Search results for "classical"
showing 10 items of 2294 documents
Comparing non-perturbative models of the breakup of neutron-halo nuclei
2012
Breakup reactions of loosely-bound nuclei are often used to extract structure and/or astrophysical information. Here we compare three non-perturbative reaction theories often used when analyzing breakup experiments, namely the continuum discretized coupled channel model, the time-dependent approach relying on a semiclassical approximation, and the dynamical eikonal approximation. Our test case consists of the breakup of 15C on Pb at 68 MeV/nucleon and 20 MeV/nucleon.
Zur Begründung eines Variationsprinzipes für zerfallende Systeme
1976
Taking into account the circumstance that the decay of an unstable microscopic system into two fragments is established by the counting of one of the decay products in a detector, the observed exponential decay law then asserts only knowledge of the spatiotemporal behaviour of the probability density (and therewith knowledge of the decaying state) at a large finite distance from the site of decay. We therefore formulate a variational principle, of which stationary functions show this decay behaviour. In addition to the resonant wave functions there are also solutions of the variational principle, which decrease exponentially with increasing distance, i.e., functions which could be used to d…
Spacetime Foam Model of the Schwarzschild Horizon
2003
We consider a spacetime foam model of the Schwarzschild horizon, where the horizon consists of Planck size black holes. According to our model the entropy of the Schwarzschild black hole is proportional to the area of its event horizon. It is possible to express geometrical arguments to the effect that the constant of proportionality is, in natural units, equal to one quarter.
Two-dimensional approach to relativistic positioning systems
2006
A relativistic positioning system is a physical realization of a coordinate system consisting in four clocks in arbitrary motion broadcasting their proper times. The basic elements of the relativistic positioning systems are presented in the two-dimensional case. This simplified approach allows to explain and to analyze the properties and interest of these new systems. The positioning system defined by geodesic emitters in flat metric is developed in detail. The information that the data generated by a relativistic positioning system give on the space-time metric interval is analyzed, and the interest of these results in gravimetry is pointed out.
Positioning in a flat two-dimensional space-time: the delay master equation
2010
The basic theory on relativistic positioning systems in a two-dimensional space-time has been presented in two previous papers [Phys. Rev. D {\bf 73}, 084017 (2006); {\bf 74}, 104003 (2006)], where the possibility of making relativistic gravimetry with these systems has been analyzed by considering specific examples. Here we study generic relativistic positioning systems in the Minkowski plane. We analyze the information that can be obtained from the data received by a user of the positioning system. We show that the accelerations of the emitters and of the user along their trajectories are determined by the sole knowledge of the emitter positioning data and of the acceleration of only one …
On the determination of the proton RMS-radius from electron scattering data
1975
It is shown that the proton rms radius should be determined from fitting a polynomial of second order to the low-q 2 form factors. The commonly used polynomial of first order yields radius values which are too small. The proton rms radius has been redetermined from an analysis of the electron scattering data measured at three laboratories. The best fit value is 〈r E 2 〉1/2=0.87±0.02 fm.
NON-PERTURBATIVE VACUUM WAVE-FUNCTIONAL AND CLOSED STRING EQUATIONS OF MOTION
1989
The anomalous conformal dependence of the vacuum wave-functional is studied in the non-perturbative regime of the closed bosonic string theory. It is shown that the vanishing of the vacuum expectation value of the stress-energy tensor trace leads to the implementation of a suitable variational condition on the wave-functional, provided that the dilaton condensate be taken as a conformal compensator for the graviton condensate of the embedding space.
Quantum bubble dynamics in the presence of gravity
1991
Abstract The dynamics of spherical quantum bubbles in 3+1 dimensions is governed by a Klein-Gordon-type equation which simulates the quantum mechanical motion of a relativistic point particle in 1+1 dimensions. This dimensional reduction is especially clear in the minisuperspace formulation first used in quantum cosmology and adapted here to quantum bubble dynamics. The payoff of this formulation is the discovery of the gravitational analogue of the Klein effect, namely the crossing of positive and negative energy levels of the particle spectrum induced by an external gravitational field. This phenomenon gives rise to a finite probability that a vacuum bubble might tunnel from an initial bo…
Coulomb-Fourier representation approach to three-body scattering with charged particles
2004
Abstract We present a novel approach for calculating charged-composite particle scattering. It consists in eliminating by means of a suitably chosen representation that part of the interaction which is of longest range and, hence, gives rise to all the troublesome feaures which plague charged particle scattering theories. In this paper only the simplest case is considered, namely that of two charged and one neutral particles which interact via pairwise strong potentials, and a repulsive Coulomb potential between the charged particles.
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 …