Double parton scattering theory overview

The dynamics of double hard scattering in proton-proton collisions is quite involved compared with the familiar case of single hard scattering. In this contribution, we review our theoretical understanding of double hard scattering and of its interplay with other reaction mechanisms.Comment: 25 pages, 7 figures. Prepared for: Multiple Parton Interactions at the LHC, Eds. P. Bartalini and J. R. Gaunt, World Scientific, Singapor

Double parton scattering in the ultraviolet: addressing the double counting problem

In proton-proton collisions there is a smooth transition between the regime of double parton scattering, initiated by two pairs of partons at a large relative distance, and the regime where a single parton splits into a parton pair in one or both protons. We present a scheme for computing both contributions in a consistent and practicable way.Comment: 5 pages, 3 figures. To appear in the proeceedings of MPI@LHC 2015, Trieste, Italy, 23-27 November 201

Distinguished orbits and the L-S category of simply connected compact Lie groups

We show that the Lusternik-Schnirelmann category of a simple, simply connected, compact Lie group G is bounded above by the sum of the relative categories of certain distinguished conjugacy classes in G corresponding to the vertices of the fundamental alcove for the action of the affine Weyl group on the Lie algebra of a maximal torus of G.Comment: 10 pages, 2 figure

The Auslander-Reiten Components in the Rhombic Picture

For an indecomposable module $M$ over a path algebra of a quiver of type $\widetilde{\mathbb A}_n$, the Gabriel-Roiter measure gives rise to four new numerical invariants; we call them the multiplicity, and the initial, periodic and final parts. We describe how these invariants for $M$ and for its dual specify the position of $M$ in the Auslander-Reiten quiver of the algebra.Comment: 29 pages; 6 figures; references added to Section 1 as per the referee's suggestions; to appear in Communications in Algebr

Double hard scattering without double counting

Double parton scattering in proton-proton collisions includes kinematic regions in which two partons inside a proton originate from the perturbative splitting of a single parton. This leads to a double counting problem between single and double hard scattering. We present a solution to this problem, which allows for the definition of double parton distributions as operator matrix elements in a proton, and which can be used at higher orders in perturbation theory. We show how the evaluation of double hard scattering in this framework can provide a rough estimate for the size of the higher-order contributions to single hard scattering that are affected by double counting. In a numeric study, we identify situations in which these higher-order contributions must be explicitly calculated and included if one wants to attain an accuracy at which double hard scattering becomes relevant, and other situations where such contributions may be neglected.Comment: 80 pages, 20 figures. v2: clarifications in section 4, extended section 8, small changes elsewher

Optimized Unrestricted Kohn-Sham Potentials from Ab Initio Spin Densities

The reconstruction of the exchange-correlation potential from accurate ab initio electron densities can provide insights into the limitations of the currently available approximate functionals and provide guidance for devising improved approximations for density-functional theory (DFT). For open-shell systems, the spin density is introduced as an additional fundamental variable in Spin-DFT. Here, we consider the reconstruction of the corresponding unrestricted Kohn-Sham potentials from accurate ab initio spin densities. In particular, we investigate whether it is possible to reconstruct the spin exchange-correlation potential, which determines the spin density in spin-unrestricted Kohn-Sham-DFT, despite the numerical difficulties inherent to the optimization of potentials with finite orbital basis sets. We find that the recently developed scheme for unambiguously singling out an optimal optimized potential [J. Chem. Phys. 135, 244102 (2011)] can provide such spin potentials accurately. This is demonstrated for two test cases, the lithium atom and the dioxygen molecule, and target (spin) densities from Full-CI and CASSCF calculations, respectively

Assessment of Policy Instruments Toward a Sustainable Traffic System -A backcasting approach for Stockhom 2030

Finding strategies for preventing the process of global warming is growing urgent. Our intention is to highlight the future requirements and expectations on transport related sustainability measures (e.g. mobility management services, road tolls, CO2-taxes and renewable fuel systems) assisting the reaching of a long-term sustainability target of greenhouse gas emissions at the year 2030. We will employ the transport demand model SAMPERS and the traffic assignment model EMME/2 in order to investigate the effect from specific changes to the traffic network of Stockholm 2030, e.g. the environmental and socioeconomic impact from reduced number of commute trips, reduced car ownership, and new price structures and restrictions on private vehicle travel. In connection to this, we also quantify negative side effects (so-called rebound effects) coupled to efficiencies in the traffic network. We use an appraisal framework, influenced by backcasting, in order to assess the impact from the specific policies in relation to the United Nation’s (IPCC) requirements for a sustainable level of CO2-emissions. The findings from this study point at the inevitable need for at least a 50% renewable fuel mix in the traffic system if reaching the target 2030. Single-handedly, travel demand measures are insufficient to accomplish the CO2-emission target for 2030. Nevertheless, reducing traffic volumes by just a few percent might contribute to savings in emission costs, accident costs and aggregate travel time costs in the traffic system. Such measures are needed in order to mitigate the transition from fossil- to renewable fuels.

Efficient tunable generic model for fluid bilayer membranes

We present a model for the efficient simulation of generic bilayer membranes. Individual lipids are represented by one head- and two tail-beads. By means of simple pair potentials these robustly self-assemble to a fluid bilayer state over a wide range of parameters, without the need for an explicit solvent. The model shows the expected elastic behavior on large length scales, and its physical properties (eg fluidity or bending stiffness) can be widely tuned via a single parameter. In particular, bending rigidities in the experimentally relevant range are obtained, at least within $3-30 k_{\text{B}}T$. The model is naturally suited to study many physical topics, including self-assembly, fusion, bilayer melting, lipid mixtures, rafts, and protein-bilayer interactions.Comment: 4 Pages 4 Figure