Baryon structure in a quark-confining non-local NJL model

We study the nucleon and diquarks in a non-local Nambu-Jona-Lasinio model. For certain parameters the model exhibits quark confinement, in the form of a propagator without real poles. After truncation of the two-body channels to the scalar and axial-vector diquarks, a relativistic Faddeev equation for nucleon bound states is solved in the covariant diquark-quark picture. The dependence of the nucleon mass on diquark masses is studied in detail. We find parameters that lead to a simultaneous reasonable description of pions and nucleons. Both the diquarks contribute attractively to the nucleon mass. Axial-vector diquark correlations are seen to be important, especially in the confining phase of the model. We study the possible implications of quark confinement for the description of the diquarks and the nucleon. In particular, we find that it leads to a more compact nucleon.Comment: 21 pages (RevTeX), 18 figures (eps

Lattice Fundamental Measure Theory beyond 0D Cavities: Dimers on Square Lattices

Using classical density functional theory, we study the behavior of dimers, i.e. hard rods of length $L=2$, on a two-dimensional cubic lattice. For deriving a free energy functional, we employ Levy's prescription which is based on the minimization of a microscopic free energy with respect to the many-body probability under the constraint of a fixed density profile. Using that, we recover the functional originally found by Lafuente and Cuesta and derive an extension. With this extension, the free energy functional is exact on cavities that can hold at most two particles simultaneously. The new functional improves the prediction of the free energy in bulk as well as in highly confined systems, especially for high packing fractions, in comparison to that of Lafuente and Cuesta.Comment: 26 pages, 7 figures, Paper is submitted to J.Stat.Phy

Baryon Operators and Baryon Spectroscopy

The issues involved in a determination of the baryon resonance spectrum in lattice QCD are discussed. The variational method is introduced and the need to construct a sufficient basis of interpolating operators is emphasised. The construction of baryon operators using group-theory techniques is outlined. We find that the use both of quark-field smearing and link-field smearing in the operators is essential firstly to reduce the coupling of operators to high-frequency modes and secondly to reduce the gauge-field fluctuations in correlators. We conclude with a status report of our current investigation of baryon spectroscopy.Comment: Invited talk at Workshop on Computational Hadron Physics, Cyprus, Sept. 14-17, 200

Empirical approach for the residual flexural tensile strength of steel fiber-reinforced concrete based on notched three-point bending tests

When designing steel fiber-reinforced concrete, for example, according to Model Code 2010, the residual flexural strength values must be specified as fundamental properties. It is often difficult to establish the relationship between residual flexural strength values and the required dosage of steel fibers depending on the type of steel fibers and the concrete quality. For an estimation of the presumably necessary dosage of steel fibers, various empirical approaches exist for the approximate determination of the residual flexural strength values, which, however, are based on different tests and have been almost exclusively been derived on the basis of few or “own” test results of the respective institute. For this reason, the validity of the respective approximation approach is often limited. Using the bending beam database “Steel Fibre Reinforced Concrete”, selected approaches were systematically analyzed and an improved approach for determining the residual flexural strength values of steel fiber-reinforced concrete was developed

Nucleons or diquarks? Competition between clustering and color superconductivity in quark matter

We study the instabilities of quark matter in the framework of a generalized Nambu--Jona-Lasinio model, in order to explore possible competition between three-quark clustering to form nucleons and diquark formation leading to color superconductivity. Nucleon and $\Delta$ solutions are obtained for the relativistic Faddeev equation at finite density and their binding energies are compared with those for the scalar and axial-vector diquarks found from the Bethe-Salpeter equation. In a model with interactions in both scalar and axial diquark channels, bound nucleons exist up to nuclear matter density. However, except at densities below about a quarter of that of nuclear matter, we find that scalar diquark formation is energetically favored. This raises the question of whether a realistic phase diagram of baryonic matter can be obtained from any model which does not incorporate color confinement.Comment: 23 pages (RevTeX), 5 figures (epsf

Entrepreneurship during the Covid-19 Pandemic: A global study of entrepreneurs' challenges, resilience, and well-being

Summary: Small and medium-sized enterprises (SMEs including the self-employed) account for 90% of businesses globally and provide 70% of employment worldwide. These businesses, typically entrepreneur led, are threatened by the Covid-19 pandemic, meaning that millions of jobs are at risk. This report presents insights from a global study conducted during the pandemic in 2020. We surveyed over 5,000 entrepreneurs in 23 countries that represent 3/4 of the world’s economic output. Most entrepreneurs faced significant challenges threatening the survival of their businesses. We also see resilience in how entrepreneurs navigated the crisis through being agile, adaptive, and exploring new opportunities, utilizing government support, giving back to society, and even harbouring growth ambitions beyond the pandemic. Entrepreneurs’ mental well-being dropped by 12% in the pandemic presenting another threat to their businesses. We chart stressors and well-being resources including social support and self-care strategies that entrepreneurs engaged to stay productive. We close the report (1) by reflecting on five trends for the post-Covid economy and formulate actionable policy recommendations of how entrepreneurs and SMEs can be supported in light of these trends (digitalisation; ‘local’ focus, inclusive business models, developing personal and business resilience), and (2) offer five practical steps for entrepreneurs to protect their well-being

Can triad forestry reconcile Europe’s biodiversity and forestry strategies? A critical evaluation of forest zoning

Balancing increasing demand for wood products while also maintaining forest biodiversity is a paramount challenge. Europe’s Biodiversity and Forest Strategies for 2030 attempt to address this challenge. Together, they call for strict protection of 10% of land area, including all primary and old growth forests, increasing use of ecological forestry, and less reliance on monocultural plantations. Using data on country wide silvicultural practices and a new database on strict forest reserves across Europe, we assess how triad forest zoning could help meet these goals. Our analysis reveals that zoning in Europe is overwhelmingly focused on wood production, while there has been little concomitant protection of forests in strict reserves. Moreover, most strict forest reserves are\50 ha in size, likely too small to capture the minimum dynamic area necessary to sustain many taxa. We outline research priorities to meet future demands for timber while minimizing the impact on native biodiversity. Biodiversity conservation, Disturbance, Forest management, Forest reserve, Land sharing/sparing, Wood productionpublishedVersio

Protein Short-Time Diffusion in a Naturally Crowded Environment.

The interior of living cells is a dense and polydisperse suspension of macromolecules. Such a complex system challenges an understanding in terms of colloidal suspensions. As a fundamental test we employ neutron spectroscopy to measure the diffusion of tracer proteins (immunoglobulins) in a cell-like environment (cell lysate) with explicit control over crowding conditions. In combination with Stokesian dynamics simulation, we address protein diffusion on nanosecond time scales where hydrodynamic interactions dominate over negligible protein collisions. We successfully link the experimental results on these complex, flexible molecules with coarse-grained simulations providing a consistent understanding by colloid theories. Both experiments and simulations show that tracers in polydisperse solutions close to the effective particle radius Reff = ⟨ Ri3⟩1/3 diffuse approximately as if the suspension was monodisperse. The simulations further show that macromolecules of sizes R > Reff ( R < Reff) are slowed more (less) effectively even at nanosecond time scales, which is highly relevant for a quantitative understanding of cellular processes