119983228
Renormalization of semiclassical field theories
Abstract We discuss a simple model which shares some of the essential features of the semiclassical theory of gravitation. In this model, a classical scalar field υ interacts with a quantized field φ. We describe a consistent and unambiguous renormalization scheme for the model.
117120091
A uniqueness result for quantum field theory on spacetimes with bifurcate Killing horizons
123297693
Sufficient conditions for quasifree states and an improved uniqueness theorem for quantum fields on space–times with horizons
Let ω be a state on the Weyl algebra over a symplectic space. We prove that if either (i) the ‘‘liberation’’ of ω is pure or (ii) the restriction of ω to each of two generating Weyl subalgebras is quasifree and pure, then ω is quasifree and pure [and, in case (i) is equal to its liberation, in case (ii) is uniquely determined by its restrictions]. [Here, we define the liberation of a (sufficiently regular) state to be the quasifree state with the same two point function.] Results (i) and (ii) permit one to drop the quasifree assumption in a result due to Wald and the author concerning linear scalar quantum fields on space–times with bifurcate Killing horizons and thus to conclude that, on a large subalgebra of the field algebra for such a system, there is a unique stationary state whose two point function has the Hadamard form. The paper contains a number of further related developments including: (a) (i) implies a uniqueness result, e.g., for the usual free field in Minkowski space. We compare and contra...
16748405
The robustness of a many-body decoherence formula of Kay under changes in graininess and shape of the bodies
In "Decoherence of macroscopic closed systems within Newtonian quantum gravity" (Kay B S 1998 Class. Quantum Grav. 15 L89-L98) it was argued that, given a many-body Schrodinger wave function ψ(x1, . . . , xN) for the centre-of- mass degrees of freedom of a closed system of N identical uniform-mass balls of mass M and radius R, taking account of quantum gravitational effects and then tracing over the gravitational field amounts to multiplying the position-space density matrix
120058153
Theorems on the uniqueness and thermal properties of stationary, nonsingular, quasifree states on spacetimes with a bifurcate killing horizon
Abstract This paper is concerned with the study of quasifree states of a linear, scalar quantum field in globally hyperbolic spacetimes possessing a one-parameter group of isometries with a bifurcate Killing horizon. Some results on the uniqueness and thermal properties of such states are well known in the special cases of Minkowski, Schwarzschild, and deSitter spacetimes, and our main aim is to present new stronger results and to generalize them to this wide class of spacetimes. As a preliminary to proving our theorems, we develop some aspects of the theory of globally of hyperbolic spacetimes with a bifurcate Killing horizon, we give some new results on the structure of Bose quasifree states of linear fields (the class which includes all the usual “Fock vacua”), and we clarify and further develop the notion of a “Hadamard state”. We then consider the quasifre e states on these spacetimes which have vanishing one-point function, are invariant under the one-parameter isometry group, and are nonsingular in a neighborhood of the horizon in the sense that their two-point function is of the Hadamard form there. We prove that, on a large subalgebra of observables (which are determined by observables localized in compact regions of the horizon) such states are unique and pure. Furthermore, if the spacetime admits a certain discrete “wedge reflection” isometry (as holds automatically in the analytic case) we prove that this state - if it exists - must be a KMS state at the Hawking temperature T = κ /2 π when restricted to those observables in our subalgebra which are localized in one of the (“right” or “left”) wedges of the spacetime where the Killing orbits are timelike near the horizon. Here, κ denotes the surface g ravity of the horizon. Under the further assumption that the nonsingularity of the state holds globally and that there are no “zero modes” in the one-partic le Hilbert space belonging to the state, we extend the uniqueness result to all observables localized in the full “domain of determinacy” of the hori zon. However, existence of states satisfying the hypotheses of our theorems does not hold in general and, indeed, we prove the nonexistence of any stationary (not necessarily quasifree) Hadamard state on the Schwarzschild-deSitter and Kerr spacetimes. We remark that nowhere in the analysis do we need to assume any form of Einstein's equations.
123597708
A uniqueness result in the Segal–Weinless approach to linear Bose fields
We prove a theorem, which, while it fits naturally into the Segal–Weinless approach to quantization seems to have been overlooked in the literature: Let (D,σ) be a symplectic space, and T (t) a one parameter group of symplectics on (D,σ). Let (H, 2Im〈⋅ ‖ ⋅〉) be a complex Hilbert space considered as a real symplectic space, and U(t) a one‐parameter unitary group on H with strictly positive energy. Suppose there is a linear symplectic map K from D to H with dense range, intertwining T (t) and U(t). Then K is unique up to unitary equivalence.
18182800
Population of positive-parity states in Sc 53 through one-proton knockout
The one-proton knockout reaction {sup 9}Be({sup 54}Ti,{sup 53}Sc+{gamma})X at 72 MeV/nucleon has been measured. The location of the first 3/2{sup -} state at 2110(3) keV was confirmed, and new {gamma}-ray transitions were observed at 1111(2), 1273(2), 1539(4), and 2495(5) keV. Large spectroscopic strength to excited states in {sup 53}Sc was found and attributed to the knockout of sd-shell protons.
121267185
Properties of excited states in Ge77
The nucleus $^{77}\mathrm{Ge}$ was studied through the $^{76}\mathrm{Ge}(^{13}\mathrm{C},^{12}\mathrm{C})^{77}\mathrm{Ge}$ reaction at a sub-Coulomb energy. The angular distributions of $\ensuremath{\gamma}$ rays depopulating excited states in $^{77}\mathrm{Ge}$ were measured in order to constrain spin and parity assignments. Some of these assignments are of use in connection with neutrinoless double beta decay, where the population of states near the Fermi surface of $^{76}\mathrm{Ge}$ was recently explored using transfer reactions.