Generalized CCR Flows

CCR flows associated to closed convex cones

Let $P$ be a closed convex cone in $\mathbb{R}^{d}$ which we assume to be spanning and pointed i.e. $P-P=\mathbb{R}^{d}$ and $P \cap -P=\{0\}$. In this article, we consider CCR flows over $P$ associated to isometric representations that arises out of $P$-invariant closed subsets, also called as $P$-modules, of $\mathbb{R}^{d}$. We show that for two $P$-modules the associated CCR flows are cocycle conjugate if and only if the modules are translates of each other.

CAR flows on type III factors and its extendability

In this paper using one of the necessary conditions obtained for extendability in [BISSar], we prove that the CAR flows ([Amo01]) on type III factors arising from most quasi-free states are not extendable. As a consequence we find the super product system of CAR flows. We know from [Arv03] that CCR flows and CAR flows on type I factors with the same Arveson index are cocycle conjugate. But our result together with [BISSar] will show that CCR flows and CAR flows on type III factors are not cocycle conjugate.

The heat flow of the CCR algebra

Let P and Q be the canonical operators acting on the Hilbert space of all L^2 functions on the real line, defined appropriately on a common dense domain. The derivations D_P(A) = i(PA - AP) and D_Q(A) = i(QA - AQ) act on the *-algebra of all integral operators having smooth kernels of compact support, for example, and one may consider the noncommutative "Laplacian" L(A) = D_P^2(A) + D_Q^2(A), as a linear mapping of this *-algebra into itself. L generates a semigroup of normal completely positive maps on B(H), and we establish some basic properties of this semigroup and its minimal dilation to …

E-semigroups over closed convex cones

We initiate a study of E-semigroups over convex cones. We prove a structure theorem for E-semigroups which leave the algebra of compact operators invariant. Then we study in detail the CCR flows, E$_0$semigroups constructed from isometric representations, by describing their units and gauge groups. We exhibit an uncountable family of $2-$parameter CCR flows, containing mutually non-cocycle-conjugate E$_0$-$semigroups.

Every sum system is divisible

We show that every sum system is divisible. Combined with B. V. R. Bhat and R. Srinivasan's result, this shows that every product system arising from a sum system (and every generalized CCR flow) is either of type I or type III. A necessarily and sufficient condition for such a product system to be of type I is obtained.

Decompositions of Beurling Type for E_0-Semigroups

We define tensor product decompositions of $E_0$-semigroups with a structure analogous to a classical theorem of Beurling. Such decompositions can be characterized by adaptedness and exactness of unitary cocycles. For CCR-flows we show that such cocycles are convergent.

Decomposability of multiparameter CAR flows

Let $P$ be a closed convex cone in $\mathbb{R}^d$ which is assumed to be spanning $\mathbb{R}^d$ and contains no line. In this article, we consider a family of CAR flows over $P$ and study the decomposability of the associated product systems. We establish a necessary and sufficient condition for CAR flow to be decomposable. As a consequence we show that there are uncountable many CAR flows which are cocycle conjugate to the corresponding CCR flows.

On the classification and modular extendability of E$_0$-semigroups on factors

In this paper we study modular extendability and equimodularity of endomorphisms and E$_0$-semigroups on factors with respect to f.n.s. weights. We show that modular extendability is a property that does not depend on the choice of weights, it is a cocycle conjugacy invariant and it is preserved under tensoring. We say that a modularly extendable E$_0$-semigroup is of type EI, EII or EIII if its modular extension is of type I, II or III, respectively. We prove that all types exist on properly infinite factors. We also compute the coupling index and the relative commutant index for the CAR flow…

Pure E_0-semigroups and absorbing states

An E_0-semigroup acting on B(H) is called pure if the intersection of the ranges $α_t(B(H))$, $t>0$, is the algebra of scalars. We determine all pure E_0-semigroups which have a weakly continuous invariant state $ω$ and which are minimal in an appropriate sense. In such cases, for every normal state $ρ$ there is convergence to equilibrium in the trace norm $\lim_{t\to\infty}\| ρ\circα_t - ω\| = 0.$ A normal state $ω$ with this property is called an absorbing state. Such E_0-semigroups mest be cocycle perturbations of CAR/CCR flows, and we develop systematic methods for constructing those pertu…

路空间、连续张量积与E_0半群

Path spaces, continuous tensor products, and E_0 semigroups

我们对希尔伯特空间中所有连续的张量积系统进行分类，这些连续的张量积系统在它们具有相关的对数结构的意义上是“无限可分的”。将这些结果应用到E_0半群理论中，得到了具有足够多"可分解"算子的E_0半群必与CCR流上循环共轭.一个 * 路空间 * 是拓扑空间中路集合的抽象，在它上面给出了一个连接的结合规则。度量路径空间是由路径空间P和函数g组成的一对（P，g）：P^2-->复数，其行为就好像它是乘法内积的对数。与无限可分乘积系统相关的对数结构就是这样的对象。前面的结果是基于度量路径空间的分类。