89,797 research outputs found
Nonsequential Double Ionization with Polarization-gated Pulses
We investigate laser-induced nonsequential double ionization by a
polarization-gated laser pulse, constructed employing two counter-rotating
circularly polarized few cycle pulses with a time delay . We address the
problem within a classical framework, and mimic the behavior of the
quantum-mechanical electronic wave packet by means of an ensemble of classical
electron trajectories. These trajectories are initially weighted with the
quasi-static tunneling rate, and with suitably chosen distributions for the
momentum components parallel and perpendicular to the laser-field polarization,
in the temporal region for which it is nearly linearly polarized. We show that,
if the time delay is of the order of the pulse length, the
electron-momentum distributions, as functions of the parallel momentum
components, are highly asymmetric and dependent on the carrier-envelope (CE)
phase. As this delay is decreased, this asymmetry gradually vanishes. We
explain this behavior in terms of the available phase space, the quasi-static
tunneling rate and the recollision rate for the first electron, for different
sets of trajectories. Our results show that polarization-gating technique may
provide an efficient way to study the NSDI dynamics in the single-cycle limit,
without employing few-cycle pulses.Comment: 17 pages, 6 figure
The follow-up EVN observations of twelve GPS radio sources at 5 GHz
We defined a sub-sample of twelve GPS sources which have not been observed
with the VLBI before, from the Parkes half-Jansky sample, and carried out VLBI
observations at 1.6 GHz and 5 GHz with the European VLBI Network (EVN) in 2006
and 2008, respectively, to classify the source structure and to find compact
symmetric objects (CSOs). Additionally, we carried out the 4.85 GHz flux
density observations for these sources with the Urumqi 25-m telescope between
the years 2007 and 2009 to study whether there is any variability in the total
flux density of the GPS sources. The results of the 5 GHz VLBI observations and
total flux densities of these sources are presented in this paper. From the
VLBI morphologies, the spectral indices of components and the total flux
variability of the twelve targets, we firmly classify three sources J0210+0419,
J11350021, and J2058+0540 as CSOs, and classify J1057+0012, J1203+0414, and
J16000037 as core-jet sources. The others J0323+0534, J04330229,
J0913+1454, J1109+1043, and J1352+0232 are labelled CSO candidates, and
J1352+1107 is a complex feature. Apart from core-jet sources, the total flux
densities of the CSOs and candidates are quite stable at 5 GHz both during a
long-term of 20 years relative to the PKS90 data and in a period between
2007 and 2009. The total flux densities are resolved-out by more than 20\% in
the 5 GHz VLBI images for 6 sources, probably because of diffuse emission. In
addition, we estimated the jet viewing angles for the confirmed CSOs
by using the double-lobe flux ratio of the sources, the result being indicative
of relatively large for the CSOs.Comment: 9 pages, 12 figures, accepted for publication in A&A
Centrality, system size and energy dependences of charged-particle pseudo-rapidity distribution
Utilizing the three-fireball picture within the quark combination model, we
study systematically the charged particle pseudorapidity distributions in both
Au+Au and Cu+Cu collision systems as a function of collision centrality and
energy, 19.6, 62.4, 130 and 200 GeV, in full pseudorapidity
range. We find that: (i)the contribution from leading particles to
distributions increases with the decrease of the collision
centrality and energy respectively; (ii)the number of the leading particles is
almost independent of the collision energy, but it does depend on the nucleon
participants ; (iii)if Cu+Cu and Au+Au collisions at the same
collision energy are selected to have the same , the resulting of
charged particle distributions are nearly identical, both in the
mid-rapidity particle density and the width of the distribution. This is true
for both 62.4 GeV and 200 GeV data. (iv)the limiting fragmentation phenomenon
is reproduced. (iiv) we predict the total multiplicity and pseudorapidity
distribution for the charged particles in Pb+Pb collisions at TeV. Finally, we give a qualitative analysis of the
and as function of
and from RHIC to LHC.Comment: 12 pages, 8 figure
Consistent Anisotropic Repulsions for Simple Molecules
We extract atom-atom potentials from the effective spherical potentials that
suc cessfully model Hugoniot experiments on molecular fluids, e.g., and
. In the case of the resulting potentials compare very well with the
atom-atom potentials used in studies of solid-state propertie s, while for
they are considerably softer at short distances. Ground state (T=0K) and
room temperatu re calculations performed with the new potential resolve
the previous discrepancy between experimental and theoretical results.Comment: RevTeX, 5 figure
A study of the parity-odd nucleon-nucleon potential
We investigate the parity-violating nucleon-nucleon potential as obtained in
chiral effective field theory. By using resonance saturation we compare the
chiral potential to the more traditional one-meson exchange potential. In
particular, we show how parameters appearing in the different approaches can be
compared with each other and demonstrate that analyses of parity violation in
proton-proton scattering within the different approaches are in good agreement.
In the second part of this work, we extend the parity-violating potential to
next-to-next-to-leading order. We show that generally it includes both
one-pion- and two-pion-exchange corrections, but the former play no significant
role. The two-pion-exchange corrections depend on five new low-energy constants
which only become important if the leading-order weak pion-nucleon constant
turns out to be very small.Comment: Published versio
At a cost: the real effects of Transfer Pricing Regulations
Unilateral adoption of transfer pricing regulations may have a negative impact on real investment by multinational corporations (MNCs). This paper uses a quasi-experimental research design, exploiting unique panel data on domestic and multinational companies in 27 countries during 2006-2014, to find that MNC affliates reduce their investment by over 11 percent following the introduction of transfer pricing regulations. There is no significant reduction in total investment by the MNC group, suggesting that these investments are most likely shifted to affliates in other countries. The impact of transfer pricing regulations corresponds to an increase in the "TPR-adjusted" corporate tax rate by almost one quarter
Rotating Superconductors and the Frame-independent London Equation
A frame-independent, thermodynamically exact London equation is presented,
which is especially valid for rotating superconductors. A direct result is the
unexpectedly high accuracy () for the usual expression of the
London moment.Comment: 4 pages, 0 figure
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