High-momentum tails as magnetic structure probes for strongly-correlated SU(κ)SU(\kappa) fermionic mixtures in one-dimensional traps

A universal $k^{-4}$ decay of the large-momentum tails of the momentum distribution, fixed by Tan's contact coefficients, constitutes a direct signature of strong correlations in a short-range interacting quantum gas. Here we consider a repulsive multicomponent Fermi gas under harmonic confinement, as in the experiment of Pagano et al. [Nat. Phys. {\bf 10}, 198 (2014)], realizing a gas with tunable $SU(\kappa)$ symmetry. We exploit an exact solution at infinite repulsion to show a direct correspondence between the value of the Tan's contact for each of the $\kappa$ components of the gas and the Young tableaux for the $S_N$ permutation symmetry group identifying the magnetic structure of the ground-state. This opens a route for the experimental determination of magnetic configurations in cold atomic gases, employing only standard (spin-resolved) time-of-flight techniques. Combining the exact result with matrix-product-states simulations, we obtain the Tan's contact at all values of repulsive interactions. We show that a local density approximation (LDA) on the Bethe-Ansatz equation of state for the homogeneous mixture is in excellent agreement with the results for the harmonically confined gas. At strong interactions, the LDA predicts a scaling behavior of the Tan's contact. This provides a useful analytical expression for the dependence on the number of fermions, number of components and on interaction strength. Moreover, using a virial approach in the limit of infinite interactions, we show that the contact increases with the temperature and the number of components. At zero temperature, we predict that the weight of the momentum distribution tails increases with interaction strength and the number of components if the population per component is kept constant. This latter property was experimentally observed in Ref.~[Nat. Phys. {\bf 10}, 198 (2014)].Comment: 13 pages, 6 figure

The Tensor Networks Anthology: Simulation techniques for many-body quantum lattice systems

We present a compendium of numerical simulation techniques, based on tensor network methods, aiming to address problems of many-body quantum mechanics on a classical computer. The core setting of this anthology are lattice problems in low spatial dimension at finite size, a physical scenario where tensor network methods, both Density Matrix Renormalization Group and beyond, have long proven to be winning strategies. Here we explore in detail the numerical frameworks and methods employed to deal with low-dimension physical setups, from a computational physics perspective. We focus on symmetries and closed-system simulations in arbitrary boundary conditions, while discussing the numerical data structures and linear algebra manipulation routines involved, which form the core libraries of any tensor network code. At a higher level, we put the spotlight on loop-free network geometries, discussing their advantages, and presenting in detail algorithms to simulate low-energy equilibrium states. Accompanied by discussions of data structures, numerical techniques and performance, this anthology serves as a programmer's companion, as well as a self-contained introduction and review of the basic and selected advanced concepts in tensor networks, including examples of their applications.Comment: 115 pages, 56 figure

Genetic association of apolipoprotein E with optic disc size

INTRODUCTION. The purpose of this clinical non-interventional cross-sectional study was to evaluate the role of apolipoprotein E (ApoE) gene alleles (e2, e3, e4) in the determination of optic disc size. MATERIALS AND METHODS. In 32 normal controls, 54 patients with ocular hypertension (OHT), and 96 patients with primary open-angle the optic disc size was determined by planimetry using 15° colour stereo photographs. In all individuals ApoE genotyping was performed. RESULTS. The size of the optic disc was significantly different between subjects with e3e2, e3e3, and e4e3 allele (Kruskal-Wallis-test, Chi-Square: 6.95, p = 0.031; 2.39, 2.77, and 2.78 mm2, respectively). CONCLUSIONS. The results suggest that ApoE gene alleles are associated with optic disc size. ApoE may act as a modulator gene for optic disc morphogenesis

Cold atoms meet lattice gauge theory

The central idea of this review is to consider quantum field theory models relevant for particle physics and replace the fermionic matter in these models by a bosonic one. This is mostly motivated by the fact that bosons are more ‘accessible’ and easier to manipulate for experimentalists, but this ‘substitution’ also leads to new physics and novel phenomena. It allows us to gain new information about among other things confinement and the dynamics of the deconfinement transition. We will thus consider bosons in dynamical lattices corresponding to the bosonic Schwinger or Z2 Bose–Hubbard models. Another central idea of this review concerns atomic simulators of paradigmatic models of particle physics theory such as the Creutz–Hubbard ladder, or Gross–Neveu–Wilson and Wilson–Hubbard models. This article is not a general review of the rapidly growing field—it reviews activities related to quantum simulations for lattice field theories performed by the Quantum Optics Theory group at ICFO and their collaborators from 19 institutions all over the world. Finally, we will briefly describe our efforts to design experimentally friendly simulators of these and other models relevant for particle physics. This article is part of the theme issue ‘Quantum technologies in particle physics’

One-dimensional interacting fermionic systems : a study of geometry, topology and symmetry in synthetic quantum matter

In den vergangenen Jahren hat es einen gewaltigen Fortschritt in der Handhabung ultrakalter Gase gegeben. Laser-Kühlmethoden erlauben Zugang zum Quantenregime und Experimente haben eine Präzision erreicht, die die Kontrolle und Messung einzelner Atome zulässt. Durch ausgefeilte Lasertechniken können optische Gitter mit verschiedenen Geometrien erzeugt, Wechselwirkungen präzise eingestellt und neue Konzepte wie z.B. künstliche Eichfelder umgesetzt werden. Einerseits erlauben kalte Atome als Quantensimulatoren die Studie kondensierter Materie - die relevanten Freiheitsgrade des Ursprungssystems werden dafür auf das experimentell besser zugängliche Setup abgebildet. Andererseits ermöglicht die Kombination verschiedener experimenteller Komponenten das Design neuer Materialien, sogenannter synthetischer Quantenmaterie, die nicht zwangsläufig außerhalb der Versuchsumgebung existiert. Gleichzeitig erweitern Konzepte aus der Quanteninformation unser Verständnis von Quantenphasen insgesamt. Das Konzept der Quantenverschränkung revolutioniert die Beschreibung von Vielteilchensystemen, indem es (Hilbertraum-)Wellenfunktionen durch intuitive Tensornetzwerke ersetzt. Das Verständnis dieser Tensoren als elementare Bausteine ermöglicht die Erklärung von Phänomenen wie topologischen Zuständen in einem Bottom-up-Ansatz. Zudem erlauben Tensornetzwerke eine effiziente Beschreibung von Vielteilchen-Zuständen und können deshalb für numerische Simulationen genutzt werden. In dieser Arbeit konzentrieren wir uns auf eindimensionale fermionische Systeme und untersuchen den Einfluss von verschiedenen Faktoren wie z.B. Wechselwirkungen, inneren Freiheitsgraden, künstlichen Eichfeldern, Symmetrien und verschiedenförmigen Potentialen. Während die Wirkung der Einzelkomponenten wohlbekannt sein mag, bietet die Kombination verschiedener solcher Faktoren spannende neue Physik. Die theoretische Untersuchung wird durch die Möglichkeit der Realisierung in den oben genannten Experimenten ermutigt. Wir nutzen dazu - neben analytischen und störungstheoretischen Ansätzen - Tensornetzwerk-Methoden als numerische Technik. Insbesondere untersuchen wir drei Beispiele exotischer eindimensionaler fermionischer Systeme: (i) eine Creutz-Hubbard-Leiter, in der Wechselwirkungen und topologische Eigenschaften im Wettstreit stehen; wir erforschen das gesamte Phasendiagramm und erklären die (topologischen) Übergänge durch effektive Theorien; (ii) ein ringförmiges System mit einer ähnlichen mikroskopischen Leiterarchitektur, die als effektive Theorie relativistischer, masseloser Fermionen verstanden werden kann; für diese sogenannten Weyl-Fermionen erforschen wir die Gleichstrom-Antwort auf externe Felder; wir finden, dass Wechselwirkungen in bestimmten Parameterbereichen den diamagnetischen Strom entlang des Rings verstärken; (iii) ein fermionisches Multikomponentengas mit SU(N)-Wechselwirkungen in einer harmonischen Falle; wir bieten ein pädagogisches Verständnis der Symmetrie und stellen eine Verbindung zur Magnetisierung und zur experimentell messbaren Impulsverteilung der Energiezustände her.Recent years have seen a tremendous step forward in the manipulation of ultracold atomic gases. Laser cooling techniques give access to the quantum regime and experiments have reached a level, at which control and measurement of individual atoms is possible. Sophisticated laser schemes provide optical lattices with different geometries, and allow the precise tuning of interactions and the realization of new concepts such as artificial gauge fields. On the one hand, cold atoms can be used as quantum simulators to study condensed matter systems by mapping the relevant degrees of freedom of the original system to the experimentally better accessible setup. On the other hand, combining different experimental features permits the design of new phases of matter, so-called synthetic quantum matter, which may or may not exist outside the experimental environment. At the same time, concepts from quantum information are pushing the frontier of our understanding of quantum phases as a whole. The concept of entanglement revolutionizes the description of quantum many-body states by replacing (Hilbert space) wave functions with intuition-charged tensor networks. Taking these tensors as elementary building blocks makes it possible to explain phenomena like topology in a bottom-up approach. Moreover, tensor networks permit an efficient description of quantum many-body states and are therefore exploited for numerical simulations. In this thesis, we focus on one-dimensional fermionic systems and explore the influence of different ingredients such as interactions, internal degrees of freedom, artificial gauge fields, symmetries and differently-shaped trapping potentials. While the individual effects might be well understood, the combination of these factors offers new exciting physics. Theoretical research on such systems is encouraged by the forthcoming realizability in the above-mentioned experiments. For our investigation, we employ - besides analytical and perturbative approaches - tensor network methods as a numerical means. In particular, we study three instances of exotic one-dimensional fermionic systems: (i) a Creutz-Hubbard ladder model with a competition between interactions and topological features; we lay out the complete phase diagram and explain the (topological) phase transitions through effective theories; (ii) a ring-shaped system with a similar microscopic ladder architecture, which can be understood as an effective theory of relativistic massless fermions; for these Weyl fermions, we explore the current response to external fields; we find that in certain regimes, the interactions enhance the diamagnetic current flowing along the ring; (iii) a fermionic multi-component gas in a harmonic trap interacting through SU(N)-symmetric contact potentials; we offer a pedagogic understanding of the symmetry and establish a link to the magnetization and to the experimentally accessible momentum distribution of the energy eigenstates

Increased Homocysteine Levels in Tear Fluid of Patients with Primary Open-Angle Glaucoma

Aims: We assessed homocysteine (Hcy) levels in tear fluid and plasma of patients with primary open-angle glaucoma (POAG). We determined the association between Hcy levels, dry eye syndrome and B vitamin status. Methods: This prospective case-control study included 36 patients with POAG and 36 controls. Hcy concentrations were measured by highperformance liquid chromatography. Results: Patients with POAG had significantly higher mean Hcy levels both in tear fluid (205 8 84 nmol/l; p ! 0.001, t test) and in plasma (13.43 8 3.53 _ mol/l; p = 0.001, t test) than control subjects (130 8 53 nmol/l and 10.50 8 3.33 _ mol/l, respectively). Hcy in tear fluid was significantly correlated with plasma Hcy in POAG patients (r = 0.459; p = 0.005, Pearson’s correlation), but not in controls (r = 0.068; p = 0.695). POAG patients with dry eye disease had significantly higher Hcy levels both in tear fluid and plasma than POAG patients without dry eye disease. There was no association between Hcy levels and B vitamin status in subjects with POAG. Conclusions: The study suggests increased Hcy levels in tear fluid and plasma of patients with POAG. Elevated Hcy levels might be a risk factor for POAG and dry eye syndrome in subjects with glaucoma

Involvement of medical students in a surgery congress: impact on learning motivation, decision-making for a career in surgery, and educational curriculum

During the preclinical period of medical school, the clinical relevance of theoretical knowledge is given little attention. Medical students of the second year were invited to participate in an interdisciplinary congress for robot-assisted and digital surgery. The students had to evaluate the impact of the congress on their learning motivation, decision-making for a career in surgery, and relevance for their educational curriculum. Participation in the congress increased their learning motivation for preclinical subjects, and significantly increased their interest in a surgical career. Most students considered active involvement in medical congresses a valuable supplement to the medical curriculum. Congress participation during the preclinical period was ranked positively by medical students. Greater learning motivation and enthusiasm for the pilot teaching project as well as for surgical disciplines were registered. Thus, early involvement of medical students in scientific congresses should be an integral part of their educational curriculum

Differential Membrane Proteome Analysis Reveals Novel Proteins Involved in the Degradation of Aromatic Compounds in Geobacter metallireducens*

Aromatic compounds comprise a large class of natural and man-made compounds, many of which are of considerable concern for the environment and human health. In aromatic compound-degrading anaerobic bacteria the central intermediate of aromatic catabolism, benzoyl coenzyme A, is attacked by dearomatizing benzoyl-CoA reductases (BCRs). An ATP-dependent BCR has been characterized in facultative anaerobes. In contrast, a previous analysis of the soluble proteome from the obligately anaerobic model organism Geobacter metallireducens identified genes putatively coding for a completely different dearomatizing BCR. The corresponding BamBCDEFGHI complex is predicted to comprise soluble molybdenum or tungsten, selenocysteine, and FeS cluster-containing components. To elucidate key processes involved in the degradation of aromatic compounds in obligately anaerobic bacteria, differential membrane protein abundance levels from G. metallireducens grown on benzoate and acetate were determined by the MS-based spectral counting approach. A total of 931 proteins were identified by combining one-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis with liquid chromatography-tandem mass spectrometry. Several membrane-associated proteins involved in the degradation of aromatic compounds were newly identified including proteins with similarities to modules of NiFe/heme b-containing and energy-converting hydrogenases, cytochrome bd oxidases, dissimilatory nitrate reductases, and a tungstate ATP-binding cassette transporter system. The transcriptional regulation of differentially expressed genes was analyzed by quantitative reverse transcription-PCR; in addition benzoate-induced in vitro activities of hydrogenase and nitrate reductase were determined. The results obtained provide novel insights into the poorly understood degradation of aromatic compounds in obligately anaerobic bacteria