1,291 research outputs found
An efficient method to compute the residual phase on a Lefschetz thimble
We propose an efficient method to compute the so-called residual phase that
appears when performing Monte Carlo calculations on a Lefschetz thimble. The
method is stochastic and its cost scales linearly with the physical volume,
linearly with the number of stochastic estimators and quadratically with the
length of the extra dimension along the gradient flow. This is a drastic
improvement over previous estimates of the cost of computing the residual
phase. We also report on basic tests of correctness and scaling of the code.Comment: New simulations, new plot, new appendix added. To appear in PRD. 9
pages, 3 figure
Are There Diquarks in the Nucleon?
This work is devoted to the study of diquark correlations inside the nucleon.
We analyze some matrix elements which encode information about the
non-perturbative forces, in different color anti-triplet diquark channels. We
suggest a lattice calculation to check the quark-diquark picture and clarify
the role of instanton-mediated interactions. We study in detail the physical
properties of the 0+ diquark, using the Random Instanton Liquid Model. We find
that instanton forces are sufficiently strong to form a diquark bound-state,
with a mass of ~500 MeV, which is compatible with earlier estimates. We also
compute its electro-magnetic form factor and find that the diquark is a broad
object, with a size comparable with that of the proton.Comment: Final version, accepted for publication on Phys. Rev.
Light Ion Accelerating Line (L3IA): Test Experiment at ILIL-PW
The construction of a novel Laser driven Light Ions Acceleration Line(L3IA)
is progressing rapidly towards the operation, following the recent upgrade of
the ILIL-PW laser facility. The Line was designed following the pilot
experimental activity carried out earlier at the same facility to define design
parameters and to identify main components including target control and
diagnostic equipment, also in combination with the numerical simulations for
the optimization of laser and target parameters. A preliminary set of data was
acquired following the successful commissioning of the laser system >100 TW
upgrade. Data include output from a range of different ion detectors and
optical diagnostics installed for qualification of the laser-target
interaction. An overview of the results is given along with a description of
the relevant upgraded laser facility and features.Comment: 6 pages, 7 figures, 18 references, presented at the EAAC 201
A New Idea for Stroke Rehabilitation : Bilateral Transfer Analysis from Healthy Hand to the Paretic One with a Randomized and Controlled Trial
Background: Bilateral transfer of a motor skill is a phenomenon according to which, one hand can "teach" a skill to the other hand. In this research, controlled and randomized, we tested the ability of bilateral transfer (BT) to improve the coordination of the paretic hand in patients that suffered a stroke, with the aim of restricting the field for further research on the impact of BT in rehabilitation, we analyzed the differences in the expression of BT phenomenon among sexes and side of hemyparesis. Methods: 34 right-handed patients, at the end of the rehabilitation period, were randomly divided into two groups: test and control. They all had a stroke in a single hemisphere in the previous six months and they were selected by a physical examination, the time elapsed from the stroke and cognitive requirements. The experiment consisted in training the healthy hand of each patient from the test group to execute the nine hole peg test (NHPT) 10 times a day, for 3 consecutive days, and then test the paretic hand with the same test and with bimanual tasks. The control group was not trained but went through the same analysis. Results: In the test group we found that the execution speed of NHPT with the paretic hand, after training the healthy hand, was on average 22.6% faster than the value recorded at baseline. Meanwhile, no significant difference was found in the control group. The analysis showed a greater impact of BT among male patients, who were in average 31% faster than controls, and in non dominant paretic hands, that were 30% faster after training. Conclusions: BT was present in hemiparethic patients with moderate stroke after a short time span, it was more evident among male subjects, and from the dominant hand to the paretic non-dominant one
Time evolution of stimulated Raman scattering and two-plasmon decay at laser intensities relevant for shock ignition in a hot plasma
Laser–plasma interaction (LPI) at intensities 1015–1016 W cm2 is dominated by parametric instabilities which can be
responsible for a significant amount of non-collisional absorption and generate large fluxes of high-energy nonthermal
electrons. Such a regime is of paramount importance for inertial confinement fusion (ICF) and in particular for the
shock ignition scheme. In this paper we report on an experiment carried out at the Prague Asterix Laser System (PALS)
facility to investigate the extent and time history of stimulated Raman scattering (SRS) and two-plasmon decay (TPD)
instabilities, driven by the interaction of an infrared laser pulse at an intensity 1:2 1016 W cm2 with a 100 mm
scalelength plasma produced from irradiation of a flat plastic target. The laser pulse duration (300 ps) and the high
value of plasma temperature (4 keV) expected from hydrodynamic simulations make these results interesting for a
deeper understanding of LPI in shock ignition conditions. Experimental results show that absolute TPD/SRS, driven at
a quarter of the critical density, and convective SRS, driven at lower plasma densities, are well separated in time, with
absolute instabilities driven at early times of interaction and convective backward SRS emerging at the laser peak and
persisting all over the tail of the pulse. Side-scattering SRS, driven at low plasma densities, is also clearly observed.
Experimental results are compared to fully kinetic large-scale, two-dimensional simulations. Particle-in-cell results,
beyond reproducing the framework delineated by the experimental measurements, reveal the importance of filamentation
instability in ruling the onset of SRS and stimulated Brillouin scattering instabilities and confirm the crucial role of
collisionless absorption in the LPI energy balance
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