Bloch Walls and Macroscopic String States in Bethe's solution of the Heisenberg Ferromagnetic Linear Chain

We present a calculation of the lowest excited states of the Heisenberg ferromagnet in 1-d for any wave vector. These turn out to be string solutions of Bethe's equations with a macroscopic number of particles in them. These are identified as generalized quantum Bloch wall states, and a simple physical picture provided for the same.Comment: 4 pages, RevTex, 2 figures, Submitted to Phys. Rev. Let

Linear Response Theory and Optical Conductivity of Floquet Topological Insulators

Motivated by the quest for experimentally accessible dynamical probes of Floquet topological insulators, we formulate the linear response theory of a periodically driven system. We illustrate the applications of this formalism by giving general expressions for optical conductivity of Floquet systems, including its homodyne and heterodyne components and beyond. We obtain the Floquet optical conductivity of specific driven models, including two-dimensional Dirac material such as the surface of a topological insulator, graphene, and the Haldane model irradiated with circularly or linearly polarized laser, as well as semiconductor quantum well driven by an ac potential. We obtain approximate analytical expressions and perform numerically exact calculations of the Floquet optical conductivity in different scenarios of the occupation of the Floquet bands, in particular, the diagonal Floquet distribution and the distribution obtained after a quench. We comment on experimental signatures and detection of Floquet topological phases using optical probes.Comment: 16 pages, 10 figure

Unsupervised learning framework for large-scale flight data analysis of cockpit human machine interaction issues

As the level of automation within an aircraft increases, the interactions between the pilot and autopilot play a crucial role in its proper operation. Issues with human machine interactions (HMI) have been cited as one of the main causes behind many aviation accidents. Due to the complexity of such interactions, it is challenging to identify all possible situations and develop the necessary contingencies. In this thesis, we propose a data-driven analysis tool to identify potential HMI issues in large-scale Flight Operational Quality Assurance (FOQA) dataset. The proposed tool is developed using a multi-level clustering framework, where a set of basic clustering techniques are combined with a consensus-based approach to group HMI events and create a data-driven model from the FOQA data. The proposed framework is able to effectively compress a large dataset into a small set of representative clusters within a data-driven model, enabling subject matter experts to effectively investigate identified potential HMI issues

Perception of Linguistic and Affective Prosody in Individuals with Aphasia

The current study was carried out with the aim of testing the perception of linguistic and affective prosody in individuals with aphasia. Convenient sampling was followed for the recruitment of participants. Comparative group design was used. The participants were divided into two groups. The first group comprised of 10 individuals with aphasia while the second group comprised of 10 neurologically healthy individuals. The study was carried out in native and non-native languages of the participants. Based on this premise, two tasks were configured. The first task required the participants to judge the prosody of sentences in native language and the second task required the participants to judge the sentences based on the prosody in the non-native language. Mann Whitney U test was used to compare the performance of the two groups. Statistically significant difference between the two groups was found on both the tasks. The theoretical premise suggests that the linguistic prosody is affected in left brain damaged adults however, the affective prosody is spared in this population. The findings of the current study contradicted this result as perception of linguistic and affective prosody was found to be affected in persons with aphasia

Comment on ``Can Disorder Induce a Finite Thermal Conductivity in 1D Lattices?''

In a recent paper [Phys. Rev. Lett. 86, 63 (2001)], Li et al have reported that the nonequilibrium heat conducting steady state of a disordered harmonic chain is not unique. In this comment we point out that for a large class of stochastic heat baths the uniqueness of the steady state can be proved, and therefore the findings of Li et al could be either due to their use of deterministic heat baths or insufficient equilibration times in the simulations. We give a simple example where the uniquness of the steady state can be explicitly demonstrated.Comment: 1 page, 1 figure, accepted for publication in Phys. Rev. Let