Non-critically squeezed light via spontaneous rotational symmetry breaking

We theoretically address squeezed light generation through the spontaneous breaking of the rotational invariance occuring in a type I degenerate optical parametric oscillator (DOPO) pumped above threshold. We show that a DOPO with spherical mirrors, in which the signal and idler fields correspond to first order Laguerre-Gauss modes, produces a perfectly squeezed vacuum with the shape of a Hermite-Gauss mode, within the linearized theory. This occurs at any pumping level above threshold, hence the phenomenon is non-critical. Imperfections of the rotational symmetry, due e.g. to cavity anisotropy, are shown to have a small impact, hence the result is not singular.Comment: 4 pages, 1 figure, replaced with resubmitted versio

Simulating quantum-optical phenomena with cold atoms in optical lattices

We propose a scheme involving cold atoms trapped in optical lattices to observe different phenomena traditionally linked to quantum-optical systems. The basic idea consists of connecting the trapped atomic state to a non-trapped state through a Raman scheme. The coupling between these two types of atoms (trapped and free) turns out to be similar to that describing light-matter interaction within the rotating-wave approximation, the role of matter and photons being played by the trapped and free atoms, respectively. We explain in particular how to observe phenomena arising from the collective spontaneous emission of atomic and harmonic oscillator samples such as superradiance and directional emission. We also show how the same setup can simulate Bose-Hubbard Hamiltonians with extended hopping as well as Ising models with long-range interactions. We believe that this system can be realized with state of the art technology

Noncritical generation of nonclassical frequency combs via spontaneous rotational symmetry breaking

Synchronously pumped optical parametric oscillators (SPOPOs) are optical cavities driven by mode-locked lasers, and containing a nonlinear crystal capable of down-converting a frequency comb to lower frequencies. SPOPOs have received a lot of attention lately because their intrinsic multimode nature makes them compact sources of quantum correlated light with promising applications in modern quantum information technologies. In this work we show that SPOPOs are also capable of accessing the challenging and interesting regime where spontaneous symmetry breaking confers strong nonclassical properties to the emitted light, which has eluded experimental observation so far. Apart from opening the possibility of studying experimentally this elusive regime of dissipative phase transitions, our predictions will have a practical impact, since we show that spontaneous symmetry breaking provides a specific spatiotemporal mode with large quadrature squeezing for any value of the system parameters, turning SPOPOs into robust sources of highly nonclassical light above threshold

Near-IR period-luminosity relations for pulsating stars in ω\omega Centauri (NGC 5139)

$\omega$ Centauri (NGC 5139) hosts hundreds of pulsating variable stars of different types, thus representing a treasure trove for studies of their corresponding period-luminosity (PL) relations. Our goal in this study is to obtain the PL relations for RR Lyrae, and SX Phoenicis stars in the field of the cluster, based on high-quality, well-sampled light curves in the near-infrared (IR). $\omega$ Centauri was observed using VIRCAM mounted on VISTA. A total of 42 epochs in $J$ and 100 epochs in $K_{\rm S}$ were obtained, spanning 352 days. Point-spread function photometry was performed using DoPhot and DAOPHOT in the outer and inner regions of the cluster, respectively. Based on the comprehensive catalogue of near-IR light curves thus secured, PL relations were obtained for the different types of pulsators in the cluster, both in the $J$ and $K_{\rm S}$ bands. This includes the first PL relations in the near-IR for fundamental-mode SX Phoenicis stars. The near-IR magnitudes and periods of Type II Cepheids and RR Lyrae stars were used to derive an updated true distance modulus to the cluster, with a resulting value of $(m-M)_0 = 13.708 \pm 0.035 \pm 0.10$ mag, where the error bars correspond to the adopted statistical and systematic errors, respectively. Adding the errors in quadrature, this is equivalent to a heliocentric distance of $5.52\pm 0.27$ kpc.Comment: 10 pages, 8 figures, accepted for publication in A&

Escherichia coli resistance and gut microbiota profile in pigs raised with different antimicrobial administration in feed.

Abstract: Antimicrobials have been widely used in veterinary medicine for disease treatment, disease prevention, and growth promotion. Although, the mechanisms about in-feed additives use are still not completely understood, it is accepted that its use improves feed efficiency by reducing the microbial load in the intestinal tract, thereby reducing the pressure on the immune system and increasing energy availability for the animal. However, disruption to commensal bacterial communities by antibiotics in some cases can increase the gut colonization by pathogenic bacteria. In this sense, the aim of this study was to evaluate the Escherichia coli antibiotic resistance and the gut microbiota profile from pigs raised in Brazilian farms with different in-feed antimicrobials protocols. Pigs from four farms with distinct antibiotic usage, including one farm that used no antibiotics, were followed from weaning to finishing, and the frequency of antimicrobial resistance and gut bacterial profile by 16S rRNA gene sequencing were evaluated. The gut microbial community structure was the same among all groups of pigs despite different antibiotic use on the farms; however, the antimicrobial resistance profiles of E. coli isolates were different between groups. One farm administered seven antibiotics at different times, and E. coli isolates from these pigs showed higher frequency of resistance and multidrug resistance as compared with samples from the farm that did not administer in-feed antimicrobials. The phenotypes included resistance to drugs considered critically important antimicrobial agents in veterinary medicine (ampicillin, ciprofloxacin, florfenicol, sulfonamide and tetracycline) as well as one highly important antibiotic in human medicine (colistin). Resistant E. coli strains were screened for the presence of the mcr-1 gene by PCR. The colistin-resistant strains were positive for the presence of the mcr-1 gene. These results suggest that although different antibiotic uses on-farm might not impact microbial community structure, it does impact bacterial functions, namely antibiotic resistance. Our results show that prudent use of antimicrobials is important for decreasing selective pressure for antibiotic resistance gene evolutionSafePork 2017

Discovery of a thin stellar stream in the SLAMS survey

We report the discovery of a thin stellar stream - which we name the Jet stream - crossing the constellations of Hydra and Pyxis. The discovery was made in data from the SLAMS survey, which comprises deep $g$ and $r$ imaging for a $650$ square degree region above the Galactic disc performed by the CTIO Blanco + DECam. SLAMS photometric catalogues will be made publicly available. The stream is approximately 0.18 degrees wide and 10 degrees long, though it is truncated by the survey footprint. Its colour-magnitude diagram is consistent with an old, metal-poor stellar population at a heliocentric distance of approximately 29 kpc. We corroborate this measurement by identifying a spatially coincident overdensity of likely blue horizontal branch stars at the same distance. There is no obvious candidate for a surviving stream progenitor.Comment: MNRAS accepted versio

Algebraic Properties of Qualitative Spatio-Temporal Calculi

Qualitative spatial and temporal reasoning is based on so-called qualitative calculi. Algebraic properties of these calculi have several implications on reasoning algorithms. But what exactly is a qualitative calculus? And to which extent do the qualitative calculi proposed meet these demands? The literature provides various answers to the first question but only few facts about the second. In this paper we identify the minimal requirements to binary spatio-temporal calculi and we discuss the relevance of the according axioms for representation and reasoning. We also analyze existing qualitative calculi and provide a classification involving different notions of a relation algebra.Comment: COSIT 2013 paper including supplementary materia

Generating highly squeezed Hybrid Laguerre-Gauss modes in large-Fresnel-number Degenerate Optical Parametric Oscillators

We theoretically describe the quantum properties of a large Fresnel number degenerate optical parametric oscillator with spherical mirrors that is pumped by a Gaussian beam. The resonator is tuned so that the resonance frequency of a given transverse mode family coincides with the down-converted frequency. After demonstrating that only the lower orbital angular momentum (OAM) Laguerre-Gauss modes are amplified above threshold, we focus on the quantum properties of the rest of (classically empty) modes. We find that combinations of opposite OAM (Hybrid Laguerre-Gauss modes) can exhibit arbitrary large quadrature squeezing for the lower OAM non amplified modes.Comment: 10 pages, 3 figures and 2 table

Estudio del proceso de retención de 2,4-D en un carbón activo procedente de cáscara de almendra. II.-Isotermas de retención

Retention isotherms of 2,4-D in aqueous solution on an activated carbon at 10, 20, 30, 40 and 50ºC have been obtained. The activated carbon was prepared using almond shells as raw material. The retention process has been studied using the Langmuir, B.E.T. and López-González methods, wich were adapted to adsorption from solutions. The retention capacity of this carbon was around 10-3 mols.g-1. The surface area accesible to 2,4-D molecules as well as the thermodynarnic parameters of the process have been also calculated.Se han estudiado las isotermas de retención de 2,4-D, en disolución acuosa a las temperaturas de 10, 20, 30, 40 Y 50ºC, en un carbón activo preparado a partir de cáscara de almendra. Los datos obtenidos se han ajustado a las ecuaciones de Langmuir, B.E.T. y López-González, las cuales fueron adaptadas adecuadamente a procesos de adsorción en disolución. Se ha calculado la capacidad de retención del carbón activo utilizado, que es del orden de 10-3 moles de 2,4-D por gramo de carbón. Asúnismo, se han determinado la superficie del mismo accesible a las moléculas de 2,4-D, así como las magnitudes termodinámicas aparentes del proceso