Crystallization of fractional charges in a strongly interacting quasi-helical quantum dot

The ground-state electron density of a one-dimensional spin-orbit coupled quantum dot with a Zeeman term and strong electron interaction is studied at the fractional helical liquid points. We show that at fractional filling factors $\nu=(2n+1)^{-1}$ (with $n$ a non-negative integer) the density oscillates with $N_{0}/\nu$ peak. For $n\geq 1$ a number of peaks larger than the number of electrons $N_{0}$ suggests that a crystal of fractional quasi-particles with charge $\nu e$ (with $e$ the electron charge) occurs. The reported effect is amenable of verification via transport measurements in charged AFM-coupled dot

UWB Circular Slot Antenna Provided with an Inverted-L Notch Filter for the 5 GHz WLAN Band

Abstract—The study of a planar circular slot antenna for Ultrawideband (UWB) communications is presented. The integration on this antenna of a notch filter, to reduce the possible interferences with the 5GHz WLAN communications, has been discussed in detail. Four different structures, achieved by etching a suitable pattern on the antenna circular stub, have been considered, and their features have been compared. The antenna with symmetrical and inverted-L cuts shows the best performance, and it has been therefore realized and fully characterized. It shows very good matching features over the UWB band, and notable rejection of the 5 GHz WLAN band

The luminous late-time emission of the type Ic supernova iPTF15dtg - evidence for powering from a magnetar?

iPTF15dtg is a Type Ic supernova (SN) showing a broad light curve around maximum light, consistent with massive ejecta if we assume a radioactive-powering scenario. We study the late-time light curve of iPTF15dtg, which turned out to be extraordinarily luminous for a stripped-envelope (SE) SN. We compare the observed light curves to those of other SE SNe and also with models for the $^{56}$Co decay. We analyze and compare the spectra to nebular spectra of other SE SNe. We build a bolometric light curve and fit it with different models, including powering by radioactivity, magnetar powering, as well as a combination of the two. Between 150 d and 750 d past explosion, iPTF15dtg's luminosity declined by merely two magnitudes instead of the six magnitudes expected from $^{56}$Co decay. This is the first spectroscopically-regular SE SN showing this behavior. The model with both radioactivity and magnetar powering provides the best fit to the light curve and appears to be the more realistic powering mechanism. An alternative mechanism might be CSM interaction. However, the spectra of iPTF15dtg are very similar to those of other SE SNe, and do not show signs of strong CSM interaction. iPTF15dtg is the first spectroscopically-regular SE SN whose light curve displays such clear signs of a magnetar contributing to the powering of the late time light curve. Given this result, the mass of the ejecta needs to be revised to a lower value, and therefore the progenitor mass could be significantly lower than the previously estimated $>$35 $M_{\odot}$.Comment: 9 pages, 8 figures, accepted for publication in Astronomy and Astrophysic

Gross chemical profile and calculation of nitrogen-to-protein conversion factors for five tropical seaweeds.

Despite decades of research on marine algae, there are still significant gaps in basic knowledge about chemical com-position of these organisms, especially in tropical environments. In this study, the amino acid composition and contents of total nitrogen, phosphorus, lipid, carbohydrate and protein were determined in Asparagopsis taxiformis, Centroceras clavulatum, Chaetomorpha aerea, Sargassum filipendula and Spyridia hypnoides. The seaweeds showed low lipid con-tents (lower than 5.5% d.w. in all species) and were rich in carbohydrates (more than 16% d.w. in all seaweeds). The percentage of nitrogen, phosphorus and protein varied widely among species, which red algae showed the highest con-centrations. The amino acid composition was similar among the seaweeds, which glutamic acid, aspartic acid and leu-cine as the most abundant. All species are poor in histidine. An average of 24.2% of the total nitrogen is non-proteinaceous. From data of total amino acid and total nitrogen, specific nitrogen-to-protein conversion factors were calculated for each species. The nitrogen-to-protein conversion factors calculated ranged from 4.51 to 5.21, with an overall average of 4.86. These findings show that the traditional conversion factor of 6.25 should be avoided for seaweeds, since it overestimates the actual protein content

Topological Devil's staircase in atomic two-leg ladders

We show that a hierarchy of topological phases in one dimension - a topological Devil's staircase - can emerge at fractional filling fractions in interacting systems, whose single-particle band structure describes a topological or a crystalline topological insulator. Focusing on a specific example in the BDI class, we present a field-theoretical argument based on bosonization that indicates how the system, as a function of the filling fraction, hosts a series of density waves. Subsequently, based on a numerical investigation of the low-lying energy spectrum, Wilczek-Zee phases, and entanglement spectra, we show that they are symmetry protected topological phases. In sharp contrast to the non-interacting limit, these topological density waves do not follow the bulk-edge correspondence, as their edge modes are gapped. We then discuss how these results are immediately applicable to models in the AIII class, and to crystalline topological insulators protected by inversion symmetry. Our findings are immediately relevant to cold atom experiments with alkaline-earth atoms in optical lattices, where the band structure properties we exploit have been recently realized

Supernova 2012ec: Identification of the progenitor and early monitoring with PESSTO

We present the identification of the progenitor of the Type IIP SN 2012ec in archival pre-explosion HST WFPC2 and ACS/WFC F814W images. The properties of the progenitor are further constrained by non-detections in pre-explosion WFPC2 F450W and F606W images. We report a series of early photometric and spectroscopic observations of SN 2012ec. The r'-band light curve shows a plateau with M(r')=-17.0. The early spectrum is similar to the Type IIP SN 1999em, with the expansion velocity measured at Halpha absorption minimum of -11,700 km/s (at 1 day post-discovery). The photometric and spectroscopic evolution of SN 2012ec shows it to be a Type IIP SN, discovered only a few days post-explosion (<6d). We derive a luminosity for the progenitor, in comparison with MARCS model SEDs, of log L/Lsun = 5.15+/-0.19, from which we infer an initial mass range of 14-22Msun. This is the first SN with an identified progenitor to be followed by the Public ESO Spectroscopic Survey of Transient Objects (PESSTO).Comment: 6 pages, 3 figures, MNRAS accepte