Search results for " Quantum Mechanics."

The Dynamical Problem for a Non Self-adjoint Hamiltonian

2012

After a compact overview of the standard mathematical presentations of the formalism of quantum mechanics using the language of C*- algebras and/or the language of Hilbert spaces we turn attention to the possible use of the language of Krein spaces.I n the context of the so-called three-Hilbert-space scenario involving the so-called PT-symmetric or quasi- Hermitian quantum models a few recent results are reviewed from this point of view, with particular focus on the quantum dynamics in the Schrodinger and Heisenberg representations.

Bohm’s Implicate Order, Wheeler’s Participatory Universe, Stapp’s Mindful Universe, Zurek’s Quantum Darwinism and the Buddhist Mind-Only Ground Consc…

According to quantum physicist Erich Joos the following three issues are the outstanding quantum conundrums of deep significance: 1. The meaning of the wavefunction; 2. The exact nature of the mechanism of the collapse; 3. The connection between the quantum and classical realm. In this paper I shall attempt to elucidate a possible approach to these central issues by drawing parallels between David Bohm’s notion of the implicate order, John Wheeler’s vision of the ‘Participatory Universe’, Henry Stapp’s account of the Heisenberg-von Neumann quantum ‘ontology’, Wojciech Zurek’s ‘Quantum Darwinism’ proposal and the Buddhist Mind-Only (Yogachara–Chittamatra) concept of the alayavijnana, the gro…

Generalization of thermodynamics allowing negentropic entanglement and a model for conscious information processing

2011

Costa de Beauregard considers a model for information processing by a computer based on an analogy with Carnot's heat engine. I am grateful for Stephen Paul King for bringing this article to my attention in Time discussion group and also for inspiring discussions which also led to the birth of this section. As such the model Beauregard for computer does not look convincing as a model for what happens in biological information processing. Combined with TGD based vision about living matter, the model however inspires a model for how conscious information is generated and how the second law of thermodynamics must be modified in TGD framework. The basic formulas of thermodynamics remain as such…

Analytic structure ofϕ4theory using light-by-light sum rules

2013

Abstract We apply a sum rule for the forward light-by-light scattering process within the context of the ϕ 4 quantum field theory. As a consequence of the sum rule a stringent causality criterion is presented and the resulting constraints are studied within a particular resummation of graphs. Such resummation is demonstrated to be consistent with the sum rule to all orders of perturbation theory. We furthermore show the appearance of particular non-perturbative solutions within such approximation to be a necessary requirement of the sum rule. For a range of values of the coupling constant, these solutions manifest themselves as a physical bound state and a K-matrix pole. For another domain …

Causality and the Coulomb sum rule in nuclei.

1989

The spectral function in the Jost-Lehmann-Dyson representation of causal commutators is determined for the nonrelativistic limit of inclusive lepton scattering from nuclei. From this an extrapolation of the Coulomb sum rule to higher-momentum transfers is performed which is consistent with the requirement of causality.

Process-independent strong running coupling

2016

We unify two widely different approaches to understanding the infrared behaviour of quantum chromodynamics (QCD), one essentially phenomenological, based on data, and the other computational, realised via quantum field equations in the continuum theory. Using the latter, we explain and calculate a process-independent running-coupling for QCD, a new type of effective charge that is an analogue of the Gell-Mann--Low effective coupling in quantum electrodynamics. The result is almost identical to the process-dependent effective charge defined via the Bjorken sum rule, which provides one of the most basic constraints on our knowledge of nucleon spin structure. This reveals the Bjorken sum to be…

Novel patterns for vector mesons from the large-Nc limit

2008

We report on a relation between the decay constants of \rho-like J^{PC}=1^{--} vector mesons, which arises solely from the perturbative analysis of the VV, TT and VT correlators at order \alpha_s^0 in the large-N_c limit. We find f_{V}^T/f_{V}=1/\sqrt{2} for highly excited states together with a pattern of alternation in sign. Quite remarkably, recent lattice determinations reported f_{\rho}^T/f_{\rho}=0.72(2), in excellent agreement with our large-N_c result. This seems to suggest a pattern like f_{Vn}^T/f_{Vn}=(-1)^n/\sqrt{2} for the whole (1^{--}) states. In order to test this conjecture in real QCD we construct a set of spectral sum rules, which turn out to comply nicely with this scena…

Existence, uniqueness, and construction of the density-potential mapping in time-dependent density-functional theory

2014

In this work we review the mapping from densities to potentials in quantum mechanics, which is the basic building block of time-dependent density-functional theory and the Kohn-Sham construction. We first present detailed conditions such that a mapping from potentials to densities is defined by solving the time-dependent Schr\"odinger equation. We specifically discuss intricacies connected with the unboundedness of the Hamiltonian and derive the local-force equation. This equation is then used to set up an iterative sequence that determines a potential that generates a specified density via time propagation of an initial state. This fixed-point procedure needs the invertibility of a certain…

Dynamics of a subconstituent picture of weak interactions

1985

We use sum rules in order to discuss the dynamics of the simplest subconstituent model of weak interactions with elementary spin 1/2 fermions and scalar bosons. Vacuum condensates of the scalars play an essential role and lead to features quite different from QCD. With a certain vacuum structure vector dominance of the composite W-mesons is a good approximation, and we also see a clear signal for massless fermions in the two-point function of composite fermions. Thus such a model is in good agreement with standard phenomenology. Composite Higgs particles are also investigated. The effective interaction is evidently of the gauge type.

Partial self-consistency and analyticity in many-body perturbation theory: Particle number conservation and a generalized sum rule

2016

We consider a general class of approximations which guarantees the conservation of particle number in many-body perturbation theory. To do this we extend the concept of $\Phi$-derivability for the self-energy $\Sigma$ to a larger class of diagrammatic terms in which only some of the Green's function lines contain the fully dressed Green's function $G$. We call the corresponding approximations for $\Sigma$ partially $\Phi$-derivable. A special subclass of such approximations, which are gauge-invariant, is obtained by dressing loops in the diagrammatic expansion of $\Phi$ consistently with $G$. These approximations are number conserving but do not have to fulfill other conservation laws, such…