Information erasure without an energy cost

Landauer argued that the process of erasing the information stored in a memory device incurs an energy cost in the form of a minimum amount of mechanical work. We find, however, that this energy cost can be reduced to zero by paying a cost in angular momentum or any other conserved quantity. Erasing the memory of Maxwell's demon in this way implies that work can be extracted from a single thermal reservoir at a cost of angular momentum and an increase in total entropy. The implications of this for the second law of thermodynamics are assessed.Comment: 8 pages with 1 figure. Final published versio

Coulomb-corrected quantum interference in above-threshold ionization: Working towards multi-trajectory electron holography

Using the recently developed Coulomb Quantum Orbit Strong-Field Approximation (CQSFA), we perform a systematic analysis of several features encountered in above-threshold ionization (ATI) photoelectron angle-resolved distributions (PADs), such as side lobes, and intra- and intercycle interference patterns. The latter include not only the well-known intra-cycle rings and the near-threshold fan-shaped structure, but also previously overlooked patterns. We provide a direct account of how the Coulomb potential distorts different types of interfering trajectories and changes the corresponding phase differences, and show that these patterns may be viewed as generalized holographic structures formed by up to three types of trajectories. We also derive analytical interference conditions and estimates valid in the presence or absence of the residual potential, and assess the range of validity of Coulomb-corrected interference conditions provided in the literature.Comment: 17 pages, 11 figures. Some figures have been compressed in order to comply with the arXiv requirement

A mechanistic model of connector hubs, modularity, and cognition

The human brain network is modular--comprised of communities of tightly interconnected nodes. This network contains local hubs, which have many connections within their own communities, and connector hubs, which have connections diversely distributed across communities. A mechanistic understanding of these hubs and how they support cognition has not been demonstrated. Here, we leveraged individual differences in hub connectivity and cognition. We show that a model of hub connectivity accurately predicts the cognitive performance of 476 individuals in four distinct tasks. Moreover, there is a general optimal network structure for cognitive performance--individuals with diversely connected hubs and consequent modular brain networks exhibit increased cognitive performance, regardless of the task. Critically, we find evidence consistent with a mechanistic model in which connector hubs tune the connectivity of their neighbors to be more modular while allowing for task appropriate information integration across communities, which increases global modularity and cognitive performance

Different Scenarios for Critical Glassy Dynamics

We study the role of different terms in the $N$-body potential of glass forming systems on the critical dynamics near the glass transition. Using a simplified spin model with quenched disorder, where the different terms of the real $N$-body potential are mapped into multi-spin interactions, we identified three possible scenarios. For each scenario we introduce a ``minimal'' model representative of the critical glassy dynamics near, both above and below, the critical transition lin e. For each ``minimal'' model we discuss the low temperature equilibrium dynamics.Comment: Completely revised version, 8 pages, 5 figures, typeset using EURO-LaTeX, Europhysics Letters (in press

Studies in the Helminthocladiaceae, III Liagoropsis

In the first paper in this series of studies of the Helminthocladiaceae (Dory and Abbott, 1961 ), we have shown that, in two species of Helminthocladia from Hawaii, the female reproductive structures are generally similar to those described by other workers for other species in the genus, and that vegetative structures such as internal cortical rhizoids may be used to distinguish at least the Hawaiian species. In the second paper of this series (Abbott and Dory, 1960) a new genus, Trichogloeopsis, was described as containing three species, one new and two transfers from the genus Liagora. They share a major character in common, that of sterile rhizoidal extensions of the gonimoblast, but again the three species may be distinguished from each other by their vegetative structures

Treating branch cuts in quantum trajectory models for photoelectron holography

Most implementations of Coulomb-distorted strong-field approaches that contain features such as tunneling and quantum interference use real trajectories in continuum propagation, while a fully consistent approach must use complex trajectories throughout. A key difficulty in the latter case are singularities of the Coulomb potential in the complex time plane. These singularities have the form of branch points which generate corresponding branch cuts. We present a method for treating branch cuts in quantum-trajectory models, which is subsequently applied to photoelectron holography. Our method is not numerically intensive and is applicable to Coulomb-free and Coulomb-distorted trajectories. We show that the presence of branch cuts leads to discontinuities and caustics in the holographic fringes in above-threshold ionization (ATI) photoelectron momentum distributions. These artifacts are removed with our method, provided no hard recollision takes place during the interaction. A comparison with the full solution of the time-dependent Schrodinger equation is also performed, and a discussion of the applicability range of the present approach is provided