Disentanglement in Bipartite Continuous-Variable Systems

Entanglement in bipartite continuous-variable systems is investigated in the presence of partial losses, such as those introduced by a realistic quantum communication channel, e.g. by propagation in an optical fiber. We find that entanglement can vanish completely for partial losses, in a situa- tion reminiscent of so-called entanglement sudden death. Even states with extreme squeezing may become separable after propagation in lossy channels. Having in mind the potential applications of such entangled light beams to optical communications, we investigate the conditions under which entanglement can survive for all partial losses. Different loss scenarios are examined and we derive criteria to test the robustness of entangled states. These criteria are necessary and sufficient for Gaussian states. Our study provides a framework to investigate the robustness of continuous-variable entanglement in more complex multipartite systems.Comment: Phys. Rev. A (in press

Low redshift constraints on energy-momentum-powered gravity models

There has been recent interest in the cosmological consequences of energy-momentum-powered gravity models, in which the matter side of Einstein's equations is modified by the addition of a term proportional to some power, $n$, of the energy-momentum tensor, in addition to the canonical linear term. In this work we treat these models as phenomenological extensions of the standard $\Lambda$CDM, containing both matter and a cosmological constant. We also quantitatively constrain the additional model parameters using low redshift background cosmology data that are specifically from Type Ia supernovas and Hubble parameter measurements. We start by studying specific cases of these models with fixed values of $n,$ which lead to an analytic expression for the Friedmann equation; we discuss both their current constraints and how the models may be further constrained by future observations of Type Ia supernovas for WFIRST complemented by measurements of the redshift drift by the ELT. We then consider and constrain a more extended parameter space, allowing $n$ to be a free parameter and considering scenarios with and without a cosmological constant. These models do not solve the cosmological constant problem per se. Nonetheless these models can phenomenologically lead to a recent accelerating universe without a cosmological constant at the cost of having a preferred matter density of around $\Omega_M\sim0.4$ instead of the usual $\Omega_M\sim0.3$. Finally we also briefly constrain scenarios without a cosmological constant, where the single component has a constant equation of state which needs not be that of matter; we provide an illustrative comparison of this model with a more standard dynamical dark energy model with a constant equation of state.Comment: 13+2 pages, 12+1 figures; A&A (in press

Robustness of bipartite Gaussian entangled beams propagating in lossy channels

Subtle quantum properties offer exciting new prospects in optical communications. Quantum entanglement enables the secure exchange of cryptographic keys and the distribution of quantum information by teleportation. Entangled bright beams of light attract increasing interest for such tasks, since they enable the employment of well-established classical communications techniques. However, quantum resources are fragile and undergo decoherence by interaction with the environment. The unavoidable losses in the communication channel can lead to a complete destruction of useful quantum properties -- the so-called "entanglement sudden death". We investigate the precise conditions under which this phenomenon takes place for the simplest case of two light beams and demonstrate how to produce states which are robust against losses. Our study sheds new light on the intriguing properties of quantum entanglement and how they may be tamed for future applications.Comment: To be published - Nature Photonic

Genetic diversity of Lusitano horse in Brazil using pedigree information

This study aimed to evaluate population parameters and to describe the genetic diversity of the Lusitano breed in Brazil using pedigree data. Two populations were evaluated: total population (TP) containing 18,922 animals, and reference population (RP) composed of a part of TP containing 8,329 animals, representing the last generation. The generation interval (10.1 ± 5.1 years) was in the range for horse populations. Pedigree completeness in RP shows almost 100% filling in the three most recent generations, indicating improvement in the pedigree data and accuracy of the results, and the inbreeding coefficient (4.46%) and average relatedness (5.97%) for RP, indicating control on the part of breeders. The effective population size was 89 (TP) and 90 (RP). The effective number of founders (fe) were 33 and 29, effective number of ancestors (fa) were 30 and 26, and effective number of founder genomes (fg) were 19 and 15 for TP and RP, respectively, indicating a reduction of genetic variability in the last generations. The total number of ancestors that explains 100% of the genetic diversity in the Lusitano breed in Brazil was 427 (TP) and 341 (RP). The reproductive parameters, probabilities of gene origin showing loss of variability in the last generations, and the genetic contributions of ancestors suggest the need to monitor genetic diversity over time in breeding programs to allow control of the next generations and to increase their variability.info:eu-repo/semantics/publishedVersio

Finding Out The Neurological Consequences Of Covid-19

t- Introduction: Since the first official case of COVID-19 in China in December 2019, researchers have been trying to uncover the mechanism of action of the severe acute respiratory syndrome Coronavirus 2 (Sars-CoV-2), which attacks several organs in addition to the lungs and causes circulatory changes that can lead to death not only from lung failure but also due to commitment of other organs. Objective: The aim of this study is to find out the neurological consequences of COVID-19. Material and methods: A systematic review of the literature was concretised by mobilizing the descriptors: "Sars-Cov-2", "coronavirus infections" and "Neurological Consequences". Databases were selected and seven articles were included for analysis. Results and discussion: Although the effects of Sars-CoV-2 on the lung are exemplary and frightening, the long-term effects on the nervous system may be greater and even more overwhelming, as the regeneration of nerve tissue is difficult and can lead to general disability, as the nervous system coordinates the functions of the entire body. All studies show the presence of any kind of injury (mild or severe) to Central Nervous System, but some of them highlight the need for further studies to have great certainty. Conclusion: It can be said that the studies all agree on the possibility of existing neurological sequelae and a majority agree on the need for other studies.info:eu-repo/semantics/publishedVersio

Comparative yield loss estimates due to blast in some upland rice cultivars.

Leaf and panicle blast severities and grain yield of some upland rice cultivars were measured in three successive years in field plots unprotected or protected with fungicides. The variation in disease severities in different plots was used to establish relationships between severity of leaf and panicle blast and yield. Linear multiple regression equations for each cultivar by year were developed to estimate the yield decrease in different cultivars per unit increase in disease. Leaf blast severities at maximum tillering or booting stage and panicle blast 25 days after heading accounted for variation in grain yield in most of the cultivars. General equations combining five early and eight medium-duration rice cultivars were developed. The estimated percentage losses in grain yield due to blastwere 2.7 and 1.5 for one percent increase in blast in the early and medium-duration cultivars, respectively

Equation level matching: An extension of the method of matched asymptotic expansion for problems of wave propagation

We introduce an alternative to the method of matched asymptotic expansions. In the "traditional" implementation, approximate solutions, valid in different (but overlapping) regions are matched by using "intermediate" variables. Here we propose to match at the level of the equations involved, via a "uniform expansion" whose equations enfold those of the approximations to be matched. This has the advantage that one does not need to explicitly solve the asymptotic equations to do the matching, which can be quite impossible for some problems. In addition, it allows matching to proceed in certain wave situations where the traditional approach fails because the time behaviors differ (e.g., one of the expansions does not include dissipation). On the other hand, this approach does not provide the fairly explicit approximations resulting from standard matching. In fact, this is not even its aim, which to produce the "simplest" set of equations that capture the behavior

Time evolution of non-Hermitian Hamiltonian systems

We provide time-evolution operators, gauge transformations and a perturbative treatment for non-Hermitian Hamiltonian systems, which are explicitly time-dependent. We determine various new equivalence pairs for Hermitian and non-Hermitian Hamiltonians, which are therefore pseudo-Hermitian and in addition in some cases also invariant under PT-symmetry. In particular, for the harmonic oscillator perturbed by a cubic non-Hermitian term, we evaluate explicitly various transition amplitudes, for the situation when these systems are exposed to a monochromatic linearly polarized electric field.Comment: 25 pages Latex, 1 eps figure, references adde

Glass fibre content of PP plates and their properties: part II: tensile mechanical properties

Short fibre reinforced polypropylene compounds have been used to produce composites taking advantage of its interesting properties and competitive raw material prices. For the same reason the short glass fibres are the most used reinforcement in injection moulded thermoplastic composites. In injection moulding, varying patterns of fibre orientation are obtained through the thickness direction and along the flow path. Moulding parameters such as injection flow rate or melt-temperature do affect the fibre orientation distributions in mouldings. It has been observed that the type of flow, being dominated by shear stresses (e.g. linear flow) or by extensional stresses (e.g. radial flow) affects the fibre orientation field. Other parameters may have an effect over the fibre orientation such as the fibre length distribution. During processing some degree of fibre breakage in unavoidable. The fibre contents, its length and orientation distributions cause anisotropy on mechanical properties. Efficient reinforcements are obtained in the direction of major orientation of the fibres and when longer fibres are used. In this work the effect of various fibre contents, by volume (0, 10, 20 and 25%) over the anisotropy of mechanical properties of injection moulded rectangular plates is explored. Specimens cut along and across the flow directions are subjected to tensile tests enabling to discuss the anisotropy of tensile mechanical properties.(undefined

Glass fibre contents of PP plates and their properties: part I: Shrinkage and changes in time

In this paper the results from the first part of a study on the glass fibre contents of PP plates and their properties is presented. Focus is made on the effect of the fibre volume fraction and holding pressure on the experimental as-moulded shrinkage in the flow and across flow directions. Data is also presented on the post-moulding shrinkage. For the experimental work, PP with different volume fraction of glass fibre (0, 0.1, 0.2 and 0.25) was used. The mouldings are edge gated flat rectangular plates. The moulding process was continuously monitored with pressure transducers.(undefined