397,399 research outputs found
Variational separable expansion scheme for two-body Coulomb-scattering problems
We present a separable expansion approximation method for Coulomb-like
potentials which is based on Schwinger variational principle and uses
Coulomb-Sturmian functions as basis states. The new scheme provides faster
convergence with respect to our formerly used non-variational approach.Comment: some typos correcte
Auto-parallel equation as Euler-Lagrange's equation in spaces with affine connections and metrics
The auto-parallel equation over spaces with affine connections and metrics is
considered as a result of the application of the method of Lagrangians with
covariant derivatives (MLCD) on a given Lagrangian density.Comment: 19 pages, LaTe
Fibre bundle formulation of nonrelativistic quantum mechanics. 0. Preliminary considerations: Quantum mechanics from a geometric-observer's viewpoint
We propose a version of the non-relativistic quantum mechanics in which the
pure states of a quantum system are described as sections of a Hilbert
(generally infinitely-dimensional) fibre bundle over the space-time. There
evolution is governed via (a kind of) a parallel transport in this bundle. Some
problems concerning observables are considered. There are derived the equations
of motion for the state sections and observables. We show that up to a constant
the matrix of the coefficients of the evolution operator (transport) coincides
with the matrix of the Hamiltonian of the investigated quantum system.Comment: 15 standard LaTeX 2e (11pt, A4) pages. The packages AMS-LaTeX and
amsfonts are require
Breakdown of PCAC in diffractive neutrino interactions
We test the hypothesis of partially conserved axial current (PCAC) in high
energy diffractive neutrino production of pions. Since the pion pole
contribution to the Adler relation (AR) is forbidden by conservation of the
lepton current, the heavier states, like the a_1 pole, \rho-\pi-cut, etc.,
control the lifetime of the hadronic fluctuations of the neutrino. We evaluate
the deviation from the AR in diffractive neutrino-production of pions on proton
and nuclear targets. At high energies, when all the relevant time scales
considerably exceed the size of the target, the AR explicitly breaks down on an
absorptive target, such as a heavy nucleus. In this regime, close to the black
disc limit, the off-diagonal diffractive amplitudes vanish, while the diagonal
one, \pi->\pi, which enters the AR, maximizes and saturates the unitarity
bound. At lower energies, in the regime of short lifetime of heavy hadronic
fluctuations the AR is restored, i.e. it is not altered by the nuclear effects.Comment: 10 pages, 5 figure
Smart Loads for Voltage Control in Distribution Networks
This paper shows that the smart loads (SLs) could be effective in mitigating voltage problems caused by photovoltaic (PV) generation and electric vehicle (EV) charging in low-voltage (LV) distribution networks. Limitations of the previously reported SL configuration with only series reactive compensator (SLQ) (one converter) is highlighted in this paper. To overcome these limitations, an additional shunt converter is used in back-to-back (B2B) configuration to support the active power exchanged by the series converter, which increases the flexibility of the SL without requiring any energy storage. Simulation results on a typical U.K. LV distribution network are presented to compare the effectiveness of an SL with B2B converters (SLBCs) against an SLQ in tackling under- and over-voltage problems caused by EV or PV. It is shown that SLBCs can regulate the main voltage more effectively than SLQs especially under overvoltage condition. Although two converters are required for each SLBC, it is shown that the apparent power capacity of each converter is required to be significantly less than that of an equivalent SLQ
Fragmentation of charm to charmonium in and collisions
We perform numerical comparison of the fragmentation mechanism of charmonium
production ( followed by ) with the full
leading order calculation ( at {\O} (\alpha_s^4)).
We conclude that the non-fragmentation contributions remain important up to
transverse momenta about as large as 50 GeV, thus making questionable
the applicability of the fragmentation approximation at smaller transverse
momenta.Comment: 6 pages, 7 figure
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