Conformational Dynamics Guides Coherent Exciton Migration in Conjugated Polymer Materials: A First-Principles Quantum Dynamical Study

We report on high-dimensional quantum dynamical simulations of torsion-induced exciton migration in a single-chain oligothiophene segment comprising twenty repeat units, using a first-principles parametrized Frenkel J-aggregate Hamiltonian. Starting from an initial inter-ring torsional defect, these simulations provide evidence of an ultrafast two-time scale process at low temperatures, involving exciton-polaron formation within tens of femtoseconds, followed by torsional relaxation on a ~300 femtosecond time scale. The second step is the driving force for exciton migration, as initial conjugation breaks are removed by dynamical planarization. The quantum coherent nature of the elementary exciton migration step is consistent with experimental observations highlighting the correlated and vibrationally coherent nature of the dynamics on ultrafast time scales.Comment: 4 pages, 4 figure

Attitudes towards welfare and welfare recipients are hardening

David Binder examines new research showing the hardening of public attitudes towards welfare recipients. He argues that the media has, and continues to play a major role in defining perceptions around welfare, making it easier for those in political power to pursue similar language and engage in policies that sit well with such perceptions

What should be done about the scourge of in-work poverty

Alan Milburn, the government’s social mobility ‘tsar’, last week released a report into child poverty and social mobility in which it was warned that, because work can no longer guarantee a way out of poverty, Britain risks seeing social mobility ‘go backwards’. David Binder looks at the findings of the report and examines some of the potential policy responses

Whilst there’s a worthwhile debate to be had around welfare fraud, chasing ‘benefits cheats’ misses the bigger picture

Benefit recipients are often portrayed negatively by politicians and the media. But if ‘balancing the books’ is the government’s primary aim, demonising specific groups is unlikely to be productive. David Binder suggests increasing the housing supply, introducing rent controls and looking into ways to boost incomes to reduce the need for tax credits would be a more effective approach

Reliable and Repeatable Transit Through Cislunar Space Using the 2:1 Resonant Spatial Orbit Family

This work focuses on the identification of reliable and repeatable spatial (three-dimensional) trajectories that link the Earth and the Moon. For this purpose, this paper aims to extend the 2:1 resonant prograde family and 2:1 resonant retrograde family to three dimensions and to introduce spatial orbits that are not currently present in the literature. These orbits, named the 2:1 resonant spatial family, bifurcate from the two-dimensional families and smoothly transition between them in phase space. The stability properties of this new family of resonant orbits are discussed, and, interestingly, this family includes marginally stable members. Furthermore, this new family of orbits is applied to several engineering problems in the Earth-Moon system. First, this paper selects an appropriate member of 2:1 resonant spatial family on the basis of its stability properties and relationships with other multibody orbits in the regime. Next, this work combines this trajectory with momentum exchange tethers to transit payloads throughout the system in a reliable and repeatable fashion. Finally, this paper studies the process of aborting a catch and related recovery opportunities.Comment: 33 pages, 31 figure

Dynamically Triangulated Ising Spins in Flat Space

A model describing Ising spins with short range interactions moving randomly in a plane is considered. In the presence of a hard core repulsion, which prevents the Ising spins from overlapping, the model is analogous to a dynamically triangulated Ising model with spins constrained to move on a flat surface. It is found that as a function of coupling strength and hard core repulsion the model exhibits multicritical behavior, with first and second order transition lines terminating at a tricritical point. The thermal and magnetic exponents computed at the tricritical point are consistent with the exact two-matrix model solution of the random Ising model, introduced previously to describe the effects of fluctuating geometries.Comment: (10 pages + 4 figures), CERN-Th-7577/9