On algebras satisfying $x^2x^2=N(x)x$

The commutative algebras satisfying the “adjoint identity”: , where N is a cubic form, are shown to be related to a class of generically algebraic Jordan algebras of degree at most 4 and to the pseudo-composition algebras. They are classified under a nondegeneracy condition. As byproducts, the associativity of the norm of any pseudo-composition algebra is proven and the unital commutative and power-associative algebras of degree are shown to be Jordan algebras. Received January 26, 1999; in final form August 26, 1999 / Published online July 3, 2000     

Qualitative Investigation of the Singular Cauchy Problem F(t,x, x′) = 0, x(0) = 0

We prove the existence and uniqueness of a continuously differentiable solution with required asymptotic properties.     

On free semilattice-ordered semigroups satisfying x n =x

Let B(k,0,n) denote the group with k generators which is free in the group variety defined by the identity x ⁿ =1. Let B _slo (k,1,n) denote the semilattice-ordered semigroup with k generators which is free in the semilattice-ordered semigroup variety defined by the identity x ⁿ =x. We prove a generalization of the Green-Rees theorem: B _slo (k,1,n) is finite for all k≥1 if and only if B(k,0,n−1) is finite for all k≥1. We find a formula for card(B _slo (1,1,n)). We construct B _slo (k,1,n) for some concrete values of k and n.     

Levi and Malcev Theorems for Finite-Dimensional Algebras from the Variety Defined by the Identities x2 =J(x,y, zu) =0

We study the variety of binary Lie algebras defined by the identities x2 =J(x,y,zu) =0,where J(a,b,c) denotes the Jacobian of a,b,c.Building on previous work by Carrillo,Rasskazova,Sabinina and Grishkov,in the present article it is shown that the Levi and Malcev theorems hold for this variety of algebras.     

An existence theorem for solutions tof(x) = 0

InR ¹, if a continuous function has opposite signs at the endpoints of an interval, then the function has a zero in the interval. If the function has a nonvanishing derivative at a zero, then there is an interval such that the function has opposite signs at the endpoints. In this paper each of these results is extended toR ⁿ .The research of this author has been partially supported by ONR Contract N000-14-67-A-0285-0019 (NR #047-095) and by NSF Contract SOC-7402516.     

Semigroups satisfying (xy)m = xmym

In this paper we characterize Archimedean semigroups with idempotents satisfying (xy)^m = x^my^m as exactly those semigroups which are a retract extension of a completely simple semigroup satisfying (xy)^m = x^my^m by a nil semigroup satisfying (xy)^m = x^my^m. Regular semigroups satisfying (xy)² = x²y² are exactly those semigroups which are a spined product of a band and a semigroup which is a semilattice of Abelian groups. A semigroup which is a nil extension of a regular semigroup satisfies (xy)² = x²y² if and only if it is a retract extension of a regular semigroup satisfying (xy)² = x²y² by a nil semigroup satisfying (xy)² = x²y²     

Dual representations of hulls for functions satisfying f (0) = inf f (X\{0}) *

Let Xbe a setW set of extended-real valued functions on Xand 0 an element of Xsuch that w(0) = 0 for all win W. We give a general theory of dual representations, without any extra parameters, of various hulls for extended-real valued functions on X satisfying f(0)= inf f(X\{0})We use the unifying framework of quasi-convex functions with respect to families of subsets of Xand a condition generalizing the bipolar theorem. Our results contain, as particular cases, some recent results of Thach (1991, 1993) and Rubinov and Glover (1996) on W-pseudo-affine and W-quasi-coaffine hulls.We also give some

results in the converse direction. These yield, in particular, that the bipolar theorem is equivalent to a certain property of the lower semi-continuous quasi-convex hulls of functions on locally convex spaces     

函数y=f（x）在点X=X0处可导的一个充分条件

文章分析了分段函数在分段点处导数值的常见计算错误，给出了函数y=f（x）在点x=x0处可导的一个充分条件，使得计算分段函数的导数值变得准确，简便．     

△u-a(x)u+b(x)up=0奇解的渐近性质

讨论了半线性椭圆方程△u-a(x)u+6(x)up=0奇解的渐近性质,其中u Ω→R,Ω()Rn,n≥3, n/(n - 2) ＜ p ＜ (n + 2)/(n - 2).