Semiclassical universe from first principles

Semiclassical Universe from First Principles

Causal Dynamical Triangulations in four dimensions provide a background-independent definition of the sum over space-time geometries in nonperturbative quantum gravity. We show that the macroscopic four-dimensional world which emerges in the Euclidean sector of this theory is a bounce which satisfies a semi-classical equation. After integrating out all degrees of freedom except for a global sca...

First - Principles Semiclassical Initial Value Representation

First principles semiclassical calculations of vibrational eigenfunctions.

Vibrational eigenfunctions are calculated on-the-fly using semiclassical methods in conjunction with ab initio density functional theory classical trajectories. Various semiclassical approximations based on the time-dependent representation of the eigenfunctions are tested on an analytical potential describing the chemisorption of CO on Cu(100). Then, first principles semiclassical vibrational ...

First-principles semiclassical initial value representation molecular dynamics.

In this work, we explore the use of the semiclassical initial value representation (SC-IVR) method with first-principles electronic structure approaches to carry out classical molecular dynamics. The proposed approach can extract the vibrational power spectrum of carbon dioxide from a single trajectory providing numerical results that agree with experiment and quantum calculations. The computat...

Counterfactual Causality from First Principles?

In this position paper we discuss three main shortcomings of existing approaches to counterfactual causality from the computer science perspective, and sketch lines of work to try and overcome these issues: (1) causality definitions should be driven by a set of precisely specified requirements rather than specific examples; (2) causality frameworks should support system dynamics; (3) causality ...