Truncated unity functional renormalization group for multiband systems with spin-orbit coupling

Although the functional renormalization group (fRG) is by now a well-established method for investigating correlated electron systems, it is still undergoing significant technical and conceptual improvements. In particular, the motivation to optimally exploit the parallelism of modern computing platforms has recently led to the development of the "truncated-unity" functional renormalization group (TU-fRG). Here, we review this fRG variant, and we provide its extension to multiband systems with spin-orbit coupling. Furthermore, we discuss some aspects of the implementation and outline opportunities and challenges ahead for predicting the ground-state ordering and emergent energy scales for a wide class of quantum materials.Comment: consistent with published version in Frontiers in Physics (2018

Two-photon absorption and broadband optical limiting with bis-donor stilbenes

Large two-photon absorptivities are reported for symmetrical bis-donor stilbene derivatives with dialkylamino or diphenylamino groups. These molecules exhibit strong optical limiting of nanosecond pulses over a broad spectral range in the visible. Relative to bis(di-n-butylamino)stilbene, bis(diphenylamino)stilbene exhibits a 90-nm red shift of its optical limiting band but only a minimal shift of ~13 nm of its lowest one-photon electronic absorption band. Mixtures of these compounds offer an unprecedented combination of broad optical limiting bandwidth and high linear transparency

Truncated-Unity Parquet Equations: Application to the Repulsive Hubbard Model

The parquet equations are a self-consistent set of equations for the effective two-particle vertex of an interacting many-fermion system. The application of these equations to bulk models is, however, demanding due to the complex emergent momentum and frequency structure of the vertex. Here, we show how a channel-decomposition by means of truncated unities, which was developed in the context of the functional renormalization group to efficiently treat the momentum dependence, can be transferred to the parquet equations. This leads to a significantly reduced numerical effort scaling only linearly with the number of discrete momenta. We apply this technique to the half-filled repulsive Hubbard model on the square lattice and present approximate solutions for the channel-projected vertices and the full reducible vertex.Comment: Consistent with published version in Phys. Rev.

Numerical test of the damping time of layer-by-layer growth on stochastic models

We perform Monte Carlo simulations on stochastic models such as the Wolf-Villain (WV) model and the Family model in a modified version to measure mean separation $\ell$ between islands in submonolayer regime and damping time $\tilde t$ of layer-by-layer growth oscillations on one dimension. The stochastic models are modified, allowing diffusion within interval $r$ upon deposited. It is found numerically that the mean separation and the damping time depend on the diffusion interval $r$, leading to that the damping time is related to the mean separation as ${\tilde t} \sim \ell^{4/3}$ for the WV model and ${\tilde t} \sim \ell^2$ for the Family model. The numerical results are in excellent agreement with recent theoretical predictions.Comment: 4 pages, source LaTeX file and 5 PS figure

Rigid Singularity Theorem in Globally Hyperbolic Spacetimes

We show the rigid singularity theorem, that is, a globally hyperbolic spacetime satisfying the strong energy condition and containing past trapped sets, either is timelike geodesically incomplete or splits isometrically as space $\times$ time. This result is related to Yau's Lorentzian splitting conjecture.Comment: 3 pages, uses revtex.sty, to appear in Physical Review

Demanding stories: television coverage of sustainability, climate change and material demand

This paper explores the past, present and future role of broadcasting, above all via the medium of television, in shaping how societies talk, think about and act on climate change and sustainability issues. The paper explores these broad themes via a focus on the important but relatively neglected issue of material demand and opportunities for its reduction. It takes the outputs and decision-making of one of the world’s most influential broadcasters, the BBC, as its primary focus. The paper considers these themes in terms of stories, touching on some of the broader societal frames of understanding into which they can be grouped. Media decision-makers and producers from a range of genres frequently return to the centrality of ‘story’ in the development, commissioning and production of an idea. With reference to specific examples of programming, and drawing on interviews with media practitioners, the paper considers the challenges of generating broadcast stories that can inspire engagement in issues around climate change, and specifically material demand. The concluding section proposes actions and approaches that might help to establish material demand reduction as a prominent way of thinking about climate change and environmental issues more widely. This article is part of the themed issue ‘Material demand reduction’

Laparoscopic Wide Mesocolic Excision and Central Vascular Ligation for Carcinoma of the Colon

Peer reviewe

Gravitational Waves: Just Plane Symmetry

We present some remarkable properties of the symmetry group for gravitational plane waves. Our main observation is that metrics with plane wave symmetry satisfy every system of generally covariant vacuum field equations except the Einstein equations. The proof uses the homothety admitted by metrics with plane wave symmetry and the scaling behavior of generally covariant field equations. We also discuss a mini-superspace description of spacetimes with plane wave symmetry.Comment: 10 pages, TeX, uses IOP style file

Investigating the potential to retrieve cloud droplet number concentration from ship-based measurements of spectral solar radiance during EUREC4A

Ship-based cloud remote sensing observations made onboard R/V Meteor during the ElUcidating the RolE of Cloud-Circulation Coupling in ClimAte, EUREC4A, campaign are presented and used to calculate cloud droplet number concentrations. The calculation is based on cloud liquid water path LWP and droplet effective radius reff retrieved from spectral measurements of transmitted solar radiance. It is shown that measurement uncertainties and retrieval assumptions impact the accuracy of the results. A case study indicates that the retrieval of LWP and reff is most affected by 3D-radiative effects in case of shallow cumulus and drizzle, which violates the adiabatic theory and plan-parallel geometry on which the radiative transfer simulations of the retrieval are based. Depending on the cloud thickness, the retrieval of reff might suffers from ambiguity. These retrieval uncertainties and their implications on the estimated cloud droplet number concentration are investigated by a sensitivity study. The analysis showed that most of the uncertainty is introduced by reff, whereas LWP contributes significantly to the uncertainty only for thin clouds. Therefore, it is concluded that only selected cloud cases, which do not violate the retrieval assumption, such as stratiform cloud layers, are suited to apply the retrieval approach in further studies.Fernerkundungsmessungen von Wolken auf dem Forschungsschiff R/V Meteor während der ElUcidating the RolE of Cloud-Circulation Coupling in ClimAte, EUREC4A, Kampagnewerden vorgestellt und zur Berechnung der Tröpfchenanzahlkonzentration verwendet. Die Berechnung basiert auf Messungen des Flüssigwasserpfads LWP und dem effektiven Tröpfchenradius reff, welche aus spektralen Messungen der transmittierten solaren Strahldichte abgeleitet wurden. Es wird gezeigt, dass Messunsicherheiten und Annahmen bei der Ableitung der Wolkeneigenschaften die Genauigkeit der Ergebnisse beeinflussen. Eine Fallstudie zeigt, dass die Ableitung von LWP und reff am stärksten durch 3-dimensionale Strahlungseffekte von flachen Cumuli und Nieselregen beeinflusst wird. Beides wiederspricht den Idealisierungen von adiabatischen Wolken und einer planparallelen Geometrie, auf denen die Strahlungstransfersimulationen des Verfahrens beruhen. Abhängig von der Wolkendicke kann die Ableitung von reff zusätzlich durch Mehrdeutigkeiten beeinflusst sein

CIRRUS-HL: Overview of LIM contributions

From June to July 2021, the Leipzig Institute for Meteorology (LIM) participated in the Cirrus in High Latitudes (CIRRUS-HL) campaign. Utilizing the German High Altitude Long Range Research Aircraft (HALO), 24 research flights were conducted out of Oberpfaffenhofen, Germany. The initial goal of the campaign was to sample high-latitude cirrus clouds with a combination of in-situ and remote sensing instrumentation. However, due to the global coronavirus pandemic, the flights had to be carried out from southern Germany instead of northern Sweden. Thus, the flight time in Arctic latitudes was limited. Therefore, more objectives concerning midlatitude cirrus were included in the campaign goals. LIM contributed to CIRRUS-HL with measurements by the Broadband AirCrAft RaDiometer Instrumentation (BACARDI) and the Spectral Modular Airborne Radiation measurement sysTem (SMART). While BACARDI measured broadband solar and terrestrial upward and downward irradiance, SMART measured spectrally resolved solar upward radiance as well as upward and downward irradiance.Von Juni bis Juli 2021 nahmen einige Mitarbeitende des LIM an der CIRRUS-HL Kampagne teil. Mit dem deutschen Forschungsflugzeug HALO (High Altitude Long Range Research Aircraft) wurden 24 Forschungsflüge von Oberpfaffenhofen, Deutschland, aus durchgeführt. Ursprüngliches Ziel der Kampagne war es, Zirruswolken in hohen Breitengraden mit einer Kombination aus In-situ- und Fernerkundungsinstrumenten zu untersuchen. Aufgrund der weltweiten Corona-Pandemie mussten die Flüge jedoch von Süddeutschland statt von Nordschweden aus durchgeführt werden. Daher wurden weitere Ziele in Bezug auf Zirruswolken in mittleren Breiten in die Ziele der Kampagne aufgenommen. Das LIM-Team betrieb die breitbandigen und spektralen Strahlungssensoren BACARDI (Broadband AirCrAft RaDiometer Instrumentation) und SMART (Spectral Modular Airborne Radiation measurement sysTem), wobeiBACARDI die breitbandige solare und terrestrische Auf- und Abwärtsstrahlung und SMART die spektral aufgelöste solareAuf- undAbwärtsstrahlung sowie dieAufwärtsstrahlungsdichte maß