Results 1 - 10 of 5840
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[en] In this paper we have investigated the general condition of self-adjointness of the generalised momentum operators and we have shown that it highly depends on the metric of the space. We have also discussed the domain of the generalised momentum operators at boundary conditions. (author)
[en] We modify the previous quasi-local mass definition. The new definition provides expressions of the quasi-local energy, the quasi-local linear momentum and the quasi-local mass. And they are equal to the ADM expressions at spatial infinity. Moreover, the new quasi-local energy has the positivity property.
[en] Theories with higher derivatives involve linear instabilities in the Hamiltonian commonly known as Ostrogradski ghosts and can be viewed as a very serious problem during quantization. To cure this, we have considered the properties of antilinearity that can be found inherently in the non-Hermitian Hamiltonians. Owing to the existence of antilinearity, we can construct an operator, called the V-operator, which acts as an intertwining operator between the Hamiltonian and its Hermitian conjugate. We have used this V-operator to remove the linear momentum term from the higher derivative Hamiltonian by making it non-Hermitian in the first place via an isospectral similarity transformation. The final form of the Hamiltonian is free from the Ostrogradski ghosts under some restriction on the mass term.
[en] A-entropy is investigated with respect to certain semispectral measures in a given state. It is shown that the entropy with respect to an observable describing 'simultaneous' measurement of positron and momentum is greater than the von Neumann entropy. Similar results are obtained for the fuzzy and sharp positions. The continuity properties of this entropy are also examined. (author)
[en] Deep inelastic neutron scattering measurements on normal liquid 4He at 4.25 K have been carried out at eleven densities between 0.125 (saturated vapor pressure) and 0.200 gm/cm3, at a momentum transfer of 23 /angstrom//sup /minus/1/. A sum of two Gaussians is required to characterize the scattering at all densities, even when the broadening due to instrumental resolution and corrections to the impulse approximation are included. The kinetic energy varies from 15.5 K at 0.125 gm/cm3 to 3.27 K at 0.200 gm/cm3. 24 refs., 9 figs., 2 tabs
[en] The influence of electron spectrometer alignment on the momentum resolution of electron-impact ionisation (e,2e) experiments is quantified. We show that for coplanar measurements with circular detector apertures, the azimuthal spectrometer alignment should be determined with an accuracy of ±0.001 rad to optimise the momentum resolution of an (e,2e) apparatus. Using this criterion, we predict an improvement in the (e,2e) momentum resolution of ∼30% near q=0 a.u., where quantum-mechanical scattering models predict a minimum in the triple differential cross-section (TDCS) of atomic p states. This result will assist in determining an upper limit on the effects of second order scattering processes that contribute to small momentum transfers
[en] The Kennard-type uncertainty relation ΔxΔp > ℎ/2 is formulated for a free particle with given momentum < p> inside a box with periodic boundary conditions in the large box limit. Our construction of a free particle state is analogous to that of the Bloch wave in a periodic potential. A simple Robertson-type relation, which minimizes the effect of the box boundary and may be useful in some practical applications, is also presented. (author)
[en] Experiments at the future linear collider project may answer long-standing questions in elementary particle physics and cosmology, such as what the origin of particle mass is, whether the concept of space-time should be extended, and how the universe was created. We present the technology choice, the optimization process, and the expected performance of the inner trackers currently proposed in the large-detector concept for the future linear collider project.
[en] A single component independent cluster model, based on a certain smoothness property of the amplitudes involved, is presented. The KNO (Koba, Nielsen, Olesen) multiplicity distribution function, the momentum distribution of the leading particles and clusters, as well as the relations among them are deduced