Search results for "Observable"
showing 10 items of 634 documents
Towards a kinetic theory for fermions with quantum coherence
2008
A new density matrix and corresponding quantum kinetic equations are introduced for fermions undergoing coherent evolution either in time (coherent particle production) or in space (quantum reflection). A central element in our derivation is finding new spectral solutions for the 2-point Green's functions written in the Wigner representation, that are carrying the information of the quantum coherence. Physically observable density matrix is then defined from the bare singular 2-point function by convoluting it with the extrenous information about the state of the system. The formalism is shown to reproduce familiar results from the Dirac equation approach, like Klein problem and nonlocal re…
Tau-spin correlations at the z-peak: aplanarities of the decay products
1991
8 páginas, 3 figuras, 1 tabla.-- CERN-TH-5932-90 ; FTUV-90-26.
Liquid Structure of Trihexyltetradecylphosphonium Chloride at Ambient Temperature: An X-ray Scattering and Simulation Study
2009
We report on an experimental and simulation study done on a representative room temperature ionic liquid, namely tetradecyltrihexylphosphonium chloride, at ambient conditions. The study was conducted using small and wide angle X-ray scattering and molecular dynamics simulations. Both approaches converge in indicating that this material is characterized by the existence of strong P-Cl interactions (with characteristic distances between 3.5 and 5.0 Å) and by the occurrence of nanoscale segregation, despite the symmetric nature of the cation and similarly to other room temperature ionic liquids. A good agreement is found between the structure factor and pair correlation functions obtained from…
Competition between inter- and intra- molecular energy exchanges in a simple quantum model of a dimer
2006
Abstract We propose a fully quantum model to describe the dynamics of a possible radiationless energy transfer process between identical and nearly localized molecules or monomers coupled through a dipole–dipole term. The system is studied as an environmentally isolated dimeric pair and we find that its dynamics exhibits a competition between the process ruling out the transfer of energy among different degrees of freedom of a given monomer and the one steering the intermolecular passage of excitations from a monomer to the other one. Such a competition is quantitatively characterized investigating on the temporal behaviour of quantum covariances of some couples of appropriate observables h…
The structure of the state representation of shift invariant controllable and observable group codes
2000
AbstractIn this paper an investigation on the structure of the canonical trellis section of shift invariant, l-controllable and m-observable group codes is carried out. Necessary and sufficient conditions for a set of group homomorphisms in order that they represent the trellis section of this class of codes are established.
Nuclear modification of forward Drell-Yan production at the LHC
2017
Forward Drell-Yan production at high energy can provide important constraints on gluon densities at small $x$, in the saturation regime. In this work we focus on the nuclear modification of this process, which could be measured at the LHC in the near future. For this we employ the color dipole approach, using the optical Glauber model to relate the dipole cross section of a nucleus to the one of a proton. Combining these results with our earlier results for forward $J/\psi$ production, we compute the ratio of the nuclear modification factors of these two processes. This observable was recently suggested as a way to distinguish between initial and final state effects in forward particle prod…
Realizing Undelayed N-step TD prediction with neural networks
2010
There exist various techniques to extend reinforcement learning algorithms, e.g., eligibility traces and planning. In this paper, an approach is proposed, which combines several extension techniques, such as using eligibility-like traces, using approximators as value functions and exploiting the model of the environment. The obtained method, ‘Undelayed n-step TD prediction’ (TD-P), has produced competitive results when put in conditions of not fully observable environment.
The dynamic interdependence in the demand of primary and emergency secondary care: A hidden Markov approach
2021
This paper develops an extension of the class of finite mixture models for longitudinal count data to the bivariate case by using a trivariate reduction technique and a hidden Markov chain approach. The model allows for disentangling unobservable time-varying heterogeneity from the dynamic effect of utilisation of primary and secondary care and measuring their potential substitution effect. Three points of supports adequately describe the distribution of the latent states suggesting the existence of three profiles of low, medium and high users who shows persistency in their behaviour, but not permanence as some switch to their neighbour's profile.
The welfare cost of unpriced heterogeneity in insurance markets
2016
We consider the welfare loss of unpriced heterogeneity in insurance markets, which results when private information or regulatory constraints prevent insurance companies to set premiums reflecting expected costs. We propose a methodology which uses survey data to measure this welfare loss. After identifying some “types” which determine expected risk and insurance demand, we derive the key factors defining the demand and cost functions in each market induced by these unobservable types. These are used to quantify the efficiency costs of unpriced heterogeneity. We apply our methods to the US Long-Term Care and Medigap insurance markets, where we find that unpriced heterogeneity causes substan…
The democratization process: An empirical appraisal of the role of political protest
2020
Abstract This paper analyses the role of peaceful and violent protest in the democratization process. We interpret the democratization process as a sequence of phases so as to allow citizens' and elites' preferences for democracy to vary according to the particular phase that a country is experiencing. By doing so we jointly model the probability of protest and of moving through different phases of democracy taking into account time-constant and time-varying unobserved heterogeneity. In particular, we develop a multivariate finite mixture model that introduces a latent variable to capture unobservable factors. On a sample of 171 countries from 1971 to 2010, we provide evidence that protest …