = \varepsilon Y(t, x, y),$$ where $x, X*, y, Y$ are respectively $n$ and $m$ vectors, $X — n \times n$ is the matrix, $\varepsilon$ is a small parameter, the author proves the theorem of the existence and properties of a two-dimensional local integral manifold in the neighbourhood of family of periodic solutions $$x = 0,\; y = y^0(\psi, a)$$ oi the lollowing auxiliary system $$\frac{dx}{dt} = X(y)x,$$ $$\frac{dy}{dt} = \varepsilon Y_0(x, y),$$ where $$Y_0(x, y) = \lim_{T\rightarrow 0}\int_0^T Y(t, x,y)dt.$$

A method is proposed, based on the application of the theorem of continuity and permitting the determination of which points of Landau's surface are singular points of contributions of Feinman's diagrams on a «physical sheet».

Let $\xi_1, \xi_2, ...,\xi_n,...$ be independent identically distributed random variables, $S_{n0} = 0,\; S_{nk} = \frac1{\sqrt{n}} (\xi_1 + ...+ \xi_k)$, and $f_n(x, у)$ the sequence of measurable functions for which $\lim_{n\rightarrow \infty } \sup_{x, y} |f_n(x, у)| \rightarrow 0$. Limit theorems for random variables $\sum_{k=0}^{n—1}f_n(S_{nk}, S_{nk+1})$ are obtained.

The basic result of this investigation may be formulated as follows. Consider a set of natural numbers in which the following relationship is introduced: $n_1$ precedes $n_2$ ($n_1 \preceq n_2$) if for any continuous mappings of the real line into itself the existence of a cycle of order $n_2$ follows from the existence of a cycle of order The following theorem holds.
Theorem. The introduced relationship transforms the set of natural numbers into an ordered set, ordered in the following way:
$3 \prec 5 \prec 7 \prec 9 \prec 11 \prec ... \prec 3 \cdot 2 \prec 5 \cdot 2 \prec ... \prec 3 \cdot 2^2 \prec 5 \cdot 2^2 \prec ... \prec 2^3 \prec 2^2 \prec 2 \prec 1$