Pair creation enhancement due to combined external fields

We study the creation of electron-positron pairs from the vacuum induced by a combination of a static electric field and an alternating field. We find that the overall pair production can be increased by two orders of magnitude compared to the yields associated with each field individually. We examine the interesting case where both fields are spatially localized, permitting us to examine the time evolution of the spatial density for the created particle pairs. We find that there are a variety of competing mechanisms that contribute to the total yield

Double Ionization by Strong Elliptically Polarized Laser Pulses

We join the tribute to Professor N.B. Delone in this memorial issue by presenting the results of new calculations on the effects of ellipticity on double ionization by short and strong near-optical laser pulses.Comment: 3 pages, 4 figures, accepted in Professor N.B. Delone's memorial issu

Multipartite entanglement characterization of a quantum phase transition

A probability density characterization of multipartite entanglement is tested on the one-dimensional quantum Ising model in a transverse field. The average and second moment of the probability distribution are numerically shown to be good indicators of the quantum phase transition. We comment on multipartite entanglement generation at a quantum phase transition.Comment: 10 pages, 6 figures, final versio

Electron-positron pair creation induced by quantum-mechanical tunneling

We study the creation of electron-positron pairs from the vacuum induced by two spatially displaced static electric fields. The strength and spatial width of each localized field is less than required for pair creation. If, however, the separation between the fields is less than the quantum-mechanical tunneling length associated with the corresponding quantum scattering system, the system produces a steady flux of electron-positron pairs. We compute the time dependence of the pair-creation probability by solving the Dirac equation numerically for various external field sequences. For the special case of two very narrow fields we provide an analytical expression for the pair-creation rate in the long-time limit

Influence of Sleeve Gastrectomy on NASH and Type 2 Diabetes Mellitus

Background. Nonalcoholic fatty liver disease is present in up to 85% of adipose patients and may proceed to nonalcoholic steatohepatitis (NASH). With insulin resistance and obesity being the main risk factors for NASH, the effect of isolated sleeve gastrectomy (ISG) on these parameters was examined. Methods. 236 patients underwent ISG with intraoperative liver biopsy from December 2002 to September 2009. Besides demographic data, pre-operative weight/BMI, HbA1c, AST, ALT, triglycerides, HDL and LDL levels were determined. Results. A significant correlation of NASH with higher HbA1c, AST and ALT and lower levels for HDL was observed (P < .05, <.0001, <.0001, <.01, resp.). Overall BMI decreased from 45.0 ± 6.8 to 29.7 ± 6.5 and 31.6 ± 4.4 kg/m2 at 1 and 3 years. An impaired weight loss was demonstrated for patients with NASH and patients with elevated HbA1c (plateau 28.08 kg/m2 versus 29.79 kg/m2 and 32.30 kg/m2 versus 28.79 kg/m2, resp.). Regarding NASH, a significant improvement of AST, ALT, triglyceride and HDL levels was shown (P < .0001 for all). A resolution of elevated HbA1c was observed in 21 of 23 patients. Summary. NASH patients showed a significant loss of body weight and amelioration of NASH status. ISG can be successfully performed in these patients and should be recommended for this subgroup

A mapping approach to synchronization in the "Zajfman trap": stability conditions and the synchronization mechanism

We present a two particle model to explain the mechanism that stabilizes a bunch of positively charged ions in an "ion trap resonator" [Pedersen etal, Phys. Rev. Lett. 87 (2001) 055001]. The model decomposes the motion of the two ions into two mappings for the free motion in different parts of the trap and one for a compressing momentum kick. The ions' interaction is modelled by a time delay, which then changes the balance between adjacent momentum kicks. Through these mappings we identify the microscopic process that is responsible for synchronization and give the conditions for that regime.Comment: 12 pages, 9 figures; submitted to Phys Rev

Correlation effects in two-electron model atoms in intense laser fields, Phys

We report an efficient implementation of a spatial two-zone method for solving Schrödinger&apos;s equation numerically, using a canonical basis set decomposition, and also its application to two-electron wave functions in a study of double multiphoton ionization. We make the first calculation of the time-dependent degree of electron correlation for this poorly understood process. Our results show a particularly sensitive window of intensities coinciding exactly with the well-known &quot;knee&quot; regime in ion-count data. PACS numbers: 32.80. Rm, 32.80.Fb, 42.50.Hz To date, almost all of the theoretical understanding of multiphoton processes of atoms in intense laser fields has been based on the single active electron picture. Even two-electron ionization can be so interpreted if the electrons are ejected sequentially via the AmmosovDelone-Krainov (ADK) mechanism We believe that it will prove valuable to have a better command of the role of electron-electron interaction and correlation in the two-electron ionization process than is presently available. Fundamentally, one knows that all nontrivial effects of correlation are connected to the nonfactorable e-e coupling term in the two-electron Hamiltonian, but little more than this is known. It is not known, for example, whether this term plays a persistent role during the ionization process, or if there is an intensity threshold where its effect &quot;turns on&quot; or &quot;turns off,&quot; or even if there is a particularly sensitive window of intensities where the effect of correlation is most active. It is also not known how the effect of electron correlation is synchronized, if at all, with the time development of the ionizing field. Electron correlation, per se, has not been isolated for study. However, as Grobe et al. have shown [13], there are several more or less equally sensible and closely compatible definitions of the degree of electron correlation that are, in principle, open to calculation. The difficulty in taking this route has been obtaining wave functions that are accurate enough over a sufficiently large spatial domain to permit the calculations to be made. In this Letter we show that an expansion of the twoelectron wave function into a sum of Slater determinants of one-electron orthonormal orbitals, as explained below, solves both of these problems. It provides a way to obtain two-electron wave functions efficiently over a much larger spatial domain than has been customary, and it provides the time-dependent degree of correlation during the ionization process. The penalty for this advance is that it can be implemented at the present time only within a one-dimensional (1D) model of a two-electron atom. The 1D model We will begin by confirming that our new implementation of this model is consistent with the most important characteristics of two-electron ionization data. Then we will report the first quantitative results on the timedependent behavior of the degree of two-electron correlation, and relate them to experimentally observed features. 520 0031-9007͞99͞83(3)͞520(4)$15.0

Entangled Bessel beams

Orbital angular momentum (OAM) entanglement is investigated in the Bessel-Gauss (BG) basis. Having a readily adjustable radial scale, BG modes provide a more favourable basis for OAM entanglement over Laguerre-Gaussian (LG) modes. The OAM bandwidth in terms of BG modes can be increased by selection of particular radial modes and leads to a flattening of the spectrum. The flattening of the spectrum allows for higher entanglement. We demonstrate increased entanglement in terms of BG modes by performing a Bell-type experiment and violating the appropriate Clauser Horne Shimony Holt (CHSH) inequality. In addition, we reconstruct the quantum state of BG modes entangled in high-dimensions.Comment: 8 pages, 4 figure

On the absence of bound-state stabilization through short ultra-intense fields

We address the question of whether atomic bound states begin to stabilize in the short ultra-intense field limit. We provide a general theory of ionization probability and investigate its gauge invariance. For a wide range of potentials we find an upper and lower bound by non-perturbative methods, which clearly exclude the possibility that the ultra intense field might have a stabilizing effect on the atom. For short pulses we find almost complete ionization as the field strength increases.Comment: 34 pages Late

Distribution of Husimi Zeroes in Polygonal Billiards

The zeroes of the Husimi function provide a minimal description of individual quantum eigenstates and their distribution is of considerable interest. We provide here a numerical study for pseudo- integrable billiards which suggests that the zeroes tend to diffuse over phase space in a manner reminiscent of chaotic systems but nevertheless contain a subtle signature of pseudo-integrability. We also find that the zeroes depend sensitively on the position and momentum uncertainties with the classical correspondence best when the position and momentum uncertainties are equal. Finally, short range correlations seem to be well described by the Ginibre ensemble of complex matrices.Comment: includes 13 ps figures; Phys. Rev. E (in press