Search results for "causality"

Relationship between Helicobacter pylori infection and GERD

2018

Gastroesophageal reflux disease (GERD) is due to the chronic exposure of the esophageal mucosa to acid secretion from the stomach. Helicobacter pylori (H.p.) infection, is a risk factor for the development of peptic ulcer, atrophic gastritis and gastric cancer, and causes various effects on gastric function. The relationship between GERD and H.pylori infection is still subject of debate.Background and aim: In literature no clear causal relationship has been established between GERD and H. pylori infection, although some papers support the onset of esophagitis in patients in whom the infection has been cured. Aim of this work is to review the most recent literature data about the relationshi…

The ‘Perfected System of Criticism’: Schopenhauer's Initial Disagreements with Kant

2012

AbstractI would like to know who of mycontemporaries should be more competent inKantian philosophy than me.(Schopenhauer in a letter to Rosenkranz and Schubert, 18371)In this paper the attempt is made to show how Schopenhauer's critique of Kant leads from initial disagreements to a fundamental modification, even a new formation, of the Kantian concepts of understanding, reason, imagination, perception, idea and thing-in-itself. The starting point and the core of his critique is the demand for the appreciation of intuitive knowledge which is apart from and independent of reason. The intuitive knowledge goes back to images and its highest form is aesthetic contemplation. Without a participati…

Per una rilettura kantiana del principio di causalità

2018

There is no contradiction between Kant’s statement that the proposition, “every alteration has its cause,” is of no interest to the Critique of Pure Reason because of its dependence on empirical contents (KrV, B 3) and his use of the same proposition as an example of pure a priori knowledge (KrV, B 5). There is only the arduousness and sometimes also the ambiguity of a passage in which Kant attempts to establish a new basis for the validity of the principle of causality.

Causality constraint on bound states and scattering with zero-range force, or do perturbative pions deserve another chance?

2016

Hyperbolic character of the angular moment equations of radiative transfer and numerical methods

2000

We study the mathematical character of the angular moment equations of radiative transfer in spherical symmetry and conclude that the system is hyperbolic for general forms of the closure relation found in the literature. Hyperbolicity and causality preservation lead to mathematical conditions allowing to establish a useful characterization of the closure relations. We apply numerical methods specifically designed to solve hyperbolic systems of conservation laws (the so-called Godunov-type methods), to calculate numerical solutions of the radiation transport equations in a static background. The feasibility of the method in any kind of regime, from diffusion to free-streaming, is demonstrat…

Anomalous dynamics triggered by a non-convex equation of state in relativistic flows

2017

The non-monotonicity of the local speed of sound in dense matter at baryon number densities much higher than the nuclear saturation density ($n_0 \approx 0.16\,$fm$^{-3}$) suggests the possible existence of a non-convex thermodynamics which will lead to a non-convex dynamics. Here, we explore the rich and complex dynamics that an equation of state (EoS) with non-convex regions in the pressure-density plane may develop as a result of genuinely relativistic effects, without a classical counterpart. To this end, we have introduced a phenomenological EoS, whose parameters can be restricted heeding to causality and thermodynamic stability constraints. This EoS shall be regarded as a toy-model wi…

On the singular behaviour of scattering amplitudes in quantum field theory

2014

We analyse the singular behaviour of one-loop integrals and scattering amplitudes in the framework of the loop--tree duality approach. We show that there is a partial cancellation of singularities at the loop integrand level among the different components of the corresponding dual representation that can be interpreted in terms of causality. The remaining threshold and infrared singularities are restricted to a finite region of the loop momentum space, which is of the size of the external momenta and can be mapped to the phase-space of real corrections to cancel the soft and collinear divergences.

Spectral incoherent solitons: a localized soliton behavior in the frequency domain

2008

We show both theoretically and experimentally in an optical fiber system that a noninstantaneous nonlinear environment supports the existence of spectral incoherent solitons. Contrary to conventional solitons, spectral incoherent solitons do not exhibit a confinement in the spatiotemporal domain, but exclusively in the frequency domain. The theory reveals that the causality condition inherent to the nonlinear response function is the key property underlying the existence of spectral incoherent solitons. These solitons constitute nonequilibrium stable states of the incoherent field and are shown to be robust with respect to binary collisions.

Non-locality and causal evolution in QFT

2006

Non locality appearing in QFT during the free evolution of localized field states and in the Feynman propagator function is analyzed. It is shown to be connected to the initial non local properties present at the level of quantum states and then it does not imply a violation of Einstein's causality. Then it is investigated a simple QFT system with interaction, consisting of a classical source coupled linearly to a quantum scalar field, that is exactly solved. The expression for the time evolution of the state describing the system is given. The expectation value of any arbitrary ``good'' local observable, expressed as a function of the field operator and its space and time derivatives, is o…

Nonlocal field correlations and dynamical Casimir-Polder forces between one excited- and two ground-state atoms

2006

The problem of nonlocality in the dynamical three-body Casimir-Polder interaction between an initially excited and two ground-state atoms is considered. It is shown that the nonlocal spatial correlations of the field emitted by the excited atom during the initial part of its spontaneous decay may become manifest in the three-body interaction. The observability of this new phenomenon is discussed.