Ab-initio Gorkov-Green's function calculations of open-shell nuclei

We present results from a new ab-initio method that uses the self-consistent Gorkov Green's function theory to address truly open-shell systems. The formalism has been recently worked out up to second order and is implemented here in nuclei for the first time on the basis of realistic nuclear forces. We find good convergence of the results with respect to the basis size in Ca44 and Ni74 and discuss quantities of experimental interest including ground-state energies, pairing gaps and particle addition/removal spectroscopy. These results demonstrate that the Gorkov method is a valid alternative to multireference approaches for tackling degenerate or near degenerate quantum systems. In particular, it increases the number of mid-mass nuclei accessible in an ab-initio fashion from a few tens to a few hundreds.Comment: 5 pages, 3 figure

Ab-initio self-consistent Gorkov-Green's function calculations of semi-magic nuclei - II. Numerical implementation at second order with a two-nucleon interaction

The newly developed Gorkov-Green's function approach represents a promising path to the ab initio description of medium-mass open-shell nuclei. We discuss the implementation of the method at second order with a two-body interaction, with particular attention to the numerical solution of Gorkov's equation. Different sources of theoretical error and degrees of self-consistency are investigated. We show that Krylov projection techniques with a multi-pivot Lanczos algorithm efficiently handle the growth of poles in the one-body Green's function when Gorkov's equation is solved self-consistently. The end result is a tractable, accurate and gently scaling ab initio scheme applicable to full isotopic chains in the medium-mass region.Comment: 17 pages, 13 figure

Toward the Ab-initio Description of Medium Mass Nuclei

As ab-initio calculations of atomic nuclei enter the A=40-100 mass range, a great challenge is how to approach the vast majority of open-shell (degenerate) isotopes. We add realistic three-nucleon interactions to the state of the art many-body Green's function theory of closed-shells, and find that physics of neutron driplines is reproduced with very good quality. Further, we introduce the Gorkov formalism to extend ab-initio theory to semi-magic, fully open-shell, isotopes. Proof-of-principle calculations for Ca-44 and Ni-74 confirm that this approach is indeed feasible. Combining these two advances (open-shells and three-nucleon interactions) requires longer, technical, work but it is otherwise within reach.Comment: Contribution to Summary Report of EURISOL Topical and Town Meetings, 15-19 October 2012; missing affiliations added and corrected errors in Tab

Radii and binding energies in oxygen isotopes: a puzzle for nuclear forces

We present a systematic study of both nuclear radii and binding energies in (even) oxygen isotopes from the valley of stability to the neutron drip line. Both charge and matter radii are compared to state-of-the-art {\it ab initio} calculations along with binding energy systematics. Experimental matter radii are obtained through a complete evaluation of the available elastic proton scattering data of oxygen isotopes. We show that, in spite of a good reproduction of binding energies, {\it ab initio} calculations with conventional nuclear interactions derived within chiral effective field theory fail to provide a realistic description of charge and matter radii. A novel version of two- and three-nucleon forces leads to considerable improvement of the simultaneous description of the three observables for stable isotopes, but shows deficiencies for the most neutron-rich systems. Thus, crucial challenges related to the development of nuclear interactions remain.Comment: 6 pages, 5 figures, Submitted to Nature Physics, April 12th 2016; first version (v1 Arxiv) Internal Report Preprint Irfu-18 December 2015. 6 p., 5 fig., Submitted to Physical Review Letters, April 29, May 3rd 2016; 2nd version. Int. Rep. Irfu-24 May 2016. Published in PRL, 27 July 2016 with the modified title (Radii and binding energies in oxygen isotopes: a challenge for nuclear forces

Effects of frequency correlation in linear optical entangling gate operated with independent photons

Bose-Einstein coalescence of independent photons at the surface of a beam splitter is the physical process that allows linear optical quantum gates to be built. When distinct parametric down-conversion events are used as an independent photon source, distinguishability arises form the energy correlation of each photon with its twin. We find that increasing the pump bandwidth may help in improving the visibility of non-classical interference and reaching a level of near perfect indistinguishability. PACS: 03.67.Mn, 42.65.Lm, 42.50.St.Comment: Replaced with published versio

The LHC (CMS) Discovery Potential for Models with Effective Supersymmetry and Nonuniversal Gaugino Masses

We investigate squark and gluino pair production at LHC (CMS) with subsequent decays into quarks, leptons and LSP in models with effective supersymmetry where third generation of squarks is relatively light while the first two generations of squarks are heavy. We consider the general case of nonuniversal gaugino masses. Visibility of signal by an excess over SM background in (n \geq 2)jets + (m \geq 0)leptons + E^{miss}_T events depends rather strongly on the relation between LSP, second neutralino, gluino and squark masses and it decreases with the increase of LSP mass. We find that for relatively heavy gluino it is very difficult to detect SUSY signal even for light 3^{rd} generation squarks (m_{\tilde q_3}\le 1 TeV) if the LSP mass is closed to the 3^{rd} generation squark mass.Comment: 1 latex (35 pages), 4 eps (figures) file

Self-consistent Gorkov Green's function calculations of one-nucleon spectral properties

Results from the newly developed Gorkov self-consistent Green's function approach are presented. Ab-initio spectral strength distributions for one-nucleon addition or removal calculated in doubly-closed shell 40Ca and in semi-magic 44Ca are briefly discussed. The object of the present communication is to illustrate the potential spectroscopic reach of the method

Gorkov self-consistent Green's function calculations of semi-magic nuclei

The first nuclear structure application of the newly developed Gorkov self-consistent Green's function method is presented. The approach aims to describe many-nucleon systems from an ab-initio standpoint featuring an explicit treatment of pairing correlations. In the present work calculations of binding energies of calcium isotopes are reported and compared with experimental data and other theoretical references

A tradeoff in simultaneous quantum-limited phase and loss estimation in interferometry

Interferometry with quantum light is known to provide enhanced precision for estimating a single phase. However, depending on the parameters involved, the quantum limit for the simultaneous estimation of multiple parameters may not attainable, leading to trade-offs in the attainable precisions. Here we study the simultaneous estimation of two parameters related to optical interferometry: phase and loss, using a fixed number of photons. We derive a trade-off in the estimation of these two parameters which shows that, in contrast to single-parameter estimation, it is impossible to design a strategy saturating the quantum Cramer-Rao bound for loss and phase estimation in a single setup simultaneously. We design optimal quantum states with a fixed number of photons achieving the best possible simultaneous precisions. Our results reveal general features about concurrently estimating Hamiltonian and dissipative parameters, and has implications for sophisticated sensing scenarios such as quantum imaging.Comment: 9 pages, 6 figure

Modelagem de cana de açúcar para previsão de produtividade de canaviais no Brasil e na Austrália.

Un modelo de previsión del rendimiento potencial de la productividad, sin restricciones de la nutrición y el agua, para la cultura de caña de azúcar ha sido construido para analizar la sostenibilidad de la nueva ampliación de zonas de cultivo, con el foco en la producción de etanol. Fueran ajustados los valores del rendimiento potencial en términos de masa seca (MS) de la caña de azúcar para estimar la absorción del dióxido de carbono (CO2), en relación con la temperatura del aire y la radiación solar. Son estimados mensualmente la producción de MS, durante el ciclo de cultivo. La MS debe considerar una tasa fotosintética con pierdas por la manutención de la respiración, la senescencia de hojas y sierpes que restarán en el campo durante el ciclo. El modelo BRCANE es compuesto por las ecuaciones que describen el comportamiento fisiológico debido a las condiciones del ambiente térmico promedio de las variables, constantes, que se obtuvo a través de la literatura y ajusta los resultados de acuerdo con los datos experimentales. El MS estimado por el modelo se contrasta con los datos obtenidos en el ciclo de experimentación sobre el terreno de regadío (variedades RB72 454, NA 56-79, CB 41-76, CB 47-355, CP 51-22, Q138 y Q141), en El Estado de São Paulo (Brasil) y en Bundaberg SES, de Queensland (Australia). Los resultados del total de MS se modificaron en el tallo de toneladas por hectárea a través de ecuación linear para cada variedad, con coeficientes de regresión superiores a 0,88. El modelo se presentó coherente con las simulaciones MS durante el ciclo, así como en la predicción del rendimiento.JAIIO - CAI 2010