Search results for "theory of relativity"
showing 10 items of 61 documents
Hadron Structure Studied with the Electromagnetic Probe - from Giant Resonances to Meson Production
2000
The development of theoretical photonuclear physics over the last 40 years is illustrated by a few selected examples highlighting a number of important issues like collective motion in nuclei, the role of subnuclear degrees of freedom, relativity and meson production.
Quasistationary solutions of self-gravitating scalar fields around black holes
2015
Recent perturbative studies have shown the existence of long-lived, quasistationary configurations of scalar fields around black holes. In particular, such configurations have been found to survive for cosmological time scales, which is a requirement for viable dark matter halo models in galaxies based on such types of structures. In this paper we perform a series of numerical relativity simulations of dynamical nonrotating black holes surrounded by self-gravitating scalar fields. We solve numerically the coupled system of equations formed by the Einstein and the Klein-Gordon equations under the assumption of spherical symmetry using spherical coordinates. Our results confirm the existence …
Newtonian and relativistic emission coordinates
2009
Emission coordinates are those generated by positioning systems. Positioning systems are physical systems constituted by four emitters broadcasting their respective times by means of sound or light signals. We analyze the incidence of the space-time causal structure on the construction of emission coordinates. The Newtonian case of four emitters at rest is analyzed and contrasted with the corresponding situation in special relativity.
Higher-order gravity in higher dimensions: geometrical origins of four-dimensional cosmology?
2017
Determining cosmological field equations represents a still very debated matter and implies a wide discussion around different theoretical proposals. A suitable conceptual scheme could be represented by gravity models that naturally generalize Einstein Theory like higher order gravity theories and higher dimensional ones. Both of these two different approaches allow to define, at the effective level, Einstein field equations equipped with source-like energy momentum tensors of geometrical origin. In this paper, it is discussed the possibility to develop a five dimensional fourth order gravity model whose lower dimensional reduction could provide an interpretation of cosmological four dimens…
Special Relativity and the Single Antiproton: Fortyfold Improved Comparison ofp¯andpCharge-to-Mass Ratios
1995
The measured ratio of charge-to-mass ratios for the antiproton and proton is $1.0000000015\ifmmode\pm\else\textpm\fi{}0.0000000011$. This $1$ part in ${10}^{9}$ comparison ( $1$ ppb) is possible because a single $\overline{p}$ or $p$ is now directly observed while trapped in an open access Penning trap. The comparison is the most accurate mass spectrometry of particles with opposite charge, and is the most sensitive test of $\mathrm{CPT}$ invariance for a baryon system. It is 40 times more accurate than our earlier comparison with many trapped antiprotons and protons, and is more than 45 000 times more accurate than earlier comparisons made with other techniques.
The Geometry of Space-Time and Its Deformations from a Physical Perspective
2007
We start with an epistemological introduction on the evolution of the concepts of space and time and more generally of physical concepts in the context of the relation between mathematics and physics from the point of view of deformation theory. The concepts of relativity, including anti de Sitter space-time, and of quantization, are important paradigms; we briefly present these and some consequences. The importance of symmetries and of space-time in fundamental physical theories is stressed. The last section deals with “composite elementary particles” in anti de Sitter space-time and ends with speculative ideas around possible quantized anti de Sitter structures in some parts of the univer…
Probing Models of Extended Gravity using Gravity Probe B and LARES experiments
2014
We consider models of Extended Gravity and in particular, generic models containing scalar-tensor and higher-order curvature terms, as well as a model derived from noncommutative spectral geometry. Studying, in the weak-field approximation, the geodesic and Lense-Thirring processions, we impose constraints on the free parameters of such models by using the recent experimental results of the Gravity Probe B and LARES satellites.
A missing link: What is behind de Broglie's "Periodic phenomenon"?
1996
The present work constitutes an attempt to give the interpretation of de Broglie's internal periodic phenomenon which ascribes the frequencym0c2/h to each single entity in its eigensystem of coordinates. This phenomenon provides existence in principle of the ideal proper-time scale, making it possible to identify the geometric proper-time interval with a physically existing one, thus ensuring the realization of basic postulates of the relativity theory. According to the latter, neither time nor de Broglie's frequency are invariant with respect to the Lorentz transformation of the coordinate system. A search for the fundamental invariant demands passing over to dimensionless quantities, and …
Building a numerical relativistic non-ideal magnetohydrodynamics code for astrophysical applications
2013
AbstractIncluding resistive effects in relativistic magnetized plasmas is a challenging task, that a number of authors have recently tackled employing different methods. From the numerical point of view, the difficulty in including non-ideal terms arises from the fact that, in the limit of very high plasma conductivity (i.e., close to the ideal MHD limit), the system of governing equations becomes stiff, and the standard explicit integrating methods produce instabilities that destroy the numerical solution. To deal with such a difficulty, we have extended the relativistic MHD code MR-GENESIS, to include a number of Implicit Explicit Runge-Kutta (IMEX-RK) numerical methods. To validate the i…
Mass and Gravity
2014
The book starts with a survey on the development of the concept ‘mass’ and of theories of gravity, beginning with Greek’s ideas on mass, Galileo’s experiments, Newton’s laws and their extension by Einstein’s theory of relativity. Data from measurements of the gravitational force on Sun, planets and the Moon are presented. Kepler’s laws on moving masses in the gravitational field are discussed as well as new discoveries on the expansion of the universe. Fundamental interactions of particles and particle/wave duality are described. The Theory of Everything is mentioned. The definition of the international unit of mass is reported as well as alternatives like watt or voltage balance, counting …