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 Physics , 1998, Abstract: It is shown that $\alpha^2$-term of sum rules for the total cross sections of interaction of elementary atoms with matter ones, obtained in ref.[Denisenko K. and Mrowczynski S., Phys. Rev. D36 (1987) 1529] is wrong. New sum rules valid up to terms of order $\alpha^2$ are derived.
 Physics , 2001, DOI: 10.1103/PhysRevD.65.096001 Abstract: It is shown that the corrections of $\alpha^2$ order to the total cross sections for interaction of elementary hydrogen-like atoms with target atoms, reported in the previously published paper [S.Mrowczynski, Phys.Rev. D36, 1520 (1987)], do not include some terms of the same order of magnitude. That results in a significant contribution of these corrections in particular cases. The full $\alpha^2$-corrections have been derived and it is shown that they are really small and could be omitted for most practical applications.
 Physics , 2012, DOI: 10.1103/PhysRevA.85.052707 Abstract: The many-body system comprising a He nucleus, three electrons, and a positron has been studied using the exact diagonalization technique. The purpose has been to clarify to which extent the system can be considered as a distinguishable positronium (Ps) atom interacting with a He atom and, thereby, to pave the way to a practical atomistic modeling of Ps states and annihilation in matter. The maximum value of the distance between the positron and the nucleus is constrained and the Ps atom at different distances from the nucleus is identified from the electron and positron densities, as well as from the electron-positron distance and center-of-mass distributions. The polarization of the Ps atom increases as its distance from the nucleus decreases. A depletion of the He electron density, particularly large at low density values, has been observed. The ortho-Ps pick-off annihilation rate calculated as the overlap of the positron and the free He electron densities has to be corrected for the observed depletion, specially at large pores/voids.
 Physics , 2008, DOI: 10.1103/PhysRevC.79.035801 Abstract: We study the collective density modes which can affect neutron-star thermodynamics in the baryonic density range between nuclear saturation ($\rho_0$) and $3\rho_0$. In this region, the expected constituents of neutron-star matter are mainly neutrons, protons and electrons ($npe$ matter), under the constraint of beta equilibrium. The elementary excitations of this $npe$ medium are studied in the RPA framework. We emphasize the effect of Coulomb interaction, in particular the electron screening of the proton plasmon mode. For the treatment of the nuclear interaction, we compare two modern Skyrme forces and a microscopic approach. The importance of the nucleon effective mass is observed.
 Imre Ferenc Barna Physics , 2006, Abstract: With the help of the boost operator we can model the interaction between a weakly interacting particle(WIMP) of dark matter(DAMA) and an atomic nuclei. Via this "kick" we calculate the total electronic excitation cross section of the helium atom. The bound spectrum of He is calculated through a diagonalization process with a configuration interaction (CI) wavefunction built up from Slater orbitals. All together 19 singly- and doubly-excited atomic sates were taken with total angular momenta of L=0,1 and 2. Our calculation may give a rude estimation about the magnitude of the total excitation cross section which could be measured in later scintillator experiments. The upper limit of the excitation cross section is $9.7\cdot 10^{-8}$ barn.
 Physics , 2005, Abstract: This chapter deals with atom-wall interaction occurring in the "long-range" regime (typical distances: 1-1000 nm), when the electromagnetic fluctuations of an isolated atom are modified by the vicinity with a surface. Various regimes of interaction are discussed in an Introductory part, from Cavity Quantum ElectroDynamics modifications of the spontaneous emission, to Casimir effect, with emphasis on the atom-surface van der Waals interaction, characterized as a near-field interaction governed by a z-3 dependence. The major part of the Chapter focuses on the experimental measurements of this van der Waals interaction, reviewing various recent techniques, and insists upon optical techniques, and notably selective reflection spectroscopy which is particularly well-suited when excited atoms are considered. A review of various experiments illustrates the specific effects associated with a resonant coupling between the atomic excitation and surface modes, from van der Waals repulsion to surface-induced resonant transfer, and with anisotropy effects, including metastability transfer induced by a quadrupole contribution in the interaction. The effects of a thermal excitation of the surface -with a possible remote energy transfer to an atom-, and of interaction with nanobodies -which are intrinsically non planar- are notably discussed among the prospects.
 Maxim Dvornikov Physics , 2015, Abstract: The description of physical processes in accelerated frames opens a window to numerous new phenomena. One can encounter these effects both in the subatomic world and on a macroscale. In the present work we review our recent results on the study of the electroweak interaction of particles with an accelerated background matter. In our analysis we choose the noninertial comoving frame, where matter is at rest. Our study is based on the solution of the Dirac equation, which exactly takes into account both the interaction with matter and the nonintertial effects. First, we study the interaction of ultrarelativistic neutrinos, electrons and quarks with the rotating matter. We consider the influence of the matter rotation on the resonance in neutrino oscillations and the generation of anomalous electric current of charged particles along the rotation axis. Then, we study the creation of neutrino-antineutrino pairs in a linearly accelerated matter. The applications of the obtained results for elementary particle physics and astrophysics are discussed.
 Physics , 2000, DOI: 10.1103/PhysRevD.63.084010 Abstract: It is believed that there may have been a large number of black holes formed in the very early universe. These would have quantised masses. A charged elementary black hole'' (with the minimum possible mass) can capture electrons, protons and other charged particles to form a black hole atom''. We find the spectrum of such an object with a view to laboratory and astronomical observation of them, and estimate the lifetime of the bound states. There is no limit to the charge of the black hole, which gives us the possibility of observing Z>137 bound states and transitions at the lower continuum. Negatively charged black holes can capture protons. For Z>1, the orbiting protons will coalesce to form a nucleus (after beta-decay of some protons to neutrons), with a stability curve different to that of free nuclei. In this system there is also the distinct possibility of single quark capture. This leads to the formation of a coloured black hole that plays the role of an extremely heavy quark interacting strongly with the other two quarks. Finally we consider atoms formed with much larger black holes.
 Physics , 2011, DOI: 10.1103/PhysRevC.84.035806 Abstract: The thermal evolution of neuron stars depends on the elementary excitations affecting the stellar matter. In particular, the low-energy excitations, whose energy is proportional to the transfered momentum, can play a major role in the emission and propagation of neutrinos. In this paper, we focus on the density modes associated with the proton component in the homogeneous matter of the outer core of neutron stars (at density between one and three times the nuclear saturation density, where the baryonic constituants are expected to be neutrons and protons). In this region, it is predicted that the protons are superconductor. We study the respective roles of the proton pairing and Coulomb interaction in determining the properties of the modes associated with the proton component. This study is performed in the framework of the Random Phase Approximation, generalized in order to describe the response of a superfluid system.The formalism we use ensures that the Generalized Ward's Identities are satisfied. An important conclusion of this work is the presence of a pseudo-Goldstone mode associated with the proton superconductor in neutron-star matter. Indeed, the Goldstone mode, which characterizes a pure superfluid, is suppressed in usual superconductors due to the long-range Coulomb interaction, which only allows a plasmon mode. However, for the proton component of stellar matter, the Coulomb field is screened by the electrons and a pseudo-Goldstone mode occurs, with a velocity increased by the Coulomb interaction.
 Physics , 1999, Abstract: Quantum calculations are developed on the dynamical system consisting of the cosmic axions, photons and Rydberg atoms which are interacting in the resonant microwave cavity. The time evolution is determined for the number of Rydberg atoms in the upper state which are excited by absorbing the axion-converted and thermal background photons. The calculations are made, in particular, by taking into account the actual experimental situation such as the motion and uniform distribution of the Rydberg atoms in the incident beam and also the spatial variation of the electric field in the cavity. Some essential aspects on the axion-photon-atom interaction in the resonant cavity are clarified by these detailed calculations. Then, by using these results the detection sensitivity of the Rydberg atom cavity detector is estimated properly. This systematic quantum analysis enables us to provide the optimum experimental setup for the dark matter axion search with Rydberg atom cavity detector.
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