Results 1 - 10 of 4579
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[en] We present the first study of pairing in nuclei including three-nucleon forces. We perform systematic calculations of the odd-even mass staggering generated using a microscopic pairing interaction at first order in chiral low-momentum interactions. Significant repulsive contributions from the leading chiral three-nucleon forces are found. Two- and three-nucleon interactions combined account for approximately 70% of the experimental pairing gaps, which leaves room for self-energy and induced interaction effects that are expected to be overall attractive in nuclei.
[en] We address the problem of the ground-state character of LaH3, a semiconductor compound predicted to be semimetallic within density-functional theory. An ab initio, quasiparticle calculation is peformed whose results indicate a very large 1.1 eV opening of the band gap. Such results are obtained using the GW approximation in the calculation of the self-energy operator. The results are compared to existing experimental data
[en] The thermal conductivity of pionic medium has been evaluated with the help of its standard expression from the relaxation time approximation, where inverse of pion relaxation time or pion thermal width has been obtained from the imaginary part of pion self-energy. In the real-time formalism of thermal field theory, the finite temperature calculations of pion self-energy for πσ and πρ loops have been done. The numerical value of our thermal conductivity increases with temperature very softly, though at particular temperature, our estimation has to consider a large band of phenomenological uncertainty. (author)
[en] A hypothesis on the effective stimulant of the cometary nucleous activity in suggested. The model of nucleus structure plurality was derived on the basis of the hypothesis on the tidal mechanism of the structure origin. The conclusion is drawn from the concer being devised on the quiding role of self-energy of the plural cometary nucleus in the physical behaviour of the most active comets, as a relatively low energy of the impact mechanism is capable of supporting a very high level of the solar energy consumption for the sublimation of the cometary substance (or volatile impurities) from the cloud of ice dust in the comet nuclear region. The self-activity of the plural cometary nucleus damps gradually in proportion to its evolution transformation into the system with a collisionless structure. A sudden cut-off of the impact mechanism is related to elimination of large lump suite around the chief mass of the plural nucleus; the simplest reason of this fact lies in the intensive tidal effect on the suite. More complicated (two-stage) process of the impact mechanism cut-off follows after nontidal fission of the main mass of the cometary nucleus. The suite is lost then due to a sharp decrease in its counter-tidal stability
[en] We extend a previously developed formulation of QED based on self-energy to include the effect of perfectly conducting boundaries on spontaneous emission. The method is quite general and applicable to any quantum system and many boundary geometries. In particular, we compute the spontaneous emission rate of an atom near a conducting plate, inside a spherical cavity and between parallel plates, we give general formulas and predict both enhanced and inhibited rates, in agreement with recent experiments. (author)
[en] The one-loop graviton contributions to the graviton self-energy is calculated in a two-parameter gauge. The Slavnov and BRS identities are shown to be satisfied. A one-parameter family of gauges is also found in which the appropriate counterterm is part of a generally covariant object. Contrary to previous speculation, the spin-two and spin-zero parts of the counterterm can change sign. The significance of this result is discussed in detail. (author)
[en] The attractive interaction energy between a positronium atom and a metal surface has been numerically evaluated using our earlier-derived expression. In this derivation the interaction energy is obtained by considering the multipolar excitations of the positronium atom and excitations of the surface plasmons. It is shown that the interaction energy saturates to a constant value at the surface, and near the surface the interaction energy is considerably weaker than that given by the well-known semiclassical Lifshitz result
[en] Primordial inflation results in the production of a vast ensemble of highly infrared, massless, minimally coupled scalars. We use a recent fully renormalized computation of the one loop contribution to the graviton self-energy from these scalars to show that they have no effect on the propagation of dynamical gravitons. Our computation motivates a conjecture for the first correction to the vacuum state wave functional of gravitons. We comment as well on performing the same analysis for the more interesting contribution from inflationary gravitons, and on inferring one loop corrections to the force of gravity.
[en] The one loop effects of two dimension-six operators on gauge boson self-energies are computed within an effective field theory framework. These self-energies are translated into effects on precision electroweak observables, and bounds are obtained on the operator coefficients. The effective field theory framework allows for the divergences that arise in the loop calculations to be properly handled, and for unambiguous bounds on the coefficients to be obtained. We find that the coefficients are only weakly bounded, in contrast to previous calculations that obtained much stronger bounds. We argue that the results of these previous calculations are specious
[en] Based on an extensive study of the Dyson-Schwinger equations for a fully dressed quark propagator in the 'rainbow' approximation, a parametrized form of the quark propagator is suggested. The corresponding quark self-energy Σf and the structure of non-local quark vacuum condensate (0| : q-bar (x)q(0): |0) are investigated. The algebraic form of the quark propagator proposed in this work describes a confining quark propagation, and is quite convenient to be used in any numerical calculations.