Tensor network states and geometry

Tensor network states are used to approximate ground states of local Hamiltonians on a lattice in D spatial dimensions. Different types of tensor network states can be seen to generate different geometries. Matrix product states (MPS) in D=1 dimensions, as well as projected entangled pair states (PEPS) in D>1 dimensions, reproduce the D-dimensional physical geometry of the lattice model; in contrast, the multi-scale entanglement renormalization ansatz (MERA) generates a (D+1)-dimensional holographic geometry. Here we focus on homogeneous tensor networks, where all the tensors in the network are copies of the same tensor, and argue that certain structural properties of the resulting many-body states are preconditioned by the geometry of the tensor network and are therefore largely independent of the choice of variational parameters. Indeed, the asymptotic decay of correlations in homogeneous MPS and MERA for D=1 systems is seen to be determined by the structure of geodesics in the physical and holographic geometries, respectively; whereas the asymptotic scaling of entanglement entropy is seen to always obey a simple boundary law -- that is, again in the relevant geometry. This geometrical interpretation offers a simple and unifying framework to understand the structural properties of, and helps clarify the relation between, different tensor network states. In addition, it has recently motivated the branching MERA, a generalization of the MERA capable of reproducing violations of the entropic boundary law in D>1 dimensions.Comment: 18 pages, 18 figure

From thermal rectifiers to thermoelectric devices

We discuss thermal rectification and thermoelectric energy conversion from the perspective of nonequilibrium statistical mechanics and dynamical systems theory. After preliminary considerations on the dynamical foundations of the phenomenological Fourier law in classical and quantum mechanics, we illustrate ways to control the phononic heat flow and design thermal diodes. Finally, we consider the coupled transport of heat and charge and discuss several general mechanisms for optimizing the figure of merit of thermoelectric efficiency.Comment: 42 pages, 22 figures, review paper, to appear in the Springer Lecture Notes in Physics volume "Thermal transport in low dimensions: from statistical physics to nanoscale heat transfer" (S. Lepri ed.

Many body physics from a quantum information perspective

The quantum information approach to many body physics has been very successful in giving new insight and novel numerical methods. In these lecture notes we take a vertical view of the subject, starting from general concepts and at each step delving into applications or consequences of a particular topic. We first review some general quantum information concepts like entanglement and entanglement measures, which leads us to entanglement area laws. We then continue with one of the most famous examples of area-law abiding states: matrix product states, and tensor product states in general. Of these, we choose one example (classical superposition states) to introduce recent developments on a novel quantum many body approach: quantum kinetic Ising models. We conclude with a brief outlook of the field.Comment: Lectures from the Les Houches School on "Modern theories of correlated electron systems". Improved version new references adde

Global maps of soil temperature.

Research in global change ecology relies heavily on global climatic grids derived from estimates of air temperature in open areas at around 2 m above the ground. These climatic grids do not reflect conditions below vegetation canopies and near the ground surface, where critical ecosystem functions occur and most terrestrial species reside. Here, we provide global maps of soil temperature and bioclimatic variables at a 1-km <sup>2</sup> resolution for 0-5 and 5-15 cm soil depth. These maps were created by calculating the difference (i.e. offset) between in situ soil temperature measurements, based on time series from over 1200 1-km <sup>2</sup> pixels (summarized from 8519 unique temperature sensors) across all the world's major terrestrial biomes, and coarse-grained air temperature estimates from ERA5-Land (an atmospheric reanalysis by the European Centre for Medium-Range Weather Forecasts). We show that mean annual soil temperature differs markedly from the corresponding gridded air temperature, by up to 10°C (mean = 3.0 ± 2.1°C), with substantial variation across biomes and seasons. Over the year, soils in cold and/or dry biomes are substantially warmer (+3.6 ± 2.3°C) than gridded air temperature, whereas soils in warm and humid environments are on average slightly cooler (-0.7 ± 2.3°C). The observed substantial and biome-specific offsets emphasize that the projected impacts of climate and climate change on near-surface biodiversity and ecosystem functioning are inaccurately assessed when air rather than soil temperature is used, especially in cold environments. The global soil-related bioclimatic variables provided here are an important step forward for any application in ecology and related disciplines. Nevertheless, we highlight the need to fill remaining geographic gaps by collecting more in situ measurements of microclimate conditions to further enhance the spatiotemporal resolution of global soil temperature products for ecological applications

The role of endocrine and metabolic system in COVID-19 disease - the transcampus experience and review of evidence from international collaborating groups.

The COVID-19 Pandemic has led to a world health crisis with major socioeconomic consequences that have deeply affected our daily lives. Until the end of May 2022, more than 500 million people have been infected by COVID-19 and more than 6 million have died from the disease. Unprecedented efforts in research, illustrated by the more than 250 000 publications in PubMed, have led to the identification of important pathophysiological mechanisms affected by SARS-CoV-2 and have resulted in the development of effective vaccines and treatment protocols for patients with COVID-19

PCSK9-Inhibitoren – Durchbruch bei der LDL-Cholesterin-Senkung?

Die Proproteinkonvertase-Subtilisin / Kexin-Typ-9 (PCSK9) spielt eine wichtige Rolle im LDL-Cholesterin(LDL-C)-Stoffwechsel. So weisen Menschen mit Mutationen im PCSK9-Gen, die zu einer Funktionseinschränkung des Enzyms führen, deutlich erniedrigte LDL-C-Plasmaspiegel auf. PCSK9 wird in der Leber sezerniert, bindet an den LDL-Rezeptor und bewirkt, dass er mit dem gebundenen LDL-C lysosomal abgebaut wird. Bei den derzeitigen PCSK9 Inhibitoren handelt es sich um monoklonale Antikörper, die PCSK9 spezifisch binden und funktionell neutralisieren. Somit kann der Rezeptor vom LDL-C dissoziieren und wird nicht abgebaut, sondern recycelt, was die LDL Rezeptordichte der Hepatozyten erhöht und die LDL-C Clearance steigert. Die subkutan applizierten PCSK9 Inhibitoren Alirocumab und Evolocumab bewirkten in klinischen Studien Senkungen des LDL-C von maximal ca. 70 % bei mit Statin behandelten und unbehandelten Patienten. Das Nebenwirkungspotenzial erscheint bisher vertretbar. Weil diese Wirkstoffe einen hohen klinischen Nutzen erwarten lassen, wurden sie von der EMA im Sommer 2015 bereits vor Abschluss der Studien zu patientenrelevanten Endpunkten (kardiovaskuläre Morbidität und Mortalität) zugelassen. Eine bessere Beurteilung des tatsächlichen Nutzens sowie der Langzeitsicherheit der PCSK9-Inhibitoren wird erst nach Publikation der Ergebnisse der Outcome-Studien ab 2017 möglich sein

Melanoma Cell-Intrinsic PD-1 Receptor Functions Promote Tumor Growth

Summary Therapeutic antibodies targeting programmed cell death 1 (PD-1) activate tumor-specific immunity and have shown remarkable efficacy in the treatment of melanoma. Yet, little is known about tumor cell-intrinsic PD-1 pathway effects. Here, we show that murine and human melanomas contain PD-1-expressing cancer subpopulations and demonstrate that melanoma cell-intrinsic PD-1 promotes tumorigenesis, even in mice lacking adaptive immunity. PD-1 inhibition on melanoma cells by RNAi, blocking antibodies, or mutagenesis of melanoma-PD-1 signaling motifs suppresses tumor growth in immunocompetent, immunocompromised, and PD-1-deficient tumor graft recipient mice. Conversely, melanoma-specific PD-1 overexpression enhances tumorigenicity, as does engagement of melanoma-PD-1 by its ligand, PD-L1, whereas melanoma-PD-L1 inhibition or knockout of host-PD-L1 attenuate growth of PD-1-positive melanomas. Mechanistically, the melanoma-PD-1 receptor modulates downstream effectors of mTOR signaling. Our results identify melanoma cell-intrinsic functions of the PD-1:PD-L1 axis in tumor growth and suggest that blocking melanoma-PD-1 might contribute to the striking clinical efficacy of anti-PD-1 therapy