Color Superconductivity in Compact Stars and Gamma Ray Bursts

We study the effects of color superconductivity on the structure and formation of compact stars. We show that it is possible to satisfy most of recent observational boundaries on masses and radii if a diquark condensate forms in a hybrid or a quark star. Moreover, we find that a huge amount of energy, of the order of $10^{53}$ erg, can be released in the conversion from a (metastable) hadronic star into a (stable) hybrid or quark star, if the presence of a color superconducting phase is taken into account. Accordingly to the scenario proposed in Astrophys.J.586(2003)1250, the energy released in this conversion can power a Gamma Ray Burst. This mechanism can explain the recent observations indicating a delay, of the order of days or years, between a few Supernova explosions and the subsequent Gamma Ray Burst.Comment: 15 pages, 4 figures, 1 tabl

Formation of Quark Phases in compact stars and their connection to Gamma-Ray-Bursts

We analyse the occurrence of quiescent times in the temporal structure of the Gamma-Ray-Bursts (GRBs) light curves. We show that if a long quiescent time is present, it is possible to divide the total duration of GRBs into three periods: the pre-quiescence emission, the quiescent time and the post-quiescence emission. We then discuss a model of the GRBs inner engine based on the formation of quark phases during the life of an hadronic star. Within this model the pre-quiescence emission is interpreted as due to the deconfinement of quark inside an hadronic star and the formation of 2SC quark matter. The post-quiescence emission is due to the conversion of 2SC into the Color-Flavor-Locking (CFL) phase. The temporal delay between these two processes is connected with the nucleation time of the CFL phase in the 2SC phase and it can be associated with the observed quiescent times in the GRBs light curves. The stability of CFL cores in compact stars is also discussed.Comment: 6 pages, 3 figures, to appear in the proceedings of 3th International Conference on Nuclear Physics in Astrophysics (NPAIII), 26 - 31 March 2007 Dresden, German

Gapless color-flavor locked phase in quark and hybrid stars

We study the effects of the gapless color-flavor locked (gCFL) phase on the equation of state of strongly interacting matter in the range of baryonic chemical potential involved in a compact star. We analyze the possibility of a phase transition from hadronic matter to gCFL quark matter and we discuss, for different values of the strange quark mass and diquark coupling strength, the existence of a gCFL phase in quark or hybrid stars. The mass-radius relation and the structure of compact stars containing the gCFL phase are shown and the physical relevance of this superconducting phase inside a stellar object is also discussed.Comment: 7 pages, 11 figure

Explaining the magnetic moment reduction of Fullerene encapsulated Gadolinium through a theoretical model

We propose a Theoretical model accounting for the recently observed reduced magnetic moment of Gadolinium in fullerenes. While this reduction has been observed also for other trivalent rare-hearth atoms (Dy3+, Er3+, Ho3+) in fullerenes and can be ascribed to crystal field effects, the explanation of this phenomena for Gd3+ is not straightforward due to the sphericity of its ground state (S=7/2, L=0). In our model the momentum lowering is the result of a subtle interplay between hybridisation and spin-orbit interaction

MMHelper: An automated framework for the analysis of microscopy images acquired with the mother machine

This is the final version. Available from Nature Research via the DOI in this record.Live-cell imaging in microfluidic devices now allows the investigation of cellular heterogeneity within microbial populations. In particular, the mother machine technology developed by Wang et al. has been widely employed to investigate single-cell physiological parameters including gene expression, growth rate, mutagenesis, and response to antibiotics. One of the advantages of the mother machine technology is the ability to generate vast amounts of images; however, the time consuming analysis of these images constitutes a severe bottleneck. Here we overcome this limitation by introducing MMHelper (https://doi.org/10.5281/zenodo.3254394), a publicly available custom software implemented in Python which allows the automated analysis of brightfield or phase contrast, and any associated fluorescence, images of bacteria confined in the mother machine. We show that cell data extracted via MMHelper from tens of thousands of individual cells imaged in brightfield are consistent with results obtained via semi-automated image analysis based on ImageJ. Furthermore, we benchmark our software capability in processing phase contrast images from other laboratories against other publicly available software. We demonstrate that MMHelper has over 90% detection efficiency for brightfield and phase contrast images and provides a new open-source platform for the extraction of single-bacterium data, including cell length, area, and fluorescence intensity.Royal SocietyWellcome TrustMRCBBSR

Temporal evolution of jet induced scour depth in cohesionless granular beds and the phenomenological theory of turbulence

In this work, we investigate the temporal evolution of the jet-driven scour depth in a pothole lying on a cohesionless granular bed by using diverse approaches. First, we present new experiments which encompass cases with jet angles ranging from 45° to 90° from the horizontal, several initial water depths, and different particle sizes, supplementing experiments developed recently by the last two authors. In particular, we address relatively large angles, mostly absent in previous analyses. Our results initially confirm the existence of two very different stages in the scour process, essentially overlooked in datasets used to obtain the traditional formulas—developing and developed phases; they then provide unprecedented evidence of the very distinct behavior at 90°, characterized by a step-wise behavior. Second, after revisiting the rationale of a theory for the equilibrium condition developed elsewhere by the first author and a collaborator, we employ the existing and new datasets to determine the multiplicative constants embedded in the equilibrium scour formulas. Third, we present a novel theory for the temporal evolution of the scour depth during the developed phase (but with good prediction capabilities in the developing phase as well). By invoking the conservation of mass of sediment in the pothole, in addition to the energy conservation within the pothole and the phenomenological theory of turbulence, we obtain ordinary differential equations which we solve by numerical means. We validate the theory using our new and other datasets. Finally, we provide interesting interpretations of the scour process by using the results of the theory