Search results for "Relativity"
showing 10 items of 1213 documents
Nonthermal effects of acceleration in the resonance interaction between two uniformly accelerated atoms
2016
We study the resonance interaction between two uniformly accelerated identical atoms, one excited and the other in the ground state, prepared in a correlated (symmetric or antisymmetric) state and interacting with the scalar field or the electromagnetic field in the vacuum state. In this case (resonance interaction), the interatomic interaction is a second-order effect in the atom-field coupling. We separate the contributions of vacuum fluctuations and radiation reaction to the resonance energy shift of the system, and show that only radiation reaction contributes, while Unruh thermal fluctuations do not affect the resonance interaction. We also find that beyond a characteristic length scal…
Exact solution of generalized Tavis - Cummings models in quantum optics
1996
Quantum inverse methods are developed for the exact solution of models which describe N two-level atoms interacting with one mode of the quantized electromagnetic field containing an arbitrary number of excitations M. Either a Kerr-type nonlinearity or a Stark-shift term can be included in the model, and it is shown that these two cases can be mapped from one to the other. The method of solution provides a general framework within which many related problems can similarly be solved. Explicit formulae are given for the Rabi splitting of the models for some N and M, on- and off-resonance. It is also shown that the solution of the pure Tavis - Cummings model can be reduced to solving a homogen…
The RADECS 2008 workshop overview
2008
The 8th European Workshop on Radiation and its Effects on Components and Systems, RADECS 2008, was held September 10–12, 2008 at the University of Jyvaskyla, Finland. The venue took place at the University's Agora Building locating close to the Alba hotel, where most of the attendees were accommodated. The host of the event was the Department of Physics and its Industrial Applications group served as the organizer. The group runs the Radiation Effects Facility, RADEF, in the Department's Accelerator Laboratory.
Integral display for non-static observers
2017
We propose to combine the Kinect and the Integral-Imaging technologies for the implementation of Integral Display. The Kinect device permits the determination, in real time, of (x,y,z) position of the observer relative to the monitor. Due to the active condition of its IR technology, the Kinect provides the observer position even in dark environments. On the other hand, SPOC 2.0 algorithm permits to calculate microimages adapted to the observer 3D position. The smart combination of these two concepts permits the implementation, for the first time we believe, of an Integral Display that provides the observer with color 3D images of real scenes that are viewed with full parallax and which are…
Algunos problemas en la enseñanza de la relatividad
2021
Resumen. La relatividad es una parte importante de la física moderna. En este artículo se analiza su enseñanza-aprendizaje en la enseñanza secundaria y se muestran sus principales dificultades. El artículo argumenta razonadamente contra prácticas tradicionales en la enseñanza de la relatividad y finalmente apunta una nueva aproximación a su enseñanza. Palabras clave. Enseñanza-aprendizaje, relatividad, didáctica de la física. Summary. Relativity is a very important part of modern physics. In this paper we analyze the teaching and learning of the theory of relativity at secondary school level and we show the pupils¿ main difficulties. This article presents some reasoned arguments against tra…
On the validity of non-Markovian master equation approaches for the entanglement dynamics of two-qubit systems
2010
In the framework of the dissipative dynamics of coupled qubits interacting with independent reservoirs, a comparison between non-Markovian master equation techniques and an exact solution is presented here. We study various regimes in order to find the limits of validity of the Nakajima–Zwanzig and the time-convolutionless master equations in the description of the entanglement dynamics. A comparison between the performances of the concurrence and the negativity as entanglement measures for the system under study is also presented.
Evolutionary sequences of rotating protoneutron stars
2004
We investigate the evolution of rigidly and differentially rotating protoneutron stars (PNSs) during the first twenty seconds of their life. We solve the equations describing stationary axisymmetric configurations in general relativity coupled to a finite temperature, relativistic equation of state, to obtain a sequence of quasi-equilibrium configurations describing the evolution of newly born neutron stars. Our estimates show that the scale of variation of the angular velocity in a PNSs is of the order of 7-10 km. We obtain the maximum rotation frequency that can be reached as the protoneutron stars deleptonizes and cools down, as well as other relevant parameters such as total angular mom…
Postmortem Imaging in Mass Disasters
2019
The term “mass casualty” in the forensic field refers to a sudden tragic event involving a large number of people; such an event determines the need to perform a large number of autopsy exams, possibly in a short time. Mass casualties tend to involve emergencies that are unexpected and result in stressful situation when even those with no or scarce interest or experience could be called to play a role. Radiology could be helpful in the task of identifying victims, in cooperation with a multidisciplinary team, usually headed by a forensic specialist.
Optical Dark Rogue Wave
2016
AbstractPhotonics enables to develop simple lab experiments that mimic water rogue wave generation phenomena, as well as relativistic gravitational effects such as event horizons, gravitational lensing and Hawking radiation. The basis for analog gravity experiments is light propagation through an effective moving medium obtained via the nonlinear response of the material. So far, analogue gravity kinematics was reproduced in scalar optical wave propagation test models. Multimode and spatiotemporal nonlinear interactions exhibit a rich spectrum of excitations, which may substantially expand the range of rogue wave phenomena and lead to novel space-time analogies, for example with multi-parti…
On new ways of group methods for reduction of evolution-type equations
2005
AbstractNew exact solutions of the evolution-type equations are constructed by means of a non-point (contact) symmetries. Also we analyzed the discrete symmetries of Maxwell equations in vacuum and decoupled ones to the four independent equations that can be solved independently.