Topological States on the Gold Surface

Gold surfaces host special electronic states that have been understood as a prototype of Shockley surface states (SSs). These SSs are commonly employed to benchmark the capability of angle-resolved photoemission spectroscopy (ARPES) and scanning tunneling spectroscopy. We find that these Shockley SSs can be reinterpreted as topologically derived surface states (TDSSs) of a topological insulator (TI), a recently discovered quantum state. Based on band structure calculations, the Z2 topological invariant can be well defined to characterize the nontrivial features of gold that we detect by ARPES. The same TDSSs are also recognized on surfaces of other well-known noble metals (e.g., silver, copper, platinum, and palladium). Besides providing a new understanding of noble metal SSs, finding topological states on late transition metals provokes interesting questions on the role of topological effects in surface-related processes, such as adsorption and catalysis.Comment: 21 pages, 3 figure

The true price of external health effects from food consumption

Although global food consumption costs more in terms of impact on human life than money is spent on it, health costs have not been consistently quantified or included in food prices to date. In this paper, a method to determine the external health costs of nutrition and dietetics is developed by employing the cost-of-illness (COI) and true cost accounting (TCA) approaches. This is done exemplarily for the reference country Germany. The results show that 601.50 € per capita and 50.38 billion € in total external health costs are incurred annually due to nutrition. Overall, most costs are accrued through excessive meat consumption (32.56% of costs), deficient whole grain intake (15.42% of costs), and insufficient uptake of legumes (10.19% of costs). Comparing the external health costs with the external environmental costs in Germany, it can be seen that of the total annual costs of around 153.86 billion €, 67.26% originate from environmental impacts and 32.74% from impacts on human life. In order to achieve the 17 Sustainable Development Goals and to increase family as well as public health, there is a need to internalise these external costs into actual food prices

Semiconductor Fab Scheduling with Self-Supervised and Reinforcement Learning

Semiconductor manufacturing is a notoriously complex and costly multi-step process involving a long sequence of operations on expensive and quantity-limited equipment. Recent chip shortages and their impacts have highlighted the importance of semiconductors in the global supply chains and how reliant on those our daily lives are. Due to the investment cost, environmental impact, and time scale needed to build new factories, it is difficult to ramp up production when demand spikes. This work introduces a method to successfully learn to schedule a semiconductor manufacturing facility more efficiently using deep reinforcement and self-supervised learning. We propose the first adaptive scheduling approach to handle complex, continuous, stochastic, dynamic, modern semiconductor manufacturing models. Our method outperforms the traditional hierarchical dispatching strategies typically used in semiconductor manufacturing plants, substantially reducing each order's tardiness and time until completion. As a result, our method yields a better allocation of resources in the semiconductor manufacturing process

Cyclic A_\infty Structures and Deligne's Conjecture

First we describe a class of homotopy Frobenius algebras via cyclic operads which we call cyclic $A_\infty$ algebras. We then define a suitable new combinatorial operad which acts on the Hochschild cochains of such an algebra in a manner which encodes the homotopy BV structure. Moreover we show that this operad is equivalent to the cellular chains of a certain topological (quasi)-operad of CW complexes whose constituent spaces form a homotopy associative version of the Cacti operad of Voronov. These cellular chains thus constitute a chain model for the framed little disks operad, proving a cyclic $A_\infty$ version of Deligne's conjecture. This chain model contains the minimal operad of Kontsevich and Soibelman as a suboperad and restriction of the action to this suboperad recovers their results in the unframed case. Additionally this proof recovers the work of Kaufmann in the case of a strict Frobenius algebra. We then extend our results to cyclic $A_\infty$ categories, with an eye toward the homotopy BV structure present on the Hochschild cochains of the Fukaya category of a suitable symplectic manifold.Comment: extended results to cyclic A_infty categories; added additional citations, motivation, and future directions; to appear in Algebraic & Geometric Topolog

New neighborhood, old habits? Delivery preferences of residents in new development areas and their assessment of alternative parcel logistics concepts: a case study of Berlin

Various alternative solutions for sustainable last-mile parcel deliveries have been piloted and partially put into operation in Europe in the past decade. However, these delivery concepts have mainly been considered in inner-city areas. There are a few examples of the application of these concepts in peripheral urban areas, where new housing is being built to accommodate high population pressure. However, it is unclear whether the delivery preferences of residents in new neighbourhoods differ from those of the population average. This research conducted a case study in the western outskirts of Berlin, examining two newly built neighbourhoods and one existing residential area. Results from three survey waves of residents (N=645) show that conventional doorstep delivery is preferred by 80% of the respondents. Nonetheless, there is a high willingness to use alternative delivery options, and respondents see benefits in climate-friendly delivery methods. This research also examines the willingness to pay for alternative parcel logistics concepts, which seems to be too low at the moment (at around €1 per shipment) to compensate for the additional costs of an operational change. However, the results also show an increasing awareness of and preferences for new delivery concepts, thus providing practical implications for planners and logistics operators alike

Blowing out the Candle: How to Quench Galaxies at High Redshift -- an Ensemble of Rapid Starbursts, AGN Feedback and Environment

Recent observations with JWST and ALMA have revealed extremely massive quiescent galaxies at redshifts of z=3 and higher, indicating both rapid onset and quenching of star formation. Using the cosmological simulation suite Magneticum Pathfinder we reproduce the observed number densities and stellar masses, with 36 quenched galaxies of stellar mass larger than 3e10Msun at z=3.42. We find that these galaxies are quenched through a rapid burst of star-formation and subsequent AGN feedback caused by a particularly isotropic collapse of surrounding gas, occurring on timescales of around 200Myr or shorter. The resulting quenched galaxies host stellar components which are kinematically fast rotating and alpha-enhanced, while exhibiting a steeper metallicity and flatter age gradient compared to galaxies of similar stellar mass. The gas of the galaxies has been metal enriched and ejected. We find that quenched galaxies do not inhabit the densest nodes, but rather sit in local underdensities. We analyze observable metrics to predict future quenching at high redshifts, finding that on shorter timescales <500Myr the ratio M_bh/M_* is the best predictor, followed by the burstiness of the preceding star-formation, t50-t90 (time to go from 50% to 90% stellar mass). On longer timescales, >1Gyr, the environment becomes the strongest predictor, followed by t50-t90, indicating that at high redshifts the consumption of old and lack of new gas are more relevant for long-term prevention of star-formation than the presence of a massive AGN. We predict that relics of such high-z quenched galaxies should best be characterized by a strong alpha enhancement.Comment: 22 pages, 13 figures, Submitted to ApJ, Comments welcom

Vertical bonding distances and interfacial band structure of PTCDA on a Sn-Ag surface alloy

Molecular materials enable a vast variety of functionalities for novel electronic and spintronic devices. The unique possibility to alter or substitute organic molecules or metallic substrates offers the opportunity to modify and optimize interfacial properties for almost any desired field of application. For this reason, we extend the successful approach to control molecular interfaces by surface alloying. We present a comprehensive characterization of the structural and electronic properties of the interface formed between the prototypical molecule PTCDA and a Sn-Ag surface alloy grown on an Ag(111) single crystal surface. We monitor the changes of adsorption height of the surface alloy atoms and electronic valence band structure upon adsorption of one layer of PTCDA using the normal incidence x-ray standing wave technique in combination with momentum-resolved photoelectron spectroscopy. We find that the vertical buckling and the surface band structure of the SnAg$_2$ surface alloy is not altered by the adsorption of one layer of PTCDA, in contrast to our recent study of PTCDA on a PbAg$_2$ surface alloy [Phys. Rev. Lett. 117, 096805 (2016)] . In addition, the vertical adsorption geometry of PTCDA and the interfacial energy level alignment indicate the absence of any chemical interaction between the molecule and the surface alloy. We attribute the different interactions at these PTCDA/surface alloy interfaces to the presence or absence of local $\sigma$-bonds between the PTCDA oxygen atoms and the surface atoms. Combining our findings with results from literature, we are able to propose an empiric rule for engineering the surface band structure of alloys by adsorption of organic molecules

Simulating the LOcal Web (SLOW) -- III: Synchrotron Emission from the Local Cosmic Web

Aims: Detecting diffuse synchrotron emission from the cosmic web is still a challenge for current radio telescopes. We aim to make predictions for the detectability of cosmic web filaments from simulations. Methods: We present the first cosmological MHD simulation of a 500 $h^{-1} c$Mpc volume with an on-the-fly spectral cosmic ray (CR) model. This allows us to follow the evolution of populations of CR electrons and protons within every resolution element of the simulation. We model CR injection at shocks, while accounting for adiabatic changes to the CR population and high energy loss processes of electrons. The synchrotron emission is then calculated from the aged electron population, using the simulated magnetic field, as well as different models for origin and amplification of magnetic fields. We use constrained initial conditions, which closely resemble the local Universe and compare the results of the cosmological volume to zoom-in simulation of the Coma cluster, to study the impact of resolution and turbulent re-acceleration of CRs on the results. Results: We find consistent injection of CRs at accretion shocks onto cosmic web filaments and galaxy clusters. This leads to diffuse emission from filaments of the order $S_\nu \approx 0.1 \: \mu$Jy beam$^{-1}$ for a potential LOFAR observation at 144 MHz, when assuming the most optimistic magnetic field model and the inclusion of an on-the-fly treatment of re-acceleration of electrons by turbulence. The flux can be increased by up-to two orders of magnitude for different choices of CR injection parameters. This can bring the flux within a factor of 10 of the current limits for direct detection. We find a spectral index of the simulated synchrotron emission from filaments of {\alpha} {\approx} 1.0 - 1.5.Comment: 23 pages, 12 figures, submitted to A&A. Comments welcome

A symplectic proof of a theorem of Franks

A celebrated theorem in two-dimensional dynamics due to John Franks asserts that every area preserving homeomorphism of the sphere has either two or infinitely many periodic points. In this work we reprove Franks' theorem under the additional assumption that the map is smooth. Our proof uses only tools from symplectic topology and thus differs significantly from all previous proofs. A crucial role is played by the results of Ginzburg and Kerman concerning resonance relations for Hamiltonian diffeomorpisms.Comment: 15 pages. Minor changes. Final version to appear in Compositio Mathematic