11 research outputs found
Further Representations of the Canonical Commutation Relations
We construct a new class of representations of the canonical commutation
relations, which generalizes previously known classes. We perturb the
infinitesimal generator of the initial Fock representation (i.e. the free
quantum field) by a function of the field which is square-integrable with
respect to the associated Gaussian measure. We characterize which such
perturbations lead to representations of the canonical commutation relations.
We provide conditions entailing the irreducibility of such representations,
show explicitly that our class of representations subsumes previously studied
classes, and give necessary and sufficient conditions for our representations
to be unitarily equivalent, resp. quasi-equivalent, with Fock, coherent or
quasifree representations
Geometric Modular Action and Spacetime Symmetry Groups
A condition of geometric modular action is proposed as a selection principle
for physically interesting states on general space-times. This condition is
naturally associated with transformation groups of partially ordered sets and
provides these groups with projective representations. Under suitable
additional conditions, these groups induce groups of point transformations on
these space-times, which may be interpreted as symmetry groups. The
consequences of this condition are studied in detail in application to two
concrete space-times -- four-dimensional Minkowski and three-dimensional de
Sitter spaces -- for which it is shown how this condition characterizes the
states invariant under the respective isometry group. An intriguing new
algebraic characterization of vacuum states is given. In addition, the logical
relations between the condition proposed in this paper and the condition of
modular covariance, widely used in the literature, are completely illuminated.Comment: 83 pages, AMS-TEX (format changed to US letter size
The second law of thermodynamics, TCP, and Einstein causality in anti-de Sitter space-time
If the vacuum is passive for uniformly accelerated observers in anti-de
Sitter space-time (i.e. cannot be used by them to operate a "perpetuum
mobile"), they will (a) register a universal value of the Hawking-Unruh
temperature, (b) discover a TCP symmetry, and (c) find that observables in
complementary wedge-shaped regions are commensurable (local) in the vacuum
state. These results are model independent and hold in any theory which is
compatible with some weak notion of space-time localization.Comment: 8 pages, slightly improved results, minor changes in the expository
part, new title; to appear in "Classical and Quantum Gravity
Further Representations of the Canonical Commutation Relations
. We construct a new class of representations of the canonical commutation relations, which generalizes previously known classes. We perturb the infinitesimal generator of the initial Fock representation (i.e. the free quantum field) by a function of the field which is square-integrable with respect to the associated Gaussian measure. We characterize which such perturbations lead to representations of the canonical commutation relations. We provide conditions entailing the irreducibility of such representations, show explicitly that our class of representations subsumes previously studied classes, and give necessary and sufficient conditions for our representations to be unitarily equivalent, resp. quasi-equivalent, with Fock, coherent or quasifree representations. Typeset by A M S-T E X 2 MARTIN FLORIG AND STEPHEN J. SUMMERS I. Introduction The canonical commutation relations (henceforth the CCR) were initially introduced in 1927 by Dirac as generalizations of Heisenberg's commuta..