Topology by dissipation

Topological states of fermionic matter can be induced by means of a suitably engineered dissipative dynamics. Dissipation then does not occur as a perturbation, but rather as the main resource for many-body dynamics, providing a targeted cooling into a topological phase starting from an arbitrary initial state. We explore the concept of topological order in this setting, developing and applying a general theoretical framework based on the system density matrix which replaces the wave function appropriate for the discussion of Hamiltonian ground-state physics. We identify key analogies and differences to the more conventional Hamiltonian scenario. Differences mainly arise from the fact that the properties of the spectrum and of the state of the system are not as tightly related as in a Hamiltonian context. We provide a symmetry-based topological classification of bulk steady states and identify the classes that are achievable by means of quasi-local dissipative processes driving into superfluid paired states. We also explore the fate of the bulk-edge correspondence in the dissipative setting, and demonstrate the emergence of Majorana edge modes. We illustrate our findings in one- and two-dimensional models that are experimentally realistic in the context of cold atoms.Comment: 61 pages, 8 figure

Improving rainfall nowcasting and urban runoff forecasting through dynamic radar-raingauge rainfall adjustment

The insufficient accuracy of radar rainfall estimates is a major source of uncertainty in short-term quantitative precipitation forecasts (QPFs) and associated urban flood forecasts. This study looks at the possibility of improving QPFs and urban runoff forecasts through the dynamic adjustment of radar rainfall estimates based on raingauge measurements. Two commonly used techniques (Kriging with External Drift (KED) and mean field bias correction) were used to adjust radar rainfall estimates for a large area of the UK (250,000 km2) based on raingauge data. QPFs were produced using original radar and adjusted rainfall estimates as input to a nowcasting algorithm. Runoff forecasts were generated by feeding the different QPFs into the storm water drainage model of an urban catchment in London. The performance of the adjusted precipitation estimates and the associated forecasts was tested using local rainfall and flow records. The results show that adjustments done at too large scales cannot provide tangible improvements in rainfall estimates and associated QPFs and runoff forecasts at small scales, such as those of urban catchments. Moreover, the results suggest that the KED adjusted rainfall estimates may be unsuitable for generating QPFs, as this method damages the continuity of spatial structures between consecutive rainfall fields

Monitoring urban heat island through google earth engine. Potentialities and difficulties in different cities of the United States

The aim of this work is to exploit the large-scale analysis capabilities of the innovative Google Earth Engine platform in order to investigate the temporal variations of the Urban Heat Island phenomenon as a whole. A intuitive methodology implementing a large-scale correlation analysis between the Land Surface Temperature and Land Cover alterations was thus developed. The results obtained for the Phoenix MA are promising and show how the urbanization heavily affects the magnitude of the UHI effects with significant increases in LST. The proposed methodology is therefore able to efficiently monitor the UHI phenomenon

Atoms and Quantum Dots With a Large Number of Electrons: the Ground State Energy

We compute the ground state energy of atoms and quantum dots with a large number N of electrons. Both systems are described by a non-relativistic Hamiltonian of electrons in a d-dimensional space. The electrons interact via the Coulomb potential. In the case of atoms (d=3), the electrons are attracted by the nucleus, via the Coulomb potential. In the case of quantum dots (d=2), the electrons are confined by an external potential, whose shape can be varied. We show that the dominant terms of the ground state energy are those given by a semiclassical Hartree-exchange energy, whose N to infinity limit corresponds to Thomas-Fermi theory. This semiclassical Hartree-exchange theory creates oscillations in the ground state energy as a function of N. These oscillations reflect the dynamics of a classical particle moving in the presence of the Thomas-Fermi potential. The dynamics is regular for atoms and some dots, but in general in the case of dots, the motion contains a chaotic component. We compute the correlation effects. They appear at the order N ln N for atoms, in agreement with available data. For dots, they appear at the order N.Comment: 30 pages, 1 figur

Atomic Quantum Simulation of Dynamical Gauge Fields coupled to Fermionic Matter: From String Breaking to Evolution after a Quench

Using a Fermi-Bose mixture of ultra-cold atoms in an optical lattice, we construct a quantum simulator for a U(1) gauge theory coupled to fermionic matter. The construction is based on quantum links which realize continuous gauge symmetry with discrete quantum variables. At low energies, quantum link models with staggered fermions emerge from a Hubbard-type model which can be quantum simulated. This allows us to investigate string breaking as well as the real-time evolution after a quench in gauge theories, which are inaccessible to classical simulation methods.Comment: 14 pages, 5 figures. Main text plus one general supplementary material and one basic introduction to the topic. Published versio

Constraining the Dark Matter decay lifetime with very deep observations of the Perseus cluster with the MAGIC telescopes

We present preliminary results on Dark Matter searches from observations of the Perseus galaxy cluster with the MAGIC Telescopes. MAGIC is a system of two Imaging Atmospheric Cherenkov Telescopes located in the Canary island of La Palma, Spain. Galaxy clusters are the largest known gravitationally bound structures in the Universe, with masses of ~10^15 Solar masses. There is strong evidence that galaxy clusters are Dark Matter dominated objects, and therefore promising targets for Dark Matter searches, particularly for decay signals. MAGIC has taken almost 300 hours of data on the Perseus Cluster between 2009 and 2015, the deepest observational campaign on any galaxy cluster performed so far in the very high energy range of the electromagnetic spectrum. We analyze here a small sample of this data and search for signs of dark matter in the mass range between 100 GeV and 20 TeV. We apply a likelihood analysis optimized for the spectral and morphological features expected in the dark matter decay signals. This is the first time that a dedicated Dark Matter optimization is applied in a MAGIC analysis, taking into account the inferred Dark Matter distribution of the source. The results with the full dataset analysis will be published soon by the MAGIC Collaboration

Evolutionary analysis of gene ages across TADs associates chromatin topology with whole-genome duplications

\ua9 2024 The AuthorsTopologically associated domains (TADs) are interaction subnetworks of chromosomal regions in 3D genomes. TAD boundaries frequently coincide with genome breaks while boundary deletion is under negative selection, suggesting that TADs may facilitate genome rearrangements and evolution. We show that genes co-localize by evolutionary age in humans and mice, resulting in TADs having different proportions of younger and older genes. We observe a major transition in the age co-localization patterns between the genes born during vertebrate whole-genome duplications (WGDs) or before and those born afterward. We also find that genes recently duplicated in primates and rodents are more frequently essential when they are located in old-enriched TADs and interact with genes that last duplicated during the WGD. Therefore, the evolutionary relevance of recent genes may increase when located in TADs with established regulatory networks. Our data suggest that TADs could play a role in organizing ancestral functions and evolutionary novelty

Influence of the level of neurological deficit on the efficacy of cell therapy in a model of severe traumatic brain injury

Objetivo: Determinar si el nivel de déficit neurológico influye en la eficacia de la terapia celular con células madre mesenquimales (CMM) de la médula ósea en un modelo experimental crónico de lesión cerebral traumática. Material y métodos: Se sometió a ratas Wistar adultas a un modelo de lesión cerebral traumática. Dos meses después, se clasificaron en función de su nivel de déficit neurológico mediante dos tests funcionales: Escala de valoración sensitivo-motora y Tiempo de permanencia en la zona interior (Video-Tracking-Box test, VTB test). Se inyectó suero salino solo o CMM en suero salino en el tejido cerebral dañado de los animales que obtuvieron la clasificación neurológica de lesión moderada o grave según el nivel permanente de su déficit funcional. Todos los animales se evaluaron durante los dos meses siguientes para determinar la posible eficacia de la administración de las CMM. Al finalizar el estudio, los animales se eutanasiaron y se estudiaron sus cerebros. Resultados: Se constata una recuperación funcional significativa en los animales con lesión moderada que recibieron las CMM, pero no en los animales con lesión grave cuando se compara con los controles. Conclusiones: Las conclusiones obtenidas sugieren que la gravedad de la lesión neurológica puede influir en la potencial eficacia de la terapia celular cuando es aplicada en una lesión cerebral traumática crónicaObjective: To study if the level of neurological deficit influences the efficacy of cell therapy with bone marrow stromal cells (BMSC), in an experimental model of chronic traumatic brain injury (TBI). Material and methods: Adult Wistar rats were subjected to a model of traumatic brain injury. Two months later they were classified according to their level of neurological deficit. For that, two functional tests: Scale of sensory- motor assessment and time spent in the inner zone in the Video-Tracking-Box test, were used. Saline alone or BMSC in saline was injected into the damaged brain tissue of animals suffering a permanent level of functional deficit classified as moderate or severe. All experimental groups were evaluated during the next two months to determine the potential effectiveness of the intracerebral administration of BMSC. At the end of the study animals were euthanized and their brains were studied. Results: The results show a significant functional recovery in animals with moderate injury who received BMSC, but there was no significant recovery in animals with severe traumatic brain injury when compared with controls. Conclusion: The severity of neurologic injury may influence the potential efficacy of cell therapy applied to chronic TBIEsta investigación ha sido financiada por FUNDACIÓN MAPFR