COMPARATIVE PROBABILITY ON THE C* ALGEBRA OF COMPACT OPERATORS

Abstract

Let A be a von Neumann algebra on a Hilbert space H and let P(A) denote the projections of A. A comparative probability (CP) on A (or more correctly on P(A)) is a preorder ? on P(A) satisfying:

0 ? P ? P ε P(A) with Q ≠ 0 for some Q ε P(A).

If P, Q ε P(A) then either P ? Q or Q ? P.

If P, Q and R are all in P(A) and P⊥R, Q⊥R, then P ? Q ? P + R ? Q + R.

Let τ be any of the usual locally convex topologies on A. We say ? is τ continuous if the interval topology induced on P(A) by ? is weaker than the τ topology on P(A). If μ an additive (completely additive) measure on P(A) then μ induces a uniformly (weakly) continuous CP ?μ on P(A) given by P ?_μ Q if μ(P) ? μ(Q). We show that if A is the C* algebra C(H) of compact operators on an infinite dimensional Hilbert space H, the converse is true under an extra boundedness condition on the CP which is automatically satisfied whenever the identity is present in A = P(C(H)).     

A note on the modality of parabolic subgroups

For an algebraic group R acting morphically on an algebraic variety X the modality of the action, mod(R : X), is the maximal number of parameters on which a family of R-orbits on X depends upon.Let G be a simple algebraic group defined over an algebraically closed field K of characteristic 0. Let P be a parabolic subgroup of G. Then P acts on its unipotent radical P_u via conjugation. The modality of P is defined as mod P mod(P : P_u).Let r and s be the semisimple rank of G and P respectively. We show that there is a quadratic polynomial ƒ with rational coefficients such that the modality of P is at least ƒ(r − s). In particular, the modality of a Borel subgroup B of G grows at least quadratically with r. As a consequence, we obtain a finiteness result for algebraic groups from [8]: there is only a finite number of simple algebraic groups admitting parabolic subgroups of prescribed semisimple rank and prescribed modality. Combining our lower bounds with upper bounds from [6], we can compute the modality of Borel subgroups in some small rank cases.     

Irreducible Components of Fixed Point Subvarieties of Flag Varieties

Suppose G is a connected reductive algebraic group, P is a parabolic subgroup of G, L is a Levi factor of P, and e is a regular nilpotent element in Lie L. We assume that the characteristic of the underlying field is good for G. Choose a maximal torus, T, and a Borel subgroup, B, of G, so that T?B∩L, B ? P and e ∈ Lie B. Let β be the variety of Borel subgroups of G and let ??_e be the subset of ?? consisting of Borel subgroups whose Lie algebras contain e. Finally, let W be the Weyl group of G with respect to T. For ω ∈ W let ??_ω be the B-orbit in ?? containing ^ωB. We consider the intersections ??_ω ∩ ??_e. The main result is that if dim ??_ω ∩ ??_e = dim ??_e, then ??_ω ∩ ??_e is an affine space. Thus, the irreducible components of ??_e are indexed by Weyl group elements. It is also shown that if G is of type A, then this set of Weyl group elements is a right cell in W.     

Minimal extensions of Π01 classes

A minimal extension of a Π⁰₁ class P is a Π⁰₁ class Q such that P ? Q, Q – P is infinite, and for any Π⁰₁ class R, if P ? R ? Q, then either R – P is finite or Q – R is finite; Q is a nontrivial minimal extension of P if in addition P and Q′ have the same Cantor‐Bendixson derivative. We show that for any class P which has a single limit point A, and that point of degree ≤ 0 , P admits a nontrivial minimal extension. We also show that as long as P is infinite, then P does not admit any decidable nontrivial minimal extension Q. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Asymptotic Primes of Delta Closures of Ideals

Abstract

For an ideal H in a Noetherian ring R let H? = ∪{H ⁱ⁺¹ : _R H ⁱ | i ≥ 0} and for a multiplicatively closed set Δ of nonzero ideals of R let H _Δ = ∪{HK: _R K | K ? Δ}. It is shown that four standard results concerning the associated prime ideals of the integral closure (bR)_a of a regular principal ideal bR do not hold for certain Δ closures (bR)_Δ of bR. To do this it is first shown that if I is an ideal in R such that height (I) ≥ 1, then each radical ideal J of R containing I is of the form J = K? :_R cR for some ideal K closely related to I, and if I _a :_R J ? U = ∪{I?R _P ∩ R | P is a minimal prime divisor of J} (where I _a is the integral closure of I), then J = I _Δ :_R CR and I ? I _Δ ? I _a).     

An estimate of the speed of convergence in the multidmensional central limit theorem without moment hypotheses

Letx ₁, ...,x _n , (n ? 1) be independent random vectors in R_d and b be a vector in R_d. For an arbitrary Borel set A in Rd we set $$\begin{gathered} P_n \left( A \right) = P\left\{ {X_1 + ... + X_n - b \in A} \right\}, \hfill \\ \Delta _n \left( A \right) = \left| {P_n \left( A \right) - \Phi \left( A \right)} \right|, \hfill \\ \end{gathered} $$ where Φ(A) is the probability function of a standard normal vector in R_d. In this note are obtained estimates for Δ_n(A), where A belongs to the class of convex Borel sets in R_d.     

On dimensional properties of the generalized Smirnov's spaces

We show that the transfinite inductive dimensions modulo PP-trind and P-trInd introduced in M.G. Charalambous (1997) [2] differ by simple spaces, where P is the absolutely additive Borel class A(α) or the absolutely multiplicative Borel class M(α), 0?α<ω₁.     

WATTS THEOREMS FOR ASSOCIATIVE RINGS

Let R be an associative ring. In this paper we consider the category CMod-R of right R-modules M such that M ? Hom _R (R, M) and the category DMod-R of right R-modules M such that M ? _R R ? M. Given two associative rings R and R′, we study the functors F : CMod-R → CMod-R′ that can be written as Hom _R (P, ?) and the functors G : DMod-R → DMod-R′ that can be written as – ? _R Q and we give some results that extend the known Watts theorems for rings with identity to associative rings that need not be unital.     

Uniformly converging random variables for weakly converging laws

 Let {P _n , n ?ℕ} be a sequence of Borel probability measures on a compact and connected metric space X. We show that in case the measures P _n converge weakly to a fully supported limit measure P, there exist uniformly converging random variables X _n , n ?ℕ with these given laws. Connectivity and compactness are necessary conditions for our theorem to hold. We also present a decent generalization. We prove our theorem by means of a comparison of the Prokhorov and the so-called minimal L ^∞ metric. Then we only need to use the Strassen-Dudley theorem and Kellerer's measure extension theorem for decomposable families. Received: 2 November 2000 / Revised version: 5 January 2002/ Published online: 1 July 2002     

Borel and Julia directions of meromorphic Schröder functions II

Let R(w) be a non-inear rational function and s be a complex constant with | s | > 1. It is showed that for any solution f (z) of the Schr?der equation f (sz) = R(f (z)), Julia directions of f (z) are also Borel directions of f (z). Received: 2 May 2005; revised: 22 December 2005     

On the Chow Ring of a Flag

Let G be a reductive linear algebraic group over an algebraically closed field K, let P? be a parabolic subgroup scheme of G containing a Borel subgroup B, and let P = P?_red ? P? be its reduced part. Then P is reduced, a variety, one of the well known classical parabolic subgroups. For char(K) = p > 3, a classification of the P?'s has been given in [W1]. The Chow ring of G/P only depends on the root system of G. Corresponding to the natural projection from G/P to G/P? there is a map of Chow rings from A(G/P?) to A(G/P). This map will be explicitly described here. Let P = B, and let p > 3. A formula for the multiplication of elements in A(G/P?) will be derived. We will prove that A(G/P?) ? A(G/P) (abstractly as rings) if and only if G/P ? G/P? as varieties, i. e., the Chow ring is sensitive to the thickening. Furthermore, in certain cases A(G/P?) is not any more generated by the elements corresponding to codimension one Schubert cells.     

Automorphisms of the standard Borel subalgebra of Lie algebra of Cm type over a commutative ring

All automorphisms of the standard Borel subalgebra of the symplectic algebra sp(2m,?R) are determined, provided that R is a commutative ring with identity, 2 is invertible in R.     

On the quotient between length and multiplicity

In this paper, the exchange ring R with the (general) ?₀-comparability is studied. A ring R is said to satisfy the general ?₀-comparability, if for any idempotent elements f, g ∈ R, there exist a positive integer n and a central idempotent element e ∈ R such that f Re ?_⊕ n[gRe] and gR(1 ? e) ?_⊕ n[f R(1 ? e)]. It is proved that the (general) ?₀-comparability for exchange rings is preserved under taking factor rings, matrix rings and corners. The ?₀-comparability condition for exchange rings R is characterized by the order structure of several partially ordered sets of ideals of R. For any exchange ring R with general ?₀-comparability and any proper ideal I of R not contained in J(R), it is proved that if I contains no nonzero central idempotents of R, then: 1) There exists an infinite set of nonzero idempotent elements {f _i ∣ i = 1,2, …} in I such that f ₁ R ?_⊕ f ₂ R ?_⊕ …, and n(f _n R) ?_⊕ R _R for all n ≥ 1; 2) For any m ≥ 1, there exist nonzero orthogonal idempotents e ₁, e ₂ …, e _m in I such that e ₁ R ⊕ e ₂ R ⊕ … ⊕ e _m R ?_⊕ I _R and e _i R ? e _j R for all i, j. For any exchange ring R with primitive factor rings artinian, if R satisfies the general ?₀-comparability, then in every ideal I of R not contained in J(R), there is a central idempotent element of R.     

Spectra of Maximal 1-Sided Ideals and Primitive Ideals

R is any ring with identity. Let Spec _r (R) (resp. Max _r (R), Prim _r (R)) denote the set of all right prime ideals (resp. all maximal right ideals, all right primitive ideals) of R and let U _r (eR) = {P ? Spec _r (R)| e ? P}. Let  = ∪_{P?Prim r (R)} Spec _r ^P (R), where Spec _r ^P (R) = {Q ?Spec _r ^P (R)|P is the largest ideal contained in Q}. A ring is called right quasi-duo if every maximal right ideal is 2-sided. In this article, we study the properties of the weak Zariski topology on  and the relationships among various ring-theoretic properties and topological conditions on it. Then the following results are obtained for any ring R: (1) R is right quasi-duo ring if and only if  is a space with Zariski topology if and only if, for any Q ? , Q is irreducible as a right ideal in R. (2) For any clopen (i.e., closed and open) set U in ? = Max _r (R) ∪  Prim _r (R) (resp.  = Prim _r (R)) there is an element e in R with e ² ? e ? J(R) such that U = U _r (eR) ∩  ? (resp. U = U _r (eR) ∩  ), where J(R) is the Jacobson of R. (3) Max _r (R) ∪  Prim _r (R) is connected if and only if Max _l (R) ∪  Prim _l (R) is connected if and only if Prim _r (R) is connected.     

Smooth automorphisms and path-connectedness in Borel dynamics

Let Aut(X, B) be the group of all Borel automorphisms of a standard Borel space (X, B). We study topological properties of Aut(X, B) with respect to the uniform and weak topologies, τ and p, defined in [Bezuglyi S., Dooley A.H., Kwiatkowski J., Topologies on the group of Borel automorphisms of a standard Borel space, Preprint 2003]. It is proved that the class of smooth automorphisms is dense in (Aut(X, B), p). Let Ctbl(X) denote the group of Borel automorphisms with countable support. It is shown that the topological group Aut₀(X, B) = Aut(X, B)/Ctbl(X) is path-connected with respect to the quotient topology τ₀. It is also proved that Aut₀(X, B) has the Rokhlin property in the quotient topology p₀, i.e., the action of Aut₀(X,B) on itself by conjugation is topologically transitive.     

Commutative Rings Whose Cozero-Divisor Graphs are Unicyclic or of Bounded Degree

Let R be a commutative ring with unity. The cozero-divisor graph of R, denoted by Γ′(R), is a graph with vertex set W*(R), where W*(R) is the set of all nonzero and nonunit elements of R, and two distinct vertices a and b are adjacent if and only if a ? Rb and b ? Ra, where Rc is the ideal generated by the element c in R. Recently, it has been proved that for every nonlocal finite ring R, Γ′(R) is a unicyclic graph if and only if R ? ?₂ × ?₄, ?₃ × ?₃, ?₂ × ?₂[x]/(x ²). We generalize the aforementioned result by showing that for every commutative ring R, Γ′(R) is a unicyclic graph if and only if R ? ?₂ × ?₄, ?₃ × ?₃, ?₂ × ?₂[x]/(x ²), ?₂[x, y]/(x, y)², ?₄[x]/(2x, x ²). We prove that for every positive integer Δ, the set of all commutative nonlocal rings with maximum degree at most Δ is finite. Also, we classify all rings whose cozero-divisor graph has maximum degree 3. Among other results, it is shown that for every commutative ring R, gr(Γ′(R)) ∈ {3, 4, ∞}.     

Good fuzzy preorders on fuzzy power structures

This paper deals with good fuzzy preorders on fuzzy power structures. It is shown that a fuzzy preorder R on an algebra (X,\mathbbF){(X,\mathbb{F})} is compatible if and only if it is Hoare good, if and only if it is Smyth good.     

Oscillations of Higher Order Neutral Differential Equations with Variable Coefficients

We obtain sufficient conditions for the oscillation of all solutions of the higher order neutral differential equation dⁿ/d^m[y(t) + P(t) y(t - μ)] + Q(t) y(t ?σ) = 0, t ≧ t₀ where n ≧ 1, P ? C[t₀, ∞), R ], Q ? C[t₀, ∞), R ] and τ, μ ? R ⁺. Our results extend and improve several known results in the literature.     

When Are Covers Relative to Two Classes Isomorphic

Let ?₁ ? ?₂ be classes of right R-modules, we introduce ?₁-covering modules and projective modules relative to ?₂ to characterize the relations between the existences of ?₁-covers, ?₂-covers and the classes ?₁, ?₂. As corollaries, every module in ? _n is an ?-covering module if and only if every flat cover is an ? _n -cover for each right module if and only if R is a von Neumann regular ring whenever wD(R) < ∞; every flat right R-module is projective relative to 𝒫 if and only if every flat cover is a projective cover for each right module if and only if R is right perfect.     

Remarks on nonmeasurable unions of big point families

We show that under some conditions on a family A ? I there exists a subfamily A₀ ? A such that ∪ A₀ is nonmeasurable with respect to a fixed ideal I with Borel base of a fixed uncountable Polish space. Our result applies to the classical ideal of null subsets of the real line and to the ideal of first category subsets of the real line (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)