The consistent histories approach to quantum mechanics is traditionally based on linearly ordered sequences of events. We extend the histories formalism to sets of events whose causal ordering is described by directed acyclic graphs. The need for a global time is eliminated and our construction reflects the causal structure faithfully.

In this paper we suggest a numerical implementation based on plain Monte Carlo simulation of the conditional expectations in the following Markovian setting: Suppose (X(i),Fi), 0 ≤ i ≤ k, is a possibly high-dimensional Markov process and the cashflow is of the form Z(i) = f(i,X(i)). Assume a consistent stopping family τ(i) depends on ω only through the path of X and that for each i the event {τ...

The vertical transition energies for butadiene have been calculated using the CIS/6-3 1 1 (2+)G* theoretical model. The observed energies were satisfactorily reproduced. The charge distribution for each of the excited states was calculated so that the change from the ground-state distribution could be examined. The nature of the Rydberg states are discussed. Quantitative information on the degr...

The decoherent (consistent) histories formalism has been proposed as a means of eliminating measurements as a fundamental concept in quantum mechanics. In this formalism, probabilities can be assigned to any description which satisfies a particular consistency condition. The formalism, however, admits incompatible descriptions which cannot be combined, unlike classical physics. This seems to le...

Denial of service (DoS) and Distributed Denial of Service (DDoS) attacks continue to threaten the reliability of networking systems. Previous approaches for protecting networks from DoS attacks are reactive in that they wait for an attack to be launched before taking appropriate measures to protect the network. This leaves the door open for other attacks that use more sophisticated methods to m...

Several theoretical methods are employed to characterize the intramolecular proton transfer in the ground state and in the lowest-lying 3nπ∗ and 3ππ∗ excited states of 1-amino-3-propenal. The geometrical parameters, the relative energy of the two tautomeric forms, the energy barrier for the proton transfer, and the energy difference between the ground and the excited states predicted by the dif...

A general theory for response properties is presented which is applicable to perturbations affecting the molecular basis set, notably nuclear derivatives. A perturbation-independent Fock space is introduced, and the necessary reorthonormalization of a truncated basis set after a perturbation is explicitly incorporated in the Hamiltonian. Explicit formulas for MCSCF firstand second-order propert...

A major problem in the consistent-histories approach to quantum theory is contending with the potentially large number of consistent sets of history propositions. One possibility is to find a scheme in which a unique set is selected in some way. However, in this paper we consider the alternative approach in which all consistent sets are kept, leading to a type of ‘many world-views’ picture of t...

The possibility that quantum mechanics itself could be non-linear has run up against difficulties with relativistic covariance. Most of the schemes proposed up to now engender superluminal communication, and those that don’t, have been equivalent to linear theories. We show in a simplified model that a proposal based on the consistent histories approach to quantum mechanics avoids the usual dif...

Synopsis We present a combined experimental and theoretical study focused on the ionic states of the N2O4 molecule. Experimental results regarding photoionization induced by the synchrotron radiation SOLEIL in the 13.5-15.5 eV energy range were obtained using the electron-ion velocity vector correlation method. The potential energy curves for the dissociation of the N-N bond were computed withi...