Dynamical signatures of topological order in the driven-dissipative Kitaev chain

We investigate the effects of dissipation and driving on topological order in superconducting nanowires. Rather than studying the non-equilibrium steady state, we propose a method to classify and detect dynamical signatures of topological order in open quantum systems. Bulk winding numbers for the Lindblad generator $\hat{\mathcal{L}}$ of the dissipative Kitaev chain are found to be linked to the presence of Majorana edge master modes -- localized eigenmodes of $\hat{\mathcal{L}}$. Despite decaying in time, these modes provide dynamical fingerprints of the topological phases of the closed system, which are now separated by intermediate regions where winding numbers are ill-defined and the bulk-boundary correspondence breaks down. Combining these techniques with the Floquet formalism reveals higher winding numbers and different types of edge modes under periodic driving. Finally, we link the presence of edge modes to a steady state current.Comment: Submission to SciPost. 29 pages, 8 figure

The importance of the western Weddell Sea to Weddell Sea Deep Water formation

The dense water flowing out from the Weddell Sea (WS), the Weddell Sea Deep Water (WSDW), significantly contributes to Antarctic Bottom Water (AABW) and plays an important role in the Meridional Overturning Circulation. However, the relative importance of the western Weddell Sea as a major source region remains unclear. Several studies hypothesized that the continental shelf off Larsen Ice Shelf (LIS) is important for deep and bottom water production, but the role of the Larsen Ice Shelf remains speculative. In this work the importance of the western WS including the LIS to the production of WSDW is investigated using in situ observations and results from numerical simulations. Measurements made during the Polarstern cruise ANT XXIX-3 (2013) in the northwestern WS add evidence to the importance of the western WS as a dense water source. An Optimum Multiparameter Analysis shows that the dense water found near the shelf break in front of the former Larsen A and B ice shelves, together with a very dense water observed off Larsen C Ice Shelf, increases the thickness and changes the _/S characteristics of WSDW that leaves the WS through gaps in the South Scotia Ridge to form AABW. A numerical experiment performed with the Finite Element Sea-ice Ocean Model (FESOM) was used to verify the hypothesis that the continental shelf of the western WS is important for dense water formation. The model results show the changes in the thermohaline properties of the WSDW flowing along the continental slope of the western WS, as well as an increase in the transport downstream. The variability along the continental slope can be explained by fluctuations of the large-scale circulation, namely theWeddell Gyre. In addition, there is no indication that dense waters are formed in the continental shelf of the western WS, and the exchanges between continental shelf and continental slope are small. These results suggest that the area is not important for WSDW formation as previously inferred from the sparse observations mainly along the continental slope. Instead, the western WS seems to be a region where the characteristics of WSDW are determined due to mixing of waters formed upstream. Two sensitivity experiments were designed to investigate whether LIS plays an indirect role in the dense water production: (1) Larsen B Ice Shelf was added to the grid, (2) Larsen C Ice Shelf was completely removed from the grid. The experiments show that LIS plays an important role for the waters on the continental shelf but has only minor importance for the WSDW. Given the disagreement between the hypothesis derived from the observations and the model results, more in situ data are needed to determine whether the western Weddell Sea is a region where dense water is formed or whether it only serves as a conduit for dense waters formed further upstream, which interact in the western WS before reaching the final WSDW characteristics

The importance of the western Weddell Sea to Weddell Sea Deep Water formation

The dense water flowing out from the Weddell Sea (WS), the Weddell Sea Deep Water (WSDW), significantly contributes to Antarctic Bottom Water (AABW) and plays an important role in the Meridional Overturning Circulation. However, the relative importance of the western Weddell Sea as a major source region remains unclear. Several studies hypothesized that the continental shelf off Larsen Ice Shelf (LIS) is important for deep and bottom water production, but the role of the Larsen Ice Shelf remains speculative. In this work the importance of the western WS including the LIS to the production of WSDW is investigated using in situ observations and results from numerical simulations. Measurements made during the Polarstern cruise ANT XXIX-3 (2013) in the northwestern WS add evidence to the importance of the western WS as a dense water source. An Optimum Multiparameter Analysis shows that the dense water found near the shelf break in front of the former Larsen A and B ice shelves, together with a very dense water observed off Larsen C Ice Shelf, increases the thickness and changes the _/S characteristics of WSDW that leaves the WS through gaps in the South Scotia Ridge to form AABW. A numerical experiment performed with the Finite Element Sea-ice Ocean Model (FESOM) was used to verify the hypothesis that the continental shelf of the western WS is important for dense water formation. The model results show the changes in the thermohaline properties of the WSDW flowing along the continental slope of the western WS, as well as an increase in the transport downstream. The variability along the continental slope can be explained by fluctuations of the large-scale circulation, namely theWeddell Gyre. In addition, there is no indication that dense waters are formed in the continental shelf of the western WS, and the exchanges between continental shelf and continental slope are small. These results suggest that the area is not important for WSDW formation as previously inferred from the sparse observations mainly along the continental slope. Instead, the western WS seems to be a region where the characteristics of WSDW are determined due to mixing of waters formed upstream. Two sensitivity experiments were designed to investigate whether LIS plays an indirect role in the dense water production: (1) Larsen B Ice Shelf was added to the grid, (2) Larsen C Ice Shelf was completely removed from the grid. The experiments show that LIS plays an important role for the waters on the continental shelf but has only minor importance for the WSDW. Given the disagreement between the hypothesis derived from the observations and the model results, more in situ data are needed to determine whether the western Weddell Sea is a region where dense water is formed or whether it only serves as a conduit for dense waters formed further upstream, which interact in the western WS before reaching the final WSDW characteristics

Symmetry-protected coherent relaxation of open quantum systems

We compute the effect of Markovian bulk dephasing noise on the staggered magnetization of the spin-1/2 XXZ Heisenberg chain, as the system evolves after a N\'eel quench. For sufficiently weak system-bath coupling, the unitary dynamics are found to be preserved up to a single exponential damping factor. This is a consequence of the interplay between $\mathbb{PT}$ symmetry and weak symmetries, which strengthens previous predictions for $\mathbb{PT}$-symmetric Liouvillian dynamics. Requirements are a non-degenerate $\mathbb{PT}$-symmetric generator of time evolution $\hat{\mathcal{L}}$, a weak parity symmetry and an observable that is anti-symmetric under this parity transformation. The spectrum of $\hat{\mathcal{L}}$ then splits up into symmetry sectors, yielding the same decay rate for all modes that contribute to the observable's time evolution. This phenomenon may be realized in trapped ion experiments and has possible implications for the control of decoherence in out-of-equilibrium many-body systems.Comment: 9 pages, 3 figures. Added discussion at end of section II

Migrating tide climatologies measured by a high-latitude array of SuperDARN HF radars

This study uses hourly meteor wind measurements from a longitudinal array of 10 high-latitude SuperDARN high-frequency (HF) radars to isolate the migrating diurnal, semidiurnal, and terdiurnal tides at mesosphere–lower-thermosphere (MLT) altitudes. The planetary-scale array of radars covers 180∘ of longitude, with 8 out of 10 radars being in near-continuous operation since the year 2000. Time series spanning 16 years of tidal amplitudes and phases in both zonal and meridional wind are presented, along with their respective annual climatologies. The method to isolate the migrating tides from SuperDARN meteor winds is validated using 2 years of winds from a high-altitude meteorological analysis system. The validation steps demonstrate that, given the geographical spread of the radar stations, the derived tidal modes are most closely representative of the migrating tides at 60∘ N. Some of the main characteristics of the observed migrating tides are that the semidiurnal tide shows sharp phase jumps around the equinoxes and peak amplitudes during early fall and that the terdiurnal tide shows a pronounced secondary amplitude peak around day of year (DOY) 265. In addition, the diurnal tide is found to show a bi-modal circular polarization phase relation between summer and winter.publishedVersio

Generalized local fractions – a method for the calculation of sensitivities to emissions from multiple sources for chemically active species, illustrated using the EMEP MSC-W model (rv5.5)

This paper presents an extension of the original Local Fraction methodology to allow the tracking of the sensitivity of chemically active air pollutants to emission sources. The generalized Local Fractions are defined as the linear sensitivities of chemical species to source emission changes, as propagated through the full set of non-linear chemical transformations. The method allows us to simultaneously track sensitivities from hundreds of sources (typically countries or emission sectors) in a single simulation. The current work describes how the non-linear chemical transformations are taken into account in a rigorous manner while validating the implementation of the method in the European Monitoring and Evaluation Programme (EMEP) Meteorological Synthesizing Centre – West (MSC-W) chemistry-transport model by examples. While effectively producing the same results as a direct “brute-force” method, where the impact of emission reductions in each source has to be computed in a separate scenario simulation, the generalized Local Fractions are an order of magnitude more computationally efficient when large numbers of scenarios are considered.</p

Sobre a relação TS na porção central do atlântico sudoeste: uma contribuição para o estudo da variabilidade oceânica no entorno da Cadeia Vitória-Trindade

The MOVAR (Monitoring the variability of heat transport between Rio de Janeiro-RJ and Trindade Island-ES) project was created in order to study the oceanic circulation south of the Vitória-Trindade seamount chain. The periodic sampling in the area is possible by using ships of opportunity to launch expendable bathythermographs (XBT). In order to investigate the oceanic volume flows using the geostrophic method based on the measured data, which is the temperature only, we have chosen to use a methodology based on the regional correlation between temperature and salinity (TS). Within this context, polynomials of order 1 to 10 were obtained and tested, in order to enable the estimation of salinity as a function of temperature. Hence, to reach this purpose, TS data from the WOD-05 (World Ocean Data Base 2005) as well as ARGO profiles available in the region were used. After a sequence of tests, the polynomials of first to fourth order were discarded, while the remaining polynomials were used to estimate the transport along three sections. The results obtained with the polynomials were very similar to each other leading to the choice of the simpler equation, P5, to represent the TS relation for the region. Estimates of transport were satisfactory and indicated that the polynomial can be used for this purpose.O projeto MOVAR (Monitoramento da Variabilidade do Transporte de Calor entre o Rio de Janeiro-RJ e a Ilha da Trindade-ES) foi criado com intuito de estudar a circulação na região oceânica ao sul da Cadeia Submarina de Vitória-Trindade. A amostragem periódica na área é possível graças ao uso de navios de oportunidade para lançar batitermógrafos descartáveis (XBT). Para investigar os fluxos oceânicos de volume usando o método geostrófico com base nos dados mensurados, temperatura apenas, optou-se por utilizar uma metodologia baseada na correlação regional entre temperatura e salinidade (TS). Dentro deste contexto, foram obtidos e testados polinômios de ordem 1 a 10 que possibilitassem estimar a salinidade em função da temperatura. Para tal foram utilizados dados TS do WOD-05 (World Ocean Data Base 2005) e dos perfiladores ARGO disponíveis na região. Após uma seqüência de testes, os polinômios de primeira a quarta ordem foram descartados, sendo os demais utilizados para estimar o transporte ao longo de três seções. Os resultados obtidos com os polinômios foram muito semelhantes entre si, levando à escolha da equação mais simples, P5, para representar a relação TS da região. As estimativas de transporte foram satisfatórias e indicaram que o polinômio pode ser utilizado para este fim